0.18.0

	CanCreate(user, newMeta *meta.Meta) bool

	// User is allowed to read zettel
	CanRead(user, m *meta.Meta) bool

	// User is allowed to write zettel.
	CanWrite(user, oldMeta, newMeta *meta.Meta) bool

	// User is allowed to rename zettel
	CanRename(user, m *meta.Meta) bool

	// User is allowed to delete zettel.
	CanDelete(user, m *meta.Meta) bool

	// User is allowed to refresh box data.
	CanRefresh(user *meta.Meta) bool
}

func (ap *anonPolicy) CanRead(user, m *meta.Meta) bool {
	return ap.pre.CanRead(user, m) && ap.checkVisibility(m)
}

func (ap *anonPolicy) CanWrite(user, oldMeta, newMeta *meta.Meta) bool {
	return ap.pre.CanWrite(user, oldMeta, newMeta) && ap.checkVisibility(oldMeta)
}

func (ap *anonPolicy) CanRename(user, m *meta.Meta) bool {
	return ap.pre.CanRename(user, m) && ap.checkVisibility(m)
}

func (ap *anonPolicy) CanDelete(user, m *meta.Meta) bool {
	return ap.pre.CanDelete(user, m) && ap.checkVisibility(m)
}

func (ap *anonPolicy) CanRefresh(user *meta.Meta) bool {
	if ap.authConfig.GetExpertMode() || ap.authConfig.GetSimpleMode() {

		return err
	}
	if pp.policy.CanWrite(user, oldZettel.Meta, zettel.Meta) {
		return pp.box.UpdateZettel(ctx, zettel)
	}
	return box.NewErrNotAllowed("Write", user, zid)
}

func (pp *polBox) AllowRenameZettel(ctx context.Context, zid id.Zid) bool {
	return pp.box.AllowRenameZettel(ctx, zid)
}

func (pp *polBox) RenameZettel(ctx context.Context, curZid, newZid id.Zid) error {
	z, err := pp.box.GetZettel(ctx, curZid)
	if err != nil {
		return err
	}
	user := server.GetUser(ctx)
	if pp.policy.CanRename(user, z.Meta) {
		return pp.box.RenameZettel(ctx, curZid, newZid)
	}
	return box.NewErrNotAllowed("Rename", user, curZid)
}

func (pp *polBox) CanDeleteZettel(ctx context.Context, zid id.Zid) bool {
	return pp.box.CanDeleteZettel(ctx, zid)
}

func (pp *polBox) DeleteZettel(ctx context.Context, zid id.Zid) error {
	z, err := pp.box.GetZettel(ctx, zid)

}

func (*defaultPolicy) CanCreate(_, _ *meta.Meta) bool { return true }
func (*defaultPolicy) CanRead(_, _ *meta.Meta) bool   { return true }
func (d *defaultPolicy) CanWrite(user, oldMeta, _ *meta.Meta) bool {
	return d.canChange(user, oldMeta)
}
func (d *defaultPolicy) CanRename(user, m *meta.Meta) bool { return d.canChange(user, m) }
func (d *defaultPolicy) CanDelete(user, m *meta.Meta) bool { return d.canChange(user, m) }

func (*defaultPolicy) CanRefresh(user *meta.Meta) bool { return user != nil }

func (d *defaultPolicy) canChange(user, m *meta.Meta) bool {
	metaRo, ok := m.Get(api.KeyReadOnly)
	if !ok {

	}
	switch userRole := o.manager.GetUserRole(user); userRole {
	case meta.UserRoleReader, meta.UserRoleCreator:
		return false
	}
	return o.userCanCreate(user, newMeta)
}

func (o *ownerPolicy) CanRename(user, m *meta.Meta) bool {
	if user == nil || !o.pre.CanRename(user, m) {
		return false
	}
	if res, ok := o.checkVisibility(user, o.authConfig.GetVisibility(m)); ok {
		return res
	}
	return o.userIsOwner(user)
}

func (o *ownerPolicy) CanDelete(user, m *meta.Meta) bool {
	if user == nil || !o.pre.CanDelete(user, m) {
		return false
	}
	if res, ok := o.checkVisibility(user, o.authConfig.GetVisibility(m)); ok {
		return res

	return m != nil && p.post.CanRead(user, m)
}

func (p *prePolicy) CanWrite(user, oldMeta, newMeta *meta.Meta) bool {
	return oldMeta != nil && newMeta != nil && oldMeta.Zid == newMeta.Zid &&
		p.post.CanWrite(user, oldMeta, newMeta)
}

func (p *prePolicy) CanRename(user, m *meta.Meta) bool {
	return m != nil && p.post.CanRename(user, m)
}

func (p *prePolicy) CanDelete(user, m *meta.Meta) bool {
	return m != nil && p.post.CanDelete(user, m)
}

func (p *prePolicy) CanRefresh(user *meta.Meta) bool {
	return p.post.CanRefresh(user)

		)
		name := fmt.Sprintf("readonly=%v/withauth=%v/expert=%v/simple=%v",
			ts.readonly, ts.withAuth, ts.expert, ts.simple)
		t.Run(name, func(tt *testing.T) {
			testCreate(tt, pol, ts.withAuth, ts.readonly)
			testRead(tt, pol, ts.withAuth, ts.expert)
			testWrite(tt, pol, ts.withAuth, ts.readonly, ts.expert)
			testRename(tt, pol, ts.withAuth, ts.readonly, ts.expert)
			testDelete(tt, pol, ts.withAuth, ts.readonly, ts.expert)
			testRefresh(tt, pol, ts.withAuth, ts.expert, ts.simple)
		})
	}
}

type testAuthzManager struct {

		{writer, roTrue, roTrue, false},
		{owner, roTrue, roTrue, false},
		{owner2, roTrue, roTrue, false},
	}
	for _, tc := range testCases {
		t.Run("Write", func(tt *testing.T) {
			got := pol.CanWrite(tc.user, tc.old, tc.new)
			if tc.exp != got {
				tt.Errorf("exp=%v, but got=%v", tc.exp, got)
			}
		})
	}
}

func testRename(t *testing.T, pol auth.Policy, withAuth, readonly, expert bool) {
	t.Helper()
	anonUser := newAnon()
	creator := newCreator()
	reader := newReader()
	writer := newWriter()
	owner := newOwner()
	owner2 := newOwner2()
	zettel := newZettel()
	expertZettel := newExpertZettel()
	roFalse := newRoFalseZettel()
	roTrue := newRoTrueZettel()
	roReader := newRoReaderZettel()
	roWriter := newRoWriterZettel()
	roOwner := newRoOwnerZettel()
	notAuthNotReadonly := !withAuth && !readonly
	testCases := []struct {
		user *meta.Meta
		meta *meta.Meta
		exp  bool
	}{
		// No meta
		{anonUser, nil, false},
		{creator, nil, false},
		{reader, nil, false},
		{writer, nil, false},
		{owner, nil, false},
		{owner2, nil, false},
		// Any zettel
		{anonUser, zettel, notAuthNotReadonly},
		{creator, zettel, notAuthNotReadonly},
		{reader, zettel, notAuthNotReadonly},
		{writer, zettel, notAuthNotReadonly},
		{owner, zettel, !readonly},
		{owner2, zettel, !readonly},
		// Expert zettel
		{anonUser, expertZettel, notAuthNotReadonly && expert},
		{creator, expertZettel, notAuthNotReadonly && expert},
		{reader, expertZettel, notAuthNotReadonly && expert},
		{writer, expertZettel, notAuthNotReadonly && expert},
		{owner, expertZettel, !readonly && expert},
		{owner2, expertZettel, !readonly && expert},
		// No r/o zettel
		{anonUser, roFalse, notAuthNotReadonly},
		{creator, roFalse, notAuthNotReadonly},
		{reader, roFalse, notAuthNotReadonly},
		{writer, roFalse, notAuthNotReadonly},
		{owner, roFalse, !readonly},
		{owner2, roFalse, !readonly},
		// Reader r/o zettel
		{anonUser, roReader, false},
		{creator, roReader, false},
		{reader, roReader, false},
		{writer, roReader, notAuthNotReadonly},
		{owner, roReader, !readonly},
		{owner2, roReader, !readonly},
		// Writer r/o zettel
		{anonUser, roWriter, false},
		{creator, roWriter, false},
		{reader, roWriter, false},
		{writer, roWriter, false},
		{owner, roWriter, !readonly},
		{owner2, roWriter, !readonly},
		// Owner r/o zettel
		{anonUser, roOwner, false},
		{creator, roOwner, false},
		{reader, roOwner, false},
		{writer, roOwner, false},
		{owner, roOwner, false},
		{owner2, roOwner, false},
		// r/o = true zettel
		{anonUser, roTrue, false},
		{creator, roTrue, false},
		{reader, roTrue, false},
		{writer, roTrue, false},
		{owner, roTrue, false},
		{owner2, roTrue, false},
	}
	for _, tc := range testCases {
		t.Run("Rename", func(tt *testing.T) {
			got := pol.CanRename(tc.user, tc.meta)
			if tc.exp != got {
				tt.Errorf("exp=%v, but got=%v", tc.exp, got)
			}
		})
	}
}

import "zettelstore.de/z/zettel/meta"

type roPolicy struct{}

func (*roPolicy) CanCreate(_, _ *meta.Meta) bool   { return false }
func (*roPolicy) CanRead(_, _ *meta.Meta) bool     { return true }
func (*roPolicy) CanWrite(_, _, _ *meta.Meta) bool { return false }
func (*roPolicy) CanRename(_, _ *meta.Meta) bool   { return false }
func (*roPolicy) CanDelete(_, _ *meta.Meta) bool   { return false }
func (*roPolicy) CanRefresh(user *meta.Meta) bool  { return user != nil }

type BaseBox interface {
	// Location returns some information where the box is located.
	// Format is dependent of the box.
	Location() string

	// GetZettel retrieves a specific zettel.
	GetZettel(ctx context.Context, zid id.Zid) (zettel.Zettel, error)

	// AllowRenameZettel returns true, if box will not disallow renaming the zettel.
	AllowRenameZettel(ctx context.Context, zid id.Zid) bool

	// RenameZettel changes the current Zid to a new Zid.
	RenameZettel(ctx context.Context, curZid, newZid id.Zid) error

	// CanDeleteZettel returns true, if box could possibly delete the given zettel.
	CanDeleteZettel(ctx context.Context, zid id.Zid) bool

	// DeleteZettel removes the zettel from the box.
	DeleteZettel(ctx context.Context, zid id.Zid) error
}

type UpdateReason uint8

// Values for Reason
const (
	_        UpdateReason = iota
	OnReady               // Box is started and fully operational
	OnReload              // Box was reloaded
	OnZettel              // Something with a zettel happened

)

// UpdateInfo contains all the data about a changed zettel.
type UpdateInfo struct {
	Box    BaseBox
	Reason UpdateReason
	Zid    id.Zid
}

// UpdateFunc is a function to be called when a change is detected.
type UpdateFunc func(UpdateInfo)




// Subject is a box that notifies observers about changes.
type Subject interface {
	// RegisterObserver registers an observer that will be notified
	// if one or all zettel are found to be changed.
	RegisterObserver(UpdateFunc)
}

	"zettelstore.de/z/zettel/id"
	"zettelstore.de/z/zettel/meta"
)

func init() {
	manager.Register(
		" comp",
		func(u *url.URL, cdata *manager.ConnectData) (box.ManagedBox, error) {
			return getCompBox(cdata.Number, cdata.Enricher, cdata.Mapper), nil
		})
}

type compBox struct {
	log      *logger.Logger
	number   int
	enricher box.Enricher
	mapper   manager.Mapper
}

var myConfig *meta.Meta
var myZettel = map[id.Zid]struct {
	meta    func(id.Zid) *meta.Meta
	content func(context.Context, *compBox) []byte
}{

	// id.MustParse(api.ZidConsole):              {genConsoleM, genConsoleC},
	id.MustParse(api.ZidBoxManager): {genManagerM, genManagerC},
	// id.MustParse(api.ZidIndex):                {genIndexM, genIndexC},
	// id.MustParse(api.ZidQuery):                {genQueryM, genQueryC},
	id.MustParse(api.ZidMetadataKey):          {genKeysM, genKeysC},
	id.MustParse(api.ZidParser):               {genParserM, genParserC},
	id.MustParse(api.ZidStartupConfiguration): {genConfigZettelM, genConfigZettelC},
	id.MustParse(api.ZidWarnings):             {genWarningsM, genWarningsC},
	id.MustParse(api.ZidMapping):              {genMappingM, genMappingC},
}

// Get returns the one program box.
func getCompBox(boxNumber int, mf box.Enricher, mapper manager.Mapper) *compBox {
	return &compBox{
		log: kernel.Main.GetLogger(kernel.BoxService).Clone().
			Str("box", "comp").Int("boxnum", int64(boxNumber)).Child(),
		number:   boxNumber,
		enricher: mf,
		mapper:   mapper,
	}
}

// Setup remembers important values.
func Setup(cfg *meta.Meta) { myConfig = cfg.Clone() }

func (*compBox) Location() string { return "" }

				cb.enricher.Enrich(ctx, m, cb.number)
				handle(m)
			}
		}
	}
	return nil
}

func (*compBox) AllowRenameZettel(_ context.Context, zid id.Zid) bool {
	_, ok := myZettel[zid]
	return !ok
}

func (cb *compBox) RenameZettel(_ context.Context, curZid, _ id.Zid) (err error) {
	if _, ok := myZettel[curZid]; ok {
		err = box.ErrReadOnly
	} else {
		err = box.ErrZettelNotFound{Zid: curZid}
	}
	cb.log.Trace().Err(err).Msg("RenameZettel")
	return err
}

func (*compBox) CanDeleteZettel(context.Context, id.Zid) bool { return false }

func (cb *compBox) DeleteZettel(_ context.Context, zid id.Zid) (err error) {
	if _, ok := myZettel[zid]; ok {
		err = box.ErrReadOnly
	} else {

//-----------------------------------------------------------------------------
// Copyright (c) 2024-present Detlef Stern
//
// This file is part of Zettelstore.
//
// Zettelstore is licensed under the latest version of the EUPL (European Union
// Public License). Please see file LICENSE.txt for your rights and obligations
// under this license.
//
// SPDX-License-Identifier: EUPL-1.2
// SPDX-FileCopyrightText: 2024-present Detlef Stern
//-----------------------------------------------------------------------------

package compbox

import (
	"bytes"
	"context"

	"zettelstore.de/z/zettel/id"
	"zettelstore.de/z/zettel/meta"
)

// Zettelstore Identifier Mapping.
//
// In the first stage of migration process, it is a computed zettel showing a
// hypothetical mapping. In later stages, it will be stored as a normal zettel
// that is updated when a new zettel is created or an old zettel is deleted.

func genMappingM(zid id.Zid) *meta.Meta {
	return getTitledMeta(zid, "Zettelstore Identifier Mapping")
}

func genMappingC(ctx context.Context, cb *compBox) []byte {
	var buf bytes.Buffer
	toNew, err := cb.mapper.OldToNewMapping(ctx)
	if err != nil {
		buf.WriteString("**Error while fetching: ")
		buf.WriteString(err.Error())
		buf.WriteString("**\n")
		return buf.Bytes()
	}
	oldZids := id.NewSetCap(len(toNew))
	for zidO := range toNew {
		oldZids.Add(zidO)
	}
	first := true
	oldZids.ForEach(func(zidO id.Zid) {
		if first {
			buf.WriteString("**Note**: this mapping is preliminary.\n")
			buf.WriteString("It only shows you how it could look if the migration is done.\n")
			buf.WriteString("Use this page to update your zettel if something strange is shown.\n")
			buf.WriteString("```\n")
			first = false
		}
		buf.WriteString(zidO.String())
		buf.WriteByte(' ')
		buf.WriteString(toNew[zidO].String())
		buf.WriteByte('\n')
	})
	if !first {
		buf.WriteString("```")
	}
	return buf.Bytes()
}

	var buf bytes.Buffer
	buf.WriteString("|=Name|=Value>\n")
	fmt.Fprintf(&buf, "|Page Size|%d\n", pageSize)
	fmt.Fprintf(&buf, "|Pages|%d\n", m.HeapSys/uint64(pageSize))
	fmt.Fprintf(&buf, "|Heap Objects|%d\n", m.HeapObjects)
	fmt.Fprintf(&buf, "|Heap Sys (KiB)|%d\n", m.HeapSys/1024)
	fmt.Fprintf(&buf, "|Heap Inuse (KiB)|%d\n", m.HeapInuse/1024)


	debug := kernel.Main.GetConfig(kernel.CoreService, kernel.CoreDebug).(bool)
	if debug {
		for i, bysize := range m.BySize {
			fmt.Fprintf(&buf, "|Size %2d: %d|%d - %d → %d\n",
				i, bysize.Size, bysize.Mallocs, bysize.Frees, bysize.Mallocs-bysize.Frees)
		}
	}

//-----------------------------------------------------------------------------
// Copyright (c) 2024-present Detlef Stern
//
// This file is part of Zettelstore.
//
// Zettelstore is licensed under the latest version of the EUPL (European Union
// Public License). Please see file LICENSE.txt for your rights and obligations
// under this license.
//
// SPDX-License-Identifier: EUPL-1.2
// SPDX-FileCopyrightText: 2024-present Detlef Stern
//-----------------------------------------------------------------------------

package compbox

import (
	"bytes"
	"context"

	"zettelstore.de/z/zettel/id"
	"zettelstore.de/z/zettel/meta"
)

func genWarningsM(zid id.Zid) *meta.Meta {
	return getTitledMeta(zid, "Zettelstore Warnings")
}

func genWarningsC(ctx context.Context, cb *compBox) []byte {
	var buf bytes.Buffer
	buf.WriteString("* [[Zettel without stored creation date|query:created-missing:true]]\n")
	buf.WriteString("* [[Zettel with strange creation date|query:created<19700101000000]]\n")

	ws, err := cb.mapper.Warnings(ctx)
	if err != nil {
		buf.WriteString("**Error while fetching: ")
		buf.WriteString(err.Error())
		buf.WriteString("**\n")
		return buf.Bytes()
	}
	first := true
	ws.ForEach(func(zid id.Zid) {
		if first {
			first = false
			buf.WriteString("=== Mapper Warnings\n")
		}
		buf.WriteString("* [[")
		buf.WriteString(zid.String())
		buf.WriteString("]]\n")
	})

	return buf.Bytes()
}

 *-----------------------------------------------------------------------------
 */

*,*::before,*::after {
    box-sizing: border-box;
  }
  html {
    font-size: 1rem;
    font-family: serif;
    scroll-behavior: smooth;
    height: 100%;
  }
  body {
    margin: 0;
    min-height: 100vh;

  .zs-dropdown:hover > .zs-dropdown-content { display: block }
  main { padding: 0 1rem }
  article > * + * { margin-top: .5rem }
  article header {
    padding: 0;
    margin: 0;
  }
  h1,h2,h3,h4,h5,h6 { font-family:sans-serif; font-weight:normal }
  h1 { font-size:1.5rem;  margin:.65rem 0 }
  h2 { font-size:1.25rem; margin:.70rem 0 }
  h3 { font-size:1.15rem; margin:.75rem 0 }
  h4 { font-size:1.05rem; margin:.8rem 0; font-weight: bold }
  h5 { font-size:1.05rem; margin:.8rem 0 }
  h6 { font-size:1.05rem; margin:.8rem 0; font-weight: lighter }
  p { margin: .5rem 0 0 0 }
  p.zs-meta-zettel { margin-top: .5rem; margin-left: 0.5rem }
  li,figure,figcaption,dl { margin: 0 }
  dt { margin: .5rem 0 0 0 }
  dt+dd { margin-top: 0 }
  dd { margin: .5rem 0 0 2rem }
  dd > p:first-child { margin: 0 0 0 0 }
  blockquote {
    border-left: 0.5rem solid lightgray;
    padding-left: 1rem;
    margin-left: 1rem;
    margin-right: 2rem;
    font-style: italic;
  }
  blockquote p { margin-bottom: .5rem }
  blockquote cite { font-style: normal }
  table {
    border-collapse: collapse;
    border-spacing: 0;
    max-width: 100%;
  }

  thead>tr>td { border-bottom: 2px solid hsl(0, 0%, 70%); font-weight: bold }
  tfoot>tr>td { border-top: 2px solid hsl(0, 0%, 70%); font-weight: bold }
  td {
    text-align: left;
    padding: .25rem .5rem;
    border-bottom: 1px solid hsl(0, 0%, 85%)
  }
  main form {
    padding: 0 .5em;
    margin: .5em 0 0 0;
  }
  main form:after {
    content: ".";
    display: block;

  input.zs-secondary { float:left }
  input.zs-upload {
    padding-left: 1em;
    padding-right: 1em;
  }
  a:not([class]) { text-decoration-skip-ink: auto }
  a.broken { text-decoration: line-through }
  a.external::after { content: "➚"; display: inline-block }
  img { max-width: 100% }
  img.right { float: right }
  ol.zs-endnotes {
    padding-top: .5rem;
    border-top: 1px solid;
  }
  kbd { font-family:monospace }
  code,pre {
    font-family: monospace;
    font-size: 85%;
  }
  code {
    padding: .1rem .2rem;
    background: #f0f0f0;
    border: 1px solid #ccc;
    border-radius: .25rem;
  }
  pre {
    padding: .5rem .7rem;
    max-width: 100%;
    overflow: auto;
    border: 1px solid #ccc;
    border-radius: .5rem;
    background: #f0f0f0;
  }
  pre code {
    font-size: 95%;
    position: relative;
    padding: 0;
    border: none;
  }
  div.zs-indication {
    padding: .5rem .7rem;
    max-width: 100%;
    border-radius: .5rem;
    border: 1px solid black;
  }
  div.zs-indication p:first-child { margin-top: 0 }
  span.zs-indication {
    border: 1px solid black;
    border-radius: .25rem;
    padding: .1rem .2rem;
    font-size: 95%;
  }
  .zs-info {
    background-color: lightblue;
    padding: .5rem 1rem;
  }
  .zs-warning {
    background-color: lightyellow;
    padding: .5rem 1rem;
  }
  .zs-error {
    background-color: lightpink;
    border-style: none !important;
    font-weight: bold;
  }
  td.left { text-align:left }
  td.center { text-align:center }
  td.right { text-align:right }
  .zs-font-size-0 { font-size:75% }
  .zs-font-size-1 { font-size:83% }
  .zs-font-size-2 { font-size:100% }
  .zs-font-size-3 { font-size:117% }
  .zs-font-size-4 { font-size:150% }
  .zs-font-size-5 { font-size:200% }
  .zs-deprecated { border-style: dashed; padding: .2rem }
  .zs-meta {
    font-size:.75rem;
    color:#444;
    margin-bottom:1rem;
  }
  .zs-meta a { color:#444 }
  h1+.zs-meta { margin-top:-1rem }
  nav > details { margin-top:1rem }
  details > summary {
    width: 100%;
    background-color: #eee;
    font-family:sans-serif;
  }
  details > ul {
    margin-top:0;
    padding-left:2rem;
    background-color: #eee;
  }
  footer { padding: 0 1rem }
  @media (prefers-reduced-motion: reduce) {
    * {
      animation-duration: 0.01ms !important;
      animation-iteration-count: 1 !important;
      transition-duration: 0.01ms !important;
      scroll-behavior: auto !important;
    }
  }

            `((a (@ (href ,login-url)) "Login"))
          )
      )))
    )
    (div (@ (class "zs-dropdown"))
      (button "Lists")
      (nav (@ (class "zs-dropdown-content"))
        (a (@ (href ,list-zettel-url)) "List Zettel")
        (a (@ (href ,list-roles-url)) "List Roles")
        (a (@ (href ,list-tags-url)) "List Tags")
        ,@(if (bound? 'refresh-url) `((a (@ (href ,refresh-url)) "Refresh")))
    ))
    ,@(if new-zettel-links
      `((div (@ (class "zs-dropdown"))
        (button "New")
        (nav (@ (class "zs-dropdown-content"))
          ,@(map wui-link new-zettel-links)

	"zettelstore.de/z/zettel/id"
	"zettelstore.de/z/zettel/meta"
)

func init() {
	manager.Register(
		" const",
		func(u *url.URL, cdata *manager.ConnectData) (box.ManagedBox, error) {
			return &constBox{
				log: kernel.Main.GetLogger(kernel.BoxService).Clone().
					Str("box", "const").Int("boxnum", int64(cdata.Number)).Child(),
				number:   cdata.Number,
				zettel:   constZettelMap,
				enricher: cdata.Enricher,
			}, nil

			m := meta.NewWithData(zid, zettel.header)
			cb.enricher.Enrich(ctx, m, cb.number)
			handle(m)
		}
	}
	return nil
}

func (cb *constBox) AllowRenameZettel(_ context.Context, zid id.Zid) bool {
	_, ok := cb.zettel[zid]
	return !ok
}

func (cb *constBox) RenameZettel(_ context.Context, curZid, _ id.Zid) (err error) {
	if _, ok := cb.zettel[curZid]; ok {
		err = box.ErrReadOnly
	} else {
		err = box.ErrZettelNotFound{Zid: curZid}
	}
	cb.log.Trace().Err(err).Msg("RenameZettel")
	return err
}

func (*constBox) CanDeleteZettel(context.Context, id.Zid) bool { return false }

func (cb *constBox) DeleteZettel(_ context.Context, zid id.Zid) (err error) {
	if _, ok := cb.zettel[zid]; ok {
		err = box.ErrReadOnly
	} else {

		zettel.NewContent(contentDependencies)},
	id.BaseTemplateZid: {
		constHeader{
			api.KeyTitle:      "Zettelstore Base HTML Template",
			api.KeyRole:       api.ValueRoleConfiguration,
			api.KeySyntax:     meta.SyntaxSxn,
			api.KeyCreated:    "20230510155100",
			api.KeyModified:   "20240219145300",
			api.KeyVisibility: api.ValueVisibilityExpert,
		},
		zettel.NewContent(contentBaseSxn)},
	id.LoginTemplateZid: {
		constHeader{
			api.KeyTitle:      "Zettelstore Login Form HTML Template",
			api.KeyRole:       api.ValueRoleConfiguration,
			api.KeySyntax:     meta.SyntaxSxn,
			api.KeyCreated:    "20200804111624",
			api.KeyModified:   "20240219145200",
			api.KeyVisibility: api.ValueVisibilityExpert,
		},
		zettel.NewContent(contentLoginSxn)},
	id.ZettelTemplateZid: {
		constHeader{
			api.KeyTitle:      "Zettelstore Zettel HTML Template",
			api.KeyRole:       api.ValueRoleConfiguration,
			api.KeySyntax:     meta.SyntaxSxn,
			api.KeyCreated:    "20230510155300",
			api.KeyModified:   "20240219145100",
			api.KeyVisibility: api.ValueVisibilityExpert,
		},
		zettel.NewContent(contentZettelSxn)},
	id.InfoTemplateZid: {
		constHeader{
			api.KeyTitle:      "Zettelstore Info HTML Template",
			api.KeyRole:       api.ValueRoleConfiguration,
			api.KeySyntax:     meta.SyntaxSxn,
			api.KeyCreated:    "20200804111624",
			api.KeyModified:   "20240618170000",
			api.KeyVisibility: api.ValueVisibilityExpert,
		},
		zettel.NewContent(contentInfoSxn)},
	id.FormTemplateZid: {
		constHeader{
			api.KeyTitle:      "Zettelstore Form HTML Template",
			api.KeyRole:       api.ValueRoleConfiguration,
			api.KeySyntax:     meta.SyntaxSxn,
			api.KeyCreated:    "20200804111624",
			api.KeyModified:   "20240219145200",
			api.KeyVisibility: api.ValueVisibilityExpert,
		},
		zettel.NewContent(contentFormSxn)},
	id.RenameTemplateZid: {
		constHeader{
			api.KeyTitle:      "Zettelstore Rename Form HTML Template",
			api.KeyRole:       api.ValueRoleConfiguration,
			api.KeySyntax:     meta.SyntaxSxn,
			api.KeyCreated:    "20200804111624",
			api.KeyModified:   "20240219145200",
			api.KeyVisibility: api.ValueVisibilityExpert,
		},
		zettel.NewContent(contentRenameSxn)},
	id.DeleteTemplateZid: {
		constHeader{
			api.KeyTitle:      "Zettelstore Delete HTML Template",
			api.KeyRole:       api.ValueRoleConfiguration,
			api.KeySyntax:     meta.SyntaxSxn,
			api.KeyCreated:    "20200804111624",
			api.KeyModified:   "20240219145200",
			api.KeyVisibility: api.ValueVisibilityExpert,
		},
		zettel.NewContent(contentDeleteSxn)},
	id.ListTemplateZid: {
		constHeader{
			api.KeyTitle:      "Zettelstore List Zettel HTML Template",
			api.KeyRole:       api.ValueRoleConfiguration,

		zettel.NewContent(contentStartCodeSxn)},
	id.BaseSxnZid: {
		constHeader{
			api.KeyTitle:      "Zettelstore Sxn Base Code",
			api.KeyRole:       api.ValueRoleConfiguration,
			api.KeySyntax:     meta.SyntaxSxn,
			api.KeyCreated:    "20230619132800",
			api.KeyModified:   "20240618170100",
			api.KeyReadOnly:   api.ValueTrue,
			api.KeyVisibility: api.ValueVisibilityExpert,
			api.KeyPrecursor:  string(api.ZidSxnPrelude),
		},
		zettel.NewContent(contentBaseCodeSxn)},
	id.PreludeSxnZid: {
		constHeader{

		zettel.NewContent(contentPreludeSxn)},
	id.MustParse(api.ZidBaseCSS): {
		constHeader{
			api.KeyTitle:      "Zettelstore Base CSS",
			api.KeyRole:       api.ValueRoleConfiguration,
			api.KeySyntax:     meta.SyntaxCSS,
			api.KeyCreated:    "20200804111624",
			api.KeyModified:   "20231129112800",
			api.KeyVisibility: api.ValueVisibilityPublic,
		},
		zettel.NewContent(contentBaseCSS)},
	id.MustParse(api.ZidUserCSS): {
		constHeader{
			api.KeyTitle:      "Zettelstore User CSS",
			api.KeyRole:       api.ValueRoleConfiguration,

			api.KeyRole:       api.ValueRoleConfiguration,
			api.KeySyntax:     meta.SyntaxGif,
			api.KeyReadOnly:   api.ValueTrue,
			api.KeyCreated:    "20210504175807",
			api.KeyVisibility: api.ValueVisibilityPublic,
		},
		zettel.NewContent(contentEmoji)},










	id.TOCNewTemplateZid: {
		constHeader{
			api.KeyTitle:      "New Menu",
			api.KeyRole:       api.ValueRoleConfiguration,
			api.KeySyntax:     meta.SyntaxZmk,
			api.KeyLang:       api.ValueLangEN,
			api.KeyCreated:    "20210217161829",
			api.KeyModified:   "20231129111800",
			api.KeyVisibility: api.ValueVisibilityCreator,
		},
		zettel.NewContent(contentNewTOCZettel)},
	id.MustParse(api.ZidTemplateNewZettel): {
		constHeader{
			api.KeyTitle:                 "New Zettel",
			api.KeyRole:                  api.ValueRoleConfiguration,
			api.KeySyntax:                meta.SyntaxZmk,
			api.KeyCreated:               "20201028185209",
			api.KeyModified:              "20230929132900",

		},
		zettel.NewContent(contentRoleZettel)},
	id.MustParse(api.ZidRoleConfigurationZettel): {
		constHeader{
			api.KeyTitle:      api.ValueRoleConfiguration,
			api.KeyRole:       api.ValueRoleRole,
			api.KeySyntax:     meta.SyntaxZmk,
			api.KeyCreated:    "20231129162800",
			api.KeyLang:       api.ValueLangEN,
			api.KeyVisibility: api.ValueVisibilityLogin,
		},
		zettel.NewContent(contentRoleConfiguration)},
	id.MustParse(api.ZidRoleRoleZettel): {
		constHeader{
			api.KeyTitle:      api.ValueRoleRole,

			api.KeyLang:       api.ValueLangEN,
			api.KeyCreated:    "20240703235900",
			api.KeyVisibility: api.ValueVisibilityLogin,
		},
		zettel.NewContent(nil)},
	id.DefaultHomeZid: {
		constHeader{
			api.KeyTitle:   "Home",
			api.KeyRole:    api.ValueRoleZettel,
			api.KeySyntax:  meta.SyntaxZmk,
			api.KeyLang:    api.ValueLangEN,
			api.KeyCreated: "20210210190757",

		},
		zettel.NewContent(contentHomeZettel)},
}

//go:embed license.txt
var contentLicense []byte

//go:embed info.sxn
var contentInfoSxn []byte

//go:embed form.sxn
var contentFormSxn []byte

//go:embed rename.sxn
var contentRenameSxn []byte

//go:embed delete.sxn
var contentDeleteSxn []byte

//go:embed listzettel.sxn
var contentListZettelSxn []byte

//go:embed error.sxn

//go:embed base.css
var contentBaseCSS []byte

//go:embed emoji_spin.gif
var contentEmoji []byte




//go:embed newtoc.zettel
var contentNewTOCZettel []byte

//go:embed rolezettel.zettel
var contentRoleZettel []byte

//go:embed roleconfiguration.zettel
var contentRoleConfiguration []byte

=== Thank you for using Zettelstore!

You will find the lastest information about Zettelstore at [[https://zettelstore.de]].
Check that website regulary for [[upgrades|https://zettelstore.de/home/doc/trunk/www/download.wiki]] to the latest version.
You should consult the [[change log|https://zettelstore.de/home/doc/trunk/www/changes.wiki]] before upgrading.
Sometimes, you have to edit some of your Zettelstore-related zettel before upgrading.
Since Zettelstore is currently in a development state, every upgrade might fix some of your problems.

If you have problems concerning Zettelstore,
do not hesitate to get in [[contact with the main developer|mailto:ds@zettelstore.de]].

=== Reporting errors
If you have encountered an error, please include the content of the following zettel in your mail (if possible):
* [[Zettelstore Version|00000000000001]]: {{00000000000001}}
* [[Zettelstore Operating System|00000000000003]]
* [[Zettelstore Startup Configuration|00000000000096]]
* [[Zettelstore Runtime Configuration|00000000000100]]

Additionally, you have to describe, what you have done before that error occurs
and what you have expected instead.
Please do not forget to include the error message, if there is one.

Some of above Zettelstore zettel can only be retrieved if you enabled ""expert mode"".
Otherwise, only some zettel are linked.
To enable expert mode, edit the zettel [[Zettelstore Runtime Configuration|00000000000100]]:
please set the metadata value of the key ''expert-mode'' to true.
To do you, enter the string ''expert-mode:true'' inside the edit view of the metadata.

=== Information about this zettel
This zettel is your home zettel.
It is part of the Zettelstore software itself.
Every time you click on the [[Home|//]] link in the menu bar, you will be redirected to this zettel.

You can change the content of this zettel by clicking on ""Edit"" above.

    (p
      (a (@ (href ,web-url)) "Web")
      (@H " · ") (a (@ (href ,context-url)) "Context")
      (@H " / ") (a (@ (href ,context-full-url)) "Full")
      ,@(if (bound? 'edit-url) `((@H " · ") (a (@ (href ,edit-url)) "Edit")))
      ,@(ROLE-DEFAULT-actions (current-binding))
      ,@(if (bound? 'reindex-url) `((@H " · ") (a (@ (href ,reindex-url)) "Reindex")))
      ,@(if (bound? 'rename-url) `((@H " · ") (a (@ (href ,rename-url)) "Rename")))
      ,@(if (bound? 'delete-url) `((@H " · ") (a (@ (href ,delete-url)) "Delete")))
    )
  )
  (h2 "Interpreted Metadata")
  (table ,@(map wui-info-meta-table-row metadata))
  (h2 "References")
  ,@(if local-links `((h3 "Local")    (ul ,@(map wui-local-link local-links)))) 

This zettel lists all zettel that should act as a template for new zettel.
These zettel will be included in the ""New"" menu of the WebUI.
* [[New Zettel|00000000090001]]
* [[New Role|00000000090004]]
* [[New Tag|00000000090003]]
* [[New User|00000000090002]]

;;;----------------------------------------------------------------------------
;;; Copyright (c) 2023-present Detlef Stern
;;;
;;; This file is part of Zettelstore.
;;;
;;; Zettelstore is licensed under the latest version of the EUPL (European
;;; Union Public License). Please see file LICENSE.txt for your rights and
;;; obligations under this license.
;;;
;;; SPDX-License-Identifier: EUPL-1.2
;;; SPDX-FileCopyrightText: 2023-present Detlef Stern
;;;----------------------------------------------------------------------------

`(article
  (header (h1 "Rename Zettel " ,zid))
  (p "Do you really want to rename this zettel?")
  ,@(if incoming
    `((div (@ (class "zs-warning"))
      (h2 "Warning!")
      (p "If you rename this zettel, incoming references from the following zettel will become invalid.")
      (ul ,@(map wui-item-link incoming))
    ))
  )
  ,@(if (and (bound? 'useless) useless)
    `((div (@ (class "zs-warning"))
      (h2 "Warning!")
      (p "Renaming this zettel will also delete the following files, so that they will not be interpreted as content for this zettel.")
      (ul ,@(map wui-item useless))
    ))
  )
  (form (@ (method "POST"))
    (input (@ (type "hidden") (id "curzid") (name "curzid") (value ,zid)))
    (div
      (label (@ (for "newzid")) "New zettel id")
      (input (@ (class "zs-input") (type "text") (inputmode "numeric") (id "newzid") (name "newzid")
                (pattern "\\d{14}")
                (title "New zettel identifier, must be unique")
                (placeholder "ZID..") (value ,zid) (autofocus))))
    (div (input (@ (class "zs-primary") (type "submit") (value "Rename"))))
  )
  ,(wui-meta-desc metapairs)
)

Zettel with role ""configuration"" are used within Zettelstore to manage and to show the current configuration of the software.

Typically, there are some public zettel that show the license of this software, its dependencies, some CSS code to make the default web user interface a litte bit nicer, and the defult image to singal a broken image.



Other zettel are only visible if an user has authenticated itself, or if there is no authentication enabled.
In this case, one additional configuration zettel is the zettel containing the version number of this software.
Other zettel are showing the supported metadata keys and supported syntax values.
Zettel that allow to configure the menu of template to create new zettel are also using the role ""configuration"".

Most important is the zettel that contains the runtime configuration.
You may change its metadata value to change the behaviour of the software.

One configuration is the ""expert mode"".
If enabled, and if you are authorized so see them, you will discover some more zettel.
For example, HTML templates to customize the default web user interface, to show the application log, to see statistics about zettel boxes, to show the host name and it operating system, and many more.

You are allowed to add your own configuration zettel, for example if you want to customize the look and feel of zettel by placing relevant data into your own zettel.

By default, user zettel (for authentification) use also the role ""configuration"".
However, you are allowed to change this.

;; wui-tdata-link taks a pair (text . url) and returns a HTML link inside
;; a table data item.
(defun wui-tdata-link (q) `(td ,(wui-link q)))

;; wui-item-popup-link is like 'wui-item-link, but the HTML link will open
;; a new tab / window.
(defun wui-item-popup-link (e)
    `(li (a (@ (href ,e) (target "_blank") (rel "noopener noreferrer")) ,e)))

;; wui-option-value returns a value for an HTML option element.
(defun wui-option-value (v) `(option (@ (value ,v))))

;; wui-datalist returns a HTML datalist with the given HTML identifier and a
;; list of values.
(defun wui-datalist (id lst)

;; ROLE-DEFAULT-actions returns the default text for actions.
(defun ROLE-DEFAULT-actions (binding)
    `(,@(let ((copy-url (binding-lookup 'copy-url binding)))
             (if (defined? copy-url) `((@H " · ") (a (@ (href ,copy-url)) "Copy"))))
      ,@(let ((version-url (binding-lookup 'version-url binding)))
             (if (defined? version-url) `((@H " · ") (a (@ (href ,version-url)) "Version"))))
      ,@(let ((child-url (binding-lookup 'child-url binding)))
             (if (defined? child-url) `((@H " · ") (a (@ (href ,child-url)) "Child"))))
      ,@(let ((folge-url (binding-lookup 'folge-url binding)))
             (if (defined? folge-url) `((@H " · ") (a (@ (href ,folge-url)) "Folge"))))
    )
)

;; ROLE-tag-actions returns an additional action "Zettel" for zettel with role "tag".
(defun ROLE-tag-actions (binding)

      (a (@ (href ,info-url)) "Info") (@H " · ")
      "(" ,@(if (bound? 'role-url) `((a (@ (href ,role-url)) ,meta-role)))
          ,@(if (and (bound? 'folge-role-url) (bound? 'meta-folge-role))
                `((@H " → ") (a (@ (href ,folge-role-url)) ,meta-folge-role)))
      ")"
      ,@(if tag-refs `((@H " · ") ,@tag-refs))
      ,@(ROLE-DEFAULT-actions (current-binding))

      ,@(if predecessor-refs `((br) "Predecessor: " ,predecessor-refs))
      ,@(if precursor-refs `((br) "Precursor: " ,precursor-refs))
      ,@(if superior-refs `((br) "Superior: " ,superior-refs))
      ,@(ROLE-DEFAULT-heading (current-binding))
    )
  )
  ,@content
  ,endnotes
  ,@(if (or folge-links subordinate-links back-links successor-links)
    `((nav
      ,@(if folge-links `((details (@ (,folge-open)) (summary "Folgezettel") (ul ,@(map wui-item-link folge-links)))))
      ,@(if subordinate-links `((details (@ (,subordinate-open)) (summary "Subordinates") (ul ,@(map wui-item-link subordinate-links)))))
      ,@(if back-links `((details (@ (,back-open)) (summary "Incoming") (ul ,@(map wui-item-link back-links)))))

      ,@(if successor-links `((details (@ (,successor-open)) (summary "Successors") (ul ,@(map wui-item-link successor-links)))))

     ))
  )
)

func (dp *dirBox) stopFileServices() {
	for _, c := range dp.fCmds {
		close(c)
	}
}

func (dp *dirBox) notifyChanged(zid id.Zid) {
	if chci := dp.cdata.Notify; chci != nil {
		dp.log.Trace().Zid(zid).Msg("notifyChanged")
		chci <- box.UpdateInfo{Reason: box.OnZettel, Zid: zid}
	}
}

func (dp *dirBox) getFileChan(zid id.Zid) chan fileCmd {
	// Based on https://en.wikipedia.org/wiki/Fowler%E2%80%93Noll%E2%80%93Vo_hash_function
	sum := 2166136261 ^ uint32(zid)
	sum *= 16777619

	entry := notify.DirEntry{Zid: newZid}
	dp.updateEntryFromMetaContent(&entry, meta, zettel.Content)

	err = dp.srvSetZettel(ctx, &entry, zettel)
	if err == nil {
		err = dp.dirSrv.UpdateDirEntry(&entry)
	}
	dp.notifyChanged(meta.Zid)
	dp.log.Trace().Err(err).Zid(meta.Zid).Msg("CreateZettel")
	return meta.Zid, err
}

func (dp *dirBox) GetZettel(ctx context.Context, zid id.Zid) (zettel.Zettel, error) {
	entry := dp.dirSrv.GetDirEntry(zid)
	if !entry.IsValid() {

		// Existing zettel, but new in this box.
		entry = &notify.DirEntry{Zid: zid}
	}
	dp.updateEntryFromMetaContent(entry, meta, zettel.Content)
	dp.dirSrv.UpdateDirEntry(entry)
	err := dp.srvSetZettel(ctx, entry, zettel)
	if err == nil {
		dp.notifyChanged(zid)
	}
	dp.log.Trace().Zid(zid).Err(err).Msg("UpdateZettel")
	return err
}

func (dp *dirBox) updateEntryFromMetaContent(entry *notify.DirEntry, m *meta.Meta, content zettel.Content) {
	entry.SetupFromMetaContent(m, content, dp.cdata.Config.GetZettelFileSyntax)
}

func (dp *dirBox) AllowRenameZettel(context.Context, id.Zid) bool {
	return !dp.readonly
}

func (dp *dirBox) RenameZettel(ctx context.Context, curZid, newZid id.Zid) error {
	if curZid == newZid {
		return nil
	}
	curEntry := dp.dirSrv.GetDirEntry(curZid)
	if !curEntry.IsValid() {
		return box.ErrZettelNotFound{Zid: curZid}
	}
	if dp.readonly {
		return box.ErrReadOnly
	}

	// Check whether zettel with new ID already exists in this box.
	if dp.HasZettel(ctx, newZid) {
		return box.ErrInvalidZid{Zid: newZid.String()}
	}

	oldMeta, oldContent, err := dp.srvGetMetaContent(ctx, curEntry, curZid)
	if err != nil {
		return err
	}

	newEntry, err := dp.dirSrv.RenameDirEntry(curEntry, newZid)
	if err != nil {
		return err
	}
	oldMeta.Zid = newZid
	newZettel := zettel.Zettel{Meta: oldMeta, Content: zettel.NewContent(oldContent)}
	if err = dp.srvSetZettel(ctx, &newEntry, newZettel); err != nil {
		// "Rollback" rename. No error checking...
		dp.dirSrv.RenameDirEntry(&newEntry, curZid)
		return err
	}
	err = dp.srvDeleteZettel(ctx, curEntry, curZid)
	if err == nil {
		dp.notifyChanged(curZid)
		dp.notifyChanged(newZid)
	}
	dp.log.Trace().Zid(curZid).Zid(newZid).Err(err).Msg("RenameZettel")
	return err
}

func (dp *dirBox) CanDeleteZettel(_ context.Context, zid id.Zid) bool {
	if dp.readonly {
		return false
	}
	entry := dp.dirSrv.GetDirEntry(zid)
	return entry.IsValid()

	}
	err := dp.dirSrv.DeleteDirEntry(zid)
	if err != nil {
		return nil
	}
	err = dp.srvDeleteZettel(ctx, entry, zid)
	if err == nil {
		dp.notifyChanged(zid)
	}
	dp.log.Trace().Zid(zid).Err(err).Msg("DeleteZettel")
	return err
}

func (dp *dirBox) ReadStats(st *box.ManagedBoxStats) {
	st.ReadOnly = dp.readonly
	st.Zettel = dp.dirSrv.NumDirEntries()
	dp.log.Trace().Int("zettel", int64(st.Zettel)).Msg("ReadStats")
}

)

type zipBox struct {
	log      *logger.Logger
	number   int
	name     string
	enricher box.Enricher
	notify   chan<- box.UpdateInfo
	dirSrv   *notify.DirService
}

func (zb *zipBox) Location() string {
	if strings.HasPrefix(zb.name, "/") {
		return "file://" + zb.name
	}

			continue
		}
		zb.enricher.Enrich(ctx, m, zb.number)
		handle(m)
	}
	return nil
}

func (zb *zipBox) AllowRenameZettel(_ context.Context, zid id.Zid) bool {
	entry := zb.dirSrv.GetDirEntry(zid)
	return !entry.IsValid()
}

func (zb *zipBox) RenameZettel(_ context.Context, curZid, newZid id.Zid) error {
	err := box.ErrReadOnly
	if curZid == newZid {
		err = nil
	}
	curEntry := zb.dirSrv.GetDirEntry(curZid)
	if !curEntry.IsValid() {
		err = box.ErrZettelNotFound{Zid: curZid}
	}
	zb.log.Trace().Err(err).Msg("RenameZettel")
	return err
}

func (*zipBox) CanDeleteZettel(context.Context, id.Zid) bool { return false }

func (zb *zipBox) DeleteZettel(_ context.Context, zid id.Zid) error {
	err := box.ErrReadOnly
	entry := zb.dirSrv.GetDirEntry(zid)
	if !entry.IsValid() {

// GetQueryBool is a helper function to extract bool values from a box URI.
func GetQueryBool(u *url.URL, key string) bool {
	_, ok := u.Query()[key]
	return ok
}

// GetQueryInt is a helper function to extract int values of a specified range from a box URI.
func GetQueryInt(u *url.URL, key string, min, def, max int) int {
	sVal := u.Query().Get(key)
	if sVal == "" {
		return def
	}
	iVal, err := strconv.Atoi(sVal)
	if err != nil {
		return def
	}
	if iVal < min {
		return min
	}
	if iVal > max {
		return max
	}
	return iVal
}

	if box, isWriteBox := mgr.boxes[0].(box.WriteBox); isWriteBox {
		return box.CanCreateZettel(ctx)
	}
	return false
}

// CreateZettel creates a new zettel.
func (mgr *Manager) CreateZettel(ctx context.Context, zettel zettel.Zettel) (id.Zid, error) {
	mgr.mgrLog.Debug().Msg("CreateZettel")
	if err := mgr.checkContinue(ctx); err != nil {
		return id.Invalid, err
	}
	mgr.mgrMx.RLock()
	defer mgr.mgrMx.RUnlock()
	if box, isWriteBox := mgr.boxes[0].(box.WriteBox); isWriteBox {
		zettel.Meta = mgr.cleanMetaProperties(zettel.Meta)
		zid, err := box.CreateZettel(ctx, zettel)
		if err == nil {
			mgr.idxUpdateZettel(ctx, zettel)
		}
		return zid, err
	}
	return id.Invalid, box.ErrReadOnly
}

// GetZettel retrieves a specific zettel.
func (mgr *Manager) GetZettel(ctx context.Context, zid id.Zid) (zettel.Zettel, error) {
	mgr.mgrLog.Debug().Zid(zid).Msg("GetZettel")
	if err := mgr.checkContinue(ctx); err != nil {
		return zettel.Zettel{}, err
	}
	mgr.mgrMx.RLock()
	defer mgr.mgrMx.RUnlock()



	for i, p := range mgr.boxes {
		var errZNF box.ErrZettelNotFound
		if z, err := p.GetZettel(ctx, zid); !errors.As(err, &errZNF) {
			if err == nil {
				mgr.Enrich(ctx, z.Meta, i+1)
			}
			return z, err

		if err != nil {
			return nil, err
		}
	}
	return result, nil
}

func (mgr *Manager) HasZettel(ctx context.Context, zid id.Zid) bool {
	mgr.mgrLog.Debug().Zid(zid).Msg("HasZettel")
	if err := mgr.checkContinue(ctx); err != nil {
		return false
	}
	mgr.mgrMx.RLock()
	defer mgr.mgrMx.RUnlock()
	for _, bx := range mgr.boxes {
		if bx.HasZettel(ctx, zid) {
			return true
		}
	}
	return false
}


func (mgr *Manager) GetMeta(ctx context.Context, zid id.Zid) (*meta.Meta, error) {
	mgr.mgrLog.Debug().Zid(zid).Msg("GetMeta")
	if err := mgr.checkContinue(ctx); err != nil {
		return nil, err
	}

	m, err := mgr.idxStore.GetMeta(ctx, zid)
	if err != nil {

		return nil, err
	}
	mgr.Enrich(ctx, m, 0)
	return m, nil
}

// SelectMeta returns all zettel meta data that match the selection

// UpdateZettel updates an existing zettel.
func (mgr *Manager) UpdateZettel(ctx context.Context, zettel zettel.Zettel) error {
	mgr.mgrLog.Debug().Zid(zettel.Meta.Zid).Msg("UpdateZettel")
	if err := mgr.checkContinue(ctx); err != nil {
		return err
	}



	if box, isWriteBox := mgr.boxes[0].(box.WriteBox); isWriteBox {
		zettel.Meta = mgr.cleanMetaProperties(zettel.Meta)
		if err := box.UpdateZettel(ctx, zettel); err != nil {
			return err
		}
		mgr.idxUpdateZettel(ctx, zettel)
		return nil
	}
	return box.ErrReadOnly
}

// AllowRenameZettel returns true, if box will not disallow renaming the zettel.
func (mgr *Manager) AllowRenameZettel(ctx context.Context, zid id.Zid) bool {
	if err := mgr.checkContinue(ctx); err != nil {
		return false
	}
	mgr.mgrMx.RLock()
	defer mgr.mgrMx.RUnlock()
	for _, p := range mgr.boxes {
		if !p.AllowRenameZettel(ctx, zid) {
			return false
		}
	}
	return true
}

// RenameZettel changes the current zid to a new zid.
func (mgr *Manager) RenameZettel(ctx context.Context, curZid, newZid id.Zid) error {
	mgr.mgrLog.Debug().Zid(curZid).Zid(newZid).Msg("RenameZettel")
	if err := mgr.checkContinue(ctx); err != nil {
		return err
	}
	mgr.mgrMx.RLock()
	defer mgr.mgrMx.RUnlock()
	for i, p := range mgr.boxes {
		err := p.RenameZettel(ctx, curZid, newZid)
		var errZNF box.ErrZettelNotFound
		if err != nil && !errors.As(err, &errZNF) {
			for j := range i {
				mgr.boxes[j].RenameZettel(ctx, newZid, curZid)
			}
			return err
		}
	}
	mgr.idxRenameZettel(ctx, curZid, newZid)
	return nil
}

// CanDeleteZettel returns true, if box could possibly delete the given zettel.
func (mgr *Manager) CanDeleteZettel(ctx context.Context, zid id.Zid) bool {
	if err := mgr.checkContinue(ctx); err != nil {
		return false
	}
	mgr.mgrMx.RLock()

	}
	mgr.mgrMx.RLock()
	defer mgr.mgrMx.RUnlock()
	for _, p := range mgr.boxes {
		err := p.DeleteZettel(ctx, zid)
		if err == nil {
			mgr.idxDeleteZettel(ctx, zid)
			return nil
		}
		var errZNF box.ErrZettelNotFound
		if !errors.As(err, &errZNF) && !errors.Is(err, box.ErrReadOnly) {
			return err
		}
	}
	return box.ErrZettelNotFound{Zid: zid}

	"zettelstore.de/z/box"
	"zettelstore.de/z/zettel/id"
	"zettelstore.de/z/zettel/meta"
)

// Enrich computes additional properties and updates the given metadata.
func (mgr *Manager) Enrich(ctx context.Context, m *meta.Meta, boxNumber int) {

	// Calculate computed, but stored values.
	_, hasCreated := m.Get(api.KeyCreated)
	if !hasCreated {
		m.Set(api.KeyCreated, computeCreated(m.Zid))
	}

	if box.DoEnrich(ctx) {

	}
	return true
}

func (mgr *Manager) idxUpdateZettel(ctx context.Context, zettel zettel.Zettel) {
	var cData collectData
	cData.initialize()

	collectZettelIndexData(parser.ParseZettel(ctx, zettel, "", mgr.rtConfig), &cData)


	m := zettel.Meta
	zi := store.NewZettelIndex(m)
	mgr.idxCollectFromMeta(ctx, m, zi, &cData)
	mgr.idxProcessData(ctx, zi, &cData)
	toCheck := mgr.idxStore.UpdateReferences(ctx, zi)
	mgr.idxCheckZettel(toCheck)
}





func (mgr *Manager) idxCollectFromMeta(ctx context.Context, m *meta.Meta, zi *store.ZettelIndex, cData *collectData) {
	for _, pair := range m.ComputedPairs() {
		descr := meta.GetDescription(pair.Key)
		if descr.IsProperty() {
			continue
		}
		switch descr.Type {

	} else {
		stWords.Add(value)
	}
}

func (mgr *Manager) idxProcessData(ctx context.Context, zi *store.ZettelIndex, cData *collectData) {
	cData.refs.ForEach(func(ref id.Zid) {
		if mgr.HasZettel(ctx, ref) {
			zi.AddBackRef(ref)
		} else {
			zi.AddDeadRef(ref)
		}
	})
	zi.SetWords(cData.words)
	zi.SetUrls(cData.urls)
}

func (mgr *Manager) idxUpdateValue(ctx context.Context, inverseKey, value string, zi *store.ZettelIndex) {
	zid, err := id.Parse(value)
	if err != nil {
		return
	}
	if !mgr.HasZettel(ctx, zid) {
		zi.AddDeadRef(zid)
		return
	}
	if inverseKey == "" {
		zi.AddBackRef(zid)
		return
	}
	zi.AddInverseRef(inverseKey, zid)
}

func (mgr *Manager) idxRenameZettel(ctx context.Context, curZid, newZid id.Zid) {
	toCheck := mgr.idxStore.RenameZettel(ctx, curZid, newZid)
	mgr.idxCheckZettel(toCheck)
}

func (mgr *Manager) idxDeleteZettel(ctx context.Context, zid id.Zid) {
	toCheck := mgr.idxStore.DeleteZettel(ctx, zid)
	mgr.idxCheckZettel(toCheck)
}

func (mgr *Manager) idxCheckZettel(s *id.Set) {
	s.ForEach(func(zid id.Zid) {
		mgr.idxAr.EnqueueZettel(zid)
	})
}

)

// ConnectData contains all administration related values.
type ConnectData struct {
	Number   int // number of the box, starting with 1.
	Config   config.Config
	Enricher box.Enricher
	Notify   chan<- box.UpdateInfo
	Mapper   Mapper
}

// Mapper allows to inspect the mapping between old-style and new-style zettel identifier.
type Mapper interface {
	Warnings(context.Context) (*id.Set, error) // Fetch problematic zettel identifier

	OldToNewMapping(ctx context.Context) (map[id.Zid]id.ZidN, error)
}

// Connect returns a handle to the specified box.
func Connect(u *url.URL, authManager auth.BaseManager, cdata *ConnectData) (box.ManagedBox, error) {
	if authManager.IsReadonly() {
		rawURL := u.String()
		// TODO: the following is wrong under some circumstances:

	rtConfig     config.Config
	boxes        []box.ManagedBox
	observers    []box.UpdateFunc
	mxObserver   sync.RWMutex
	done         chan struct{}
	infos        chan box.UpdateInfo
	propertyKeys strfun.Set // Set of property key names
	zidMapper    *zidMapper

	// Indexer data
	idxLog   *logger.Logger
	idxStore store.Store
	idxAr    *anteroomQueue
	idxReady chan struct{} // Signal a non-empty anteroom to background task

	// Indexer stats data
	idxMx          sync.RWMutex
	idxLastReload  time.Time
	idxDurReload   time.Duration
	idxSinceReload uint64
}

func (mgr *Manager) setState(newState box.StartState) {
	mgr.stateMx.Lock()
	mgr.state = newState
	mgr.stateMx.Unlock()
}


func (mgr *Manager) State() box.StartState {
	mgr.stateMx.RLock()
	state := mgr.state
	mgr.stateMx.RUnlock()
	return state
}

		propertyKeys: propertyKeys,

		idxLog:   boxLog.Clone().Str("box", "index").Child(),
		idxStore: createIdxStore(rtConfig),
		idxAr:    newAnteroomQueue(1000),
		idxReady: make(chan struct{}, 1),
	}
	mgr.zidMapper = NewZidMapper(mgr)

	cdata := ConnectData{Number: 1, Config: rtConfig, Enricher: mgr, Notify: mgr.infos, Mapper: mgr.zidMapper}
	boxes := make([]box.ManagedBox, 0, len(boxURIs)+2)
	for _, uri := range boxURIs {
		p, err := Connect(uri, authManager, &cdata)
		if err != nil {
			return nil, err
		}
		if p != nil {

				reason, zid := ci.Reason, ci.Zid
				mgr.mgrLog.Debug().Uint("reason", uint64(reason)).Zid(zid).Msg("notifier")
				if ignoreUpdate(cache, now, reason, zid) {
					mgr.mgrLog.Trace().Uint("reason", uint64(reason)).Zid(zid).Msg("notifier ignored")
					continue
				}


				mgr.idxEnqueue(reason, zid)
				if ci.Box == nil {
					ci.Box = mgr
				}
				if mgr.State() == box.StartStateStarted {
					mgr.notifyObserver(&ci)
				}
			}
		case <-mgr.done:
			return
		}
	}

func (mgr *Manager) idxEnqueue(reason box.UpdateReason, zid id.Zid) {
	switch reason {
	case box.OnReady:
		return
	case box.OnReload:
		mgr.idxAr.Reset()
	case box.OnZettel:


		mgr.idxAr.EnqueueZettel(zid)
	default:
		mgr.mgrLog.Error().Uint("reason", uint64(reason)).Zid(zid).Msg("Unknown notification reason")
		return
	}
	select {
	case mgr.idxReady <- struct{}{}:

	}
	mgr.idxAr.Reset() // Ensure an initial index run
	mgr.done = make(chan struct{})
	go mgr.notifier()

	mgr.waitBoxesAreStarted()
	mgr.setState(box.StartStateStarted)

	mgr.notifyObserver(&box.UpdateInfo{Box: mgr, Reason: box.OnReady})

	go mgr.idxIndexer()
	return nil
}

func (mgr *Manager) waitBoxesAreStarted() {

// ReIndex data of the given zettel.
func (mgr *Manager) ReIndex(ctx context.Context, zid id.Zid) error {
	mgr.mgrLog.Debug().Msg("ReIndex")
	if err := mgr.checkContinue(ctx); err != nil {
		return err
	}
	mgr.infos <- box.UpdateInfo{Reason: box.OnZettel, Zid: zid}
	return nil
}

// ReadStats populates st with box statistics.
func (mgr *Manager) ReadStats(st *box.Stats) {
	mgr.mgrLog.Debug().Msg("ReadStats")
	mgr.mgrMx.RLock()

func (mgr *Manager) checkContinue(ctx context.Context) error {
	if mgr.State() != box.StartStateStarted {
		return box.ErrStopped
	}
	return ctx.Err()
}

	if zi, ok := ms.idx[zid]; ok {
		return zi
	}
	zi := &zettelData{}
	ms.idx[zid] = zi
	return zi
}

func (ms *mapStore) RenameZettel(_ context.Context, curZid, newZid id.Zid) *id.Set {
	ms.mx.Lock()
	defer ms.mx.Unlock()

	curZi, curFound := ms.idx[curZid]
	_, newFound := ms.idx[newZid]
	if !curFound || newFound {
		return nil
	}
	newZi := &zettelData{
		meta:      copyMeta(curZi.meta, newZid),
		dead:      ms.copyDeadReferences(curZi.dead),
		forward:   ms.copyForward(curZi.forward, newZid),
		backward:  nil, // will be done through tocheck
		otherRefs: nil, // TODO: check if this will be done through toCheck
		words:     copyStrings(ms.words, curZi.words, newZid),
		urls:      copyStrings(ms.urls, curZi.urls, newZid),
	}

	ms.idx[newZid] = newZi
	toCheck := ms.doDeleteZettel(curZid)
	toCheck = toCheck.IUnion(ms.dead[newZid])
	delete(ms.dead, newZid)
	toCheck = toCheck.Add(newZid) // should update otherRefs
	return toCheck
}
func copyMeta(m *meta.Meta, newZid id.Zid) *meta.Meta {
	result := m.Clone()
	result.Zid = newZid
	return result
}

func (ms *mapStore) copyDeadReferences(curDead *id.Set) *id.Set {
	// Must only be called if ms.mx is write-locked!
	curDead.ForEach(func(ref id.Zid) {
		ms.dead[ref] = ms.dead[ref].Add(ref)
	})
	return curDead.Clone()
}
func (ms *mapStore) copyForward(curForward *id.Set, newZid id.Zid) *id.Set {
	// Must only be called if ms.mx is write-locked!
	curForward.ForEach(func(ref id.Zid) {
		if fzi, found := ms.idx[ref]; found {
			fzi.backward = fzi.backward.Add(newZid)
		}

	})
	return curForward.Clone()
}
func copyStrings(msStringMap stringRefs, curStrings []string, newZid id.Zid) []string {
	// Must only be called if ms.mx is write-locked!
	if l := len(curStrings); l > 0 {
		result := make([]string, l)
		for i, s := range curStrings {
			result[i] = s
			msStringMap[s] = msStringMap[s].Add(newZid)
		}
		return result
	}
	return nil
}

func (ms *mapStore) DeleteZettel(_ context.Context, zid id.Zid) *id.Set {
	ms.mx.Lock()
	defer ms.mx.Unlock()
	return ms.doDeleteZettel(zid)
}

	// Entrich metadata with data from store.
	Enrich(ctx context.Context, m *meta.Meta)

	// UpdateReferences for a specific zettel.
	// Returns set of zettel identifier that must also be checked for changes.
	UpdateReferences(context.Context, *ZettelIndex) *id.Set

	// RenameZettel changes all references of current zettel identifier to new
	// zettel identifier.
	RenameZettel(_ context.Context, curZid, newZid id.Zid) *id.Set

	// DeleteZettel removes index data for given zettel.
	// Returns set of zettel identifier that must also be checked for changes.
	DeleteZettel(context.Context, id.Zid) *id.Set

	// Optimize removes unneeded space.
	Optimize()

//-----------------------------------------------------------------------------
// Copyright (c) 2021-present Detlef Stern
//
// This file is part of Zettelstore.
//
// Zettelstore is licensed under the latest version of the EUPL (European Union
// Public License). Please see file LICENSE.txt for your rights and obligations
// under this license.
//
// SPDX-License-Identifier: EUPL-1.2
// SPDX-FileCopyrightText: 2021-present Detlef Stern
//-----------------------------------------------------------------------------

package manager

import (
	"context"
	"maps"
	"sync"
	"time"

	"zettelstore.de/z/zettel/id"
)

// zidMapper transforms old-style zettel identifier (14 digits) into new one (4 alphanums).
//
// Since there are no new-style identifier defined, there is only support for old-style
// identifier by checking, whether they are suported as new-style or not.
//
// This will change in later versions.
type zidMapper struct {
	fetcher   zidfetcher
	defined   map[id.Zid]id.ZidN // predefined mapping, constant after creation
	mx        sync.RWMutex       // protect toNew ... nextZidN
	toNew     map[id.Zid]id.ZidN // working mapping old->new
	toOld     map[id.ZidN]id.Zid // working mapping new->old
	nextZidM  id.ZidN            // next zid for manual
	hadManual bool
	nextZidN  id.ZidN // next zid for normal zettel
}

type zidfetcher interface {
	fetchZids(context.Context) (*id.Set, error)
}

// NewZidMapper creates a new ZipMapper.
func NewZidMapper(fetcher zidfetcher) *zidMapper {
	defined := map[id.Zid]id.ZidN{
		id.Invalid: id.InvalidN,
		1:          id.MustParseN("0001"), // ZidVersion
		2:          id.MustParseN("0002"), // ZidHost
		3:          id.MustParseN("0003"), // ZidOperatingSystem
		4:          id.MustParseN("0004"), // ZidLicense
		5:          id.MustParseN("0005"), // ZidAuthors
		6:          id.MustParseN("0006"), // ZidDependencies
		7:          id.MustParseN("0007"), // ZidLog
		8:          id.MustParseN("0008"), // ZidMemory
		9:          id.MustParseN("0009"), // ZidSx
		10:         id.MustParseN("000a"), // ZidHTTP
		11:         id.MustParseN("000b"), // ZidAPI
		12:         id.MustParseN("000c"), // ZidWebUI
		13:         id.MustParseN("000d"), // ZidConsole
		20:         id.MustParseN("000e"), // ZidBoxManager
		21:         id.MustParseN("000f"), // ZidZettel
		22:         id.MustParseN("000g"), // ZidIndex
		23:         id.MustParseN("000h"), // ZidQuery
		90:         id.MustParseN("000i"), // ZidMetadataKey
		92:         id.MustParseN("000j"), // ZidParser
		96:         id.MustParseN("000k"), // ZidStartupConfiguration
		100:        id.MustParseN("000l"), // ZidRuntimeConfiguration
		101:        id.MustParseN("000m"), // ZidDirectory
		102:        id.MustParseN("000n"), // ZidWarnings
		10100:      id.MustParseN("000s"), // Base HTML Template
		10200:      id.MustParseN("000t"), // Login Form Template
		10300:      id.MustParseN("000u"), // List Zettel Template
		10401:      id.MustParseN("000v"), // Detail Template
		10402:      id.MustParseN("000w"), // Info Template
		10403:      id.MustParseN("000x"), // Form Template
		10404:      id.MustParseN("001z"), // Rename Form Template (will be removed in the future)
		10405:      id.MustParseN("000y"), // Delete Template
		10700:      id.MustParseN("000z"), // Error Template
		19000:      id.MustParseN("000q"), // Sxn Start Code
		19990:      id.MustParseN("000r"), // Sxn Base Code
		20001:      id.MustParseN("0010"), // Base CSS
		25001:      id.MustParseN("0011"), // User CSS
		40001:      id.MustParseN("000o"), // Generic Emoji
		59900:      id.MustParseN("000p"), // Sxn Prelude
		60010:      id.MustParseN("0012"), // zettel
		60020:      id.MustParseN("0013"), // confguration
		60030:      id.MustParseN("0014"), // role
		60040:      id.MustParseN("0015"), // tag
		90000:      id.MustParseN("0016"), // New Menu
		90001:      id.MustParseN("0017"), // New Zettel
		90002:      id.MustParseN("0018"), // New User
		90003:      id.MustParseN("0019"), // New Tag
		90004:      id.MustParseN("001a"), // New Role
		// 100000000,   // Manual               -> 0020-00yz
		9999999997:  id.MustParseN("00zx"), // ZidSession
		9999999998:  id.MustParseN("00zy"), // ZidAppDirectory
		9999999999:  id.MustParseN("00zz"), // ZidMapping
		10000000000: id.MustParseN("0100"), // ZidDefaultHome
	}
	toNew := maps.Clone(defined)
	toOld := make(map[id.ZidN]id.Zid, len(toNew))
	for o, n := range toNew {
		if _, found := toOld[n]; found {
			panic("duplicate predefined zid")
		}
		toOld[n] = o
	}

	return &zidMapper{
		fetcher:   fetcher,
		defined:   defined,
		toNew:     toNew,
		toOld:     toOld,
		nextZidM:  id.MustParseN("0020"),
		hadManual: false,
		nextZidN:  id.MustParseN("0101"),
	}
}

// isWellDefined returns true, if the given zettel identifier is predefined
// (as stated in the manual), or is part of the manual itself, or is greater than
// 19699999999999.
func (zm *zidMapper) isWellDefined(zid id.Zid) bool {
	if _, found := zm.defined[zid]; found || (1000000000 <= zid && zid <= 1099999999) {
		return true
	}
	if _, err := time.Parse("20060102150405", zid.String()); err != nil {
		return false
	}
	return 19700000000000 <= zid
}

// Warnings returns all zettel identifier with warnings.
func (zm *zidMapper) Warnings(ctx context.Context) (*id.Set, error) {
	allZids, err := zm.fetcher.fetchZids(ctx)
	if err != nil {
		return nil, err
	}
	warnings := id.NewSet()
	allZids.ForEach(func(zid id.Zid) {
		if !zm.isWellDefined(zid) {
			warnings = warnings.Add(zid)
		}
	})
	return warnings, nil
}

func (zm *zidMapper) GetZidN(zidO id.Zid) id.ZidN {
	zm.mx.RLock()
	if zidN, found := zm.toNew[zidO]; found {
		zm.mx.RUnlock()
		return zidN
	}
	zm.mx.RUnlock()

	zm.mx.Lock()
	defer zm.mx.Unlock()
	// Double check to avoid races
	if zidN, found := zm.toNew[zidO]; found {
		return zidN
	}

	if 1000000000 <= zidO && zidO <= 1099999999 {
		if zidO == 1000000000 {
			zm.hadManual = true
		}
		if zm.hadManual {
			zidN := zm.nextZidM
			zm.nextZidM++
			zm.toNew[zidO] = zidN
			zm.toOld[zidN] = zidO
			return zidN
		}
	}

	zidN := zm.nextZidN
	zm.nextZidN++
	zm.toNew[zidO] = zidN
	zm.toOld[zidN] = zidO
	return zidN
}

// OldToNewMapping returns the mapping of old format identifier to new format identifier.
func (zm *zidMapper) OldToNewMapping(ctx context.Context) (map[id.Zid]id.ZidN, error) {
	allZids, err := zm.fetcher.fetchZids(ctx)
	if err != nil {
		return nil, err
	}

	result := make(map[id.Zid]id.ZidN, allZids.Length())
	allZids.ForEach(func(zidO id.Zid) {
		zidN := zm.GetZidN(zidO)
		result[zidO] = zidN
	})
	return result, nil
}

	maxZettel int
	maxBytes  int
	mx        sync.RWMutex // Protects the following fields
	zettel    map[id.Zid]zettel.Zettel
	curBytes  int
}

func (mb *memBox) notifyChanged(zid id.Zid) {
	if chci := mb.cdata.Notify; chci != nil {
		chci <- box.UpdateInfo{Box: mb, Reason: box.OnZettel, Zid: zid}
	}
}

func (mb *memBox) Location() string {
	return mb.u.String()
}

	meta := zettel.Meta.Clone()
	meta.Zid = zid
	zettel.Meta = meta
	mb.zettel[zid] = zettel
	mb.curBytes = newBytes
	mb.mx.Unlock()

	mb.notifyChanged(zid)
	mb.log.Trace().Zid(zid).Msg("CreateZettel")
	return zid, nil
}

func (mb *memBox) GetZettel(_ context.Context, zid id.Zid) (zettel.Zettel, error) {
	mb.mx.RLock()
	z, ok := mb.zettel[zid]

		return box.ErrCapacity
	}

	zettel.Meta = m
	mb.zettel[m.Zid] = zettel
	mb.curBytes = newBytes
	mb.mx.Unlock()
	mb.notifyChanged(m.Zid)
	mb.log.Trace().Msg("UpdateZettel")
	return nil
}

func (*memBox) AllowRenameZettel(context.Context, id.Zid) bool { return true }

func (mb *memBox) RenameZettel(_ context.Context, curZid, newZid id.Zid) error {
	mb.mx.Lock()
	zettel, ok := mb.zettel[curZid]
	if !ok {
		mb.mx.Unlock()
		return box.ErrZettelNotFound{Zid: curZid}
	}

	// Check that there is no zettel with newZid
	if _, ok = mb.zettel[newZid]; ok {
		mb.mx.Unlock()
		return box.ErrInvalidZid{Zid: newZid.String()}
	}

	meta := zettel.Meta.Clone()
	meta.Zid = newZid
	zettel.Meta = meta
	mb.zettel[newZid] = zettel
	delete(mb.zettel, curZid)
	mb.mx.Unlock()
	mb.notifyChanged(curZid)
	mb.notifyChanged(newZid)
	mb.log.Trace().Msg("RenameZettel")
	return nil
}

func (mb *memBox) CanDeleteZettel(_ context.Context, zid id.Zid) bool {
	mb.mx.RLock()
	_, ok := mb.zettel[zid]
	mb.mx.RUnlock()
	return ok
}

func (mb *memBox) DeleteZettel(_ context.Context, zid id.Zid) error {
	mb.mx.Lock()
	oldZettel, found := mb.zettel[zid]
	if !found {
		mb.mx.Unlock()
		return box.ErrZettelNotFound{Zid: zid}
	}
	delete(mb.zettel, zid)
	mb.curBytes -= oldZettel.Length()
	mb.mx.Unlock()
	mb.notifyChanged(zid)
	mb.log.Trace().Msg("DeleteZettel")
	return nil
}

func (mb *memBox) ReadStats(st *box.ManagedBoxStats) {
	st.ReadOnly = false
	mb.mx.RLock()
	st.Zettel = len(mb.zettel)
	mb.mx.RUnlock()
	mb.log.Trace().Int("zettel", int64(st.Zettel)).Msg("ReadStats")
}

package notify

import (
	"errors"
	"fmt"
	"path/filepath"
	"regexp"
	"strings"
	"sync"

	"zettelstore.de/z/box"
	"zettelstore.de/z/kernel"
	"zettelstore.de/z/logger"
	"zettelstore.de/z/parser"
	"zettelstore.de/z/query"

// dsCreated --Start--> dsStarting
// dsStarting --last list notification--> dsWorking
// dsWorking --directory missing--> dsMissing
// dsMissing --last list notification--> dsWorking
// --Stop--> dsStopping
type DirServiceState uint8


const (
	DsCreated  DirServiceState = iota
	DsStarting                 // Reading inital scan
	DsWorking                  // Initial scan complete, fully operational
	DsMissing                  // Directory is missing
	DsStopping                 // Service is shut down
)

// DirService specifies a directory service for file based zettel.
type DirService struct {
	box      box.ManagedBox
	log      *logger.Logger
	dirPath  string
	notifier Notifier
	infos    chan<- box.UpdateInfo
	mx       sync.RWMutex // protects status, entries
	state    DirServiceState
	entries  entrySet
}

// ErrNoDirectory signals missing directory data.
var ErrNoDirectory = errors.New("unable to retrieve zettel directory information")

// NewDirService creates a new directory service.
func NewDirService(box box.ManagedBox, log *logger.Logger, notifier Notifier, chci chan<- box.UpdateInfo) *DirService {
	return &DirService{
		box:      box,
		log:      log,
		notifier: notifier,
		infos:    chci,
		state:    DsCreated,
	}
}

// State the current service state.
func (ds *DirService) State() DirServiceState {
	ds.mx.RLock()

	defer ds.mx.Unlock()
	if ds.entries == nil {
		return ds.logMissingEntry("update")
	}
	ds.entries[entry.Zid] = &entry
	return nil
}

// RenameDirEntry replaces an existing directory entry with a new one.
func (ds *DirService) RenameDirEntry(oldEntry *DirEntry, newZid id.Zid) (DirEntry, error) {
	ds.mx.Lock()
	defer ds.mx.Unlock()
	if ds.entries == nil {
		return DirEntry{}, ds.logMissingEntry("rename")
	}
	if _, found := ds.entries[newZid]; found {
		return DirEntry{}, box.ErrInvalidZid{Zid: newZid.String()}
	}
	oldZid := oldEntry.Zid
	newEntry := DirEntry{
		Zid:         newZid,
		MetaName:    renameFilename(oldEntry.MetaName, oldZid, newZid),
		ContentName: renameFilename(oldEntry.ContentName, oldZid, newZid),
		ContentExt:  oldEntry.ContentExt,
		// Duplicates must not be set, because duplicates will be deleted
	}
	delete(ds.entries, oldZid)
	ds.entries[newZid] = &newEntry
	return newEntry, nil
}

func renameFilename(name string, curID, newID id.Zid) string {
	if cur := curID.String(); strings.HasPrefix(name, cur) {
		name = newID.String() + name[len(cur):]
	}
	return name
}

// DeleteDirEntry removes a entry from the directory.
func (ds *DirService) DeleteDirEntry(zid id.Zid) error {
	ds.mx.Lock()
	defer ds.mx.Unlock()
	if ds.entries == nil {
		return ds.logMissingEntry("delete")

		ds.log.Error().Str("path", ds.dirPath).Msg("Zettel directory missing")
		return nil, true
	case Update:
		ds.mx.Lock()
		zid := ds.onUpdateFileEvent(ds.entries, ev.Name)
		ds.mx.Unlock()
		if zid != id.Invalid {
			ds.notifyChange(zid)
		}
	case Delete:
		ds.mx.Lock()
		zid := ds.onDeleteFileEvent(ds.entries, ev.Name)
		ds.mx.Unlock()
		if zid != id.Invalid {
			ds.notifyChange(zid)
		}
	default:
		ds.log.Error().Str("event", fmt.Sprintf("%v", ev)).Msg("Unknown zettel notification event")
	}
	return newEntries, true
}

func getNewZids(entries entrySet) id.Slice {
	zids := make(id.Slice, 0, len(entries))
	for zid := range entries {
		zids = append(zids, zid)
	}
	return zids
}

func (ds *DirService) onCreateDirectory(zids id.Slice, prevEntries entrySet) {
	for _, zid := range zids {
		ds.notifyChange(zid)
		delete(prevEntries, zid)
	}

	// These were previously stored, by are not found now.
	// Notify system that these were deleted, e.g. for updating the index.
	for zid := range prevEntries {
		ds.notifyChange(zid)
	}
}

func (ds *DirService) onDestroyDirectory() {
	ds.mx.Lock()
	entries := ds.entries
	ds.entries = nil
	ds.state = DsMissing
	ds.mx.Unlock()
	for zid := range entries {
		ds.notifyChange(zid)
	}
}

var validFileName = regexp.MustCompile(`^(\d{14})`)

func matchValidFileName(name string) []string {
	return validFileName.FindStringSubmatch(name)

	newLen := len(newExt)
	if oldLen != newLen {
		return newLen < oldLen
	}
	return newExt < oldExt
}

func (ds *DirService) notifyChange(zid id.Zid) {
	if chci := ds.infos; chci != nil {
		ds.log.Trace().Zid(zid).Msg("notifyChange")
		chci <- box.UpdateInfo{Box: ds.box, Reason: box.OnZettel, Zid: zid}
	}
}

	ucQuery.SetEvaluate(&ucEvaluate)
	ucTagZettel := usecase.NewTagZettel(protectedBoxManager, &ucQuery)
	ucRoleZettel := usecase.NewRoleZettel(protectedBoxManager, &ucQuery)
	ucListSyntax := usecase.NewListSyntax(protectedBoxManager)
	ucListRoles := usecase.NewListRoles(protectedBoxManager)
	ucDelete := usecase.NewDeleteZettel(logUc, protectedBoxManager)
	ucUpdate := usecase.NewUpdateZettel(logUc, protectedBoxManager)
	ucRename := usecase.NewRenameZettel(logUc, protectedBoxManager)
	ucRefresh := usecase.NewRefresh(logUc, protectedBoxManager)
	ucReIndex := usecase.NewReIndex(logUc, protectedBoxManager)
	ucVersion := usecase.NewVersion(kernel.Main.GetConfig(kernel.CoreService, kernel.CoreVersion).(string))

	a := api.New(
		webLog.Clone().Str("adapter", "api").Child(),
		webSrv, authManager, authManager, rtConfig, authPolicy)
	wui := webui.New(
		webLog.Clone().Str("adapter", "wui").Child(),
		webSrv, authManager, rtConfig, authManager, boxManager, authPolicy, &ucEvaluate)

	webSrv.Handle("/", wui.MakeGetRootHandler(protectedBoxManager))
	if assetDir := kern.GetConfig(kernel.WebService, kernel.WebAssetDir).(string); assetDir != "" {
		const assetPrefix = "/assets/"
		webSrv.Handle(assetPrefix, http.StripPrefix(assetPrefix, http.FileServer(http.Dir(assetDir))))
		webSrv.Handle("/favicon.ico", wui.MakeFaviconHandler(assetDir))
	}

	// Web user interface
	if !authManager.IsReadonly() {
		webSrv.AddZettelRoute('b', server.MethodGet, wui.MakeGetRenameZettelHandler(ucGetZettel))
		webSrv.AddZettelRoute('b', server.MethodPost, wui.MakePostRenameZettelHandler(&ucRename))
		webSrv.AddListRoute('c', server.MethodGet, wui.MakeGetZettelFromListHandler(&ucQuery, &ucEvaluate, ucListRoles, ucListSyntax))
		webSrv.AddListRoute('c', server.MethodPost, wui.MakePostCreateZettelHandler(&ucCreateZettel))
		webSrv.AddZettelRoute('c', server.MethodGet, wui.MakeGetCreateZettelHandler(
			ucGetZettel, &ucCreateZettel, ucListRoles, ucListSyntax))
		webSrv.AddZettelRoute('c', server.MethodPost, wui.MakePostCreateZettelHandler(&ucCreateZettel))
		webSrv.AddZettelRoute('d', server.MethodGet, wui.MakeGetDeleteZettelHandler(ucGetZettel, ucGetAllZettel))
		webSrv.AddZettelRoute('d', server.MethodPost, wui.MakePostDeleteZettelHandler(&ucDelete))

	webSrv.AddListRoute('x', server.MethodPost, a.MakePostCommandHandler(&ucIsAuth, &ucRefresh))
	webSrv.AddListRoute('z', server.MethodGet, a.MakeQueryHandler(&ucQuery, &ucTagZettel, &ucRoleZettel, &ucReIndex))
	webSrv.AddZettelRoute('z', server.MethodGet, a.MakeGetZettelHandler(ucGetZettel, ucParseZettel, ucEvaluate))
	if !authManager.IsReadonly() {
		webSrv.AddListRoute('z', server.MethodPost, a.MakePostCreateZettelHandler(&ucCreateZettel))
		webSrv.AddZettelRoute('z', server.MethodPut, a.MakeUpdateZettelHandler(&ucUpdate))
		webSrv.AddZettelRoute('z', server.MethodDelete, a.MakeDeleteZettelHandler(&ucDelete))
		webSrv.AddZettelRoute('z', server.MethodMove, a.MakeRenameZettelHandler(&ucRename))
	}

	if authManager.WithAuth() {
		webSrv.SetUserRetriever(usecase.NewGetUserByZid(boxManager))
	}
}

type getUserImpl struct{}

func (*getUserImpl) GetUser(ctx context.Context) *meta.Meta { return server.GetUser(ctx) }

	}
}

const (
	keyAdminPort         = "admin-port"
	keyAssetDir          = "asset-dir"
	keyBaseURL           = "base-url"

	keyDebug             = "debug-mode"
	keyDefaultDirBoxType = "default-dir-box-type"
	keyInsecureCookie    = "insecure-cookie"
	keyInsecureHTML      = "insecure-html"
	keyListenAddr        = "listen-addr"
	keyLogLevel          = "log-level"
	keyMaxRequestSize    = "max-request-size"
	keyOwner             = "owner"
	keyPersistentCookie  = "persistent-cookie"
	keyBoxOneURI         = kernel.BoxURIs + "1"
	keyReadOnly          = "read-only-mode"

	keyTokenLifetimeHTML = "token-lifetime-html"
	keyTokenLifetimeAPI  = "token-lifetime-api"
	keyURLPrefix         = "url-prefix"
	keyVerbose           = "verbose-mode"
)

func setServiceConfig(cfg *meta.Meta) bool {

		val, found := cfg.Get(key)
		if !found {
			break
		}
		err = setConfigValue(err, kernel.BoxService, key, val)
	}


	err = setConfigValue(err, kernel.ConfigService, kernel.ConfigInsecureHTML, cfg.GetDefault(keyInsecureHTML, kernel.ConfigSecureHTML))


	err = setConfigValue(err, kernel.WebService, kernel.WebListenAddress, cfg.GetDefault(keyListenAddr, "127.0.0.1:23123"))
	if val, found := cfg.Get(keyBaseURL); found {
		err = setConfigValue(err, kernel.WebService, kernel.WebBaseURL, val)
	}
	if val, found := cfg.Get(keyURLPrefix); found {
		err = setConfigValue(err, kernel.WebService, kernel.WebURLPrefix, val)
	}
	err = setConfigValue(err, kernel.WebService, kernel.WebSecureCookie, !cfg.GetBool(keyInsecureCookie))
	err = setConfigValue(err, kernel.WebService, kernel.WebPersistentCookie, cfg.GetBool(keyPersistentCookie))
	if val, found := cfg.Get(keyMaxRequestSize); found {
		err = setConfigValue(err, kernel.WebService, kernel.WebMaxRequestSize, val)
	}
	err = setConfigValue(
		err, kernel.WebService, kernel.WebTokenLifetimeAPI, cfg.GetDefault(keyTokenLifetimeAPI, ""))
	err = setConfigValue(
		err, kernel.WebService, kernel.WebTokenLifetimeHTML, cfg.GetDefault(keyTokenLifetimeHTML, ""))

	if val, found := cfg.Get(keyAssetDir); found {
		err = setConfigValue(err, kernel.WebService, kernel.WebAssetDir, val)
	}
	return err == nil
}

func setConfigValue(err error, subsys kernel.Service, key string, val any) error {

import (
	"os"

	"zettelstore.de/z/cmd"
)

// Version variable. Will be filled by build process.
var version string = ""

func main() {
	exitCode := cmd.Main("Zettelstore", version)
	os.Exit(exitCode)
}

//-----------------------------------------------------------------------------

// Package collect provides functions to collect items from a syntax tree.
package collect

import "zettelstore.de/z/ast"

// Order of internal reference within the given zettel.
func Order(zn *ast.ZettelNode) (result []*ast.Reference) {
	for _, bn := range zn.Ast {
		ln, ok := bn.(*ast.NestedListNode)
		if !ok {
			continue
		}
		switch ln.Kind {
		case ast.NestedListOrdered, ast.NestedListUnordered:
			for _, is := range ln.Items {
				if ref := firstItemZettelReference(is); ref != nil {
					result = append(result, ref)
				}
			}
		}
	}
	return result
}

func firstItemZettelReference(is ast.ItemSlice) *ast.Reference {
	for _, in := range is {
		if pn, ok := in.(*ast.ParaNode); ok {
			if ref := firstInlineZettelReference(pn.Inlines); ref != nil {
				return ref
			}
		}
	}
	return nil
}

func firstInlineZettelReference(is ast.InlineSlice) (result *ast.Reference) {
	for _, inl := range is {
		switch in := inl.(type) {
		case *ast.LinkNode:
			if ref := in.Ref; ref.IsZettel() {
				return ref
			}
			result = firstInlineZettelReference(in.Inlines)
		case *ast.EmbedRefNode:
			result = firstInlineZettelReference(in.Inlines)
		case *ast.EmbedBLOBNode:
			result = firstInlineZettelReference(in.Inlines)
		case *ast.CiteNode:
			result = firstInlineZettelReference(in.Inlines)
		case *ast.FootnoteNode:
			// Ignore references in footnotes
			continue
		case *ast.FormatNode:
			result = firstInlineZettelReference(in.Inlines)
		default:
			continue
		}
		if result != nil {
			return result
		}
	}

// Key values that are supported by Config.Get
const (
	KeyFooterZettel         = "footer-zettel"
	KeyHomeZettel           = "home-zettel"
	KeyShowBackLinks        = "show-back-links"
	KeyShowFolgeLinks       = "show-folge-links"

	KeyShowSubordinateLinks = "show-subordinate-links"
	KeyShowSuccessorLinks   = "show-successor-links"
	// api.KeyLang
)

// Config allows to retrieve all defined configuration values that can be changed during runtime.
type Config interface {

id: 20210916193200
title: Required Software
role: zettel
syntax: zmk
created: 20210916193200
modified: 20231213194509

The following software must be installed:

* A current, supported [[release of Go|https://go.dev/doc/devel/release]],
* [[Fossil|https://fossil-scm.org/]],
* [[Git|https://git-scm.org/]] (most dependencies are accessible via Git only).

Make sure that the software is in your path, e.g. via:
```sh
export PATH=$PATH:/usr/local/go/bin
export PATH=$PATH:$(go env GOPATH)/bin
```

The internal build tool need the following software.
It can be installed / updated via the build tool itself: ``go run tools/devtools/devtools.go``.

Otherwise you can install the software by hand:

* [[shadow|https://pkg.go.dev/golang.org/x/tools/go/analysis/passes/shadow]] via ``go install golang.org/x/tools/go/analysis/passes/shadow/cmd/shadow@latest``,
* [[staticcheck|https://staticcheck.io/]] via ``go install honnef.co/go/tools/cmd/staticcheck@latest``,
* [[unparam|https://mvdan.cc/unparam]][^[[GitHub|https://github.com/mvdan/unparam]]] via ``go install mvdan.cc/unparam@latest``,

* [[govulncheck|https://golang.org/x/vuln/cmd/govulncheck]] via ``go install golang.org/x/vuln/cmd/govulncheck@latest``,

id: 20210916194900
title: Checklist for Release
role: zettel
syntax: zmk
created: 20210916194900
modified: 20231213194631

# Sync with the official repository
#* ``fossil sync -u``
# Make sure that there is no workspace defined.
#* ``ls ..`` must not have a file ''go.work'', in no parent folder.
# Make sure that all dependencies are up-to-date.
#* ``cat go.mod``
# Clean up your Go workspace:
#* ``go run tools/clean/clean.go`` (alternatively: ``make clean``).
# All internal tests must succeed:
#* ``go run tools/check/check.go -r`` (alternatively: ``make relcheck``).
# The API tests must succeed on every development platform:
#* ``go run tools/testapi/testapi.go`` (alternatively: ``make api``).
# Run [[linkchecker|https://linkchecker.github.io/linkchecker/]] with the manual:
#* ``go run -race cmd/zettelstore/main.go run -d docs/manual``
#* ``linkchecker http://127.0.0.1:23123 2>&1 | tee lc.txt``
#* Check all ""Error: 404 Not Found""
#* Check all ""Error: 403 Forbidden"": allowed for endpoint ''/p'' with encoding ''html'' for those zettel that are accessible only in ''expert-mode''.
#* Try to resolve other error messages and warnings
#* Warnings about empty content can be ignored
# On every development platform, the box with 10.000 zettel must run, with ''-race'' enabled:
#* ``go run -race cmd/zettelstore/main.go run -d DIR``.
# Create a development release:
#* ``go run tools/build.go release`` (alternatively: ``make release``).
# On every platform (esp. macOS), the box with 10.000 zettel must run properly:
#* ``./zettelstore -d DIR``
# Update files in directory ''www''
#* index.wiki
#* download.wiki
#* changes.wiki
#* plan.wiki
# Set file ''VERSION'' to the new release version.
  It _must_ consist of three digits: MAJOR.MINOR.PATCH, even if PATCH is zero
# Disable Fossil autosync mode:
#* ``fossil setting autosync off``
# Commit the new release version:
#* ``fossil commit --tag release --tag vVERSION -m "Version VERSION"``
#* **Important:** the tag must follow the given pattern, e.g. ''v0.0.15''.
   Otherwise client will not be able to import ''zettelkasten.de/z''.
# Clean up your Go workspace:
#* ``go run tools/clean/clean.go`` (alternatively: ``make clean``).
# Create the release:
#* ``go run tools/build/build.go release`` (alternatively: ``make release``).
# Remove previous executables:
#* ``fossil uv remove --glob '*-PREVVERSION*'``
# Add executables for release:
#* ``cd releases``
#* ``fossil uv add *.zip``
#* ``cd ..``
#* Synchronize with main repository:

This list is used to check the generated HTML code (''ZID'' is the paceholder for the zettel identification):

* Check all zettel HTML encodings, via the path ''/z/ZID?enc=html&part=zettel''
* Check all zettel web views, via the path ''/h/ZID''
* The info page of all zettel is checked, via path ''/i/ZID''
* A subset of max. 100 zettel will be checked for the validity of their edit page, via ''/e/ZID''
* 10 random zettel are checked for a valid create form, via ''/c/ZID''
* The zettel rename form will be checked for 100 zettel, via ''/b/ZID''
* A maximum of 200 random zettel are checked for a valid delete dialog, via ''/d/ZID''

Depending on the selected Zettelstore, the command might take a long time.

You can shorten the time, if you disable any zettel query in the footer.

=== Build

id: 00001000000000
title: Zettelstore Manual
role: manual
tags: #manual #zettelstore
syntax: zmk
created: 20210126175322
modified: 20231125185455
show-back-links: false

* [[Introduction|00001001000000]]
* [[Design goals|00001002000000]]
* [[Installation|00001003000000]]
* [[Configuration|00001004000000]]
* [[Structure of Zettelstore|00001005000000]]
* [[Layout of a zettel|00001006000000]]
* [[Zettelmarkup|00001007000000]]
* [[Other markup languages|00001008000000]]
* [[Security|00001010000000]]
* [[API|00001012000000]]
* [[Web user interface|00001014000000]]
* [[Tips and Tricks|00001017000000]]
* [[Troubleshooting|00001018000000]]
* Frequently asked questions

Version: {{00001000000001}}.

Licensed under the EUPL-1.2-or-later.

id: 00001001000000
title: Introduction to the Zettelstore
role: manual
tags: #introduction #manual #zettelstore
syntax: zmk
created: 20210126175322
modified: 20240710184612

[[Personal knowledge management|https://en.wikipedia.org/wiki/Personal_knowledge_management]] involves collecting, classifying, storing, searching, retrieving, assessing, evaluating, and sharing knowledge as a daily activity.
It's done by most individuals, not necessarily as part of their main business.
It's essential for knowledge workers, such as students, researchers, lecturers, software developers, scientists, engineers, architects, etc.
Many hobbyists build up a significant amount of knowledge, even if they do not need to think for a living.
Personal knowledge management can be seen as a prerequisite for many kinds of collaboration.

Zettelstore is software that collects and relates your notes (""zettel"") to represent and enhance your knowledge, supporting the ""[[Zettelkasten method|https://en.wikipedia.org/wiki/Zettelkasten]]"".
The method is based on creating many individual notes, each with one idea or piece of information, that is related to each other.
Since knowledge is typically built up gradually, one major focus is a long-term store of these notes, hence the name ""Zettelstore"".

id: 00001002000000
title: Design goals for the Zettelstore
role: manual
tags: #design #goal #manual #zettelstore
syntax: zmk
created: 20210126175322
modified: 20230624171152

Zettelstore supports the following design goals:

; Longevity of stored notes / zettel
: Every zettel you create should be readable without the help of any tool, even without Zettelstore.
: It should be not hard to write other software that works with your zettel.
: Normal zettel should be stored in a single file.
  If this is not possible: at most in two files: one for the metadata, one for the content.
  The only exception are [[predefined zettel|00001005090000]] stored in the Zettelstore executable.
: There is no additional database.
; Single user
: All zettel belong to you, only to you.
  Zettelstore provides its services only to one person: you.
  If the computer running Zettelstore is securely configured, there should be no risk that others are able to read or update your zettel.
: If you want, you can customize Zettelstore in a way that some specific or all persons are able to read some of your zettel.
; Ease of installation
: If you want to use the Zettelstore software, all you need is to copy the executable to an appropriate file directory and start working.
: Upgrading the software is done just by replacing the executable with a newer one.
; Ease of operation
: There is only one executable for Zettelstore and one directory, where your zettel are stored.
: If you decide to use multiple directories, you are free to configure Zettelstore appropriately.
; Multiple modes of operation
: You can use Zettelstore as a standalone software on your device, but you are not restricted to it.
: You can install the software on a central server, or you can install it on all your devices with no restrictions how to synchronize your zettel.
; Multiple user interfaces
: Zettelstore provides a default [[web-based user interface|00001014000000]].
  Anybody can provide alternative user interfaces, e.g. for special purposes.
; Simple service
: The purpose of Zettelstore is to safely store your zettel and to provide some initial relations between them.
: External software can be written to deeply analyze your zettel and the structures they form.
; Security by default
: Without any customization, Zettelstore provides its services in a safe and secure manner and does not expose you (or other users) to security risks.
: If you know what use are doing, Zettelstore allows you to relax some security-related preferences.
  However, even in this case, the more secure way is chosen.
: The Zettelstore software uses a minimal design and uses other software dependencies only is essential needed.
: There will be no plugin mechanism, which allows external software to control the inner workings of the Zettelstore software.

id: 00001003000000
title: Installation of the Zettelstore software
role: manual
tags: #installation #manual #zettelstore
syntax: zmk
created: 20210126175322
modified: 20220119145756

=== The curious user
You just want to check out the Zettelstore software

* Grab the appropriate executable and copy it into any directory
* Start the Zettelstore software, e.g. with a double click[^On Windows and macOS, the operating system tries to protect you from possible malicious software. If you encounter problem, please take a look on the [[Troubleshooting|00001018000000]] page.]

* A sub-directory ""zettel"" will be created in the directory where you put the executable.
  It will contain your future zettel.
* Open the URI [[http://localhost:23123]] with your web browser.
  It will present you a mostly empty Zettelstore.
  There will be a zettel titled ""[[Home|00010000000000]]"" that contains some helpful information.
* Please read the instructions for the [[web-based user interface|00001014000000]] and learn about the various ways to write zettel.
* If you restart your device, please make sure to start your Zettelstore again.

=== The intermediate user
You already tried the Zettelstore software and now you want to use it permanently.
Zettelstore should start automatically when you log into your computer.

Please follow [[these instructions|00001003300000]].

=== The server administrator
You want to provide a shared Zettelstore that can be used from your various devices.
Installing Zettelstore as a Linux service is not that hard.

id: 00001003300000
title: Zettelstore installation for the intermediate user
role: manual
tags: #installation #manual #zettelstore
syntax: zmk
created: 20211125191727
modified: 20220114175754

You already tried the Zettelstore software and now you want to use it permanently.
Zettelstore should start automatically when you log into your computer.

* Grab the appropriate executable and copy it into the appropriate directory
* If you want to place your zettel into another directory, or if you want more than one [[Zettelstore box|00001004011200]], or if you want to [[enable authentication|00001010040100]], or if you want to tweak your Zettelstore in some other way, create an appropriate [[startup configuration file|00001004010000]].
* If you created a startup configuration file, you need to test it:
** Start a command line prompt for your operating system.
** Navigate to the directory, where you placed the Zettelstore executable.
   In most cases, this is done by the command ``cd DIR``, where ''DIR'' denotes the directory, where you placed the executable.
** Start the Zettelstore:
*** On Windows execute the command ``zettelstore.exe run -c CONFIG_FILE``
*** On macOS execute the command ``./zettelstore run -c CONFIG_FILE``
*** On Linux execute the command ``./zettelstore run -c CONFIG_FILE``
** In all cases ''CONFIG_FILE'' must be substituted by file name where you wrote the startup configuration.
** If you encounter some error messages, update the startup configuration, and try again.
* Depending on your operating system, there are different ways to register Zettelstore to start automatically:
** [[Windows|00001003305000]]
** [[macOS|00001003310000]]
** [[Linux|00001003315000]]

id: 00001003305000
title: Enable Zettelstore to start automatically on Windows
role: manual
tags: #installation #manual #zettelstore
syntax: zmk
created: 20211125191727
modified: 20220218125541

Windows is a complicated beast. There are several ways to automatically start Zettelstore.

=== Startup folder

One way is to use the [[autostart folder|https://support.microsoft.com/en-us/windows/add-an-app-to-run-automatically-at-startup-in-windows-10-150da165-dcd9-7230-517b-cf3c295d89dd]].
Open the folder where you have placed in the Explorer.

=== Task scheduler

The Windows Task scheduler allows you to start Zettelstore as an background task.

This is both an advantage and a disadvantage.

On the plus side, Zettelstore runs in the background, and it does not disturbs you.
All you have to do is to open your web browser, enter the appropriate URL, and there you go.

On the negative side, you will not be notified when you enter the wrong data in the Task scheduler and Zettelstore fails to start.
This can be mitigated by first using the command line prompt to start Zettelstore with the appropriate options.
Once everything works, you can register Zettelstore to be automatically started by the task scheduler.
There you should make sure that you have followed the first steps as described on the [[parent page|00001003300000]].

Create a new action.

{{00001003305112}}

The next steps are the trickiest.

If you did not created a startup configuration file, then create an action that starts a program.
Enter the file path where you placed the Zettelstore executable.
The ""Browse ..."" button helps you with that.[^I store my Zettelstore executable in the sub-directory ''bin'' of my home directory.]

It is essential that you also enter a directory, which serves as the environment for your zettelstore.
The (sub-) directory ''zettel'', which will contain your zettel, will be placed in this directory.
If you leave the field ""Start in (optional)"" empty, the directory will be an internal Windows system directory (most likely: ''C:\\Windows\\System32'').

id: 00001003315000
title: Enable Zettelstore to start automatically on Linux
role: manual
tags: #installation #manual #zettelstore
syntax: zmk
created: 20220114181521
modified: 20220307104944

Since there is no such thing as the one Linux, there are too many different ways to automatically start Zettelstore.

* One way is to interpret your Linux desktop system as a server and use the [[recipe to install Zettelstore on a server|00001003600000]].
** See below for a lighter alternative.
* If you are using the [[Gnome Desktop|https://www.gnome.org/]], you could use the tool [[Tweak|https://wiki.gnome.org/action/show/Apps/Tweaks]] (formerly known as ""GNOME Tweak Tool"" or just ""Tweak Tool"").
  It allows to specify application that should run on startup / login.
* [[KDE|https://kde.org/]] provides a system setting to [[autostart|https://docs.kde.org/stable5/en/plasma-workspace/kcontrol/autostart/]] applications.
* [[Xfce|https://xfce.org/]] allows to specify [[autostart applications|https://docs.xfce.org/xfce/xfce4-session/preferences#application_autostart]].
* [[LXDE|https://www.lxde.org/]] uses [[LXSession Edit|https://wiki.lxde.org/en/LXSession_Edit]] to allow users to specify autostart applications.

If you use a different desktop environment, it often helps to to provide its name and the string ""autostart"" to google for it with the search engine of your choice.

Yet another way is to make use of the middleware that is provided.
Many Linux distributions make use of [[systemd|https://systemd.io/]], which allows to start processes on behalf of an user.
On the command line, adapt the following script to your own needs and execute it:
```
# mkdir -p "$HOME/.config/systemd/user"
# cd "$HOME/.config/systemd/user"
# cat <<__EOF__ > zettelstore.service
[Unit]
Description=Zettelstore

id: 00001004000000
title: Configuration of Zettelstore
role: manual
tags: #configuration #manual #zettelstore
syntax: zmk
created: 20210126175322
modified: 20210510153233

There are some levels to change the behavior and/or the appearance of Zettelstore.

# The first level is the way to start Zettelstore services and to manage it via command line (and, in part, via a graphical user interface).
#* [[Command line parameters|00001004050000]]
# As an intermediate user, you usually want to have more control over how Zettelstore is started.
  This may include the URI under which your Zettelstore is accessible, or the directories in which your Zettel are stored.
  You may want to permanently store the command line parameters so that you don't have to specify them every time you start Zettelstore.
#* [[Zettelstore startup configuration|00001004010000]]

id: 00001004010000
title: Zettelstore startup configuration
role: manual
tags: #configuration #manual #zettelstore
syntax: zmk
created: 20210126175322
modified: 20240710183532

The configuration file, specified by the ''-c CONFIGFILE'' [[command line option|00001004051000]], allows you to specify some startup options.
These cannot be stored in a [[configuration zettel|00001004020000]] because they are needed before Zettelstore can start or because of security reasons.
For example, Zettelstore needs to know in advance on which network address it must listen or where zettel are stored.
An attacker that is able to change the owner can do anything.
Therefore, only the owner of the computer on which Zettelstore runs can change this information.

  A value of ""0"" (the default) disables it.
  The administrator console will only be enabled if Zettelstore is started with the [[''run'' sub-command|00001004051000]].

  On most operating systems, the value must be greater than ""1024"" unless you start Zettelstore with the full privileges of a system administrator (which is not recommended).

  Default: ""0""
; [!asset-dir|''asset-dir'']
: Allows to specify a directory whose files are allowed be transferred directly with the help of the web server.
  The URL prefix for these files is ''/assets/''.
  You can use this if you want to transfer files that are too large for a zettel, such as presentation, PDF, music or video files.

  Files within the given directory will not be managed by Zettelstore.[^They will be managed by Zettelstore just in the very special case that the directory is one of the configured [[boxes|#box-uri-x]].]

  If you specify only the URL prefix in your web client, the contents of the directory are listed.
  To avoid this, create an empty file in the directory named ""index.html"".

: Specifies a [[box|00001004011200]] where zettel are stored.
  During startup, __X__ is incremented, starting with one, until no key is found.
  This allows to configuring than one box.

  If no ''box-uri-1'' key is given, the overall effect will be the same as if only ''box-uri-1'' was specified with the value ""dir://.zettel"".
  In this case, even a key ''box-uri-2'' will be ignored.
; [!debug-mode|''debug-mode'']
: If set to [[true|00001006030500]], allows to debug the Zettelstore software (mostly used by the developers).
  Disables any timeout values of the internal web server and does not send some security-related data.
  Sets [[''log-level''|#log-level]] to ""debug"".


  Do not enable it for a production server.

  Default: ""false""
; [!default-dir-box-type|''default-dir-box-type'']
: Specifies the default value for the (sub-)type of [[directory boxes|00001004011400#type]], in which Zettel are typically stored.

  Default: ""false""
; [!read-only-mode|''read-only-mode'']
: If set to a [[true value|00001006030500]] the Zettelstore service puts into a read-only mode.
  No changes are possible.

  Default: ""false"".





; [!secret|''secret'']
: A string value to make the communication with external clients strong enough so that sessions of the [[web user interface|00001014000000]] or [[API access token|00001010040700]] cannot be altered by some external unfriendly party.
  The string must have a length of at least 16 bytes.

  This value is only needed to be set if [[authentication is enabled|00001010040100]] by setting the key [[''owner''|#owner]] to some user identification value.
; [!token-lifetime-api|''token-lifetime-api''], [!token-lifetime-html|''token-lifetime-html'']
: Define lifetime of access tokens in minutes.

id: 00001004011200
title: Zettelstore boxes
role: manual
tags: #configuration #manual #zettelstore
syntax: zmk
created: 20210126175322
modified: 20220307121547

A Zettelstore must store its zettel somehow and somewhere.
In most cases you want to store your zettel as files in a directory.
Under certain circumstances you may want to store your zettel elsewhere.

An example are the [[predefined zettel|00001005090000]] that come with a Zettelstore.
They are stored within the software itself.
In another situation you may want to store your zettel volatile, e.g. if you want to provide a sandbox for experimenting.

To cope with these (and more) situations, you configure Zettelstore to use one or more __boxes__.
This is done via the ''box-uri-X'' keys of the [[startup configuration|00001004010000#box-uri-X]] (X is a number).
Boxes are specified using special [[URIs|https://en.wikipedia.org/wiki/Uniform_Resource_Identifier]], somehow similar to web addresses.

id: 00001004011400
title: Configure file directory boxes
role: manual
tags: #configuration #manual #zettelstore
syntax: zmk
created: 20210126175322
modified: 20240710180215

Under certain circumstances, it is preferable to further configure a file directory box.
This is done by appending query parameters after the base box URI ''dir:\//DIR''.

The following parameters are supported:

|= Parameter:|Description|Default value:|
|type|(Sub-) Type of the directory service|(value of ""[[default-dir-box-type|00001004010000#default-dir-box-type]]"")
|worker|Number of worker that can access the directory in parallel|7
|readonly|Allow only operations that do not create or change zettel|n/a

=== Type
On some operating systems, Zettelstore tries to detect changes to zettel files outside of Zettelstore's control[^This includes Linux, Windows, and macOS.].
On other operating systems, this may be not possible, due to technical limitations.
Automatic detection of external changes is also not possible, if zettel files are put on an external service, such as a file server accessed via SMB/CIFS or NFS.

id: 00001004011600
title: Configure memory boxes
role: manual
tags: #configuration #manual #zettelstore
syntax: zmk
created: 20220307112918
modified: 20220307122554

Under most circumstances, it is preferable to further configure a memory box.
This is done by appending query parameters after the base box URI ''mem:''.

The following parameters are supported:

|= Parameter:|Description|Default value:|Maximum value:
|max-bytes|Maximum number of bytes the box will store|65535|1073741824 (1 GiB)
|max-zettel|Maximum number of zettel|127|65535

The default values are somehow arbitrarily, but applicable for many use cases.

While the number of zettel should be easily calculable by an user, the number of bytes might be a little more difficult.

Metadata consumes 6 bytes for the zettel identifier and for each metadata value one byte for the separator, plus the length of key and data.
Then size of the content is its size in bytes.
For text content, its the number of bytes for its UTF-8 encoding.

If one of the limits are exceeded, Zettelstore will give an error indication, based on the HTTP status code 507.

id: 00001004020000
title: Configure the running Zettelstore
role: manual
tags: #configuration #manual #zettelstore
syntax: zmk
created: 20210126175322
modified: 20231126180829
show-back-links: false

You can configure a running Zettelstore by modifying the special zettel with the ID [[00000000000100]].
This zettel is called __configuration zettel__.
The following metadata keys change the appearance / behavior of Zettelstore.
Some of them can be overwritten in an [[user zettel|00001010040200]], a subset of those may be overwritten in zettel that is currently used.
See the full list of [[metadata that may be overwritten|00001004020200]].

  May be [[overwritten|00001004020200]] in a user zettel.

; [!lang|''lang'']
: Language to be used when displaying content.

  Default: ""en"".

  This value is used as a default value, if it is not set in an user's zettel or in a zettel.
  It is also used to specify the language for all non-zettel content, e.g. lists or search results.

  Use values according to the language definition of [[RFC-5646|https://tools.ietf.org/html/rfc5646]].
; [!max-transclusions|''max-transclusions'']
: Maximum number of indirect transclusion.
  This is used to avoid an exploding ""transclusion bomb"", a form of a [[billion laughs attack|https://en.wikipedia.org/wiki/Billion_laughs_attack]].

  Default: ""1024"".
; [!show-back-links|''show-back-links''], [!show-folge-links|''show-folge-links''], [!show-subordinate-links|''show-subordinate-links''], [!show-successor-links|''show-successor-links'']
: When displaying a zettel in the web user interface, references to other zettel are normally shown below the content of the zettel.
  This affects the metadata keys [[''back''|00001006020000#back]], [[''folge''|00001006020000#folge]], [[''subordinates''|00001006020000#subordinates]], and  [[''successors''|00001006020000#successors]].

  These configuration keys may be used to show, not to show, or to close the list of referenced zettel.

  Allowed values are: ""false"" (will not show the list), ""close"" (will show the list closed), and ""open"" / """" (will show the list).

  Default: """".

id: 00001004020200
title: Runtime configuration data that may be user specific or zettel specific
role: manual
tags: #configuration #manual #zettelstore
syntax: zmk
created: 20221205155521
modified: 20231126180752

Some metadata of the [[runtime configuration|00001004020000]] may be overwritten in an [[user zettel|00001010040200]].
A subset of those may be overwritten in zettel that is currently used.
This allows to specify user specific or zettel specific behavior.

The following metadata keys are supported to provide a more specific behavior:

|=Key|User:|Zettel:|Remarks
|[[''footer-zettel''|00001004020000#footer-zettel]]|Y|N|
|[[''home-zettel''|00001004020000#home-zettel]]|Y|N|
|[[''lang''|00001004020000#lang]]|Y|Y|Making it user-specific could make zettel for other user less useful
|[[''show-back-links''|00001004020000#show-back-links]]|Y|Y|
|[[''show-folge-links''|00001004020000#show-folge-links]]|Y|Y|

|[[''show-subordinate-links''|00001004020000#show-subordinate-links]]|Y|Y|
|[[''show-successor-links''|00001004020000#show-successor-links]]|Y|Y|

id: 00001004050000
title: Command line parameters
role: manual
tags: #command #configuration #manual #zettelstore
syntax: zmk
created: 20210126175322
modified: 20221128161932

Zettelstore is not just a service that provides services of a zettelkasten.
It allows to some tasks to be executed at the command line.
Typically, the task (""sub-command"") will be given at the command line as the first parameter.

If no parameter is given, the Zettelstore is called as
```
zettelstore
```
This is equivalent to call it this way:
```sh
mkdir -p ./zettel
zettelstore run -d ./zettel -c ./.zscfg
```
Typically this is done by starting Zettelstore via a graphical user interface by double-clicking to its file icon.
=== Sub-commands
* [[``zettelstore help``|00001004050200]] lists all available sub-commands.
* [[``zettelstore version``|00001004050400]] to display version information of Zettelstore.
* [[``zettelstore run``|00001004051000]] to start the Zettelstore service.
* [[``zettelstore run-simple``|00001004051100]] is typically called, when you start Zettelstore by a double.click in your GUI.
* [[``zettelstore file``|00001004051200]] to render files manually without activated/running Zettelstore services.
* [[``zettelstore password``|00001004051400]] to calculate data for [[user authentication|00001010040200]].

Every sub-command allows the following command line options:
; [!h|''-h''] (or ''--help'')
: Does not execute the sub-command, but shows allowed command line options (except ''-h'' / ''--help'').
; [!l|''-l LOGSPEC'']

id: 00001004051100
title: The ''run-simple'' sub-command
role: manual
tags: #command #configuration #manual #zettelstore
syntax: zmk
created: 20210126175322
modified: 20221128161922

=== ``zettelstore run-simple``
This sub-command is implicitly called, when an user starts Zettelstore by double-clicking on its GUI icon.
It is s simplified variant of the [[''run'' sub-command|00001004051000]].

First, this sub-command checks if it can read a [[Zettelstore startup configuration|00001004010000]] file by trying the [[default values|00001004051000#c]].
If this is the case, ''run-simple'' just continues as the [[''run'' sub-command|00001004051000]], but ignores any command line options (including ''-d DIR'').[^This allows a [[curious user|00001003000000]] to become an intermediate user.]


If no startup configuration was found, the sub-command allows only to specify a zettel directory.
The directory will be created automatically, if it does not exist.
This is a difference to the ''run'' sub-command, where the directory must exists.
In contrast to the ''run'' sub-command, other command line parameter are not allowed.

```
zettelstore run-simple [-d DIR]
```

; [!d|''-d DIR'']

id: 00001004051400
title: The ''password'' sub-command
role: manual
tags: #command #configuration #manual #zettelstore
syntax: zmk
created: 20210126175322
modified: 20210712234305

This sub-command is used to create a hashed password for to be authenticated users.

It reads a password from standard input (two times, both must be equal) and writes the hashed password to standard output.

The general usage is:
```
zettelstore password IDENT ZETTEL-ID
```

``IDENT`` is the identification for the user that should be authenticated.
``ZETTEL-ID`` is the [[identifier of the zettel|00001006050000]] that later acts as a user zettel.

See [[Creating an user zettel|00001010040200]] for some background information.

An example:

```
# zettelstore password bob 20200911115600
Password:
   Again:
credential: $2a$10$1q92v1Ya8Too5HD/4rKpPuCP8fZTYPochsC6DcY1T4JKwhSx8uLu6
user-id: bob
```

This will produce a hashed password (""credential"") for the new user ""bob"" to be stored in zettel ""20200911115600"".

You should copy the relevant output to the zettel of the user to be secured, especially by setting the meta keys ''credential'' and ''user-id'' to the copied values.

Please note that the generated hashed password is tied to the given user identification (''user-id'') and to the identifier of its zettel.
Changing one of those will stop authenticating the user with the given password.
In this case you have to re-run this sub-command.

id: 00001004100000
title: Zettelstore Administrator Console
role: manual
tags: #configuration #manual #zettelstore
syntax: zmk
created: 20210510141304
modified: 20211103162926

The administrator console is a service accessible only on the same computer on which Zettelstore is running.
It allows an experienced user to monitor and control some of the inner workings of Zettelstore.

You enable the administrator console by specifying a TCP port number greater than zero (better: greater than 1024) for it, either via the [[command-line parameter ''-a''|00001004051000#a]] or via the ''admin-port'' key of the [[startup configuration file|00001004010000#admin-port]].

After you enable the administrator console, you can use tools such as [[PuTTY|https://www.chiark.greenend.org.uk/~sgtatham/putty/]] or other telnet software to connect to the administrator console.
In fact, the administrator console is __not__ a full telnet service.
It is merely a simple line-oriented service where each input line is interpreted separately.
Therefore, you can also use tools like [[netcat|https://nc110.sourceforge.io/]], [[socat|http://www.dest-unreach.org/socat/]], etc.

After connecting to the administrator console, there is no further authentication.
It is not needed because you must be logged in on the same computer where Zettelstore is running.
You cannot connect to the administrator console if you are on a different computer.
Of course, on multi-user systems with encrusted users, you should not enable the administrator console.

* Enable via [[command line|00001004051000#a]]
* Enable via [[configuration file|00001004010000#admin-port]]
* [[List of supported commands|00001004101000]]

id: 00001004101000
title: List of supported commands of the administrator console
role: manual
tags: #configuration #manual #zettelstore
syntax: zmk
created: 20210510141304
modified: 20220823194553

; [!bye|''bye'']
: Closes the connection to the administrator console.
; [!config|''config SERVICE'']
: Displays all valid configuration keys for the given service.

  If a key ends with the hyphen-minus character (""''-''"", U+002D), the key denotes a list value.

  ``get-config`` shows all current configuration data.

  ``get-config SERVICE`` shows only the current configuration data of the given service.

  ``get-config SERVICE KEY`` shows the current configuration data for the given service and key.
; [!header|''header'']
: Toggles the header mode, where each table is show with a header nor not.
; [!log-level|''log-level'']
: Displays or sets the [[logging level|00001004059700]] for the kernel or a service.

  ``log-level`` shows all known log level.

  ``log-level NAME`` shows log level for the given service or for the kernel.

  It may be removed without any further notice at any time.
  In most cases, it is a tool for software developers to optimize Zettelstore's internal workings.
; [!refresh|''refresh'']
: Refresh all internal data about zettel.
; [!restart|''restart SERVICE'']
: Restart the given service and all other that depend on this.
; [!services|''services'']
: Displays s list of all available services and their current status.
; [!set-config|''set-config SERVICE KEY VALUE'']
: Sets a single configuration value for the next configuration of a given service.
  It will become effective if the service is restarted.

  If the key specifies a list value, all other list values with a number greater than the given key are deleted.
  You can use the special number ""0"" to delete all values.
  E.g. ``set-config box box-uri-0 any_text`` will remove all values of the list __box-uri-__.

id: 00001005000000
title: Structure of Zettelstore
role: manual
tags: #design #manual #zettelstore
syntax: zmk
created: 20210126175322
modified: 20240710173506

Zettelstore is a software that manages your zettel.
Since every zettel must be readable without any special tool, most zettel has to be stored as ordinary files within specific directories.
Typically, file names and file content must comply to specific rules so that Zettelstore can manage them.
If you add, delete, or change zettel files with other tools, e.g. a text editor, Zettelstore will monitor these actions.

Zettelstore provides additional services to the user.
Via the builtin [[web user interface|00001014000000]] you can work with zettel in various ways.
For example, you are able to list zettel, to create new zettel, to edit them, or to delete them.
You can view zettel details and relations between zettel.

In addition, Zettelstore provides an ""application programming interface"" ([[API|00001012000000]]) that allows other software to communicate with the Zettelstore.
Zettelstore becomes extensible by external software.
For example, a more sophisticated user interface could be build, or an application for your mobile device that allows you to send content to your Zettelstore as new zettel.

=== Where zettel are stored

Your zettel are stored typically as files in a specific directory.
If you have not explicitly specified the directory, a default directory will be used.
The directory has to be specified at [[startup time|00001004010000]].
Nested directories are not supported (yet).

Every file in this directory that should be monitored by Zettelstore must have a file name that begins with 14 digits (0-9), the [[zettel identifier|00001006050000]].
If you create a new zettel via the [[web user interface|00001014000000]] or via the [[API|00001012053200]], the zettel identifier will be the timestamp of the current date and time (format is ''YYYYMMDDhhmmss'').
This allows zettel to be sorted naturally by creation time.[^Zettel identifier format will be migrated to a new format after version 0.19, without reference to the creation date. See [[Alphanumeric Zettel Identifier|00001006050200]] for some details.]

Since the only restriction on zettel identifiers are the 14 digits, you are free to use other digit sequences.[^Zettel identifier format will be migrated to a new format after version 0.19, without reference to the creation date.]
The [[configuration zettel|00001004020000]] is one prominent example, as well as these manual zettel.
You can create these special zettel identifiers either with the __rename__[^Renaming is deprecated als will be removed in version 0.19 or after.] function of Zettelstore or by manually renaming the underlying zettel files.

It is allowed that the file name contains other characters after the 14 digits.
These are ignored by Zettelstore.

Two filename extensions are used by Zettelstore:
# ''.zettel'' is a format that stores metadata and content together in one file,
# the empty file extension is used, when the content must be stored in its own file, e.g. image data;
  in this case, the filename just the 14 digits of the zettel identifier, and optional characters except the period ''"."''.  
Other filename extensions are used to determine the ""syntax"" of a zettel.
This allows to use other content within the Zettelstore, e.g. images or HTML templates.

For example, you want to store an important figure in the Zettelstore that is encoded as a ''.png'' file.
Since each zettel contains some metadata, e.g. the title of the figure, the question arises where these data should be stores.
The solution is a meta-file with the same zettel identifier, but without a filename extension.
Zettelstore recognizes this situation and reads in both files for the one zettel containing the figure.
It maintains this relationship as long as theses files exists.

In case of some textual zettel content you do not want to store the metadata and the zettel content in two different files.
Here the ''.zettel'' extension will signal that the metadata and the zettel content will be put in the same file, separated by an empty line or a line with three dashes (""''-\-\-''"", also known as ""YAML separator"").

=== Predefined zettel

Zettelstore contains some [[predefined zettel|00001005090000]] to work properly.
The [[configuration zettel|00001004020000]] is one example.
To render the builtin [[web user interface|00001014000000]], some templates are used, as well as a [[layout specification in CSS|00000000020001]].
The icon that visualizes a broken image is a [[predefined GIF image|00000000040001]].
All of these are visible to the Zettelstore as zettel.

One reason for this is to allow you to modify these zettel to adapt Zettelstore to your needs and visual preferences.

Where are these zettel stored?
They are stored within the Zettelstore software itself, because one [[design goal|00001002000000]] was to have just one executable file to use Zettelstore.
But data stored within an executable program cannot be changed later[^Well, it can, but it is a very bad idea to allow this. Mostly for security reasons.].

To allow changing predefined zettel, both the file store and the internal zettel store are internally chained together.
If you change a zettel, it will be always stored as a file.
If a zettel is requested, Zettelstore will first try to read that zettel from a file.
If such a file was not found, the internal zettel store is searched secondly.

Therefore, the file store ""shadows"" the internal zettel store.
If you want to read the original zettel, you either have to delete the zettel (which removes it from the file directory), or you have to rename[^Renaming is deprecated als will be removed in version 0.19 or after.] it to another zettel identifier.
Now we have two places where zettel are stored: in the specific directory and within the Zettelstore software.

* [[List of predefined zettel|00001005090000]]

=== Boxes: alternative ways to store zettel
As described above, a zettel may be stored as a file inside a directory or inside the Zettelstore software itself.
Zettelstore allows other ways to store zettel by providing an abstraction called __box__.[^Formerly, zettel were stored physically in boxes, often made of wood.]

A file directory which stores zettel is called a ""directory box"".
But zettel may be also stored in a ZIP file, which is called ""file box"".
For testing purposes, zettel may be stored in volatile memory (called __RAM__).
This way is called ""memory box"".

id: 00001005090000
title: List of predefined zettel
role: manual
tags: #manual #reference #zettelstore
syntax: zmk
created: 20210126175322
modified: 20240709180005

The following table lists all predefined zettel with their purpose.[^Zettel identifier format will be migrated to a new format after version 0.19.]





|= Identifier :|= Title | Purpose
| [[00000000000001]] | Zettelstore Version | Contains the version string of the running Zettelstore
| [[00000000000002]] | Zettelstore Host | Contains the name of the computer running the Zettelstore
| [[00000000000003]] | Zettelstore Operating System | Contains the operating system and CPU architecture of the computer running the Zettelstore
| [[00000000000004]] | Zettelstore License | Lists the license of Zettelstore
| [[00000000000005]] | Zettelstore Contributors | Lists all contributors of Zettelstore
| [[00000000000006]] | Zettelstore Dependencies | Lists all licensed content
| [[00000000000007]] | Zettelstore Log | Lists the last 8192 log messages
| [[00000000000008]] | Zettelstore Memory | Some statistics about main memory usage
| [[00000000000009]] | Zettelstore Sx Engine | Statistics about the [[Sx|https://t73f.de/r/sx]] engine, which interprets symbolic expressions
| [[00000000000020]] | Zettelstore Box Manager | Contains some statistics about zettel boxes and the the index process
| [[00000000000090]] | Zettelstore Supported Metadata Keys | Contains all supported metadata keys, their [[types|00001006030000]], and more
| [[00000000000092]] | Zettelstore Supported Parser | Lists all supported values for metadata [[syntax|00001006020000#syntax]] that are recognized by Zettelstore
| [[00000000000096]] | Zettelstore Startup Configuration | Contains the effective values of the [[startup configuration|00001004010000]]
| [[00000000000100]] | Zettelstore Runtime Configuration | Allows to [[configure Zettelstore at runtime|00001004020000]]
| [[00000000000102]] | Zettelstore Warnings | Warnings about potential problematic zettel identifier
| [[00000000010100]] | Zettelstore Base HTML Template | Contains the general layout of the HTML view
| [[00000000010200]] | Zettelstore Login Form HTML Template | Layout of the login form, when authentication is [[enabled|00001010040100]]
| [[00000000010300]] | Zettelstore List Zettel HTML Template | Used when displaying a list of zettel
| [[00000000010401]] | Zettelstore Detail HTML Template | Layout for the HTML detail view of one zettel
| [[00000000010402]] | Zettelstore Info HTML Template | Layout for the information view of a specific zettel
| [[00000000010403]] | Zettelstore Form HTML Template | Form that is used to create a new or to change an existing zettel that contains text
| [[00000000010404]] | Zettelstore Rename Form HTML Template | View that is displayed to change the [[zettel identifier|00001006050000]]
| [[00000000010405]] | Zettelstore Delete HTML Template | View to confirm the deletion of a zettel
| [[00000000010700]] | Zettelstore Error HTML Template | View to show an error message
| [[00000000019000]] | Zettelstore Sxn Start Code | Starting point of sxn functions to build the templates
| [[00000000019990]] | Zettelstore Sxn Base Code | Base sxn functions to build the templates
| [[00000000020001]] | Zettelstore Base CSS | System-defined CSS file that is included by the [[Base HTML Template|00000000010100]]
| [[00000000025001]] | Zettelstore User CSS | User-defined CSS file that is included by the [[Base HTML Template|00000000010100]]
| [[00000000040001]] | Generic Emoji | Image that is shown if [[original image reference|00001007040322]] is invalid
| [[00000000060010]] | zettel | [[Role zettel|00001012051800]] for the role ""[[zettel|00001006020100#zettel]]""
| [[00000000060020]] | confguration | [[Role zettel|00001012051800]] for the role ""[[confguration|00001006020100#confguration]]""
| [[00000000060030]] | role | [[Role zettel|00001012051800]] for the role ""[[role|00001006020100#role]]""
| [[00000000060040]] | tag | [[Role zettel|00001012051800]] for the role ""[[tag|00001006020100#tag]]""

| [[00000000090000]] | New Menu | Contains items that should be in the zettel template menu
| [[00000000090001]] | New Zettel | Template for a new zettel with role ""[[zettel|00001006020100#zettel]]""
| [[00000000090002]] | New User | Template for a new [[user zettel|00001010040200]]
| [[00000000090003]] | New Tag | Template for a new [[tag zettel|00001006020100#tag]]
| [[00000000090004]] | New Role | Template for a new [[role zettel|00001006020100#role]]
| [[00009999999998]] | Zettelstore Application Directory | Maps application name to application specific zettel
| [[00010000000000]] | Home | Default home zettel, contains some welcome information

If a zettel is not linked, it is not accessible for the current user.
In most cases, you must at least enable [[''expert-mode''|00001004020000#expert-mode]].

**Important:** All identifier may change until a stable version of the software is released.

id: 00001006000000
title: Layout of a Zettel
role: manual
tags: #design #manual #zettelstore
syntax: zmk
created: 20210126175322
modified: 20230403123541

A zettel consists of two parts: the metadata and the zettel content.
Metadata gives some information mostly about the zettel content, how it should be interpreted, how it is sorted within Zettelstore.
The zettel content is, well, the actual content.
In many cases, the content is in plain text form.
Plain text is long-lasting.
However, content in binary format is also possible.

This is called ""[[parsed zettel|00001012053600]]"", also retrieved with the [[endpoint|00001012920000]] ''/z/{ID}'', but with the additional query parameter ''parseonly''.
Such a zettel was read and analyzed.
It can be presented in various [[encodings|00001012920500]].[^The [[zmk encoding|00001012920522]] allows you to compare the plain, the parsed, and the evaluated form of a zettel.]

However, a zettel such as this one you are currently reading, is a ""[[evaluated zettel|00001012053500]]"", also retrieved with the [[endpoint|00001012920000]] ''/z/{ID}'' and specifying an encoding.
The biggest difference to a parsed zettel is the inclusion of [[block transclusions|00001007031100]] or [[inline transclusions|00001007040324]] for an evaluated zettel.
It can also be presented in various encoding, including the ""zmk"" encoding.
Evaluations also applies to metadata of a zettel, if appropriate.

Please note, that searching for content is based on parsed zettel.
Transcluded content will only be found in transcluded zettel, but not in the zettel that transcluded the content.
However, you will easily pick up that zettel by follow the [[backward|00001006020000#backward]] metadata key of the transcluded zettel.

id: 00001006020000
title: Supported Metadata Keys
role: manual
tags: #manual #meta #reference #zettel #zettelstore
syntax: zmk
created: 20210126175322
modified: 20240708154737

Although you are free to define your own metadata, by using any key (according to the [[syntax|00001006010000]]), some keys have a special meaning that is enforced by Zettelstore.
See the [[computed list of supported metadata keys|00000000000090]] for details.

Most keys conform to a [[type|00001006030000]].

; [!author|''author'']

; [!created|''created'']
: Date and time when a zettel was created through Zettelstore.
  If you create a zettel with an editor software outside Zettelstore, you should set it manually to an appropriate value.

  This is a computed value.
  There is no need to set it via Zettelstore.
  
  If it is not stored within a zettel, it will be computed based on the value of the [[Zettel Identifier|00001006050000]]: if it contains a value >= 19700101000000, it will be coerced to da date/time; otherwise the version time of the running software will be used.

  Please note that the value von ''created'' will be different (in most cases) to the value of [[''id''|#id]] / the zettel identifier, because it is exact up to the second.
  When calculating a zettel identifier, Zettelstore tries to set the second value to zero, if possible.
; [!created-missing|''created-missing'']
: If set to ""true"", the value of [[''created''|#created]] was not stored within a zettel.
  To allow the migration of [[zettel identifier|00001006050000]] to a new scheme, you should update the value of ''created'' to a reasonable value.
  Otherwise you might lose that information in future releases.

  This key will be removed when the migration to a new zettel identifier format has been completed.
; [!credential|''credential'']
: Contains the hashed password, as it was emitted by [[``zettelstore password``|00001004051400]].
  It is internally created by hashing the password, the [[zettel identifier|00001006050000]], and the value of the ''ident'' key.

  It is only used for zettel with a ''role'' value of ""user"".
; [!dead|''dead'']
: Property that contains all references that does __not__ identify a zettel.
; [!expire|''expire'']
: A user-entered time stamp that document the point in time when the zettel should expire.
  When a zettel is expires, Zettelstore does nothing.
  It is up to you to define required actions.
  ''expire'' is just a documentation.
  You could define a query and execute it regularly, for example [[query:expire? ORDER expire]].
  Alternatively, a Zettelstore client software could define some actions when it detects expired zettel.
; [!folge|''folge'']
: Is a property that contains identifier of all zettel that reference this zettel through the [[''precursor''|#precursor]] value.
; [!folge-role|''folge-role'']

; [!precursor|''precursor'']
: References zettel for which this zettel is a ""Folgezettel"" / follow-up zettel.
  Basically the inverse of key [[''folge''|#folge]].
; [!predecessor|''predecessor'']
: References the zettel that contains a previous version of the content.
  In contrast to [[''precursor''|#precurso]] / [[''folge''|#folge]], this is a reference because of technical reasons, not because of content-related reasons.
  Basically the inverse of key [[''successors''|#successors]].



; [!published|''published'']
: This property contains the timestamp of the mast modification / creation of the zettel.
  If [[''modified''|#modified]] is set with a valid timestamp, it contains the its value.
  Otherwise, if [[''created''|#created]] is set with a valid timestamp, it contains the its value.
  Otherwise, if the zettel identifier contains a valid timestamp, the identifier is used.
  In all other cases, this property is not set.

  It can be used for [[sorting|00001007700000]] zettel based on their publication date.

  It is a computed value.
  There is no need to set it via Zettelstore.
; [!query|''query'']
: Stores the [[query|00001007031140]] that was used to create the zettel.
  This is for future reference.
; [!read-only|''read-only'']
: Marks a zettel as read-only.
  The interpretation of [[supported values|00001006020400]] for this key depends, whether authentication is [[enabled|00001010040100]] or not.
; [!role|''role'']
: Defines the role of the zettel.
  Can be used for selecting zettel.
  See [[supported zettel roles|00001006020100]].
  If not given, it is ignored.


; [!subordinates|''subordinates'']
: Is a property that contains identifier of all zettel that reference this zettel through the [[''superior''|#superior]] value.
; [!successors|''successors'']
: Is a property that contains identifier of all zettel that reference this zettel through the [[''predecessor''|#predecessor]] value.
  Therefore, it references all zettel that contain a new version of the content and/or metadata.
  In contrast to [[''folge''|#folge]], these are references because of technical reasons, not because of content-related reasons.
  In most cases, zettel referencing the current zettel should be updated to reference a successor zettel.
  The [[query reference|00001007040310]] [[query:backward? successors?]] lists all such zettel.
; [!summary|''summary'']
: Summarizes the content of the zettel.
  You may use all [[inline-structued elements|00001007040000]] of Zettelmarkup.
; [!superior|''superior'']
: Specifies a zettel that is conceptually a superior zettel.
  This might be a more abstract zettel, or a zettel that should be higher in a hierarchy.
; [!syntax|''syntax'']
: Specifies the syntax that should be used for interpreting the zettel.
  The zettel about [[other markup languages|00001008000000]] defines supported values.
  If it is not given, it defaults to ''plain''.
; [!tags|''tags'']
: Contains a space separated list of tags to describe the zettel further.
  Each Tag must begin with the number sign character (""''#''"", U+0023).
; [!title|''title'']
: Specifies the title of the zettel.
  If not given, the value of [[''id''|#id]] will be used.
; [!url|''url'']
: Defines an URL / URI for this zettel that possibly references external material.
  One use case is to specify the document that the current zettel comments on.
  The URL will be rendered special in the [[web user interface|00001014000000]] if you use the default template.
; [!useless-files|''useless-files'']
: Contains the file names that are rejected to serve the content of a zettel.
  Is used for [[directory boxes|00001004011400]] and [[file boxes|00001004011200#file]].
  If a zettel is renamed[^Renaming a zettel is deprecated. This feature will be removed in version 0.19 or later.] or deleted, these files will be deleted.
; [!user-id|''user-id'']
: Provides some unique user identification for an [[user zettel|00001010040200]].
  It is used as a user name for authentication.

  It is only used for zettel with a ''role'' value of ""user"".
; [!user-role|''user-role'']
: Defines the basic privileges of an authenticated user, e.g. reading / changing zettel.

id: 00001006020100
title: Supported Zettel Roles
role: manual
tags: #manual #meta #reference #zettel #zettelstore
syntax: zmk
created: 20210126175322
modified: 20231129173620

The [[''role'' key|00001006020000#role]] defines what kind of zettel you are writing.
You are free to define your own roles.
It is allowed to set an empty value or to omit the role.

Some roles are defined for technical reasons:

; [!configuration|''configuration'']
: A zettel that contains some configuration data / information for the Zettelstore.
  Most prominent is [[00000000000100]], as described in [[00001004020000]].
; [!manual|''manual'']
: All zettel that document the inner workings of the Zettelstore software.
  This role is only used in this specific Zettelstore.
; [!role|''role'']
: A zettel with the role ""role"" and a title, which names a [[role|00001006020000#role]], is treated as a __role zettel__.
  Basically, role zettel describe the role, and form a hierarchiy of meta-roles.
; [!tag|''tag'']
: A zettel with the role ""tag"" and a title, which names a [[tag|00001006020000#tags]], is treated as a __tag zettel__.
  Basically, tag zettel describe the tag, and form a hierarchiy of meta-tags.
; [!zettel|''zettel'']
: A zettel that contains your own thoughts.
  The real reason to use this software.

If you adhere to the process outlined by Niklas Luhmann, a zettel could have one of the following three roles:

; [!note|''note'']

id: 00001006020400
title: Supported values for metadata key ''read-only''
role: manual
tags: #manual #meta #reference #zettel #zettelstore
syntax: zmk
created: 20210126175322
modified: 20211124132040

A zettel can be marked as read-only, if it contains a metadata value for key
[[''read-only''|00001006020000#read-only]].
If user authentication is [[enabled|00001010040100]], it is possible to allow some users to change the zettel,
depending on their [[user role|00001010070300]].
Otherwise, the read-only mark is just a binary value.

=== No authentication
If there is no metadata value for key ''read-only'' or if its [[boolean value|00001006030500]]
is interpreted as ""false"", anybody can modify the zettel.

If the metadata value is something else (the value ""true"" is recommended),
the user cannot modify the zettel through the [[web user interface|00001014000000]].
However, if the zettel is stored as a file in a [[directory box|00001004011400]],
the zettel could be modified using an external editor.

=== Authentication enabled
If there is no metadata value for key ''read-only'' or if its [[boolean value|00001006030500]]
is interpreted as ""false"", anybody can modify the zettel.

If the metadata value is the same as an explicit [[user role|00001010070300]],
users with that role (or a role with lower rights) are not allowed to modify the zettel.

; ""reader""
: Neither an unauthenticated user nor a user with role ""reader"" is allowed to modify the zettel.
  Users with role ""writer"" or the owner itself still can modify the zettel.
; ""writer""
: Neither an unauthenticated user, nor users with roles ""reader"" or ""writer"" are allowed to modify the zettel.
  Only the owner of the Zettelstore can modify the zettel.

If the metadata value is something else (one of the values ""true"" or ""owner"" is recommended),
no user is allowed modify the zettel through the [[web user interface|00001014000000]].
However, if the zettel is accessible as a file in a [[directory box|00001004011400]],
the zettel could be modified using an external editor.
Typically the owner of a Zettelstore have such an access.

id: 00001006030000
title: Supported Key Types
role: manual
tags: #manual #meta #reference #zettel #zettelstore
syntax: zmk
created: 20210126175322
modified: 20240219161909

All [[supported metadata keys|00001006020000]] conform to a type.

User-defined metadata keys conform also to a type, based on the suffix of the key.

|=Suffix|Type
| ''-date'' | [[Timestamp|00001006034500]]
| ''-number'' | [[Number|00001006033000]]
| ''-role'' | [[Word|00001006035500]]
| ''-time'' | [[Timestamp|00001006034500]]
| ''-title'' | [[Zettelmarkup|00001006036500]]
| ''-url'' | [[URL|00001006035000]]
| ''-zettel''  | [[Identifier|00001006032000]]
| ''-zid''  | [[Identifier|00001006032000]]
| ''-zids''  | [[IdentifierSet|00001006032500]]
| any other suffix | [[EString|00001006031500]]

The name of the metadata key is bound to the key type

id: 00001006031500
title: EString Key Type
role: manual
tags: #manual #meta #reference #zettel #zettelstore
syntax: zmk
created: 20210212135017
modified: 20230419175525

Values of this type are just a sequence of character, possibly an empty sequence.

An EString is the most general metadata key type, as it places no restrictions to the character sequence.[^Well, there are some minor restrictions that follow from the [[metadata syntax|00001006010000]].]

=== Allowed values
All printable characters are allowed.

=== Query comparison

id: 00001006033000
title: Number Key Type
role: manual
tags: #manual #meta #reference #zettel #zettelstore
syntax: zmk
created: 20210212135017
modified: 20230612183900

Values of this type denote a numeric integer value.

=== Allowed values
Must be a sequence of digits (""0""--""9""), optionally prefixed with a ""-"" or a ""+"" character.

=== Query comparison
[[Search operators|00001007705000]] for equality (""equal"" or ""not equal"", ""has"" or ""not has""), for lesser values (""less"" or ""not less""), or for greater values (""greater"" or ""not greater"") are executed by converting both the [[search value|00001007706000]] and the metadata value into integer values and then comparing them numerically.
Integer values must be in the range -9223372036854775808 … 9223372036854775807.
Comparisons with metadata values outside this range always returns a negative match.
Comparisons with search values outside this range will be executed as a comparison of the string representation values.

All other comparisons (""match"", ""not match"", ""prefix"", ""not prefix"", ""suffix"", and ""not suffix"") are done on the given string representation of the number.
In this case, the number ""+12"" will be treated as different to the number ""12"".

=== Sorting
Sorting is done by comparing the numeric values.

id: 00001006034000
title: TagSet Key Type
role: manual
tags: #manual #meta #reference #zettel #zettelstore
syntax: zmk
created: 20210212135017
modified: 20230419175642

Values of this type denote a (sorted) set of tags.

A set is different to a list, as no duplicate values are allowed.

=== Allowed values
Every tag must must begin with the number sign character (""''#''"", U+0023), followed by at least one printable character.
Tags are separated by space characters.

All characters are mapped to their lower case values.

=== Query comparison
All comparisons are done case-sensitive, i.e. ""#hell"" will not be the prefix of ""#Hello"".

id: 00001006035000
title: URL Key Type
role: manual
tags: #manual #meta #reference #zettel #zettelstore
syntax: zmk
created: 20210212135017
modified: 20230419175725

Values of this type denote an URL.

=== Allowed values
All characters of an URL / URI are allowed.

=== Query comparison
All comparisons are done case-insensitive.
For example, ""hello"" is the suffix of ""http://example.com/Hello"".

=== Sorting
Sorting is done by comparing the [[String|00001006033500]] values.

id: 00001006050000
title: Zettel identifier
role: manual
tags: #design #manual #zettelstore
syntax: zmk
created: 20210126175322
modified: 20240708154551

Each zettel is given a unique identifier.
To some degree, the zettel identifier is part of the metadata.
Basically, the identifier is given by the [[Zettelstore|00001005000000]] software.

=== Timestamp-based identifier

Every zettel identifier consists of 14 digits.
They resemble a timestamp: the first four digits could represent the year, the
next two represent the month, following by day, hour, minute, and second.[^Zettel identifier format will be migrated to a new format after version 0.19, without reference to the creation date.]

This allows to order zettel chronologically in a canonical way.

In most cases the zettel identifier is the timestamp when the zettel was created.

However, the Zettelstore software just checks for exactly 14 digits.
Anybody is free to assign a ""non-timestamp"" identifier to a zettel, e.g. with
a month part of ""35"" or with ""99"" as the last two digits.

Some zettel identifier are [[reserved|00001006055000]] and should not be used otherwise.
All identifiers of zettel initially provided by an empty Zettelstore begin with ""000000"", except the home zettel ''00010000000000''.
Zettel identifier of this manual have be chosen to begin with ""000010"".

A zettel can have any identifier that contains 14 digits and that is not in use
by another zettel managed by the same Zettelstore.

=== Identifiers with four alphanumeric characters
In the future, above identifier format will change.
The migration to the new format starts with Zettelstore version 0.18 and will last approximately until version 0.22.

Above described format of 14 digits will be changed to four alphanumeric characters, i.e. the digits ''0'' to ''9'', and the letters ''a'' to ''z''.
You might note that using 14 digits you are allowed a little less than 10^^14^^ Zettel, i.e. more than 999 trillion zettel, while the new scheme only allows you to create 36^^4^^-1 zettel (1679615 zettel, to be exact).
Since Zettelstore is a single-user system, more than a million zettel should be enough.
However, there must be a way to replace an identifier with 14 digits by an identifier with four characters.

As a first step, the list of [[reserved zettel identifier|00001006055000]] is updated, as well as ways of client software to use predefined identifier.

id: 00001006050200
title: Alphanumeric Zettel Identifier
role: manual
tags: #design #manual #zettelstore
syntax: zmk
created: 20240705200557
modified: 20240710173133
precursor: 00001006050000

Timestamp-based zettel identifier (14 digits) will be migrated to a new format.
Instead of using the current date and time of zettel creation, the new format is based in incrementing zettel identifier.
When creating a new zettel, its identifier is calculated by adding one to the current maximum zettel identifier.
The external representation if the new format identifier is a sequence of four alphanumeric characters, i.e. the 36
characters ''0'' … ''9'', and ''a'' … ''z''.
The external representation is basically a ""base-36"" encoding of the number.

The characters ''A'' … ''Z'' are mapped to the lower-case ''a'' … ''z''.

=== Migration process
Please note: the following is just a plan.
Plans tend to be revised if they get in contact with reality.

; Version 0.18
: Provides some tools to check your own zettelstore for problematic zettel identifier.
  For example, zettel without metadata key ''created'' should be updated by the user, especially if the zettel identifier is below ''19700101000000''.
  Most likely, this is the case for zettel created before version 0.7 (2022-08-17).

  Zettel [[Zettelstore Warnings|00000000000102]] (''00000000000102'') lists these problematic zettel identifier.[^Only visible in [[expert mode|00001004020000#expert-mode]].]
  You should update your zettel to remove these warnings to ensure a smooth migration.

  If you have developed an application, that defines a specific zettel identifier to be used as application configuration, you should must the new zettel [[Zettelstore Application Directory|00009999999998]] (''00009999999998'').

  There is an explicit, but preliminary mapping of the old format to the new one, and vice versa.
  This mapping will be calculated with the order of the identifier in the old format.
  The zettel [[Zettelstore Identifier Mapping|00009999999999]] (''00009999999999'') will show this mapping.[^Only visible in [[expert mode|00001004020000#expert-mode]].]

; Version 0.19
: The new identifier format will be used initially internal.
  The old format with 14 digits is still used to create URIs and to link zettel.

  You will have some time to update your zettel data if you detect some issues.

  Operation to rename a zettel, i.e. assigning a new identifier to a zettel, is remove permanently.
; Version 0.20
: The internal search index is based on the new format identifier.
; Version 0.21
: The new format is used to calculate URIs and to form links.
; Version 0.22
: Old format identifier are full legacy.

id: 00001006055000
title: Reserved zettel identifier
role: manual
tags: #design #manual #zettelstore
syntax: zmk
created: 20210721105704
modified: 20240708154858

[[Zettel identifier|00001006050000]] are typically created by examine the current date and time.
By renaming[^The rename operation id deprecated and will be removed in version 0.19 or later.] a zettel, you are able to provide any sequence of 14 digits[^Zettel identifier format will be migrated to a new format after version 0.19.].
If no other zettel has the same identifier, you are allowed to rename a zettel.

To make things easier, you must not use zettel identifier that begin with four zeroes (''0000'').

All zettel provided by an empty zettelstore begin with six zeroes[^Exception: the predefined home zettel ''00010000000000''. But you can [[configure|00001004020000#home-zettel]] another zettel with another identifier as the new home zettel.].
Zettel identifier of this manual have be chosen to begin with ''000010''.

However, some external applications may need at least one defined zettel identifier to work properly.
Zettel [[Zettelstore Application Directory|00009999999998]] (''00009999999998'') can be used to associate a name to a zettel identifier.
For example, if your application is named ""app"", you create a metadata key ''app-zid''.
Its value is the zettel identifier of the zettel that configures your application.

=== Reserved Zettel Identifier

|= From | To | Description
| 00000000000000 | 0000000000000 | This is an invalid zettel identifier
| 00000000000001 | 0000099999999 | [[Predefined zettel|00001005090000]]
| 00001000000000 | 0000109999999 | This [[Zettelstore manual|00001000000000]]
| 00001100000000 | 0000899999999 | Reserved, do not use.
| 00009000000000 | 0000999999999 | Reserved for applications (legacy)

Since the format of zettel identifier will change in the near future, no external application is allowed to use the range ''00000000000001'' … ''0000999999999''.

==== External Applications (Legacy)
|= From | To | Description
| 00009000001000 | 00009000001999 | [[Zettel Presenter|https://zettelstore.de/contrib]], an application to display zettel as a HTML-based slideshow

id: 00001007000000
title: Zettelmarkup
role: manual
tags: #manual #zettelmarkup #zettelstore
syntax: zmk
created: 20210126175322
modified: 20221209192105

Zettelmarkup is a rich plain-text based markup language for writing zettel content.
Besides the zettel content, Zettelmarkup is also used for specifying the title of a zettel, regardless of the syntax of a zettel.

Zettelmarkup supports the longevity of stored notes by providing a syntax that any person can easily read, as well as a computer.
Zettelmarkup can be much easier parsed / consumed by a software compared to other markup languages.
Writing a parser for [[Markdown|https://daringfireball.net/projects/markdown/syntax]] is quite challenging.
[[CommonMark|00001008010500]] is an attempt to make it simpler by providing a comprehensive specification, combined with an extra chapter to give hints for the implementation.
Zettelmarkup follows some simple principles that anybody who knows to ho write software should be able understand to create an implementation.

Zettelmarkup is a markup language on its own.
This is in contrast to Markdown, which is basically a super-set of HTML: every HTML document is a valid Markdown document.[^To be precise: the content of the ``<body>`` of each HTML document is a valid Markdown document.]
While HTML is a markup language that will probably last for a long time, it cannot be easily translated to other formats, such as PDF, JSON, or LaTeX.
Additionally, it is allowed to embed other languages into HTML, such as CSS or even JavaScript.
This could create problems with longevity as well as security problems.

id: 00001007010000
title: Zettelmarkup: General Principles
role: manual
tags: #manual #zettelmarkup #zettelstore
syntax: zmk
created: 20210126175322
modified: 20211124175047

Any document can be thought as a sequence of paragraphs and other [[block-structured elements|00001007030000]] (""blocks""), such as [[headings|00001007030300]], [[lists|00001007030200]], quotations, and code blocks.
Some of these blocks can contain other blocks, for example lists may contain other lists or paragraphs.
Other blocks contain [[inline-structured elements|00001007040000]] (""inlines""), such as text, [[links|00001007040310]], emphasized text, and images.

With the exception of lists and tables, the markup for blocks always begins at the first position of a line with three or more identical characters.
List blocks also begin at the first position of a line, but may need one or more identical character, plus a space character.
[[Table blocks|00001007031000]] begin at the first position of a line with the character ""``|``"".
Non-list blocks are either fully specified on that line or they span multiple lines and are delimited with the same three or more character.
It depends on the block kind, whether blocks are specified on one line or on at least two lines.

If a line does not begin with an explicit block element. the line is treated as a (implicit) paragraph block element that contains inline elements.
This paragraph ends when a block element is detected at the beginning of a next line or when an empty line occurs.
Some blocks may also contain inline elements, e.g. a heading.

Inline elements mostly begins with two non-space, often identical characters.
With some exceptions, two identical non-space characters begins a formatting range that is ended with the same two characters.

Exceptions are: links, images, edits, comments, and both the ""en-dash"" and the ""horizontal ellipsis"".
A link is given with ``[[...]]``{=zmk}, an images with ``{{...}}``{=zmk}, and an edit formatting with ``((...))``{=zmk}.
An inline comment, beginning with the sequence ``%%``{=zmk}, always ends at the end of the line where it begins.
The ""en-dash"" (""--"") is specified as ``--``{=zmk}, the ""horizontal ellipsis"" (""..."") as ``...``{=zmk}[^If put at the end of non-space text.].

Some inline elements do not follow the rule of two identical character, especially to specify [[footnotes|00001007040330]], [[citation keys|00001007040340]], and local marks.
These elements begin with one opening square bracket (""``[``""), use a character for specifying the kind of the inline, typically allow to specify some content, and end with one closing square bracket (""``]``"").

One inline element that does not begin with two characters is the ""entity"".
It allows to specify any Unicode character.
The specification of that character is put between an ampersand character and a semicolon: ``&...;``{=zmk}.
For example, an ""n-dash"" could also be specified as ``–``{==zmk}.

The backslash character (""``\\``"") possibly gives the next character a special meaning.
This allows to resolve some left ambiguities.
For example, a list of depth 2 will begin a line with ``** Item 2.2``{=zmk}.
An inline element to strongly emphasize some text begin with a space will be specified as ``** Text**``{=zmk}.
To force the inline element formatting at the beginning of a line, ``**\\ Text**``{=zmk} should better be specified.

Many block and inline elements can be refined by additional [[attributes|00001007050000]].
Attributes resemble roughly HTML attributes and are put near the corresponding elements by using the syntax ``{...}``{=zmk}.
One example is to make space characters visible inside a inline literal element: ``1 + 2 = 3``{-} was specified by using the default attribute: ``\`\`1 + 2 = 3\`\`{-}``.

To summarize:

* With some exceptions, blocks-structural elements begins at the for position of a line with three identical characters.
* The most important exception to this rule is the specification of lists.
* If no block element is found, a paragraph with inline elements is assumed.
* With some exceptions, inline-structural elements begins with two characters, quite often the same two characters.
* The most important exceptions are links.
* The backslash character can help to resolve possible ambiguities.
* Attributes refine some block and inline elements.
* Block elements have a higher priority than inline elements.

These principles makes automatic recognizing zettelmarkup an (relatively) easy task.
By looking at the reference implementation, a moderately skilled software developer should be able to create a appropriate software in a different programming language.

id: 00001007030000
title: Zettelmarkup: Block-Structured Elements
role: manual
tags: #manual #zettelmarkup #zettelstore
syntax: zmk
created: 20210126175322
modified: 20220311181036

Every markup for blocks-structured elements (""blocks"") begins at the very first position of a line.

There are five kinds of blocks: lists, one-line blocks, line-range blocks, tables, and paragraphs.

=== Lists

:::example
= Heading
Some text follows.
:::
This is because headings need at least three equal sign character.

A paragraph is essentially a sequence of [[inline-structured elements|00001007040000]].
Inline-structured elements cam span more than one line.
Paragraphs are separated by empty lines.

If you want to specify a second paragraph inside a list item, or if you want to continue a paragraph on a second and more line within a list item, you must begin the paragraph with a certain number of space characters.
The number of space characters depends on the kind of a list and the relevant nesting level.

A line that begins with a space character and which is outside of a list or does not contain the right number of space characters is considered to be part of a paragraph.

id: 00001007030100
title: Zettelmarkup: Description Lists
role: manual
tags: #manual #zettelmarkup #zettelstore
syntax: zmk
created: 20210126175322
modified: 20220218131155

A description list is a sequence of terms to be described together with the descriptions of each term.
Every term can described in multiple ways.

A description term (short: __term__) is specified with one semicolon (""'';''"", U+003B) at the first position, followed by a space character and the described term, specified as a sequence of line elements.
If the following lines should also be part of the term, exactly two spaces must be given at the beginning of each following line.

The description of a term is given with one colon (""'':''"", U+003A) at the first position, followed by a space character and the description itself, specified as a sequence of [[inline elements|00001007040000]].
Similar to terms, following lines can also be part of the actual description, if they begin at each line with exactly two space characters.

id: 00001007030200
title: Zettelmarkup: Nested Lists
role: manual
tags: #manual #zettelmarkup #zettelstore
syntax: zmk
created: 20210126175322
modified: 20220218133902

There are thee kinds of lists that can be nested: ordered lists, unordered lists, and quotation lists.

Ordered lists are specified with the number sign (""''#''"", U+0023), unordered lists use the asterisk (""''*''"", U+002A), and quotation lists are specified with the greater-than sing (""''>''"", U+003E).
Let's call these three characters __list characters__.

Any nested list item is specified by a non-empty sequence of list characters, followed by a space character and a sequence of [[inline elements|00001007040000]].
In case of a quotation list as the last list character, the space character followed by a sequence of inline elements is optional.
The number / count of list characters gives the nesting of the lists.
If the following lines should also be part of the list item, exactly the same number of spaces must be given at the beginning of each of the following lines as it is the lists are nested, plus one additional space character.
In other words: the inline elements must begin at the same column as it was on the previous line.

The resulting sequence on inline elements is merged into a paragraph.
Appropriately indented paragraphs can specified after the first one.
Since each blocks-structured element has to be specified at the first position of a line, none of the nested list items may contain anything else than paragraphs.

Some examples:
```zmk
# One
# Two
# Three

id: 00001007030300
title: Zettelmarkup: Headings
role: manual
tags: #manual #zettelmarkup #zettelstore
syntax: zmk
created: 20210126175322
modified: 20220218133755

To specify a (sub-) section of a zettel, you should use the headings syntax: at
the beginning of a new line type at least three equal signs (""''=''"", U+003D), plus at least one
space and enter the text of the heading as [[inline elements|00001007040000]].

```zmk
=== Level 1 Heading

====== Level 4 Heading
======= Level 5 Heading
======== Level 5 Heading
:::

=== Notes

The heading level is translated to a HTML heading by adding 1 to the level, e.g. ``=== Level 1 Heading``{=zmk} translates to ==<h2>Level 1 Heading</h2>=={=html}.
The ==<h1>=={=html} tag is rendered for the zettel title.

This syntax is often used in a similar way in wiki implementation.
However, trailing equal signs are __not__ removed, they are part of the heading text.

If you use command line tools, you can easily create a draft table of contents with the command:

```sh
grep -h '^====* ' ZETTEL_ID.zettel
```

id: 00001007030400
title: Zettelmarkup: Horizontal Rules / Thematic Break
role: manual
tags: #manual #zettelmarkup #zettelstore
syntax: zmk
created: 20210126175322
modified: 20220825185533

To signal a thematic break, you can specify a horizontal rule.
This is done by entering at least three hyphen-minus characters (""''-''"", U+002D) at the first position of a line.
You can add some [[attributes|00001007050000]], although the horizontal rule does not support the default attribute.
Any other characters in this line will be ignored.

If you do not enter the three hyphen-minus character at the very first position of a line, the are interpreted as [[inline elements|00001007040000]], typically as an ""en-dash" followed by a hyphen-minus.

Example:

```zmk
---
----{.zs-deprecated}
-----

id: 00001007030800
title: Zettelmarkup: Region Blocks
role: manual
tags: #manual #zettelmarkup #zettelstore
syntax: zmk
created: 20210126175322
modified: 20220323190829

Region blocks does not directly have a visual representation.
They just group a range of lines.
You can use region blocks to enter [[attributes|00001007050000]] that apply only to this range of lines.
One example is to enter a multi-line warning that should be visible.

This kind of line-range block begins with at least three colon characters (""'':''"", U+003A) at the first position of a line[^Since a [[description text|00001007030100]] only use exactly one colon character at the first position of a line, there is no possible ambiguity between these elements.].
You can add some [[attributes|00001007050000]] on the beginning line of a region block, following the initiating characters.
The region block does not support the default attribute, but it supports the generic attribute.

id: 00001007030900
title: Zettelmarkup: Comment Blocks
role: manual
tags: #manual #zettelmarkup #zettelstore
syntax: zmk
created: 20210126175322
modified: 20230807170858

Comment blocks are quite similar to [[verbatim blocks|00001007030500]]: both are used to enter text that should not be interpreted.
While the text entered inside a verbatim block will be processed somehow, text inside a comment block will be ignored[^Well, not completely ignored: text is read, but it will typically not rendered visible.].
Comment blocks are typically used to give some internal comments, e.g. the license of a text or some internal remarks.

Comment blocks begin with at least three percent sign characters (""''%''"", U+0025) at the first position of a line.
You can add some [[attributes|00001007050000]] on the beginning line of a comment block, following the initiating characters.

```
will be completely ignored, while
```zmk
%%%{-}
Will be rendered
%%%
```
will be rendered as some kind of comment[^This cannot be shown here, because a HTML comment will not be rendered visible; it will be in the HTML text.].

id: 00001007031000
title: Zettelmarkup: Tables
role: manual
tags: #manual #zettelmarkup #zettelstore
syntax: zmk
created: 20210126175322
modified: 20220218131107

Tables are used to show some data in a two-dimensional fashion.
In zettelmarkup, table are not specified explicitly, but by entering __table rows__.
Therefore, a table can be seen as a sequence of table rows.
A table row is nothing as a sequence of __table cells__.
The length of a table is the number of table rows, the width of a table is the maximum length of its rows.

The first cell of a row must begin with the vertical bar character (""''|''"", U+007C) at the first position of a line.
The other cells of a row begin with the same vertical bar character at later positions in that line.
A cell is delimited by the vertical bar character of the next cell or by the end of the current line.
A vertical bar character as the last character of a line will not result in a table cell.
It will be ignored.

:::example
| a1 | a2 | a3|
| b1 | b2 | b3
| c1 | c2
:::

=== Header row
If any cell in the first row of a table contains an equal sing character (""''=''"", U+003D) as the very first character, then this first row will be interpreted as a __table header__ row.

For example:
```zmk
| a1 | a2 |= a3|
| b1 | b2 | b3
| c1 | c2
```

id: 00001007031110
title: Zettelmarkup: Zettel Transclusion
role: manual
tags: #manual #zettelmarkup #zettelstore
syntax: zmk
created: 20220809132350
modified: 20220926183331

A zettel transclusion is specified by the following sequence, starting at the first position in a line: ''{{{zettel-identifier}}}''.

When evaluated, the referenced zettel is read.
If it contains some transclusions itself, these will be expanded, recursively.
When a recursion is detected, expansion does not take place.
Instead an error message replaces the transclude specification.

An error message is also given, if the zettel cannot be read or if too many transclusions are made.
The maximum number of transclusion can be controlled by setting the value [[''max-transclusions''|00001004020000#max-transclusions]] of the runtime configuration zettel.

If everything went well, the referenced, expanded zettel will replace the transclusion element.

For example, to include the text of the Zettel titled ""Zettel identifier"", just specify its identifier [[''00001006050000''|00001006050000]] in the transclude element:
```zmk
{{{00001006050000}}}
```
This will result in:
:::example
{{{00001006050000}}}
:::

Please note: if the referenced zettel is changed, all transclusions will also change.

This allows, for example, to create a bigger document just by transcluding smaller zettel.

In addition, if a zettel __z__ transcludes a zettel __t__, but the current user is not allowed to view zettel __t__ (but zettel __z__), then the transclusion will not take place.
To the current user, it seems that there was no transclusion in zettel __z__.
This allows to create a zettel with content that seems to be changed, depending on the authorization of the current user.

---
Any [[attributes|00001007050000]] added to the transclusion will set/overwrite the appropriate metadata of the included zettel.
Of course, this applies only to thoes attribtues, which have a valid name for a metadata key.
This allows to control the evaluation of the included zettel, especially for zettel containing a diagram description.

=== See also
[[Inline-mode transclusion|00001007040324]] does not work at the paragraph / block level, but is used for [[inline-structured elements|00001007040000]].

id: 00001007031140
title: Zettelmarkup: Query Transclusion
role: manual
tags: #manual #search #zettelmarkup #zettelstore
syntax: zmk
created: 20220809132350
modified: 20240219161800

A query transclusion is specified by the following sequence, starting at the first position in a line: ''{{{query:query-expression}}}''.
The line must literally start with the sequence ''{{{query:''.
Everything after this prefix is interpreted as a [[query expression|00001007700000]].

When evaluated, the query expression is evaluated, often resulting in a list of [[links|00001007040310]] to zettel, matching the query expression.
The result replaces the query transclusion element.

: The resulting list will be a numbered list.
; ''MINn'' (parameter)
: Emit only those values with at least __n__ aggregated values.
  __n__ must be a positive integer, ''MIN'' must be given in upper-case letters.
; ''MAXn'' (parameter)
: Emit only those values with at most __n__ aggregated values.
  __n__ must be a positive integer, ''MAX'' must be given in upper-case letters.
; ''TITLE'' (parameter)
: All words following ''TITLE'' are joined together to form a title.
  It is used for the ''ATOM'' and ''RSS'' action.
; ''ATOM'' (aggregate)
: Transform the zettel list into an [[Atom 1.0|https://www.rfc-editor.org/rfc/rfc4287]]-conformant document / feed.
  The document is embedded into the referencing zettel.
; ''RSS'' (aggregate)
: Transform the zettel list into a [[RSS 2.0|https://www.rssboard.org/rss-specification]]-conformant document / feed.
  The document is embedded into the referencing zettel.
; ''KEYS'' (aggregate)
: Emit a list of all metadata keys, together with the number of zettel having the key.
; ''REDIRECT'', ''REINDEX'' (aggregate)
: Will be ignored.
  These actions may have been copied from an existing [[API query call|00001012051400]] (or from a WebUI query), but are here superfluous (and possibly harmful).
; Any [[metadata key|00001006020000]] of type [[Word|00001006035500]] or of type [[TagSet|00001006034000]] (aggregates)
: Emit an aggregate of the given metadata key.

id: 00001007031200
title: Zettelmarkup: Inline-Zettel Block
role: manual
tags: #manual #zettelmarkup #zettelstore
syntax: zmk
created: 20220201142439
modified: 20221018121251

An inline-zettel block allows to specify some content with another syntax without creating a new zettel.
This is useful, for example, if you want to embed some [[Markdown|00001008010500]] content, because you are too lazy to translate Markdown into Zettelmarkup.
Another example is to specify HTML code to use it for some kind of web front-end framework.

As all other [[line-range blocks|00001007030000#line-range-blocks]], an inline-zettel block begins with at least three identical characters, starting at the first position of a line.
For inline-zettel blocks, the at-sign character (""''@''"", U+0040) is used.

You can add some [[attributes|00001007050000]] on the beginning line of a verbatim block, following the initiating characters.
The inline-zettel block uses the attribute key ""syntax"" to specify the [[syntax|00001008000000]] of the inline-zettel.
Alternatively, you can use the generic attribute to specify the syntax value.
If no value is provided, ""[[text|00001008000000#text]]"" is assumed.

Any other character in this first line will be ignored.

Text following the beginning line will not be interpreted, until a line begins with at least the same number of the same at-sign characters given at the beginning line.

id: 00001007040000
title: Zettelmarkup: Inline-Structured Elements
role: manual
tags: #manual #zettelmarkup #zettelstore
syntax: zmk
created: 20210126175322
modified: 20220920143243

Most characters you type is concerned with inline-structured elements.
The content of a zettel contains is many cases just ordinary text, lightly formatted.
Inline-structured elements allow to format your text and add some helpful links or images.
Sometimes, you want to enter characters that have no representation on your keyboard.

; Text formatting
: Every [[text formatting|00001007040100]] element begins with two same characters at the beginning.
  It lasts until the same two characters occurred the second time.
  Some of these elements explicitly support [[attributes|00001007050000]].

; Literal-like formatting
: Sometime you want to enter the text as it is.
: This is the core motivation of [[literal-like formatting|00001007040200]].

; Reference-like text
: You can reference other zettel and (external) material within one zettel.
  This kind of reference may be a link, or an images that is display inline when the zettel is rendered.
  Footnotes sometimes factor out some useful text that hinders the flow of reading text.
  Internal marks allow to reference something within a zettel.
  An important aspect of all knowledge work is to reference others work, e.g. with citation keys.
  All these elements can be subsumed under [[reference-like text|00001007040300]].

=== Other inline elements
==== Comment
A comment begins with two consecutive percent sign characters (""''%''"", U+0025).
It ends at the end of the line where it begins.

==== Backslash
The backslash character (""''\\''"", U+005C) gives the next character another meaning.
* If a space character follows, it is converted in a non-breaking space (U+00A0).
* If a line ending follows the backslash character, the line break is converted from a __soft break__ into a __hard break__.
* Every other character is taken as itself, but without the interpretation of a Zettelmarkup element.
  For example, if you want to enter a ""'']''"" into a [[footnote text|00001007040330]], you should escape it with a backslash.

==== Entities & more
Sometimes it is not easy to enter special characters.
If you know the Unicode code point of that character, or its name according to the [[HTML standard|https://html.spec.whatwg.org/multipage/named-characters.html]], you can enter it by number or by name.

Regardless which method you use, an entity always begins with an ampersand character (""''&''"", U+0026) and ends with a semicolon character (""'';''"", U+003B).
If you know the HTML name of the character you want to enter, put it between these two character.
Example: ``&`` is rendered as ::&::{=example}.

If you want to enter its numeric code point, a number sign character must follow the ampersand character, followed by digits to base 10.
Example: ``&`` is rendered in HTML as ::&::{=example}.

You also can enter its numeric code point as a hex number, if you put the letter ""x"" after the numeric sign character.
Example: ``&`` is rendered in HTML as ::&::{=example}.

According to the [[HTML Standard|https://html.spec.whatwg.org/multipage/syntax.html#character-references]], some numeric code points are not allowed.
These are all code point below the numeric value 32 (decimal) or 0x20 (hex) and all code points for [[noncharacter|https://infra.spec.whatwg.org/#noncharacter]] values.

Since some Unicode character are used quite often, a special notation is introduced for them:

* Two consecutive hyphen-minus characters result in an __en-dash__ character.
  It is typically used in numeric ranges.
  ``pages 4--7`` will be rendered in HTML as: ::pages 4--7::{=example}.
  Alternative specifications are: ``–``, ``&x8211``, and ``&#x2013``.

id: 00001007040100
title: Zettelmarkup: Text Formatting
role: manual
tags: #manual #zettelmarkup #zettelstore
syntax: zmk
created: 20210126175322
modified: 20231113191353

Text formatting is the way to make your text visually different.
Every text formatting element begins with two same characters.
It ends when these two same characters occur the second time.
It is possible that some [[attributes|00001007050000]] follow immediately, without any separating character.

Text formatting can be nested, up to a reasonable limit.

The following characters begin a text formatting:

* The low line character (""''_''"", U+005F) emphasizes its text.
** Example: ``abc __def__ ghi`` is rendered in HTML as: ::abc __def__ ghi::{=example}.
* The asterisk character (""''*''"", U+002A) strongly emphasized its enclosed text.
** Example: ``abc **def** ghi`` is rendered in HTML as: ::abc **def** ghi::{=example}.
* The greater-than sign character (""''>''"", U+003E) marks text as inserted.
** Example: ``abc >>def>> ghi`` is rendered in HTML as: ::abc >>def>> ghi::{=example}.
* Similar, the tilde character (""''~''"", U+007E) marks deleted text.
** Example: ``abc ~~def~~ ghi`` is rendered in HTML as: ::abc ~~def~~ ghi::{=example}.
* The circumflex accent character (""''^''"", U+005E) allows to enter super-scripted text.
** Example: ``e=mc^^2^^`` is rendered in HTML as: ::e=mc^^2^^::{=example}.
* The comma character (""'',''"", U+002C) produces sub-scripted text.
** Example: ``H,,2,,O`` is rendered in HTML as: ::H,,2,,O::{=example}.
* The quotation mark character (""''"''"", U+0022) marks an inline quotation, according to the [[specified language|00001007050100]].
** Example: ``""To be or not""`` is rendered in HTML as: ::""To be or not""::{=example}.
** Example: ``""Sein oder nicht""{lang=de}`` is rendered in HTML as: ::""Sein oder nicht""{lang=de}::{=example}.
* The number sign (""''#''"", U+0023) marks the text visually, where the mark does not belong to the text itself.
  It is typically used to highlight some text that is important for you, but was not important for the original author.
** Example: ``abc ##def## ghi`` is rendered in HTML as: ::abc ##def## ghi::{=example}.
* The colon character (""'':''"", U+003A) mark some text that should belong together. It fills a similar role as [[region blocks|00001007030800]], but just for inline elements.
** Example: ``abc ::def::{=example} ghi`` is rendered in HTML as: abc ::def::{=example} ghi.

id: 00001007040200
title: Zettelmarkup: Literal-like formatting
role: manual
tags: #manual #zettelmarkup #zettelstore
syntax: zmk
created: 20210126175322
modified: 20220311185110

There are some reasons to mark text that should be rendered as uninterpreted:
* Mark text as literal, sometimes as part of a program.
* Mark text as input you give into a computer via a keyboard.
* Mark text as output from some computer, e.g. shown at the command line.

=== Literal text

* ``==The result is: 42=={-}`` renders in HTML as ::==The result is: 42=={-}::{=example}.

Attributes can be specified, the default attribute has the same semantic as for literal text.

=== Inline-zettel snippet
To specify an inline snippet in a different [[syntax|00001008000000]], delimit your text with two at-sign characters (""''@''"", U+0040) on each side.

You can add some [[attributes|00001007050000]] immediate after the two closing at-sign characters to specify the syntax to use.
Either use the attribute key ""syntax"" or use the generic attribute to specify the syntax value.
If no value is provided, ""[[text|00001008000000#text]]"" is assumed.

Examples:
* ``A @@-->@@ B`` renders in HTML as ::A @@-->@@ B::{=example}.
* ``@@<small>@@{=html}Small@@</small>@@{=html}`` renders in HTML as ::@@<small>@@{=html}Small@@</small>@@{=html}::{=example}.

To some degree, an inline-zettel snippet is the @@<small>@@{=html}smaller@@</small>@@{=html} sibling of the [[inline-zettel block|00001007031200]].
For HTML syntax, the same rules apply.

=== Math mode / $$\TeX$$ input
This allows to enter text, that is typically interpreted by $$\TeX$$ or similar software.
The main difference to all other literal-like formatting above is that the backslash character (""''\\''"", U+005C) has no special meaning.
Therefore it is well suited the enter text with a lot of backslash characters.

Math mode text is delimited with two dollar signs (""''$''"", U+0024) on each side.

You can add some [[attributes|00001007050000]] immediate after the two closing at-sign characters to specify the syntax to use.
Either use the attribute key ""syntax"" or use the generic attribute to specify the syntax value.
If no syntax value is provided, math mode text roughly corresponds to literal text.

id: 00001007040310
title: Zettelmarkup: Links
role: manual
tags: #manual #zettelmarkup #zettelstore
syntax: zmk
created: 20210810155955
modified: 20221024173849

There are two kinds of links, regardless of links to (internal) other zettel or to (external) material.
Both kinds begin with two consecutive left square bracket characters (""''[''"", U+005B) and ends with two consecutive right square bracket characters (""'']''"", U+005D).
If the content starts with more than two left square bracket characters, all but the last two will be treated as text.

The first form provides some text plus the link specification, delimited by a vertical bar character (""''|''"", U+007C): ``[[text|linkspecification]]``.
The text is a sequence of [[inline elements|00001007040000]].
However, it should not contain links itself.

The second form just provides a link specification between the square brackets.
Its text is derived from the link specification, e.g. by interpreting the link specification as text: ``[[linkspecification]]``.

=== Link specifications
The link specification for another zettel within the same Zettelstore is just the [[zettel identifier|00001006050000]].
To reference some content within a zettel, you can append a number sign character (""''#''"", U+0023) and the name of the mark to the zettel identifier.
The resulting reference is called ""zettel reference"".

If the link specification begins with the string ''query:'', the text following this string will be interpreted as a [[query expression|00001007700000]].
The resulting reference is called ""query reference"".
When this type of references is rendered, it will typically reference a list of all zettel that fulfills the query expression.

A link specification starting with one slash character (""''/''"", U+002F), or one or two full stop characters (""''.''"", U+002E) followed by a slash character,
will be interpreted as a local reference, called __hosted reference__.
Such references will be interpreted relative to the web server hosting the Zettelstore.

If a link specification begins with two slash characters (called __based reference__), it will be interpreted relative to the value of [[''url-prefix''|00001004010000#url-prefix]].

To specify some material outside the Zettelstore, just use an normal Uniform Resource Identifier (URI) as defined by [[RFC\ 3986|https://tools.ietf.org/html/rfc3986]].

=== Other topics
If the link references another zettel, and this zettel is not readable for the current user, because of a missing access rights, then only the associated text is presented.

id: 00001007040320
title: Zettelmarkup: Inline Embedding / Transclusion
role: manual
tags: #manual #zettelmarkup #zettelstore
syntax: zmk
created: 20210810155955
modified: 20221024173926

To some degree, an specification for embedded material is conceptually not too far away from a specification for [[linked material|00001007040310]].
Both contain a reference specification and optionally some text.
In contrast to a link, the specification of embedded material must currently resolve to some kind of real content.
This content replaces the embed specification.

An embed specification begins with two consecutive left curly bracket characters (""''{''"", U+007B) and ends with two consecutive right curly bracket characters (""''}''"", U+007D).
The curly brackets delimits either a reference specification or some text, a vertical bar character and the link specification, similar to a link.
If the content starts with more than two left curly bracket characters, all but the last two will be treated as text.

One difference to a link: if the text was not given, an empty string is assumed.

The reference must point to some content, either zettel content or URL-referenced content.
If the current user is not allowed to read the referenced zettel, the inline transclusion / embedding is ignored.
If the referenced zettel does not exist, or is not readable because of other reasons, a [[spinning emoji|00000000040001]] is presented as a visual hint:
 
Example: ``{{00000000000000}}`` will be rendered as ::{{00000000000000}}::{=example}.

id: 00001007040322
title: Zettelmarkup: Image Embedding
role: manual
tags: #manual #zettelmarkup #zettelstore
syntax: zmk
created: 20210811154251
modified: 20221112111054

Image content is assumed, if an URL is used or if the referenced zettel contains an image.

Supported formats are:

* Portable Network Graphics (""PNG""), as defined by [[RFC\ 2083|https://tools.ietf.org/html/rfc2083]].
* Graphics Interchange Format (""GIF"), as defined by [[https://www.w3.org/Graphics/GIF/spec-gif89a.txt]].
* JPEG / JPG, defined by the __Joint Photographic Experts Group__.
* Scalable Vector Graphics (SVG), defined by [[https://www.w3.org/Graphics/SVG/]]
* WebP, defined by [[Google|https://developers.google.com/speed/webp]]

If the text is given, it will be interpreted as an alternative textual representation, to help persons with some visual disabilities.

[[Attributes|00001007050000]] are supported.
They must follow the last right curly bracket character immediately.
One prominent example is to specify an explicit title attribute that is shown on certain web browsers when the zettel is rendered in HTML:

Examples:
* [!spin|``{{Spinning Emoji|00000000040001}}{title=Emoji width=30}``] is rendered as ::{{Spinning Emoji|00000000040001}}{title=Emoji width=30}::{=example}.
* The above image is also the placeholder for a non-existent zettel:

** ``{{00000000009999}}`` will be rendered as ::{{00000000009999}}::{=example}.

id: 00001007040324
title: Zettelmarkup: Inline-mode Transclusion
role: manual
tags: #manual #zettelmarkup #zettelstore
syntax: zmk
created: 20210811154251
modified: 20231222164501

Inline-mode transclusion applies to all zettel that are parsed in a non-trivial way, e.g. as structured textual content.
For example, textual content is assumed if the [[syntax|00001006020000#syntax]] of a zettel is ""zmk"" ([[Zettelmarkup|00001007000000]]), or ""markdown"" / ""md"" ([[Markdown|00001008010000]]).

Since this type of transclusion is at the level of [[inline-structured elements|00001007040000]], the transclude specification must be replaced with some inline-structured elements.

First, the referenced zettel is read.
If it contains other transclusions, these will be expanded, recursively.
When an endless recursion is detected, expansion does not take place.
Instead an error message replaces the transclude specification.

The result of this (indirect) transclusion is searched for inline-structured elements.

* If only an [[zettel identifier|00001006050000]] was specified, the first top-level [[paragraph|00001007030000#paragraphs]] is used.
  Since a paragraph is basically a sequence of inline-structured elements, these elements will replace the transclude specification.

  Example: ``{{00010000000000}}`` (see [[00010000000000]]) is rendered as ::{{00010000000000}}::{=example}.

* If a fragment identifier was additionally specified, the element with the given fragment is searched:
** If it specifies a [[heading|00001007030300]], the next top-level paragraph is used.

   Example: ``{{00010000000000#reporting-errors}}`` is rendered as ::{{00010000000000#reporting-errors}}::{=example}.

** In case the fragment names a [[mark|00001007040350]], the inline-structured elements after the mark are used.
   Initial spaces and line breaks are ignored in this case.

   Example: ``{{00001007040322#spin}}`` is rendered as ::{{00001007040322#spin}}::{=example}.

** Just specifying the fragment identifier will reference something in the current page.
   This is not allowed, to prevent a possible endless recursion.

* If the reference is a [[hosted or based|00001007040310#link-specifications]] link / URL to an image, that image will be rendered.

  Example: ``{{//z/00000000040001}}{alt=Emoji}`` is rendered as ::{{//z/00000000040001}}{alt=Emoji}::{=example}

If no inline-structured elements are found, the transclude specification is replaced by an error message.

To avoid an exploding ""transclusion bomb"", a form of a [[billion laughs attack|https://en.wikipedia.org/wiki/Billion_laughs_attack]] (also known as ""XML bomb""), the total number of transclusions / expansions is limited.
The limit can be controlled by setting the value [[''max-transclusions''|00001004020000#max-transclusions]] of the runtime configuration zettel.

=== See also
[[Full transclusion|00001007031100]] does not work inside some text, but is used for [[block-structured elements|00001007030000]].

id: 00001007040340
title: Zettelmarkup: Citation Key
role: manual
tags: #manual #zettelmarkup #zettelstore
syntax: zmk
created: 20210810155955
modified: 20220218133447

A citation key references some external material that is part of a bibliographical collection.

Currently, Zettelstore implements this only partially, it is ""work in progress"".

However, the syntax is: beginning with a left square bracket and followed by an at sign character (""''@''"", U+0040), a the citation key is given.
The key is typically a sequence of letters and digits.
If a comma character (""'',''"", U+002C) or a vertical bar character is given, the following is interpreted as [[inline elements|00001007040000]].
A right square bracket ends the text and the citation key element.

id: 00001007701000
title: Query: Search Expression
role: manual
tags: #manual #search #zettelstore
syntax: zmk
created: 20230707205043
modified: 20230707210039

In its simplest form, a search expression just contains a string to be search for with the help of a full-text search.
For example, the string ''syntax'' will search for all zettel containing the word ""syntax"".

If you want to search for all zettel with a title containing the word ""syntax"", you must specify ''title:syntax''.
""title"" denotes the [[metadata key|00001006010000]], in this case the [[supported metadata key ""title""|00001006020000#title]].
The colon character (""'':''"") is a [[search operator|00001007705000]], in this example to specify a match.
""syntax"" is the [[search value|00001007706000]] that must match to the value of the given metadata key, here ""title"".

id: 00001007702000
title: Search term
role: manual
tags: #manual #search #zettelstore
syntax: zmk
created: 20220805150154
modified: 20230925173539

A search term allows you to specify one search restriction.
The result [[search expression|00001007700000]], which contains more than one search term, will be the applications of all restrictions.

A search term can be one of the following (the first three term are collectively called __search literals__):
* A metadata-based search, by specifying the name of a [[metadata key|00001006010000]], followed by a [[search operator|00001007705000]], followed by an optional [[search value|00001007706000]].

  All zettel containing the given metadata key with a allowed value (depending on the search operator) are selected.

  If no search value is given, then all zettel containing the given metadata key are selected (or ignored, for a negated search operator).
* An optional [[search operator|00001007705000]], followed by a [[search value|00001007706000]].

  This specifies a full-text search for the given search value.

  However, the operators ""less"" and ""greater"" are not supported, they are internally translated into the ""match"" operators.

id: 00001007705000
title: Search operator
role: manual
tags: #manual #search #zettelstore
syntax: zmk
created: 20220805150154
modified: 20230612180539

A search operator specifies how the comparison of a search value and a zettel should be executed.
Every comparison is done case-insensitive, treating all uppercase letters the same as lowercase letters.

The following are allowed search operator characters:
* The exclamation mark character (""''!''"", U+0021) negates the meaning.
* The equal sign character (""''=''"", U+003D) compares on equal content (""equals operator"").
* The tilde character (""''~''"", U+007E) compares on matching (""match operator"").
* The left square bracket character (""''[''"", U+005B) matches if there is some prefix (""prefix operator"").
* The right square bracket character (""'']''"", U+005D) compares a suffix relationship (""suffix operator"").
* The colon character (""'':''"", U+003A) compares depending on the on the actual [[key type|00001006030000]] (""has operator"").
  In most cases, it acts as a equals operator, but for some type it acts as the match operator.
* The less-than sign character (""''<''"", U+003C) matches if the search value is somehow less then the metadata value (""less operator"").
* The greater-than sign character (""''>''"", U+003E) matches if the search value is somehow greater then the metadata value (""greater operator"").
* The question mark (""''?''"", U+003F) checks for an existing metadata key (""exist operator"").
  In this case no [[search value|00001007706000]] must be given.

Since the exclamation mark character can be combined with the other, there are 18 possible combinations:
# ""''!''"": is an abbreviation of the ""''!~''"" operator.
# ""''~''"": is successful if the search value matched the value to be compared.
# ""''!~''"": is successful if the search value does not match the value to be compared.

id: 00001007720300
title: Query: Context Directive
role: manual
tags: #manual #search #zettelstore
syntax: zmk
created: 20230707204706
modified: 20240209191045

A context directive calculates the __context__ of a list of zettel identifier.
It starts with the keyword ''CONTEXT''.

Optionally you may specify some context details, after the keyword ''CONTEXT'', separated by space characters.
These are:
* ''FULL'': additionally search for zettel with the same tags,
* ''BACKWARD'': search for context only though backward links,
* ''FORWARD'': search for context only through forward links,
* ''COST'': one or more space characters, and a positive integer: set the maximum __cost__ (default: 17),
* ''MAX'': one or more space characters, and a positive integer: set the maximum number of context zettel (default: 200).

If no ''BACKWARD'' and ''FORWARD'' is specified, a search for context zettel will be done though backward and forward links.

The cost of a context zettel is calculated iteratively:
* Each of the specified zettel hast a cost of one.
* A zettel found as a single folge zettel or single precursor zettel has the cost of the originating zettel, plus one.
* A zettel found as a single subordinate zettel or single superior zettel has the cost of the originating zettel, plus 1.2.
* A zettel found as a single successor zettel or single predecessor zettel has the cost of the originating zettel, plus seven.
* A zettel found via another link without being part of a [[set of zettel identifier|00001006032500]], has the cost of the originating zettel, plus two.
* A zettel which is part of a set of zettel identifier, has the cost of the originating zettel, plus one of the four choices above and multiplied with roughly a linear-logarithmic value based on the size of the set.
* A zettel with the same tag, has the cost of the originating zettel, plus a linear-logarithmic number based on the number of zettel with this tag.
  If a zettel belongs to more than one tag compared with the current zettel, there is a discount of 90% per additional tag.
  This only applies if the ''FULL'' directive was specified.

id: 00001007780000
title: Formal syntax of query expressions
role: manual
tags: #manual #reference #search #zettelstore
syntax: zmk
created: 20220810144539
modified: 20240219155949

```
QueryExpression   := ZettelList? QueryDirective* SearchExpression ActionExpression?
ZettelList        := (ZID (SPACE+ ZID)*).
ZID               := '0'+ ('1' .. '9'') DIGIT*
                   | ('1' .. '9') DIGIT*.
QueryDirective    := ContextDirective

                   | ('!')? ('~' | ':' | '[' | '}').
ExistOperator     := '?'
                   | '!' '?'.
PosInt            := '0'
                   | ('1' .. '9') DIGIT*.
ActionExpression  := '|' (Word (SPACE+ Word)*)?
Action            := Word
                   | 'ATOM'
                   | 'KEYS'
                   | 'N' NO-SPACE*
                   | 'MAX' PosInt
                   | 'MIN' PosInt
                   | 'REDIRECT'
                   | 'REINDEX'
                   | 'RSS'
                   | 'TITLE' (SPACE Word)* .
Word              := NO-SPACE NO-SPACE*
```

id: 00001007800000
title: Zettelmarkup: Summary of Formatting Characters
role: manual
tags: #manual #reference #zettelmarkup #zettelstore
syntax: zmk
created: 20210126175322
modified: 20231113191330

The following table gives an overview about the use of all characters that begin a markup element.

|= Character :|= [[Blocks|00001007030000]] <|= [[Inlines|00001007040000]] <
| ''!''  | (free) | (free)
| ''"''  | [[Verse block|00001007030700]] | [[Short inline quote|00001007040100]]
| ''#''  | [[Ordered list|00001007030200]] | [[marked / highlighted text|00001007040100]]
| ''$''  | (reserved) | (reserved)
| ''%''  | [[Comment block|00001007030900]] | [[Comment|00001007040000]]
| ''&''  | (free) | [[Entity|00001007040000]]
| ''\'''  | (free)  | [[Computer input|00001007040200]]
| ''(''  | (free) | (free)
| '')''  | (free) | (free)
| ''*''  | [[Unordered list|00001007030200]] | [[strongly emphasized text|00001007040100]]
| ''+''  | (free) | (free)
| '',''  | (free) | [[Sub-scripted text|00001007040100]]
| ''-''  | [[Horizontal rule|00001007030400]] | ""[[en-dash|00001007040000]]""
| ''.''  | (free) | (free)
| ''/''  | (free) | (free)
| '':''  | [[Region block|00001007030800]] / [[description text|00001007030100]] | [[Inline region|00001007040100]]
| '';''  | [[Description term|00001007030100]] | (free)
| ''<''  | [[Quotation block|00001007030600]] | (free)

id: 00001007906000
title: Zettelmarkup: Second Steps
role: manual
tags: #manual #tutorial #zettelmarkup #zettelstore
syntax: zmk
created: 20220811115501
modified: 20220926183427

After you have [[learned|00001007903000]] the basic concepts and markup of Zettelmarkup (paragraphs, emphasized text, and lists), this zettel introduces you into the concepts of links, thematic breaks, and headings.

=== Links
A Zettelstore is much more useful, if you connect related zettel.
If you read a zettel later, this allows you to know about the context of a zettel.
[[Zettelmarkup|00001007000000]] allows you to specify such a connection.
A connection can be specified within a paragraph via [[Links|00001007040310]].

* A link always starts with two left square bracket characters and ends with two right square bracket characters: ''[[...]]''.
* Within these character sequences you specify the [[zettel identifier|00001006050000]] of the zettel you want to reference: ''[[00001007903000]]'' will connect to zettel containing the first steps into Zettelmarkup.
* In addition, you should give the link a more readable description.
  This is done by prepending the description before the reference and use the vertical bar character to separate both: ''[[First Steps|00001007903000]]''.

You are not restricted to reference your zettel.
Alternatively, you might specify an URL of an external website: ''[[Zettelstore|https://zettelstore.de]]''.
Of course, if you just want to specify the URL, you are allowed to omit the description: ''[[https://zettelstore.de]]''

|= Zettelmarkup | Rendered output | Remark
| ''[[00001007903000]]'' | [[00001007903000]] | If no description is given, the zettel identifier acts as a description
| ''[[First Steps|00001007903000]]'' | [[First Steps|00001007903000]] | The description should be chosen so that you are not confused later
| ''[[https://zettelstore.de]]'' | [[https://zettelstore.de]] | A link to an external URL is rendered differently
| ''[[Zettelstore|https://zettelstore.de]]'' | [[Zettelstore|https://zettelstore.de]] | You can use any URL your browser is able to support

id: 00001008010500
title: CommonMark
role: manual
tags: #manual #markdown #zettelstore
syntax: zmk
created: 20220113183435
modified: 20221018123145
url: https://commonmark.org/

[[CommonMark|https://commonmark.org/]] is a Markdown dialect, an [[attempt|https://xkcd.com/927/]] to unify all the different, divergent dialects of Markdown by providing an unambiguous syntax specification for Markdown, together with a suite of comprehensive tests to validate implementation.

Time will show, if this attempt is successful.

However, CommonMark is a well specified Markdown dialect, in contrast to most (if not all) other dialects.
Other software adopts CommonMark somehow, notably [[GitHub Flavored Markdown|https://github.github.com/gfm/]] (GFM).
But they provide proprietary extensions, which makes it harder to change to another CommonMark implementation if needed.
Plus, they sometimes build on an older specification of CommonMark.

Zettelstore supports the latest CommonMark [[specification version 0.30 (2021-06-19)|https://spec.commonmark.org/0.30/]].
If possible, Zettelstore will adapt to newer versions when they are available.

To provide CommonMark support, Zettelstore uses currently the [[Goldmark|https://github.com/yuin/goldmark]] implementation, which passes all validation tests of CommonMark.
Internally, CommonMark is translated into some kind of super-set of [[Zettelmarkup|00001007000000]], which additionally allows to use HTML code.[^Effectively, Markdown and CommonMark are itself super-sets of HTML.]
This Zettelmarkup super-set is later [[encoded|00001012920500]], often into [[HTML|00001012920510]].
Because Zettelstore HTML encoding philosophy differs a little bit to that of CommonMark, Zettelstore itself will not pass the CommonMark test suite fully.
However, no CommonMark language element will fail to be encoded as HTML.
In most cases, the differences are not visible for an user, but only by comparing the generated HTML code.

Be aware, depending on the value of the startup configuration key [[''insecure-html''|00001004010000#insecure-html]], HTML code found within a CommonMark document or within the mentioned kind of super-set of Zettelmarkup will typically be ignored for security-related reasons.

id: 00001010000000
title: Security
role: manual
tags: #configuration #manual #security #zettelstore
syntax: zmk
created: 20210126175322
modified: 20221018123622

Your zettel could contain sensitive content.
You probably want to ensure that only authorized person can read and/or modify them.
Zettelstore ensures this in various ways.

=== Local first
The Zettelstore is designed to run on your local computer.
If you do not configure it in other ways, no person from another computer can connect to your Zettelstore.
You must explicitly configure it to allow access from other computers.

In the case that you own multiple computers, you do not have to access the Zettelstore remotely.
You could install Zettelstore on each computer and set-up some software to synchronize your zettel.
Since zettel are stored as ordinary files, this task could be done in various ways.

=== Read-only
You can start the Zettelstore in an read-only mode.
Nobody, not even you as the owner of the Zettelstore, can change something via its interfaces[^However, as an owner, you have access to the files that store the zettel. If you modify the files, these changes will be reflected via its interfaces.].

You enable read-only mode through the key ''readonly'' in the [[startup configuration zettel|00001004010000#readonly]] or with the ''-r'' option of the ``zettelstore run`` sub-command.

=== Authentication
The Zettelstore can be configured that a user must authenticate itself to gain access to the content.

* [[How to enable authentication|00001010040100]]
* [[How to add a new user|00001010040200]]
* [[How users are authenticated|00001010040400]] (some technical background)
* [[Authenticated sessions|00001010040700]]

=== Authorization
Once you have enabled authentication, it is possible to allow others to access your Zettelstore.
Maybe, others should be able to read some or all of your zettel.
Or you want to allow them to create new zettel, or to change them.
It is up to you.

If someone is authenticated as the owner of the Zettelstore (hopefully you), no restrictions apply.
But as an owner, you can create ""user zettel"" to allow others to access your Zettelstore in various ways.
Even if you do not want to share your Zettelstore with other persons, creating user zettel can be useful if you plan to access your Zettelstore via the [[API|00001012000000]].

Additionally, you can specify that a zettel is publicly visible.
In this case no one has to authenticate itself to see the content of the zettel.
Or you can specify that a zettel is visible only to the owner.
In this case, no authenticated user will be able to read and change that protected zettel.

* [[Visibility rules for zettel|00001010070200]]
* [[User roles|00001010070300]] define basic rights of an user
* [[Authorization and read-only mode|00001010070400]]
* [[Access rules|00001010070600]] define the policy which user is allowed to do what operation.

=== Encryption
When Zettelstore is accessed remotely, the messages that are sent between Zettelstore and the client must be encrypted.
Otherwise, an eavesdropper could fetch sensible data, such as passwords or precious content that is not for the public.

The Zettelstore itself does not encrypt messages.
But you can put a server in front of it, which is able to handle encryption.
Most generic web server software do allow this.

To enforce encryption, [[authenticated sessions|00001010040700]] are marked as secure by default.
If you still want to access the Zettelstore remotely without encryption, you must change the startup configuration.
Otherwise, authentication will not work.

* [[Use a server for encryption|00001010090100]]

id: 00001010040200
title: Creating an user zettel
role: manual
tags: #authentication #configuration #manual #security #zettelstore
syntax: zmk
created: 20210126175322
modified: 20221205160251

All data to be used for authenticating a user is store in a special zettel called ""user zettel"". 
A user zettel must have set the following two metadata fields:

; ''user-id'' (""user identification"")
: The unique identification to be specified for authentication.
; ''credential''
: A hashed password as generated by the [[``zettelstore password``{=sh}|00001004051400]] command.

A user zettel may additionally contain metadata that [[overwrites corresponding values|00001004020200]] of the [[runtime configuration|00001004020000]].

A user zettel can only be created by the owner of the Zettelstore.

The owner should execute the following steps to create a new user zettel:

# Create a new zettel.
# Save the zettel to get a [[identifier|00001006050000]] for this zettel.
# Choose a unique identification for the user.
#* If the identifier is not unique, authentication will not work for this user.
# Execute the [[``zettelstore password``|00001004051400]] command.
#* You have to specify the user identification and the zettel identifier
#* If you should not know the password of the new user, send her/him the user identification and the user zettel identifier, so that the person can create the hashed password herself.
# Edit the user zettel and add the hashed password under the meta key ''credential'' and the user identification under the key ''user-id''.

id: 00001010040400
title: Authentication process
role: manual
tags: #authentication #configuration #manual #security #zettelstore
syntax: zmk
created: 20210126175322
modified: 20211127174943

When someone tries to authenticate itself with an user identifier / ""user name"" and a password, the following process is executed:

# If meta key ''owner'' of the configuration zettel does not have a valid [[zettel identifier|00001006050000]] as value, authentication fails.
# Retrieve all zettel, where the meta key ''user-id'' has the same value as the given user identification. If the list is empty, authentication fails.
# From above list, the zettel with the numerically smallest identifier is selected.
  Or in other words: the oldest zettel is selected[^This is done to prevent an attacker from creating a new note with the same user identification].
# If the zettel does not have a value for the meta key ''credential'', authentication fails.
# The value of the meta key ''credential'' is compared with the given password.

id: 00001010040700
title: Access token
role: manual
tags: #authentication #configuration #manual #security #zettelstore
syntax: zmk
created: 20210126175322
modified: 20211202120950

If an user is authenticated, an ""access token"" is created that must be sent with every request to prove the identity of the caller.
Otherwise the user will not be recognized by Zettelstore.

If the user was authenticated via the [[web user interface|00001014000000]], the access token is stored in a [[""session cookie""|https://en.wikipedia.org/wiki/HTTP_cookie#Session_cookie]].
When the web browser is closed, theses cookies are not saved.
If you want web browser to store the cookie as long as lifetime of that token, the owner must set ''persistent-cookie'' of the [[startup configuration|00001004010000]] to ''true''.

If the web browser remains inactive for a period, the user will be automatically logged off, because each access token has a limited lifetime.
The maximum length of this period is specified by the ''token-lifetime-html'' value of the startup configuration.
Every time a web page is displayed, a fresh token is created and stored inside the cookie.

If the user was authenticated via the API, the access token will be returned as the content of the response.
Typically, the lifetime of this token is more short term, e.g. 10 minutes.
It is specified by the ''token-lifetime-api'' value of the startup configuration.
If you need more time, you can either [[re-authenticate|00001012050200]] the user or use an API call to [[renew the access token|00001012050400]].

If you remotely access your Zettelstore via HTTP (not via HTTPS, which allows encrypted communication), your must set the ''insecure-cookie'' value of the startup configuration to ''true''.
In most cases, such a scenario is not recommended, because user name and password will be transferred as plain text.
You could make use of such scenario if you know all parties that access the local network where you access the Zettelstore.

id: 00001010070200
title: Visibility rules for zettel
role: manual
tags: #authorization #configuration #manual #security #zettelstore
syntax: zmk
created: 20210126175322
modified: 20220923104643

For every zettel you can specify under which condition the zettel is visible to others.
This is controlled with the metadata key [[''visibility''|00001006020000#visibility]].
The following values are supported:

; [!public|""public""]
: The zettel is visible to everybody, even if the user is not authenticated.

  This is for zettel with sensitive content that might irritate the owner.
  Computed zettel with internal runtime information are examples for such a zettel.

When you install a Zettelstore, only [[some zettel|query:visibility:public]] have visibility ""public"".
One is the zettel that contains [[CSS|00000000020001]] for displaying the [[web user interface|00001014000000]].
This is to ensure that the web interface looks nice even for not authenticated users.
Another is the zettel containing the Zettelstore [[license|00000000000004]].
The [[default image|00000000040001]], used if an image reference is invalid, is also public visible.

Please note: if [[authentication is not enabled|00001010040100]], every user has the same rights as the owner of a Zettelstore.
This is also true, if the Zettelstore runs additionally in [[read-only mode|00001004010000#read-only-mode]].
In this case, the [[runtime configuration zettel|00001004020000]] is shown (its visibility is ""owner"").
The [[startup configuration|00001004010000]] is not shown, because the associated computed zettel with identifier ''00000000000096'' is stored with the visibility ""expert"".
If you want to show such a zettel, you must set ''expert-mode'' to true.

id: 00001010070400
title: Authorization and read-only mode
role: manual
tags: #authorization #configuration #manual #security #zettelstore
syntax: zmk
created: 20210126175322
modified: 20211103164251

It is possible to enable both the read-only mode of the Zettelstore __and__ authentication/authorization.
Both modes are independent from each other.
This gives four use cases:

; Not read-only, no authorization
: Zettelstore runs on your local computer and you only work with it.
; Not read-only, with authorization
: Zettelstore is accessed remotely.
  You need authentication to ensure that only valid users access your Zettelstore.
; With read-only, no authorization
: Zettelstore present publicly its full content to everybody.
; With read-only, with authorization
: Nobody is allowed to change the content of the Zettelstore, but only specific zettel should be presented to the public.

id: 00001010070600
title: Access rules
role: manual
tags: #authorization #configuration #manual #security #zettelstore
syntax: zmk
created: 20210126175322
modified: 20240708154954

Whether an operation of the Zettelstore is allowed or rejected, depends on various factors.

The following rules are checked first, in this order:

# In read-only mode, every operation except the ""Read"" operation is rejected.
# If there is no owner, authentication is disabled and every operation is allowed for everybody.

** If the zettel is the [[user zettel|00001010040200]] of the authenticated user, proceed as follows:
*** If some sensitive meta values are changed (e.g. user identifier, zettel role, user role, but not hashed password), reject the access
*** Since the user just updates some uncritical values, grant the access
   In other words: a user is allowed to change its user zettel, even if s/he has no writer privilege and if only uncritical data is changed.
** If the ''user-role'' of the user is ""reader"", reject the access.
** If the user is not allowed to create a new zettel, reject the access.
** Otherwise grant the access.
* Rename a zettel[^Renaming is deprecated. This operation will be removed in version 0.19 or later.]
** Reject the access.
   Only the owner of the Zettelstore is currently allowed to give a new identifier for a zettel.
* Delete a zettel
** Reject the access.
   Only the owner of the Zettelstore is allowed to delete a zettel.
   This may change in the future.

id: 00001012000000
title: API
role: manual
tags: #api #manual #zettelstore
syntax: zmk
created: 20210126175322
modified: 20240708154140

The API (short for ""**A**pplication **P**rogramming **I**nterface"") is the primary way to communicate with a running Zettelstore.
Most integration with other systems and services is done through the API.
The [[web user interface|00001014000000]] is just an alternative, secondary way of interacting with a Zettelstore.

=== Background
The API is HTTP-based and uses plain text and [[symbolic expressions|00001012930000]] as its main encoding formats for exchanging messages between a Zettelstore and its client software.

There is an [[overview zettel|00001012920000]] that shows the structure of the endpoints used by the API and gives an indication about its use.

=== Authentication
If [[authentication is enabled|00001010040100]], most API calls must include an [[access token|00001010040700]] that proves the identity of the caller.
* [[Authenticate an user|00001012050200]] to obtain an access token
* [[Renew an access token|00001012050400]] without costly re-authentication
* [[Provide an access token|00001012050600]] when doing an API call

=== Zettel lists
* [[List all zettel|00001012051200]]
* [[Query the list of all zettel|00001012051400]]
* [[Determine a tag zettel|00001012051600]]
* [[Determine a role zettel|00001012051800]]

=== Working with zettel
* [[Create a new zettel|00001012053200]]
* [[Retrieve metadata and content of an existing zettel|00001012053300]]
* [[Retrieve metadata of an existing zettel|00001012053400]]
* [[Retrieve evaluated metadata and content of an existing zettel in various encodings|00001012053500]]
* [[Retrieve parsed metadata and content of an existing zettel in various encodings|00001012053600]]
* [[Update metadata and content of a zettel|00001012054200]]
* [[Rename a zettel|00001012054400]] (deprecated)
* [[Delete a zettel|00001012054600]]

=== Various helper methods
* [[Retrieve administrative data|00001012070500]]
* [[Execute some commands|00001012080100]]
** [[Check for authentication|00001012080200]]
** [[Refresh internal data|00001012080500]]

id: 00001012050200
title: API: Authenticate a client
role: manual
tags: #api #manual #zettelstore
syntax: zmk
created: 20210126175322
modified: 20230412150544

Authentication for future API calls is done by sending a [[user identification|00001010040200]] and a password to the Zettelstore to obtain an [[access token|00001010040700]].
This token has to be used for other API calls.
It is valid for a relatively short amount of time, as configured with the key ''token-lifetime-api'' of the [[startup configuration|00001004010000#token-lifetime-api]] (typically 10 minutes).

The simplest way is to send user identification (''IDENT'') and password (''PASSWORD'') via [[HTTP Basic Authentication|https://tools.ietf.org/html/rfc7617]] and send them to the [[endpoint|00001012920000]] ''/a'' with a POST request:
```sh

If you do not want to use Basic Authentication, you can also send user identification and password as HTML form data:
```sh
# curl -X POST -d 'username=IDENT&password=PASSWORD' http://127.0.0.1:23123/a
("Bearer" "eyJhbGciOiJIUzUxMiJ9.eyJfdGsiOjEsImV4cCI6MTY4MTMwNDA4OCwiaWF0IjoxNjgxMzA0MDI4LCJzdWIiOiJvd25lciIsInppZCI6IjIwMjEwNjI5MTYzMzAwIn0.qIEyOMFXykCApWtBaqbSESwTL96stWl2LRICiRNAXUjcY-mwx_SSl9L5Fj2FvmrI1K1RBvWehjoq8KZUNjhJ9Q" 600)
```

In all cases, you will receive a list with three elements that will contain all [[relevant data|00001012921000]] to be used for further API calls.

**Important:** obtaining a token is a time-intensive process.
Zettelstore will delay every request to obtain a token for a certain amount of time.
Please take into account that this request will take approximately 500 milliseconds, under certain circumstances more.

However, if [[authentication is not enabled|00001010040100]] and you send an authentication request, no user identification/password checking is done and you receive an artificial token immediate, without any delay:

```sh
# curl -X POST -u IDENT:PASSWORD http://127.0.0.1:23123/a
("Bearer" "freeaccess" 316224000)
```

In this case, it is even possible to omit the user identification/password.

=== HTTP Status codes
In all cases of successful authentication, a list is returned, which contains the token as the second element.
A successful authentication is signaled with the HTTP status code 200, as usual.

Other status codes possibly send by the Zettelstore:
; ''400''
: Unable to process the request.
  In most cases the form data was invalid.
; ''401''
: Authentication failed.
  Either the user identification is invalid or you provided the wrong password.
; ''403''
: Authentication is not active.

id: 00001012051200
title: API: List all zettel
role: manual
tags: #api #manual #zettelstore
syntax: zmk
created: 20210126175322
modified: 20230807170810

To list all zettel just send a HTTP GET request to the [[endpoint|00001012920000]] ''/z''[^If [[authentication is enabled|00001010040100]], you must include the a valid [[access token|00001012050200]] in the ''Authorization'' header].
Always use the endpoint ''/z'' to work with a list of zettel.

Without further specifications, a plain text document is returned, with one line per zettel.
Each line contains in the first 14 characters the [[zettel identifier|00001006050000]].
Separated by a space character, the title of the zettel follows:

```sh

id: 00001012051400
title: API: Query the list of all zettel
role: manual
tags: #api #manual #zettelstore
syntax: zmk
created: 20220912111111
modified: 20240711161320
precursor: 00001012051200

The [[endpoint|00001012920000]] ''/z'' also allows you to filter the list of all zettel[^If [[authentication is enabled|00001010040100]], you must include the a valid [[access token|00001012050200]] in the ''Authorization'' header] and optionally to provide some actions.

A [[query|00001007700000]] is an optional [[search expression|00001007700000#search-expression]], together with an optional [[list of actions|00001007700000#action-list]] (described below).
An empty search expression will select all zettel.
An empty list of action, or no valid action, returns the list of all selected zettel metadata.

Search expression and action list are separated by a vertical bar character (""''|''"", U+007C), and must be given with the query parameter ''q''.

id: 00001012053300
title: API: Retrieve metadata and content of an existing zettel
role: manual
tags: #api #manual #zettelstore
syntax: zmk
created: 20211004093206
modified: 20230807170259

The [[endpoint|00001012920000]] to work with metadata and content of a specific zettel is ''/z/{ID}'', where ''{ID}'' is a placeholder for the [[zettel identifier|00001006050000]].

For example, to retrieve some data about this zettel you are currently viewing, just send a HTTP GET request to the endpoint ''/z/00001012053300''[^If [[authentication is enabled|00001010040100]], you must include the a valid [[access token|00001012050200]] in the ''Authorization'' header].

````sh
# curl 'http://127.0.0.1:23123/z/00001012053300'
The [[endpoint|00001012920000]] to work with metadata and content of a specific zettel is ''/z/{ID}'', where ''{ID}'' is a placeholder for the [[zettel identifier|00001006050000]].

For example, to retrieve some data about this zettel you are currently viewing, just send a HTTP GET request to the endpoint ''/z/00001012053300''[^If [[authentication is enabled|00001010040100]], you must include the a valid [[access token|00001012050200]] in the ''Authorization'' header].

```sh
...
````

Optionally, you may provide which parts of the zettel you are requesting.
In this case, add an additional query parameter ''part=PART''.

id: 00001012053400
title: API: Retrieve metadata of an existing zettel
role: manual
tags: #api #manual #zettelstore
syntax: zmk
created: 20210726174524
modified: 20230807170155

The [[endpoint|00001012920000]] to work with metadata of a specific zettel is ''/z/{ID}'', where ''{ID}'' is a placeholder for the [[zettel identifier|00001006050000]][^If [[authentication is enabled|00001010040100]], you must include the a valid [[access token|00001012050200]] in the ''Authorization'' header].

To retrieve the plain metadata of a zettel, use the query parameter ''part=meta''

````sh
# curl 'http://127.0.0.1:23123/z/00001012053400?part=meta'
title: API: Retrieve metadata of an existing zettel
role: manual

id: 00001012053500
title: API: Retrieve evaluated metadata and content of an existing zettel in various encodings
role: manual
tags: #api #manual #zettelstore
syntax: zmk
created: 20210726174524
modified: 20240620171057

The [[endpoint|00001012920000]] to work with evaluated metadata and content of a specific zettel is ''/z/{ID}'', where ''{ID}'' is a placeholder for the [[zettel identifier|00001006050000]].

For example, to retrieve some evaluated data about this zettel you are currently viewing in [[Sz encoding|00001012920516]], just send a HTTP GET request to the endpoint ''/z/00001012053500''[^If [[authentication is enabled|00001010040100]], you must include the a valid [[access token|00001012050200]] in the ''Authorization'' header] with the query parameter ''enc=sz''.
If successful, the output is a symbolic expression value:
```sh
# curl 'http://127.0.0.1:23123/z/00001012053500?enc=sz'
(BLOCK (PARA (TEXT "The ") (LINK-ZETTEL () "00001012920000" (TEXT "endpoint")) (TEXT " to work with parsed metadata and content of a specific zettel is ") (LITERAL-INPUT () "/z/{ID}") (TEXT ", where ") (LITERAL-INPUT () "{ID}") (TEXT " is a placeholder for the ") ...
```

To select another encoding, you must provide the query parameter ''enc=ENCODING''.

id: 00001012053600
title: API: Retrieve parsed metadata and content of an existing zettel in various encodings
role: manual
tags: #api #manual #zettelstore
syntax: zmk
created: 20210126175322
modified: 20240620170909

The [[endpoint|00001012920000]] to work with parsed metadata and content of a specific zettel is ''/z/{ID}'', where ''{ID}'' is a placeholder for the [[zettel identifier|00001006050000]].

A __parsed__ zettel is basically an [[unevaluated|00001012053500]] zettel: the zettel is read and analyzed, but its content is not __evaluated__.
By using this endpoint, you are able to retrieve the structure of a zettel before it is evaluated.

For example, to retrieve some data about this zettel you are currently viewing, just send a HTTP GET request to the endpoint ''/z/00001012053600''[^If [[authentication is enabled|00001010040100]], you must include the a valid [[access token|00001012050200]] in the ''Authorization'' header] with the query parameter ''parseonly'' (and other appropriate query parameter).
For example:
```sh
# curl 'http://127.0.0.1:23123/z/00001012053600?enc=sz&parseonly'
(BLOCK (PARA (TEXT "The ") (LINK-ZETTEL () "00001012920000" (TEXT "endpoint")) (TEXT " to work with parsed metadata and content of a specific zettel is ") (LITERAL-INPUT () "/z/{ID}") (TEXT ", where ") ...
```

Similar to [[retrieving an encoded zettel|00001012053500]], you can specify an [[encoding|00001012920500]] and state which [[part|00001012920800]] of a zettel you are interested in.

id: 00001012054400
title: API: Rename a zettel
role: manual
tags: #api #manual #zettelstore #deprecated
syntax: zmk
created: 20210713150005
modified: 20240708154151

**Note:** this operation is deprecated and will be removed in version 0.19 (or later).
Do not use it anymore.

If your client application depends on this operation, please get in contact with the [[author/maintainer|00000000000005]] of Zettelstore to find a solution.

---
**Deprecated**

Renaming a zettel is effectively just specifying a new identifier for the zettel.
Since more than one [[box|00001004011200]] might contain a zettel with the old identifier, the rename operation must success in every relevant box to be overall successful.
If the rename operation fails in one box, Zettelstore tries to rollback previous successful operations.

As a consequence, you cannot rename a zettel when its identifier is used in a read-only box.
This applies to all [[predefined zettel|00001005090000]], for example.

The [[endpoint|00001012920000]] to rename a zettel is ''/z/{ID}'', where ''{ID}'' is a placeholder for the [[zettel identifier|00001006050000]].
You must send a HTTP MOVE request to this endpoint, and you must specify the new zettel identifier as an URL, placed under the HTTP request header key ''Destination''.
```
# curl -X MOVE -H "Destination: 10000000000001" http://127.0.0.1:23123/z/00001000000000
```

Only the last 14 characters of the value of ''Destination'' are taken into account and those must form an unused [[zettel identifier|00001006050000]].
If the value contains less than 14 characters that do not form an unused zettel identifier, the response will contain a HTTP status code ''400''.
All other characters, besides those 14 digits, are effectively ignored.
However, the value should form a valid URL that could be used later to [[read the content|00001012053300]] of the freshly renamed zettel.

=== HTTP Status codes
; ''204''
: Rename was successful, there is no body in the response.
; ''400''
: Request was not valid.
  For example, the HTTP header did not contain a valid ''Destination'' key, or the new identifier is already in use.
; ''403''
: You are not allowed to delete the given zettel.
  In most cases you have either not enough [[access rights|00001010070600]] or at least one box containing the given identifier operates in read-only mode.
; ''404''
: Zettel not found.
  You probably used a zettel identifier that is not used in the Zettelstore.

=== Rationale for the MOVE method
HTTP [[standardizes|https://www.rfc-editor.org/rfc/rfc7231.txt]] eight methods.
None of them is conceptually close to a rename operation.

Everyone is free to ""invent"" some new method to be used in HTTP.
To avoid a divergency, there is a [[methods registry|https://www.iana.org/assignments/http-methods/]] that tracks those extensions.
The [[HTTP Extensions for Web Distributed Authoring and Versioning (WebDAV)|https://www.rfc-editor.org/rfc/rfc4918.txt]] defines the method MOVE that is quite close to the desired rename operation.
In fact, some command line tools use a ""move"" method for renaming files.

Therefore, Zettelstore adopts somehow WebDAV's MOVE method and its use of the ''Destination'' HTTP header key.

id: 00001012080200
title: API: Check for authentication
role: manual
tags: #api #manual #zettelstore
syntax: zmk
created: 20220103224858
modified: 20220908163156

API clients typically wants to know, whether [[authentication is enabled|00001010040100]] or not.
If authentication is enabled, they present some form of user interface to get user name and password for the actual authentication.
Then they try to [[obtain an access token|00001012050200]].
If authentication is disabled, these steps are not needed.

To check for enabled authentication, you must send a HTTP POST request to the [[endpoint|00001012920000]] ''/x'' and you must specify the query parameter ''cmd=authenticated''.

```sh

id: 00001012080500
title: API: Refresh internal data
role: manual
tags: #api #manual #zettelstore
syntax: zmk
created: 20211230230441
modified: 20220923104836

Zettelstore maintains some internal data to allow faster operations.

One example is the [[content search|00001012051400]] for a term: Zettelstore does not need to scan all zettel to find all occurrences for the term.
Instead, all word are stored internally, with a list of zettel where they occur.

Another example is the way to determine which zettel are stored in a [[ZIP file|00001004011200]].
Scanning a ZIP file is a lengthy operation, therefore Zettelstore maintains a directory of zettel for each ZIP file.

All these internal data may become stale.
This should not happen, but when it comes e.g. to file handling, every operating systems behaves differently in very subtle ways.

To avoid stopping and re-starting Zettelstore, you can use the API to force Zettelstore to refresh its internal data if you think it is needed.
To do this, you must send a HTTP POST request to the [[endpoint|00001012920000]] ''/x'' and you must specify the query parameter ''cmd=refresh''.

```sh
# curl -X POST 'http://127.0.0.1:23123/x?cmd=refresh'
```

id: 00001012920000
title: Endpoints used by the API
role: manual
tags: #api #manual #reference #zettelstore
syntax: zmk
created: 20210126175322
modified: 20240708155042

All API endpoints conform to the pattern ''[PREFIX]LETTER[/ZETTEL-ID]'', where:
; ''PREFIX''
: is the URL prefix (default: ""/""), configured via the ''url-prefix'' [[startup configuration|00001004010000]],
; ''LETTER''
: is a single letter that specifies the resource type,
; ''ZETTEL-ID''
: is an optional 14 digits string that uniquely [[identify a zettel|00001006050000]].

The following letters are currently in use:

|= Letter:| Without zettel identifier | With [[zettel identifier|00001006050000]] | Mnemonic
| ''a'' | POST: [[client authentication|00001012050200]] | | **A**uthenticate
|       | PUT: [[renew access token|00001012050400]] |
| ''x'' | GET: [[retrieve administrative data|00001012070500]] | | E**x**ecute
|       | POST: [[execute command|00001012080100]]
| ''z'' | GET: [[list zettel|00001012051200]]/[[query zettel|00001012051400]] | GET: [[retrieve zettel|00001012053300]] | **Z**ettel
|       | POST: [[create new zettel|00001012053200]] | PUT: [[update zettel|00001012054200]]
|       |  | DELETE: [[delete zettel|00001012054600]]
|       |  | MOVE: [[rename zettel|00001012054400]][^Renaming a zettel is deprecated and will be removed in version 0.19 or later.]

The full URL will contain either the ""http"" oder ""https"" scheme, a host name, and an optional port number.

The API examples will assume the ""http"" schema, the local host ""127.0.0.1"", the default port ""23123"", and the default empty ''PREFIX'' ""/"".
Therefore, all URLs in the API documentation will begin with ""http://127.0.0.1:23123/"".

id: 00001012920516
title: Sz Encoding
role: manual
tags: #api #manual #reference #zettelstore
syntax: zmk
created: 20220422181104
modified: 20230403161458

A zettel representation that is a [[s-expression|00001012930000]] (also known as symbolic expression).

It is (relatively) easy to parse and contain all relevant information of a zettel, metadata and content.
For example, take a look at the Sz encoding of this page, which is available via the ""Info"" sub-page of this zettel: 

* [[//z/00001012920516?enc=sz&part=zettel]],
* [[//z/00001012920516?enc=sz&part=meta]],
* [[//z/00001012920516?enc=sz&part=content]].

Some zettel describe the [[Sz encoding|00001012931000]] in a more detailed way.

If transferred via HTTP, the content type will be ''text/plain''.

id: 00001012920525
title: SHTML Encoding
role: manual
tags: #api #manual #reference #zettelstore
syntax: zmk
created: 20230316181044
modified: 20230403150657

A zettel representation that is a [[s-expression|00001012930000]], syntactically similar to the [[Sz encoding|00001012920516]], but denotes [[HTML|00001012920510]] semantics.
It is derived from a XML encoding in s-expressions, called [[SXML|https://en.wikipedia.org/wiki/SXML]].

It is (relatively) easy to parse and contains everything to transform it into real HTML.
In contrast to HTML, SHTML is easier to parse and to manipulate.
For example, take a look at the SHTML encoding of this page, which is available via the ""Info"" sub-page of this zettel: 

Internally, if a zettel should be transformed into HTML, the zettel is translated into the [[Sz encoding|00001012920516]], which is transformed into this SHTML encoding to produce the [[HTML encoding|00001012920510]].

=== Syntax of SHTML
There are only two types of elements: atoms and lists, similar to the Sz encoding.

A list always starts with the left parenthesis (""''(''"", U+0028) and ends with a right parenthesis (""'')''"", U+0029).
A list may contain a possibly empty sequence of elements, i.e. lists and / or atoms.
Before the last element of a list of at least to elements, a full stop character (""''.''"", U+002E) signal a pair as the last two elements.
This allows a more space economic storage of data.

An HTML tag like ``< a href="link">Text</a>`` is encoded in SHTML with a list, where the first element is a symbol named a the tag.
The second element is an optional encoding of the tag's attributes.
Further elements are either other tag encodings or a string.
The above tag is encoded as ``(a (@ (href . "link")) "Text")``.
Also possible is to encode the attribute without pairs: ``(a (@ (href "link")) "Text")`` (note the missing full stop character).

id: 00001012921200
title: API: Encoding of Zettel Access Rights
role: manual
tags: #api #manual #reference #zettelstore
syntax: zmk
created: 20220201173115
modified: 20240708155122

Various API calls return a symbolic expression list ''(rights N)'', with ''N'' as a number, that encodes the access rights the user currently has.
''N'' is an integer number between 0 and 62.[^Not all values in this range are used.]

The value ""0"" signals that something went wrong internally while determining the access rights.

A value of ""1"" says, that the current user has no access right for the given zettel.
In most cases, this value will not occur, because only zettel are presented, which are at least readable by the current user.

Values ""2"" to ""62"" are binary encoded values, where each bit signals a special right.

|=Bit number:|Bit value:|Meaning
| 1 |  2 | User is allowed to create a new zettel
| 2 |  4 | User is allowed to read the zettel
| 3 |  8 | User is allowed to update the zettel
| 4 | 16 | User is allowed to rename the zettel[^Renaming a zettel is deprecated and will be removed in version 0.19 or later.]
| 5 | 32 | User is allowed to delete the zettel

The algorithm to calculate the actual access rights from the value is relatively simple:
# Search for the biggest bit value that is less than the rights value.
  This is an access right for the current user.
# Subtract the bit value from the rights value.
  Remember the difference as the new rights value.

id: 00001012930500
title: Syntax of Symbolic Expressions
role: manual
tags: #manual #reference #zettelstore
syntax: zmk
created: 20230403151127
modified: 20240413160345

=== Syntax of lists
A list always starts with the left parenthesis (""''(''"", U+0028) and ends with a right parenthesis (""'')''"", U+0029).
A list may contain a possibly empty sequence of elements, i.e. lists and / or atoms.

Internally, lists are composed of __cells__.
A cell allows to store two values.

=== Syntax of numbers (atom)
A number is a non-empty sequence of digits (""0"" ... ""9"").
The smallest number is ``0``, there are no negative numbers.

=== Syntax of symbols (atom)
A symbol is a non-empty sequence of printable characters, except left or right parenthesis.
Unicode characters of the following categories contains printable characters in the above sense: letter (L), number (N), punctuation (P), symbol (S).
Symbols are case-sensitive, i.e. ""''ZETTEL''"" and ""''zettel''"" denote different symbols.

=== Syntax of string (atom)

A string starts with a quotation mark (""''"''"", U+0022), contains a possibly empty sequence of Unicode characters, and ends with a quotation mark.
To allow a string to contain a quotations mark, it must be prefixed by one backslash (""''\\''"", U+005C).
To allow a string to contain a backslash, it also must be prefixed by one backslash.
Unicode characters with a code less than U+FF are encoded by by the sequence ""''\\xNM''"", where ''NM'' is the hex encoding of the character.
Unicode characters with a code less than U+FFFF are encoded by by the sequence ""''\\uNMOP''"", where ''NMOP'' is the hex encoding of the character.
Unicode characters with a code less than U+FFFFFF are encoded by by the sequence ""''\\UNMOPQR''"", where ''NMOPQR'' is the hex encoding of the character.
In addition, the sequence ""''\\t''"" encodes a horizontal tab (U+0009), the sequence ""''\\n''"" encodes a line feed (U+000A).

=== See also
* Currently, Zettelstore uses [[Sx|https://t73f.de/r/sx]] (""Symbolic eXpression framework"") to implement symbolic expressions.
  The project page might contain additional information about the full syntax.

  Zettelstore only uses lists, numbers, string, and symbols to represent zettel.

id: 00001012931000
title: Encoding of Sz
role: manual
tags: #api #manual #reference #zettelstore
syntax: zmk
created: 20230403153903
modified: 20240123120319

Zettel in a [[Sz encoding|00001012920516]] are represented as a [[symbolic expression|00001012930000]].
To process these symbolic expressions, you need to know, how a specific part of a zettel is represented by a symbolic expression.

Basically, each part of a zettel is represented as a list, often a nested list.
The first element of that list is always an unique symbol, which denotes that part.
The meaning / semantic of all other elements depend on that symbol.

=== Zettel
A full zettel is represented by a list of two elements.
The first elements represents the metadata, the second element represents the zettel content.

:::syntax

id: 00001012931400
title: Encoding of Sz Block Elements
role: manual
tags: #api #manual #reference #zettelstore
syntax: zmk
created: 20230403161803
modified: 20240123120132

=== ''PARA''
:::syntax
__Paragraph__ **=** ''(PARA'' [[__InlineElement__|00001012931600]] … '')''.
:::
A paragraph is just a list of inline elements.

:::
A list element is either a block or an inline.
If it is a block, it may contain a nested list.
=== ''DESCRIPTION''
:::syntax
__Description__ **=** ''(DESCRIPTION'' __DescriptionTerm__ __DescriptionValues__ __DescriptionTerm__ __DescriptionValues__ … '')''.
:::
A description is a sequence of one ore more terms and values.

:::syntax
__DescriptionTerm__ **=** ''('' [[__InlineElement__|00001012931600]] … '')''.
:::
A description term is just an inline-structured value.

:::syntax

Attributes may further specify the quotation.
The inline typically describes author / source of the quotation.

:::syntax
__VerseRegion__ **=** ''(REGION-VERSE'' [[__Attributes__|00001012931000#attribute]] ''('' [[__BlockElement__|00001012931400]] … '')'' [[__InlineElement__|00001012931600]] … '')''.
:::
A block region just treats the block to contain a verse.
Soft line break are transformed into hard line breaks to save the structure of the verse / poem.
Attributes may further specify something.
The inline typically describes author / source of the verse.

=== ''VERBATIM-*''
The following lists specifies some literal text of more than one line.
The structure is always the same, the initial symbol denotes the actual usage.
The content is encoded as a string, most likely to contain control characters that signals the end of a line.

id: 00001012931600
title: Encoding of Sz Inline Elements
role: manual
tags: #api #manual #reference #zettelstore
syntax: zmk
created: 20230403161845
modified: 20240620170546

=== ''TEXT''
:::syntax
__Text__ **=** ''(TEXT'' String '')''.
:::
Specifies the string as some text content, including white space characters.

=== ''EMBED-BLOB''
:::syntax
__EmbedBLOB__ **=** ''(EMBED-BLOB'' [[__Attributes__|00001012931000#attribute]] String,,1,, String,,2,, '')''.
:::
If used if some processed image has to be embedded inside some inline material.
The first string specifies the syntax of the image content.
The second string contains the image content.
If the syntax is ""SVG"", the image content is not further encoded.
Otherwise a base64 encoding is used.

=== ''CITE''
:::syntax
__CiteBLOB__ **=** ''(CITE'' [[__Attributes__|00001012931000#attribute]] String [[__InlineElement__|00001012931600]] … '')''.
:::
The string contains the citation key.

__InsertFormat__ **=** ''(FORMAT-INSERT'' [[__Attributes__|00001012931000#attribute]] [[__InlineElement__|00001012931600]] … '')''.
:::
The inline text should be treated as inserted.

:::syntax
__MarkFormat__ **=** ''(FORMAT-MARK'' [[__Attributes__|00001012931000#attribute]] [[__InlineElement__|00001012931600]] … '')''.
:::
The inline text should be treated as highlighted for the reader (but was not important fto the original author).

:::syntax
__QuoteFormat__ **=** ''(FORMAT-QUOTE'' [[__Attributes__|00001012931000#attribute]] [[__InlineElement__|00001012931600]] … '')''.
:::
The inline text should be treated as quoted text.

:::syntax

__HTMLLiteral__ **=** ''(LITERAL-HTML'' [[__Attributes__|00001012931000#attribute]] String '')''.
:::
The string contains text that should be treated as HTML code.

:::syntax
__InputLiteral__ **=** ''(LITERAL-INPUT'' [[__Attributes__|00001012931000#attribute]] String '')''.
:::
The string contains text that should be treated as input entered by an user.

:::syntax
__MathLiteral__ **=** ''(LITERAL-MATH'' [[__Attributes__|00001012931000#attribute]] String '')''.
:::
The string contains text that should be treated as special code to be interpreted as mathematical formulas.

:::syntax
__OutputLiteral__ **=** ''(LITERAL-OUTPUT'' [[__Attributes__|00001012931000#attribute]] String '')''.
:::
The string contains text that should be treated as computer output to be read by an user.

:::syntax
__ZettelLiteral__ **=** ''(LITERAL-ZETTEL'' [[__Attributes__|00001012931000#attribute]] String '')''.
:::
The string contains text that should be treated as (nested) zettel content.

id: 00001012931900
title: Encoding of Sz Reference Values
role: manual
tags: #api #manual #reference #zettelstore
syntax: zmk
created: 20230405123046
modified: 20240122094720

A reference is encoded as the actual reference value, and a symbol describing the state of that actual reference value.

:::syntax
__Reference__ **=** ''('' __ReferenceState__ String '')''.
:::
The string contains the actual reference value.

  This value is only possible before evaluating the zettel.
; ''SELF''
: The reference value is a reference to the same zettel, to a specific mark.
; ''FOUND''
: The reference value is a valid reference to an existing zettel.
  This value is only possible after evaluating the zettel.
; ''BROKEN''
: The reference value is a valid reference to an missing zettel.
  This value is only possible after evaluating the zettel.
; ''HOSTED''
: The reference value starts with one slash character, denoting an absolute local reference.
; ''BASED''
: The reference value starts with two slash characters, denoting a local reference interpreted relative to the Zettelstore base URL.
; ''QUERY''
: The reference value contains a query expression.
; ''EXTERNAL''
: The reference value contains a full URL, referencing a resource outside of the Zettelstore server.

id: 00001017000000
title: Tips and Tricks
role: manual
tags: #manual #zettelstore
syntax: zmk
created: 20220803170112
modified: 20231012154803

=== Welcome Zettel
* **Problem:** You want to put your Zettelstore into the public and need a starting zettel for your users.
  In addition, you still want a ""home zettel"", with all your references to internal, non-public zettel.
  Zettelstore only allows to specify one [[''home-zettel''|00001004020000#home-zettel]].
* **Solution 1:**
*# Create a new zettel with all your references to internal, non-public zettel.
   Let's assume this zettel receives the zettel identifier ''20220803182600''.
*# Create the zettel that should serve as the starting zettel for your users.
   It must have syntax [[Zettelmarkup|00001008000000#zmk]], i.e. the syntax metadata must be set to ''zmk''.
   If needed, set the runtime configuration [[''home-zettel|00001004020000#home-zettel]] to the value of the identifier of this zettel.
*# At the beginning of the start zettel, add the following [[Zettelmarkup|00001007000000]] text in a separate paragraph: ``{{{20220803182600}}}`` (you have to adapt to the actual value of the zettel identifier for your non-public home zettel).
* **Discussion:** As stated in the description for a [[transclusion|00001007031100]], a transclusion will be ignored, if the transcluded zettel is not visible to the current user.
  In effect, the transclusion statement (above paragraph that contained ''{{{...}}}'') is ignored when rendering the zettel.
* **Solution 2:** Set a user-specific value by adding metadata ''home-zettel'' to the [[user zettel|00001010040200]].
* **Discussion:** A value for ''home-zettel'' is first searched in the user zettel of the current authenticated user.
  Only if it is not found, the value is looked up in the runtime configuration zettel.
  If multiple user should use the same home zettel, its zettel identifier must be set in all relevant user zettel.

  In general, the mapping must follow the pattern: ``(ROLE . ID)``, where ''ROLE'' is the placeholder for the role, and ''ID'' for the zettel identifier containing CSS code.
  For example, if you also want the role ""configuration"" to be rendered using that CSS, the code should be something like ``(set! CSS-ROLE-map '(("zettel" . "20220825200100") ("configuration" . "20220825200100")))``.
* **Discussion:** you have to ensure that the CSS zettel is allowed to be read by the intended audience of the zettel with that given role.
  For example, if you made zettel with a specific role public visible, the CSS zettel must also have a [[''visibility: public''|00001010070200]] metadata.

=== Zettel synchronization with iCloud (Apple)
* **Problem:** You use Zettelstore on various macOS computers and you want to use the sameset of zettel across all computers.
* **Solution:** Place your zettel in an iCloud folder.

  To configure Zettelstore to use the folder, you must specify its location within you directory structure as [[''box-uri-X''|00001004010000#box-uri-x]] (replace ''X'' with an appropriate number).
  Your iCloud folder is typically placed in the folder ''~/Library/Mobile Documents/com~apple~CloudDocs''.
  The ""''~''"" is a shortcut and specifies your home folder.

  Unfortunately, Zettelstore does not yet support this shortcut.
  Therefore you must replace it with the absolute name of your home folder.
  In addition, a space character is not allowed in an URI.
  You have to replace it with the sequence ""''%20''"".

  Let us assume, that you stored your zettel box inside the folder ""zettel"", which is located top-level in your iCloud folder.
  In this case, you must specify the following box URI within the startup configuration: ''box-uri-1: dir:///Users/USERNAME/Library/Mobile%20Documents/com~apple~CloudDocs/zettel'', replacing ''USERNAME'' with the username of that specific computer (and assuming you want to use it as the first box).
* **Solution 2:** If you typically start your Zettelstore on the command line, you could use the ''-d DIR'' option for the [[''run''|00001004051000#d]] sub-command.
  In this case you are allowed to use the character ""''~''"".

  ''zettelstore run -d ~/Library/Mobile\\ Documents/com\\~apple\\~CloudDocs/zettel''

  (The ""''\\''"" is needed by the command line processor to mask the following character to be processed in unintended ways.)
* **Discussion:** Zettel files are synchronized between your computers via iCloud.
  Is does not matter, if one of your computer is offline / switched off.
  iCloud will synchronize the zettel files if it later comes online.

  However, if you use more than one computer simultaneously, you must be aware that synchronization takes some time.
  It might take several seconds, maybe longer, that new new version of a zettel appears on the other computer.
  If you update the same zettel on multiple computers at nearly the same time, iCloud will not be able to synchronize the different versions in a safe manner.
  Zettelstore is intentionally not aware of any synchronization within its zettel boxes.

  If Zettelstore behaves strangely after a synchronization took place, the page about [[Troubleshooting|00001018000000#working-with-files]] might contain some useful information.

id: 00001018000000
title: Troubleshooting
role: manual
tags: #manual #zettelstore
syntax: zmk
created: 20211027105921
modified: 20240221134749

This page lists some problems and their solutions that may occur when using your Zettelstore.

=== Installation
* **Problem:** When you double-click on the Zettelstore executable icon, macOS complains that Zettelstore is an application from an unknown developer.
  Therefore, it will not start Zettelstore.
** **Solution:** Press the ''Ctrl'' key while opening the context menu of the Zettelstore executable with a right-click.
   A dialog is then opened where you can acknowledge that you understand the possible risks when you start Zettelstore.
   This dialog is only resented once for a given Zettelstore executable.
* **Problem:** When you double-click on the Zettelstore executable icon, Windows complains that Zettelstore is an application from an unknown developer.
** **Solution:** Windows displays a dialog where you can acknowledge possible risks and allows to start Zettelstore.

=== Authentication
* **Problem:** [[Authentication is enabled|00001010040100]] for a local running Zettelstore and there is a valid [[user zettel|00001010040200]] for the owner.
  But entering user name and password at the [[web user interface|00001014000000]] seems to be ignored, while entering a wrong password will result in an error message.
** **Explanation:** A local running Zettelstore typically means, that you are accessing the Zettelstore using an URL with schema ''http://'', and not ''https://'', for example ''http://localhost:23123''.
   The difference between these two is the missing encryption of user name / password and for the answer of the Zettelstore if you use the ''http://'' schema.
   To be secure by default, the Zettelstore will not work in an insecure environment.
** **Solution 1:** If you are sure that your communication medium is safe, even if you use the ''http:/\/'' schema (for example, you are running the Zettelstore on the same computer you are working on, or if the Zettelstore is running on a computer in your protected local network), then you could add the entry ''insecure-cookie: true'' in you [[startup configuration|00001004010000#insecure-cookie]] file.
** **Solution 2:** If you are not sure about the security of your communication medium (for example, if unknown persons might use your local network), then you should run an [[external server|00001010090100]] in front of your Zettelstore to enable the use of the ''https://'' schema.

=== Working with Zettel Files
* **Problem:** When you delete a zettel file by removing it from the ""disk"", e.g. by dropping it into the trash folder, by dragging into another folder, or by removing it from the command line, Zettelstore sometimes did not detect that change.
  If you access the zettel via Zettelstore, an error is reported.
** **Explanation:** Sometimes, the operating system does not tell Zettelstore about the removed zettel.
   This occurs mostly under MacOS.
** **Solution 1:** If you are running Zettelstore in [[""simple-mode""|00001004051100]] or if you have enabled [[''expert-mode''|00001004020000#expert-mode]], you are allowed to refresh the internal data by selecting ""Refresh"" in the Web User Interface (you find it in the menu ""Lists"").
** **Solution 2:** There is an [[API|00001012080500]] call to make Zettelstore aware of this change.
** **Solution 3:** If you have an enabled [[Administrator Console|00001004100000]] you can use the command [[''refresh''|00001004101000#refresh]] to make your changes visible.
** **Solution 4:** You configure the zettel box as [[""simple""|00001004011400]].

=== HTML content is not shown
* **Problem:** You have entered some HTML code as content for your Zettelstore, but this content is not shown on the Web User Interface.

  You may have entered a Zettel with syntax [[""html""|00001008000000#html]], or you have used an [[inline-zettel block|00001007031200]] with syntax ""html"", or you entered a Zettel with syntax [[""markdown""|00001008000000#markdown]] (or ""md"") and used some HTML code fragments.
** **Explanation:** Working with HTML code from unknown sources may lead so severe security problems.
   The HTML code may force web browsers to load more content from external server, it may contain malicious JavaScript code, it may reference to CSS artifacts that itself load from external servers and may contains malicious software.
   Zettelstore tries to do its best to ignore problematic HTML code, but it may fail.
   Either because of unknown bugs or because of yet unknown changes in the future.

   Zettelstore sets a restrictive [[Content Security Policy|https://www.w3.org/TR/CSP/]], but this depends on web browsers to implement them correctly and on users to not disable it.
   Zettelstore will not display any HTML code, which contains a ``<script>>`` or an ``<iframe>`` tag.
   But attackers may find other ways to deploy their malicious code.

   Therefore, Zettelstore disallows any HTML content as a default.
   If you know what you are doing, e.g. because you will never copy HTML code you do not understand, you can relax this default.
** **Solution 1:** If you want zettel with syntax ""html"" not to be ignored, you set the startup configuration key [[''insecure-html''|00001004010000#insecure-html]] to the value ""html"".
** **Solution 2:** If you want zettel with syntax ""html"" not to be ignored, **and** want to allow HTML in Markdown, you set the startup configuration key [[''insecure-html''|00001004010000#insecure-html]] to the value ""markdown"".
** **Solution 3:** If you want zettel with syntax ""html"" not to be ignored, **and** want to allow HTML in Markdown, **and** want to use HTML code within Zettelmarkup, you set the startup configuration key [[''insecure-html''|00001004010000#insecure-html]] to the value ""zettelmarkup"".