//-----------------------------------------------------------------------------
// Copyright (c) 2021-present Detlef Stern
//
// This file is part of zettelstore-client.
//
// Zettelstore client 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 api contains common definitions used for client and server.
package api



import "t73f.de/r/zsc/domain/id"

















// ZettelMeta is a map containg the normalized metadata of a zettel.
type ZettelMeta map[string]string

// ZettelRights is an integer that encode access rights for a zettel.
type ZettelRights uint8

// Values for ZettelRights, can be or-ed
const (
	ZettelCanNone   ZettelRights = 1 << iota
	ZettelCanCreate              // Current user is allowed to create a new zettel
	ZettelCanRead                // Requesting user is allowed to read the zettel
	ZettelCanWrite               // Requesting user is allowed to update the zettel
	placeholdergo1               // Was assigned to rename right, which is now removed
	ZettelCanDelete              // Requesting user is allowed to delete the zettel
	ZettelMaxRight               // Sentinel value
)

// MetaRights contains the metadata of a zettel, and its rights.
type MetaRights struct {
	Meta   ZettelMeta
	Rights ZettelRights
}

// ZidMetaRights contains the identifier, the metadata of a zettel, and its rights.
type ZidMetaRights struct {
	ID     id.Zid
	Meta   ZettelMeta
	Rights ZettelRights
}

// ZettelData contains all data for a zettel.
//
//   - Meta is a map containing the metadata of the zettel.
//   - Rights is an integer specifying the access rights.
//   - Encoding is a string specifying the encoding of the zettel content.
//   - Content is the zettel content itself.
type ZettelData struct {
	Meta     ZettelMeta
	Rights   ZettelRights
	Encoding string
	Content  string // raw, uninterpreted zettel content
}

// Aggregate maps metadata keys to list of zettel identifier.
type Aggregate map[string][]id.Zid

//-----------------------------------------------------------------------------
// Copyright (c) 2021-present Detlef Stern
//
// This file is part of zettelstore-client.
//
// Zettelstore client 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 api

import "fmt"









































































































































// Additional HTTP constants.
const (


	HeaderAccept      = "Accept"
	HeaderContentType = "Content-Type"
	HeaderDestination = "Destination"
	HeaderLocation    = "Location"
)

// Values for HTTP query parameter.
const (
	QueryKeyCommand   = "cmd"
	QueryKeyEncoding  = "enc"
	QueryKeyParseOnly = "parseonly"
	QueryKeyPart      = "part"
	QueryKeyPhrase    = "phrase"
	QueryKeyQuery     = "q"
	QueryKeyRole      = "role"
	QueryKeySeed      = "_seed"
	QueryKeyTag       = "tag"
)

// Supported encoding values.
const (
	EncodingHTML  = "html"  // Plain HTML
	EncodingMD    = "md"    // Markdown
	EncodingSHTML = "shtml" // SxHTML
	EncodingSz    = "sz"    // Structure of zettel, encoded a an S-expression
	EncodingText  = "text"  // plain text content
	EncodingZMK   = "zmk"   // Zettelmarkup

	EncodingPlain = "plain" // Plain zettel, no processing
	EncodingData  = "data"  // Plain zettel, metadata as S-Expression

)

var mapEncodingEnum = map[string]EncodingEnum{
	EncodingHTML:  EncoderHTML,
	EncodingMD:    EncoderMD,
	EncodingSHTML: EncoderSHTML,
	EncodingSz:    EncoderSz,
	EncodingText:  EncoderText,
	EncodingZMK:   EncoderZmk,

	EncodingPlain: EncoderPlain,
	EncodingData:  EncoderData,

}
var mapEnumEncoding = map[EncodingEnum]string{}

func init() {
	for k, v := range mapEncodingEnum {
		mapEnumEncoding[v] = k
	}

	EncoderSHTML
	EncoderSz
	EncoderText
	EncoderZmk

	EncoderPlain
	EncoderData

)

// String representation of an encoder key.
func (e EncodingEnum) String() string {
	if f, ok := mapEnumEncoding[e]; ok {
		return f
	}
	return fmt.Sprintf("*Unknown*(%d)", e)
}

// Supported part values.
const (
	PartMeta    = "meta"
	PartContent = "content"
	PartZettel  = "zettel"
)

// Command to be executed atthe Zettelstore
type Command string

// Supported command values.
const (
	CommandAuthenticated = Command("authenticated")
	CommandRefresh       = Command("refresh")
)

// Supported search operator representations.
const (
	BackwardDirective = "BACKWARD" // Backward-only context
	ContextDirective  = "CONTEXT"  // Context directive
	CostDirective     = "COST"     // Maximum cost of a context operation
	ForwardDirective  = "FORWARD"  // Forward-only context
	FullDirective     = "FULL"     // Include tags in context
	IdentDirective    = "IDENT"    // Use only specified zettel
	ItemsDirective    = "ITEMS"    // Select list elements in a zettel
	MaxDirective      = "MAX"      // Maximum number of context results
	MinDirective      = "MIN"      // Minimum number of context results
	LimitDirective    = "LIMIT"    // Maximum number of zettel
	OffsetDirective   = "OFFSET"   // Offset to start returned zettel list
	OrDirective       = "OR"       // Combine several search expression with an "or"
	OrderDirective    = "ORDER"    // Specify metadata keys for the order of returned list
	PhraseDirective   = "PHRASE"   // Only unlinked zettel with given phrase
	PickDirective     = "PICK"     // Pick some random zettel
	RandomDirective   = "RANDOM"   // Order zettel list randomly
	ReverseDirective  = "REVERSE"  // Reverse the order of a zettel list
	UnlinkedDirective = "UNLINKED" // Search for zettel that contain a phase(s) but do not link

	ActionSeparator = "|" // Separates action list of previous elements of query expression

	KeysAction     = "KEYS"     // Provide metadata key used
	MinAction      = "MIN"      // Return only those values with a minimum amount of zettel
	MaxAction      = "MAX"      // Return only those values with a maximum amount of zettel
	NumberedAction = "NUMBERED" // Return a numbered list
	RedirectAction = "REDIRECT" // Return the first zettel in list
	ReIndexAction  = "REINDEX"  // Ensure that zettel is/are indexed.

	ExistOperator    = "?"  // Does zettel have metadata with given key?
	ExistNotOperator = "!?" // True id zettel does not have metadata with given key.

	SearchOperatorNot        = "!"
	SearchOperatorEqual      = "="  // True if values are equal
	SearchOperatorNotEqual   = "!=" // False if values are equal
	SearchOperatorHas        = ":"  // True if values are equal/included
	SearchOperatorHasNot     = "!:" // False if values are equal/included
	SearchOperatorPrefix     = "["  // True if value is prefix of the other
	SearchOperatorNoPrefix   = "![" // False if value is prefix of the other
	SearchOperatorSuffix     = "]"  // True if value is suffix of other
	SearchOperatorNoSuffix   = "!]" // False if value is suffix of other
	SearchOperatorMatch      = "~"  // True if value is included in other
	SearchOperatorNoMatch    = "!~" // False if value is included in other
	SearchOperatorLess       = "<"  // True if value is smaller than other
	SearchOperatorNotLess    = "!<" // False if value is smaller than other
	SearchOperatorGreater    = ">"  // True if value is greater than other
	SearchOperatorNotGreater = "!>" // False if value is greater than other
)

// QueryPrefix is the prefix that denotes a query expression within a reference.
const QueryPrefix = "query:"

//-----------------------------------------------------------------------------
// Copyright (c) 2020-present Detlef Stern
//
// This file is part of zettelstore-client.
//
// Zettelstore client 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: 2020-present Detlef Stern
//-----------------------------------------------------------------------------

package api

import (
	"t73f.de/r/webs/urlbuilder"
	"t73f.de/r/zsc/domain/id"
)



// URLBuilder should be used to create zettelstore URLs.
type URLBuilder struct {
	base   urlbuilder.URLBuilder
	prefix string





}

// NewURLBuilder creates a new URL builder with the given prefix and key.
func NewURLBuilder(prefix string, key byte) *URLBuilder {
	for len(prefix) > 0 && prefix[len(prefix)-1] == '/' {
		prefix = prefix[0 : len(prefix)-1]
	}

	result := URLBuilder{prefix: prefix}


	if key != '/' {
		result.base.AddPath(string([]byte{key}))


	}





	return &result
}


// Clone an URLBuilder.
func (ub *URLBuilder) Clone() *URLBuilder {




	cpy := new(URLBuilder)
	ub.base.Copy(&cpy.base)
	cpy.prefix = ub.prefix
	return cpy
}

// SetZid sets the zettel identifier.
func (ub *URLBuilder) SetZid(zid id.Zid) *URLBuilder {




	ub.base.AddPath(zid.String())
	return ub
}

// AppendPath adds a new path element.
func (ub *URLBuilder) AppendPath(p string) *URLBuilder {
	ub.base.AddPath(p)






	return ub
}

// AppendKVQuery adds a new key/value query parameter.
func (ub *URLBuilder) AppendKVQuery(key, value string) *URLBuilder {

	ub.base.AddQuery(key, value)
	return ub
}

// AppendQuery adds a new query.
//
// Basically the same as [URLBuilder.AppendKVQuery]([api.QueryKeyQuery], value)
func (ub *URLBuilder) AppendQuery(value string) *URLBuilder {
	if value != "" {

		ub.base.AddQuery(QueryKeyQuery, value)
	}
	return ub
}

// ClearQuery removes all query parameters.
func (ub *URLBuilder) ClearQuery() *URLBuilder {

	ub.base.RemoveQueries()

	return ub
}

// SetFragment sets the fragment.
func (ub *URLBuilder) SetFragment(s string) *URLBuilder {

	ub.base.SetFragment(s)
	return ub
}

// String produces a string value.
func (ub *URLBuilder) String() string {

	return ub.prefix + ub.base.String()































}

//-----------------------------------------------------------------------------
// Copyright (c) 2021-present Detlef Stern
//
// This file is part of zettelstore-client.
//
// Zettelstore client 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 client provides a client for accessing the Zettelstore via its API.
package client

import (

	"bytes"
	"context"
	"fmt"
	"io"
	"net"
	"net/http"
	"net/url"
	"strconv"
	"strings"
	"time"

	"t73f.de/r/sx"
	"t73f.de/r/sx/sxreader"
	"t73f.de/r/zsc/api"
	"t73f.de/r/zsc/domain/id"
	"t73f.de/r/zsc/sexp"
)

// Client contains all data to execute requests.
type Client struct {
	base      string
	username  string
	password  string
	token     string
	tokenType string
	expires   time.Time
	client    http.Client
}

// Base returns the base part of the URLs that are used to communicate with a Zettelstore.
func (c *Client) Base() string { return c.base }

// NewClient creates a new client with a given base URL to a Zettelstore.
func NewClient(u *url.URL) *Client {
	myURL := *u
	myURL.User = nil
	myURL.ForceQuery = false
	myURL.RawQuery = ""
	myURL.Fragment = ""
	myURL.RawFragment = ""
	base := myURL.String()



	c := Client{
		base: base,
		client: http.Client{
			Timeout: 10 * time.Second,
			Transport: &http.Transport{
				DialContext: (&net.Dialer{
					Timeout: 5 * time.Second, // TCP connect timeout
				}).DialContext,
				TLSHandshakeTimeout: 5 * time.Second,
			},
		},
	}
	return &c
}

// AllowRedirect will modify the client to not follow redirect status code when
// using the Zettelstore. The original behaviour can be restored by setting
// allow to false.
func (c *Client) AllowRedirect(allow bool) {
	if allow {
		c.client.CheckRedirect = func(*http.Request, []*http.Request) error {
			return http.ErrUseLastResponse
		}
	} else {
		c.client.CheckRedirect = nil
	}
}

// Error encapsulates the possible client call errors.
//
//   - StatusCode is the HTTP status code, e.g. 200
//   - Message is the HTTP message, e.g. "OK"
//   - Body is the HTTP body returned by a request.
type Error struct {
	StatusCode int
	Message    string
	Body       []byte
}

// Error returns the error as a string.
func (err *Error) Error() string {
	var body string
	if err.Body == nil {
		body = "nil"
	} else if bl := len(err.Body); bl == 0 {
		body = "empty"
	} else {

	return &Error{
		StatusCode: resp.StatusCode,
		Message:    resp.Status[4:],
		Body:       body,
	}
}

// NewURLBuilder creates a new URL builder for the client with the given key.
//
// key is one of the defined lower case letters to specify an endpoint.
// See [Endpoints used by the API] for details.
//
// [Endpoints used by the API]: https://zettelstore.de/manual/h/00001012920000
func (c *Client) NewURLBuilder(key byte) *api.URLBuilder {
	return api.NewURLBuilder(c.base, key)
}
func (*Client) newRequest(ctx context.Context, method string, ub *api.URLBuilder, body io.Reader) (*http.Request, error) {
	return http.NewRequestWithContext(ctx, method, ub.String(), body)
}

func (c *Client) executeRequest(req *http.Request) (*http.Response, error) {
	if c.token != "" {
		req.Header.Add("Authorization", c.tokenType+" "+c.token)
	}
	resp, err := c.client.Do(req)
	if err != nil {
		if resp != nil && resp.Body != nil {
			_ = resp.Body.Close()
		}
		return nil, err
	}
	return resp, err
}

func (c *Client) buildAndExecuteRequest(
	ctx context.Context,
	method string,
	ub *api.URLBuilder,
	body io.Reader,
) (*http.Response, error) {
	req, err := c.newRequest(ctx, method, ub, body)
	if err != nil {
		return nil, err
	}
	err = c.updateToken(ctx)
	if err != nil {
		return nil, err
	}



	return c.executeRequest(req)
}

// SetAuth sets authentication data.
//
// username and password are the same values that are used to authenticate via the Web-UI.
func (c *Client) SetAuth(username, password string) {
	c.username = username
	c.password = password
	c.token = ""
	c.tokenType = ""
	c.expires = time.Time{}
}

func (c *Client) executeAuthRequest(req *http.Request) error {
	resp, err := c.executeRequest(req)
	if err != nil {
		return err
	}
	defer func() { _ = resp.Body.Close() }()
	if resp.StatusCode != http.StatusOK {
		return statusToError(resp)
	}
	rd := sxreader.MakeReader(resp.Body)
	obj, err := rd.Read()
	if err != nil {
		return err
	}
	vals, err := sexp.ParseList(obj, "ssi")
	if err != nil {
		return err
	}
	token := vals[1].(sx.String).GetValue()
	if len(token) < 4 {
		return fmt.Errorf("no valid token found: %q", token)
	}
	c.token = token
	c.tokenType = vals[0].(sx.String).GetValue()
	c.expires = time.Now().Add(time.Duration(vals[2].(sx.Int64)*9/10) * time.Second)
	return nil
}

func (c *Client) updateToken(ctx context.Context) error {
	if c.username == "" {
		return nil
	}
	if time.Now().After(c.expires) {
		return c.Authenticate(ctx)
	}
	return c.RefreshToken(ctx)
}

// Authenticate sets a new token by sending user name and password.
//
// [Client.SetAuth] should be called before.
func (c *Client) Authenticate(ctx context.Context) error {
	authData := url.Values{"username": {c.username}, "password": {c.password}}
	req, err := c.newRequest(ctx, http.MethodPost, c.NewURLBuilder('a'), strings.NewReader(authData.Encode()))
	if err != nil {
		return err
	}
	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
	return c.executeAuthRequest(req)
}

// RefreshToken updates the access token
//
// [Client.SetAuth] should be called before.
func (c *Client) RefreshToken(ctx context.Context) error {
	req, err := c.newRequest(ctx, http.MethodPut, c.NewURLBuilder('a'), nil)
	if err != nil {
		return err
	}
	return c.executeAuthRequest(req)
}

// CreateZettel creates a new zettel and returns its URL.
//
// data contains the zettel metadata and content, as it is stored in a file in a zettel box,
// or as returned by [Client.GetZettel].
// Metadata is separated from zettel content by an empty line.
func (c *Client) CreateZettel(ctx context.Context, data []byte) (id.Zid, error) {
	ub := c.NewURLBuilder('z')
	resp, err := c.buildAndExecuteRequest(ctx, http.MethodPost, ub, bytes.NewBuffer(data))
	if err != nil {
		return id.Invalid, err
	}
	defer func() { _ = resp.Body.Close() }()
	if resp.StatusCode != http.StatusCreated {
		return id.Invalid, statusToError(resp)
	}
	b, err := io.ReadAll(resp.Body)
	if err != nil {
		return id.Invalid, err
	}

	return id.Parse(string(b))


}

// CreateZettelData creates a new zettel and returns its URL.
//
// data contains the zettel date, encoded as explicit struct.
func (c *Client) CreateZettelData(ctx context.Context, data api.ZettelData) (id.Zid, error) {
	var buf bytes.Buffer
	if _, err := sx.Print(&buf, sexp.EncodeZettel(data)); err != nil {
		return id.Invalid, err
	}
	ub := c.NewURLBuilder('z').AppendKVQuery(api.QueryKeyEncoding, api.EncodingData)
	resp, err := c.buildAndExecuteRequest(ctx, http.MethodPost, ub, &buf)
	if err != nil {
		return id.Invalid, err
	}
	defer func() { _ = resp.Body.Close() }()
	rdr := sxreader.MakeReader(resp.Body)
	obj, err := rdr.Read()
	if resp.StatusCode != http.StatusCreated {
		return id.Invalid, statusToError(resp)
	}
	if err != nil {
		return id.Invalid, err
	}
	return makeZettelID(obj)
}






















































































































func makeZettelID(obj sx.Object) (id.Zid, error) {
	val, isInt64 := obj.(sx.Int64)
	if !isInt64 || val <= 0 {
		return id.Invalid, fmt.Errorf("invalid zettel ID: %v", val)
	}
	sVal := strconv.FormatInt(int64(val), 10)
	if len(sVal) < 14 {
		sVal = "00000000000000"[0:14-len(sVal)] + sVal
	}
	zid, err := id.Parse(sVal)
	if err != nil {
		return id.Invalid, fmt.Errorf("invalid zettel ID %v: %w", val, err)
	}
	return zid, nil
}

























// UpdateZettel updates an existing zettel, specified by its zettel identifier.





















//



















// data contains the zettel metadata and content, as it is stored in a file in a zettel box,




// or as returned by [Client.GetZettel].

























// Metadata is separated from zettel content by an empty line.









































































func (c *Client) UpdateZettel(ctx context.Context, zid id.Zid, data []byte) error {
	ub := c.NewURLBuilder('z').SetZid(zid)
	resp, err := c.buildAndExecuteRequest(ctx, http.MethodPut, ub, bytes.NewBuffer(data))
	if err != nil {
		return err
	}
	defer func() { _ = resp.Body.Close() }()
	if resp.StatusCode != http.StatusNoContent {
		return statusToError(resp)
	}
	return nil
}

// UpdateZettelData updates an existing zettel, specified by its zettel identifier.
func (c *Client) UpdateZettelData(ctx context.Context, zid id.Zid, data api.ZettelData) error {
	var buf bytes.Buffer
	if _, err := sx.Print(&buf, sexp.EncodeZettel(data)); err != nil {
		return err
	}
	ub := c.NewURLBuilder('z').SetZid(zid).AppendKVQuery(api.QueryKeyEncoding, api.EncodingData)
	resp, err := c.buildAndExecuteRequest(ctx, http.MethodPut, ub, &buf)
	if err != nil {
		return err
	}
	defer func() { _ = resp.Body.Close() }()

















	if resp.StatusCode != http.StatusNoContent {
		return statusToError(resp)
	}
	return nil
}

// DeleteZettel deletes a zettel with the given identifier.
func (c *Client) DeleteZettel(ctx context.Context, zid id.Zid) error {
	ub := c.NewURLBuilder('z').SetZid(zid)
	resp, err := c.buildAndExecuteRequest(ctx, http.MethodDelete, ub, nil)
	if err != nil {
		return err
	}
	defer func() { _ = resp.Body.Close() }()
	if resp.StatusCode != http.StatusNoContent {
		return statusToError(resp)
	}
	return nil
}

// ExecuteCommand will execute a given command at the Zettelstore.
//
// See [API commands] for a list of valid commands.
//
// [API commands]: https://zettelstore.de/manual/h/00001012080100
func (c *Client) ExecuteCommand(ctx context.Context, command api.Command) error {
	ub := c.NewURLBuilder('x').AppendKVQuery(api.QueryKeyCommand, string(command))
	resp, err := c.buildAndExecuteRequest(ctx, http.MethodPost, ub, nil)
	if err != nil {
		return err
	}
	defer func() { _ = resp.Body.Close() }()
	if resp.StatusCode != http.StatusNoContent {
		return statusToError(resp)
	}
	return nil
}

//-----------------------------------------------------------------------------
// Copyright (c) 2022-present Detlef Stern
//
// This file is part of zettelstore-client.
//
// Zettelstore client 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: 2022-present Detlef Stern
//-----------------------------------------------------------------------------

package client_test

import (
	"context"
	"flag"
	"net/http"
	"net/url"
	"testing"

	"t73f.de/r/zsc/api"

	"t73f.de/r/zsc/client"
	"t73f.de/r/zsc/domain/id"
)

func TestZettelList(t *testing.T) {
	c := getClient()
	_, err := c.QueryZettel(context.Background(), "")
	if err != nil {
		t.Error(err)
		return
	}
}

func TestGetProtectedZettel(t *testing.T) {
	c := getClient()
	_, err := c.GetZettel(context.Background(), id.ZidStartupConfiguration, api.PartZettel)
	if err != nil {
		if cErr, ok := err.(*client.Error); ok && cErr.StatusCode == http.StatusForbidden {
			return
		} else {
			t.Error(err)
		}
		return
	}
}

func TestGetSzZettel(t *testing.T) {
	c := getClient()



	value, err := c.GetEvaluatedSz(context.Background(), id.ZidDefaultHome, api.PartContent)
	if err != nil {
		t.Error(err)
		return
	}
	if value.IsNil() {
		t.Error("No data")
	}

//-----------------------------------------------------------------------------
// Copyright (c) 2021-present Detlef Stern
//
// This file is part of zettelstore-client.
//
// Zettelstore client 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 client

import (
	"bufio"
	"bytes"
	"context"
	"fmt"
	"io"
	"net/http"

	"t73f.de/r/sx"
	"t73f.de/r/sx/sxreader"
	"t73f.de/r/zsc/api"
	"t73f.de/r/zsc/domain/id"
	"t73f.de/r/zsc/sexp"
	"t73f.de/r/zsx"
)

var bsLF = []byte{'\n'}

// QueryZettel returns a list of all Zettel based on the given query.
//
// query is a search expression, as described in [Query the list of all zettel].
//
// The functions returns a slice of bytes slices, where each byte slice contains the
// zettel identifier within its first 14 bytes. The next byte is a space character,
// followed by the title of the zettel.
//
// [Query the list of all zettel]: https://zettelstore.de/manual/h/00001012051400
func (c *Client) QueryZettel(ctx context.Context, query string) ([][]byte, error) {
	ub := c.NewURLBuilder('z').AppendQuery(query)
	resp, err := c.buildAndExecuteRequest(ctx, http.MethodGet, ub, nil)
	if err != nil {
		return nil, err
	}
	defer func() { _ = resp.Body.Close() }()
	data, err := io.ReadAll(resp.Body)
	switch resp.StatusCode {
	case http.StatusOK:
	case http.StatusNoContent:
		return nil, nil
	default:
		return nil, statusToError(resp)
	}
	if err != nil {
		return nil, err
	}
	lines := bytes.Split(data, bsLF)
	if len(lines[len(lines)-1]) == 0 {
		lines = lines[:len(lines)-1]
	}
	return lines, nil
}

// QueryZettelData returns a list of zettel metadata.
//
// query is a search expression, as described in [Query the list of all zettel].
//
// The functions returns the normalized query and its human-readable representation as
// its first two result values.
//
// [Query the list of all zettel]: https://zettelstore.de/manual/h/00001012051400
func (c *Client) QueryZettelData(ctx context.Context, query string) (string, string, []api.ZidMetaRights, error) {
	ub := c.NewURLBuilder('z').AppendKVQuery(api.QueryKeyEncoding, api.EncodingData).AppendQuery(query)
	resp, err := c.buildAndExecuteRequest(ctx, http.MethodGet, ub, nil)
	if err != nil {
		return "", "", nil, err
	}
	defer func() { _ = resp.Body.Close() }()
	rdr := sxreader.MakeReader(resp.Body).SetListLimit(0) // No limit b/c number of zettel may be more than 100000. We must trust the server
	obj, err := rdr.Read()
	switch resp.StatusCode {
	case http.StatusOK:
	case http.StatusNoContent:
		return "", "", nil, nil
	default:
		return "", "", nil, statusToError(resp)
	}
	if err != nil {
		return "", "", nil, err
	}
	vals, err := sexp.ParseList(obj, "yppr")
	if err != nil {
		return "", "", nil, err
	}
	qVals, err := sexp.ParseList(vals[1], "ys")
	if err != nil {
		return "", "", nil, err
	}
	hVals, err := sexp.ParseList(vals[2], "ys")
	if err != nil {
		return "", "", nil, err
	}
	metaList, err := parseMetaList(vals[3].(*sx.Pair))
	return zsx.GoValue(qVals[1]), zsx.GoValue(hVals[1]), metaList, err
}

func parseMetaList(metaPair *sx.Pair) ([]api.ZidMetaRights, error) {
	var result []api.ZidMetaRights
	for node := metaPair; !sx.IsNil(node); {
		elem, isPair := sx.GetPair(node)
		if !isPair {
			return nil, fmt.Errorf("meta-list not a proper list: %v", metaPair.String())
		}
		node = elem.Tail()
		vals, err := sexp.ParseList(elem.Car(), "yppp")
		if err != nil {
			return nil, err
		}

		if errSym := sexp.CheckSymbol(vals[0], "zettel"); errSym != nil {
			return nil, errSym
		}

		idVals, err := sexp.ParseList(vals[1], "yi")
		if err != nil {
			return nil, err
		}
		if errSym := sexp.CheckSymbol(idVals[0], "id"); errSym != nil {
			return nil, errSym
		}
		zid, err := makeZettelID(idVals[1])
		if err != nil {
			return nil, err
		}

		meta, err := sexp.ParseMeta(vals[2].(*sx.Pair))
		if err != nil {
			return nil, err
		}

		rights, err := sexp.ParseRights(vals[3])
		if err != nil {
			return nil, err
		}

		result = append(result, api.ZidMetaRights{
			ID:     zid,
			Meta:   meta,
			Rights: rights,
		})
	}
	return result, nil
}

// QueryAggregate returns a aggregate as a result of a query.
// It is most often used in a query with an action, where the action is either
// a metadata key of type Word or of type TagSet.
//
// query is a search expression, as described in [Query the list of all zettel].
// It must contain an aggregate action.
//
// [Query the list of all zettel]: https://zettelstore.de/manual/h/00001012051400
func (c *Client) QueryAggregate(ctx context.Context, query string) (api.Aggregate, error) {
	lines, err := c.QueryZettel(ctx, query)
	if err != nil {
		return nil, err
	}
	if len(lines) == 0 {
		return nil, nil
	}
	agg := make(api.Aggregate, len(lines))
	for _, line := range lines {
		if fields := bytes.Fields(line); len(fields) > 1 {
			key := string(fields[0])
			for _, field := range fields[1:] {
				if zid, zidErr := id.Parse(string(field)); zidErr == nil {
					agg[key] = append(agg[key], zid)
				}
			}
		}
	}
	return agg, nil
}

// TagZettel returns the identifier of the tag zettel for a given tag.
//
// This method only works if c.AllowRedirect(true) was called.
func (c *Client) TagZettel(ctx context.Context, tag string) (id.Zid, error) {
	return c.fetchTagOrRoleZettel(ctx, api.QueryKeyTag, tag)
}

// RoleZettel returns the identifier of the tag zettel for a given role.
//
// This method only works if c.AllowRedirect(true) was called.
func (c *Client) RoleZettel(ctx context.Context, role string) (id.Zid, error) {
	return c.fetchTagOrRoleZettel(ctx, api.QueryKeyRole, role)
}

func (c *Client) fetchTagOrRoleZettel(ctx context.Context, key, val string) (id.Zid, error) {
	if c.client.CheckRedirect == nil {
		panic("client does not allow to track redirect")
	}
	ub := c.NewURLBuilder('z').AppendKVQuery(key, val)
	resp, err := c.buildAndExecuteRequest(ctx, http.MethodGet, ub, nil)
	if err != nil {
		return id.Invalid, err
	}
	defer func() { _ = resp.Body.Close() }()
	data, err := io.ReadAll(resp.Body)
	if err != nil {
		return id.Invalid, err
	}

	switch resp.StatusCode {
	case http.StatusNotFound:
		return id.Invalid, nil
	case http.StatusFound:
		return id.Parse(string(data))
	default:
		return id.Invalid, statusToError(resp)
	}
}

// GetZettel returns a zettel as a byte slice.
//
// part must be one of "meta", "content", or "zettel".
//
// The format of the byte slice is described in [Layout of a zettel].
//
// [Layout of a zettel]: https://zettelstore.de/manual/h/00001006000000
func (c *Client) GetZettel(ctx context.Context, zid id.Zid, part string) ([]byte, error) {
	ub := c.NewURLBuilder('z').SetZid(zid)
	if part != "" && part != api.PartContent {
		ub.AppendKVQuery(api.QueryKeyPart, part)
	}
	resp, err := c.buildAndExecuteRequest(ctx, http.MethodGet, ub, nil)
	if err != nil {
		return nil, err
	}
	defer func() { _ = resp.Body.Close() }()
	data, err := io.ReadAll(resp.Body)
	switch resp.StatusCode {
	case http.StatusOK:
	case http.StatusNoContent:
		return nil, nil
	default:
		return nil, statusToError(resp)
	}
	return data, err
}

// GetZettelData returns a zettel as a struct of its parts.
func (c *Client) GetZettelData(ctx context.Context, zid id.Zid) (api.ZettelData, error) {
	ub := c.NewURLBuilder('z').SetZid(zid)
	ub.AppendKVQuery(api.QueryKeyEncoding, api.EncodingData)
	ub.AppendKVQuery(api.QueryKeyPart, api.PartZettel)
	resp, err := c.buildAndExecuteRequest(ctx, http.MethodGet, ub, nil)
	if err == nil {
		defer func() { _ = resp.Body.Close() }()
		if resp.StatusCode != http.StatusOK {
			return api.ZettelData{}, statusToError(resp)
		}
		rdr := sxreader.MakeReader(resp.Body)
		obj, err2 := rdr.Read()
		if err2 == nil {
			return sexp.ParseZettel(obj)
		}
	}
	return api.ZettelData{}, err
}

// GetParsedZettel return a parsed zettel in a specified text-based encoding.
//
// A parsed zettel is just read from its box and is not processed any further.
//
// Valid encoding values are given as constants. They are described in more
// detail in [Encodings available via the API].
//
// [Encodings available via the API]: https://zettelstore.de/manual/h/00001012920500
func (c *Client) GetParsedZettel(ctx context.Context, zid id.Zid, enc api.EncodingEnum) ([]byte, error) {
	return c.getZettelString(ctx, zid, enc, true)
}

// GetEvaluatedZettel return an evaluated zettel in a specified text-based encoding.
//
// An evaluated zettel was parsed, and any transclusions etc. are resolved.
// This is the zettel representation you typically see on the Web UI.
//
// Valid encoding values are given as constants. They are described in more
// detail in [Encodings available via the API].
//
// [Encodings available via the API]: https://zettelstore.de/manual/h/00001012920500
func (c *Client) GetEvaluatedZettel(ctx context.Context, zid id.Zid, enc api.EncodingEnum) ([]byte, error) {
	return c.getZettelString(ctx, zid, enc, false)
}

func (c *Client) getZettelString(ctx context.Context, zid id.Zid, enc api.EncodingEnum, parseOnly bool) ([]byte, error) {
	ub := c.NewURLBuilder('z').SetZid(zid)
	ub.AppendKVQuery(api.QueryKeyEncoding, enc.String())
	ub.AppendKVQuery(api.QueryKeyPart, api.PartContent)
	if parseOnly {
		ub.AppendKVQuery(api.QueryKeyParseOnly, "")
	}
	resp, err := c.buildAndExecuteRequest(ctx, http.MethodGet, ub, nil)
	if err != nil {
		return nil, err
	}
	defer func() { _ = resp.Body.Close() }()
	switch resp.StatusCode {
	case http.StatusOK:
	case http.StatusNoContent:
	default:
		return nil, statusToError(resp)
	}
	return io.ReadAll(resp.Body)
}

// GetParsedSz returns a part of an parsed zettel as a Sexpr-decoded data structure.
//
// A parsed zettel is just read from its box and is not processed any further.
//
// part must be one of "meta", "content", or "zettel".
//
// Basically, this function returns the sz encoding of a part of a zettel.
func (c *Client) GetParsedSz(ctx context.Context, zid id.Zid, part string) (sx.Object, error) {
	return c.getSz(ctx, zid, part, true)
}

// GetEvaluatedSz returns an evaluated zettel as a Sexpr-decoded data structure.
//
// An evaluated zettel was parsed, and any transclusions etc. are resolved.
// This is the zettel representation you typically see on the Web UI.
//
// part must be one of "meta", "content", or "zettel".
//
// Basically, this function returns the sz encoding of a part of a zettel.
func (c *Client) GetEvaluatedSz(ctx context.Context, zid id.Zid, part string) (sx.Object, error) {
	return c.getSz(ctx, zid, part, false)
}

func (c *Client) getSz(ctx context.Context, zid id.Zid, part string, parseOnly bool) (sx.Object, error) {
	ub := c.NewURLBuilder('z').SetZid(zid)
	ub.AppendKVQuery(api.QueryKeyEncoding, api.EncodingSz)
	if part != "" {
		ub.AppendKVQuery(api.QueryKeyPart, part)
	}
	if parseOnly {
		ub.AppendKVQuery(api.QueryKeyParseOnly, "")
	}
	resp, err := c.buildAndExecuteRequest(ctx, http.MethodGet, ub, nil)
	if err != nil {
		return nil, err
	}
	defer func() { _ = resp.Body.Close() }()
	if resp.StatusCode != http.StatusOK {
		return nil, statusToError(resp)
	}
	return sxreader.MakeReader(bufio.NewReaderSize(resp.Body, 8)).Read()
}

// GetMetaData returns the metadata of a zettel.
func (c *Client) GetMetaData(ctx context.Context, zid id.Zid) (api.MetaRights, error) {
	ub := c.NewURLBuilder('z').SetZid(zid)
	ub.AppendKVQuery(api.QueryKeyEncoding, api.EncodingData)
	ub.AppendKVQuery(api.QueryKeyPart, api.PartMeta)
	resp, err := c.buildAndExecuteRequest(ctx, http.MethodGet, ub, nil)
	if err != nil {
		return api.MetaRights{}, err
	}
	defer func() { _ = resp.Body.Close() }()
	rdr := sxreader.MakeReader(resp.Body)
	obj, err := rdr.Read()
	if resp.StatusCode != http.StatusOK {
		return api.MetaRights{}, statusToError(resp)
	}
	if err != nil {
		return api.MetaRights{}, err
	}
	vals, err := sexp.ParseList(obj, "ypp")
	if err != nil {
		return api.MetaRights{}, err
	}
	if errSym := sexp.CheckSymbol(vals[0], "list"); errSym != nil {
		return api.MetaRights{}, err
	}

	meta, err := sexp.ParseMeta(vals[1].(*sx.Pair))
	if err != nil {
		return api.MetaRights{}, err
	}

	rights, err := sexp.ParseRights(vals[2])
	if err != nil {
		return api.MetaRights{}, err
	}

	return api.MetaRights{
		Meta:   meta,
		Rights: rights,
	}, nil
}

// GetReferences returns all references / URIs of a given zettel.
//
// part must be one of "meta", "content", or "zettel".
func (c *Client) GetReferences(ctx context.Context, zid id.Zid, part string) (urls []string, err error) {
	ub := c.NewURLBuilder('r').SetZid(zid)
	if part != "" {
		ub.AppendKVQuery(api.QueryKeyPart, part)
	}
	ub.AppendKVQuery(api.QueryKeyEncoding, api.EncodingData) // data encoding is more robust.
	resp, err := c.buildAndExecuteRequest(ctx, http.MethodGet, ub, nil)
	if err != nil {
		return nil, err
	}
	defer func() { _ = resp.Body.Close() }()
	rdr := sxreader.MakeReader(resp.Body)
	obj, err := rdr.Read()
	if resp.StatusCode != http.StatusOK {
		return nil, statusToError(resp)
	}
	if err != nil {
		return nil, err
	}
	seq, isSeq := sx.GetSequence(obj)
	if !isSeq {
		return nil, fmt.Errorf("not a sequence: %T/%v", obj, obj)
	}
	for val := range seq.Values() {
		if s, isString := sx.GetString(val); isString {
			urls = append(urls, s.GetValue())
		}
	}
	return urls, nil
}

// GetVersionInfo returns version information of the Zettelstore that is used.
func (c *Client) GetVersionInfo(ctx context.Context) (VersionInfo, error) {
	resp, err := c.buildAndExecuteRequest(ctx, http.MethodGet, c.NewURLBuilder('x'), nil)
	if err != nil {
		return VersionInfo{}, err
	}
	defer func() { _ = resp.Body.Close() }()
	if resp.StatusCode != http.StatusOK {
		return VersionInfo{}, statusToError(resp)
	}
	rdr := sxreader.MakeReader(resp.Body)
	obj, err := rdr.Read()
	if err == nil {
		if vals, errVals := sexp.ParseList(obj, "iiiss"); errVals == nil {
			return VersionInfo{
				Major: int(vals[0].(sx.Int64)),
				Minor: int(vals[1].(sx.Int64)),
				Patch: int(vals[2].(sx.Int64)),
				Info:  vals[3].(sx.String).GetValue(),
				Hash:  vals[4].(sx.String).GetValue(),
			}, nil
		}
	}
	return VersionInfo{}, err
}

// VersionInfo contains version information of the associated Zettelstore.
//
//   - Major is an integer containing the major software version of Zettelstore.
//     If its value is greater than zero, different major versions are not compatible.
//   - Minor is an integer specifying the minor software version for the given major version.
//     If the major version is greater than zero, minor versions are backward compatible.
//   - Patch is an integer that specifies a change within a minor version.
//     A version that have equal major and minor versions and differ in patch version are
//     always compatible, even if the major version equals zero.
//   - Info contains some optional text, i.e. it may be the empty string. Typically, Info
//     specifies a developer version by containing the string "dev".
//   - Hash contains the value of the source code version stored in the Zettelstore repository.
//     You can use it to reproduce bugs that occured, when source code was changed since
//     its introduction.
type VersionInfo struct {
	Major int
	Minor int
	Patch int
	Info  string
	Hash  string
}

// GetApplicationZid returns the zettel identifier used to configure a client
// application with the given name.
func (c *Client) GetApplicationZid(ctx context.Context, appname string) (id.Zid, error) {
	mr, err := c.GetMetaData(ctx, id.ZidAppDirectory)
	if err != nil {
		return id.Invalid, err
	}
	key := appname + "-zid"
	val, found := mr.Meta[key]
	if !found {
		return id.Invalid, fmt.Errorf("no application registered: %v", appname)
	}
	zid, err := id.Parse(val)
	if err == nil {
		return zid, nil
	}
	return id.Invalid, fmt.Errorf("invalid identifier for application %v: %v", appname, val)
}

// Get executes a GET request to the given URL and returns the read data.
func (c *Client) Get(ctx context.Context, ub *api.URLBuilder) ([]byte, error) {
	resp, err := c.buildAndExecuteRequest(ctx, http.MethodGet, ub, nil)
	if err != nil {
		return nil, err
	}
	defer func() { _ = resp.Body.Close() }()
	switch resp.StatusCode {
	case http.StatusOK:
	case http.StatusNoContent:
		return nil, nil
	default:
		return nil, statusToError(resp)
	}
	data, err := io.ReadAll(resp.Body)
	return data, err
}

The source code contains some simple fuzzing tests. You should call them
regulary to make sure the the software will cope with unusual input.

go test -fuzz=FuzzParseBlocks t73f.de/r/zsc/sz/zmk

//-----------------------------------------------------------------------------
// Copyright (c) 2020-present Detlef Stern
//
// This file is part of zettelstore-client.
//
// Zettelstore Client 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: 2020-present Detlef Stern
//-----------------------------------------------------------------------------

// Package id provides zettel specific types, constants, and functions about
// zettel identifier.
package id

import (
	"strconv"
	"time"
)

// Zid is the internal identifier of a zettel. Typically, it is a time stamp
// of the form "YYYYMMDDHHmmSS" converted to an unsigned integer.
type Zid uint64

// LengthZid factors the constant length of a zettel identifier
const LengthZid = 14

// Some important ZettelIDs.
const (
	Invalid = Zid(0) // Invalid is a Zid that will never be valid

	maxZid = 99999999999999
)

// Predefined zettel identifier.
//
// See [List of predefined zettel].
//
// [List of predefined zettel]: https://zettelstore.de/manual/h/00001005090000
const (
	// System zettel
	ZidVersion              = Zid(1)
	ZidHost                 = Zid(2)
	ZidOperatingSystem      = Zid(3)
	ZidLicense              = Zid(4)
	ZidAuthors              = Zid(5)
	ZidDependencies         = Zid(6)
	ZidModules              = Zid(7)
	ZidLog                  = Zid(9)
	ZidMemory               = Zid(10)
	ZidSx                   = Zid(11)
	ZidHTTP                 = Zid(12)
	ZidAPI                  = Zid(13)
	ZidWebUI                = Zid(14)
	ZidConsole              = Zid(15)
	ZidBoxManager           = Zid(20)
	ZidZettel               = Zid(21)
	ZidIndex                = Zid(22)
	ZidQuery                = Zid(23)
	ZidMetadataKey          = Zid(90)
	ZidParser               = Zid(92)
	ZidStartupConfiguration = Zid(96)
	ZidConfiguration        = Zid(100)
	ZidDirectory            = Zid(101)

	// WebUI HTML templates are in the range 10000..19999
	ZidBaseTemplate   = Zid(10100)
	ZidLoginTemplate  = Zid(10200)
	ZidListTemplate   = Zid(10300)
	ZidZettelTemplate = Zid(10401)
	ZidInfoTemplate   = Zid(10402)
	ZidFormTemplate   = Zid(10403)
	ZidDeleteTemplate = Zid(10405)
	ZidErrorTemplate  = Zid(10700)

	// WebUI sxn code zettel are in the range 19000..19999
	ZidSxnStart = Zid(19000)
	ZidSxnBase  = Zid(19990)

	// CSS-related zettel are in the range 20000..29999
	ZidBaseCSS = Zid(20001)
	ZidUserCSS = Zid(25001)

	// WebUI JS zettel are in the range 30000..39999

	// WebUI image zettel are in the range 40000..49999
	ZidEmoji = Zid(40001)

	// Other sxn code zettel are in the range 50000..59999

	// Predefined Zettelmarkup zettel are in the range 60000..69999
	ZidRoleZettelZettel        = Zid(60010)
	ZidRoleConfigurationZettel = Zid(60020)
	ZidRoleRoleZettel          = Zid(60030)
	ZidRoleTagZettel           = Zid(60040)

	// Range 80000...89999 is reserved for web ui menus
	ZidTOCListsMenu = Zid(80001) // "Lists" menu

	// Range 90000...99999 is reserved for zettel templates
	ZidTOCNewTemplate    = Zid(90000)
	ZidTemplateNewZettel = Zid(90001)
	ZidTemplateNewRole   = Zid(90004)
	ZidTemplateNewTag    = Zid(90003)
	ZidTemplateNewUser   = Zid(90002)

	// Range 00000999999900...00000999999999 are predefined zettel to be searched by content.
	ZidAppDirectory = Zid(999999999)

	// Default Home Zettel
	ZidDefaultHome = Zid(10000000000)
)

// ParseUint interprets a string as a possible zettel identifier
// and returns its integer value.
func ParseUint(s string) (uint64, error) {
	res, err := strconv.ParseUint(s, 10, 47)
	if err != nil {
		return 0, err
	}
	if res == 0 || res > maxZid {
		return res, strconv.ErrRange
	}
	return res, nil
}

// Parse interprets a string as a zettel identification and
// returns its value.
func Parse(s string) (Zid, error) {
	if len(s) != LengthZid {
		return Invalid, strconv.ErrSyntax
	}
	res, err := ParseUint(s)
	if err != nil {
		return Invalid, err
	}
	return Zid(res), nil
}

// MustParse tries to interpret a string as a zettel identifier and returns
// its value or panics otherwise.
func MustParse(s string) Zid {
	zid, err := Parse(string(s))
	if err == nil {
		return zid
	}
	panic(err)
}

// String converts the zettel identification to a string of 14 digits.
// Only defined for valid ids.
func (zid Zid) String() string {
	var result [LengthZid]byte
	zid.toByteArray(&result)
	return string(result[:])
}

// Bytes converts the zettel identification to a byte slice of 14 digits.
// Only defined for valid ids.
func (zid Zid) Bytes() []byte {
	var result [LengthZid]byte
	zid.toByteArray(&result)
	return result[:]
}

// toByteArray converts the Zid into a fixed byte array, usable for printing.
//
// Based on idea by Daniel Lemire: "Converting integers to fix-digit representations quickly"
// https://lemire.me/blog/2021/11/18/converting-integers-to-fix-digit-representations-quickly/
func (zid Zid) toByteArray(result *[LengthZid]byte) {
	date := uint64(zid) / 1000000
	fullyear := date / 10000
	century, year := fullyear/100, fullyear%100
	monthday := date % 10000
	month, day := monthday/100, monthday%100
	time := uint64(zid) % 1000000
	hmtime, second := time/100, time%100
	hour, minute := hmtime/100, hmtime%100

	result[0] = byte(century/10) + '0'
	result[1] = byte(century%10) + '0'
	result[2] = byte(year/10) + '0'
	result[3] = byte(year%10) + '0'
	result[4] = byte(month/10) + '0'
	result[5] = byte(month%10) + '0'
	result[6] = byte(day/10) + '0'
	result[7] = byte(day%10) + '0'
	result[8] = byte(hour/10) + '0'
	result[9] = byte(hour%10) + '0'
	result[10] = byte(minute/10) + '0'
	result[11] = byte(minute%10) + '0'
	result[12] = byte(second/10) + '0'
	result[13] = byte(second%10) + '0'
}

// IsValid determines if zettel id is a valid one, e.g. consists of max. 14 digits.
func (zid Zid) IsValid() bool { return 0 < zid && zid <= maxZid }

// TimestampLayout to transform a date into a Zid and into other internal dates.
const TimestampLayout = "20060102150405"

// New returns a new zettel id based on the current time.
func New(withSeconds bool) Zid {
	now := time.Now().Local()
	var s string
	if withSeconds {
		s = now.Format(TimestampLayout)
	} else {
		s = now.Format("20060102150400")
	}
	res, err := Parse(s)
	if err != nil {
		panic(err)
	}
	return res
}

//-----------------------------------------------------------------------------
// Copyright (c) 2020-present Detlef Stern
//
// This file is part of zettelstore-client.
//
// Zettelstore Client 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: 2020-present Detlef Stern
//-----------------------------------------------------------------------------

// Package id_test provides unit tests for testing zettel id specific functions.
package id_test

import (
	"testing"

	"t73f.de/r/zsc/domain/id"
)

func TestIsValid(t *testing.T) {
	t.Parallel()
	validIDs := []string{
		"00000000000001",
		"00000000000020",
		"00000000000300",
		"00000000004000",
		"00000000050000",
		"00000000600000",
		"00000007000000",
		"00000080000000",
		"00000900000000",
		"00001000000000",
		"00020000000000",
		"00300000000000",
		"04000000000000",
		"50000000000000",
		"99999999999999",
		"00001007030200",
		"20200310195100",
		"12345678901234",
	}

	for i, sid := range validIDs {
		zid, err := id.Parse(sid)
		if err != nil {
			t.Errorf("i=%d: sid=%q is not valid, but should be. err=%v", i, sid, err)
		}
		s := zid.String()
		if s != sid {
			t.Errorf(
				"i=%d: zid=%v does not format to %q, but to %q", i, zid, sid, s)
		}
	}

	invalidIDs := []string{
		"", "0", "a",
		"00000000000000",
		"0000000000000a",
		"000000000000000",
		"20200310T195100",
		"+1234567890123",
	}

	for i, sid := range invalidIDs {
		if zid, err := id.Parse(sid); err == nil {
			t.Errorf("i=%d: sid=%q is valid (zid=%s), but should not be", i, sid, zid)
		}
	}
}

var sResult string // to disable compiler optimization in loop below

func BenchmarkString(b *testing.B) {
	var s string
	for b.Loop() {
		s = id.Zid(12345678901200).String()
	}
	sResult = s
}

var bResult []byte // to disable compiler optimization in loop below

func BenchmarkBytes(b *testing.B) {
	var bs []byte
	for b.Loop() {
		bs = id.Zid(12345678901200).Bytes()
	}
	bResult = bs
}

//-----------------------------------------------------------------------------
// Copyright (c) 2021-present Detlef Stern
//
// This file is part of zettelstore-client.
//
// Zettelstore Client 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 idset implements sets of zettel identifier.
package idset

import (
	"slices"
	"strings"

	"t73f.de/r/zsc/domain/id"
	"t73f.de/r/zsc/domain/meta"
)

// Set is a set of zettel identifier
type Set struct {
	seq []id.Zid
}

// String returns a string representation of the set.
func (s *Set) String() string {
	return "{" + s.MetaString() + "}"
}

// MetaString returns a string representation of the set to be stored as metadata.
func (s *Set) MetaString() string {
	if s == nil || len(s.seq) == 0 {
		return ""
	}
	var sb strings.Builder
	for i, zid := range s.seq {
		if i > 0 {
			sb.WriteByte(' ')
		}
		sb.Write(zid.Bytes())
	}
	return sb.String()
}

// MetaValue returns a metadata value representation of the set.
func (s *Set) MetaValue() meta.Value { return meta.Value(s.MetaString()) }

// New returns a new set of identifier with the given initial values.
func New(zids ...id.Zid) *Set {
	switch l := len(zids); l {
	case 0:
		return &Set{seq: nil}
	case 1:
		return &Set{seq: []id.Zid{zids[0]}}
	default:
		result := Set{seq: make([]id.Zid, 0, l)}
		result.AddSlice(zids)
		return &result
	}
}

// NewCap returns a new set of identifier with the given capacity and initial values.
func NewCap(c int, zids ...id.Zid) *Set {
	result := Set{seq: make([]id.Zid, 0, max(c, len(zids)))}
	result.AddSlice(zids)
	return &result
}

// IsEmpty returns true, if the set conains no element.
func (s *Set) IsEmpty() bool {
	return s == nil || len(s.seq) == 0
}

// Length returns the number of elements in this set.
func (s *Set) Length() int {
	if s == nil {
		return 0
	}
	return len(s.seq)
}

// Clone returns a copy of the given set.
func (s *Set) Clone() *Set {
	if s == nil || len(s.seq) == 0 {
		return nil
	}
	return &Set{seq: slices.Clone(s.seq)}
}

// Add adds a Add to the set.
func (s *Set) Add(zid id.Zid) *Set {
	if s == nil {
		return New(zid)
	}
	s.add(zid)
	return s
}

// Contains return true if the set is non-nil and the set contains the given Zettel identifier.
func (s *Set) Contains(zid id.Zid) bool { return s != nil && s.contains(zid) }

// ContainsOrNil return true if the set is nil or if the set contains the given Zettel identifier.
func (s *Set) ContainsOrNil(zid id.Zid) bool { return s == nil || s.contains(zid) }

// AddSlice adds all identifier of the given slice to the set.
func (s *Set) AddSlice(sl []id.Zid) *Set {
	if s == nil {
		return New(sl...)
	}
	s.seq = slices.Grow(s.seq, len(sl))
	for _, zid := range sl {
		s.add(zid)
	}
	return s
}

// SafeSorted returns the set as a new sorted slice of zettel identifier.
func (s *Set) SafeSorted() []id.Zid {
	if s == nil {
		return nil
	}
	return slices.Clone(s.seq)
}

// IntersectOrSet removes all zettel identifier that are not in the other set.
// Both sets can be modified by this method. One of them is the set returned.
// It contains the intersection of both, if s is not nil.
//
// If s == nil, then the other set is always returned.
func (s *Set) IntersectOrSet(other *Set) *Set {
	if s == nil || other == nil {
		return other.Clone()
	}
	topos, spos, opos := 0, 0, 0
	for spos < len(s.seq) && opos < len(other.seq) {
		sz, oz := s.seq[spos], other.seq[opos]
		if sz < oz {
			spos++
			continue
		}
		if sz > oz {
			opos++
			continue
		}
		s.seq[topos] = sz
		topos++
		spos++
		opos++
	}
	s.seq = s.seq[:topos]
	return s
}

// IUnion adds the elements of set other to s.
func (s *Set) IUnion(other *Set) *Set {
	if other == nil || len(other.seq) == 0 {
		return s
	}
	// TODO: if other is large enough (and s is not too small) -> optimize by swapping and/or loop through both
	return s.AddSlice(other.seq)
}

// ISubstract removes all zettel identifier from 's' that are in the set 'other'.
func (s *Set) ISubstract(other *Set) {
	if s == nil || len(s.seq) == 0 || other == nil || len(other.seq) == 0 {
		return
	}
	topos, spos, opos := 0, 0, 0
	for spos < len(s.seq) && opos < len(other.seq) {
		sz, oz := s.seq[spos], other.seq[opos]
		if sz < oz {
			s.seq[topos] = sz
			topos++
			spos++
			continue
		}
		if sz == oz {
			spos++
		}
		opos++
	}
	for spos < len(s.seq) {
		s.seq[topos] = s.seq[spos]
		topos++
		spos++
	}
	s.seq = s.seq[:topos]
}

// Diff returns the difference sets between the two sets: the first difference
// set is the set of elements that are in other, but not in s; the second
// difference set is the set of element that are in s but not in other.
//
// in other words: the first result is the set of elements from other that must
// be added to s; the second result is the set of elements that must be removed
// from s, so that s would have the same elemest as other.
func (s *Set) Diff(other *Set) (newS, remS *Set) {
	if s == nil || len(s.seq) == 0 {
		return other.Clone(), nil
	}
	if other == nil || len(other.seq) == 0 {
		return nil, s.Clone()
	}
	seqS, seqO := s.seq, other.seq
	var newRefs, remRefs []id.Zid
	npos, opos := 0, 0
	for npos < len(seqO) && opos < len(seqS) {
		rn, ro := seqO[npos], seqS[opos]
		if rn == ro {
			npos++
			opos++
			continue
		}
		if rn < ro {
			newRefs = append(newRefs, rn)
			npos++
			continue
		}
		remRefs = append(remRefs, ro)
		opos++
	}
	if npos < len(seqO) {
		newRefs = append(newRefs, seqO[npos:]...)
	}
	if opos < len(seqS) {
		remRefs = append(remRefs, seqS[opos:]...)
	}
	return newFromSlice(newRefs), newFromSlice(remRefs)
}

// Remove the identifier from the set.
func (s *Set) Remove(zid id.Zid) *Set {
	if s == nil || len(s.seq) == 0 {
		return nil
	}
	if pos, found := s.find(zid); found {
		copy(s.seq[pos:], s.seq[pos+1:])
		s.seq = s.seq[:len(s.seq)-1]
	}
	if len(s.seq) == 0 {
		return nil
	}
	return s
}

// Equal returns true if the other set is equal to the given set.
func (s *Set) Equal(other *Set) bool {
	if s == nil {
		return other == nil
	}
	if other == nil {
		return false
	}
	return slices.Equal(s.seq, other.seq)
}

// ForEach calls the given function for each element of the set.
//
// Every element is bigger than the previous one.
func (s *Set) ForEach(fn func(zid id.Zid)) {
	if s != nil {
		for _, zid := range s.seq {
			fn(zid)
		}
	}
}

// Pop return one arbitrary element of the set.
func (s *Set) Pop() (id.Zid, bool) {
	if s != nil {
		if l := len(s.seq); l > 0 {
			zid := s.seq[l-1]
			s.seq = s.seq[:l-1]
			return zid, true
		}
	}
	return id.Invalid, false
}

// Optimize the amount of memory to store the set.
func (s *Set) Optimize() {
	if s != nil {
		s.seq = slices.Clip(s.seq)
	}
}

// ----- unchecked base operations

func newFromSlice(seq []id.Zid) *Set {
	if l := len(seq); l == 0 {
		return nil
	}
	return &Set{seq: seq}
}

func (s *Set) add(zid id.Zid) {
	if pos, found := s.find(zid); !found {
		s.seq = slices.Insert(s.seq, pos, zid)
	}
}

func (s *Set) contains(zid id.Zid) bool {
	_, found := s.find(zid)
	return found
}

func (s *Set) find(zid id.Zid) (int, bool) {
	hi := len(s.seq)
	for lo := 0; lo < hi; {
		m := lo + (hi-lo)/2
		if z := s.seq[m]; z == zid {
			return m, true
		} else if z < zid {
			lo = m + 1
		} else {
			hi = m
		}
	}
	return hi, false
}

//-----------------------------------------------------------------------------
// Copyright (c) 2021-present Detlef Stern
//
// This file is part of zettelstore-client.
//
// Zettelstore Client 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 idset_test

import (
	"slices"
	"testing"

	"t73f.de/r/zsc/domain/id"
	"t73f.de/r/zsc/domain/id/idset"
)

func TestSetContainsOrNil(t *testing.T) {
	t.Parallel()
	testcases := []struct {
		s   *idset.Set
		zid id.Zid
		exp bool
	}{
		{nil, id.Invalid, true},
		{nil, 14, true},
		{idset.New(), id.Invalid, false},
		{idset.New(), 1, false},
		{idset.New(), id.Invalid, false},
		{idset.New(1), 1, true},
	}
	for i, tc := range testcases {
		got := tc.s.ContainsOrNil(tc.zid)
		if got != tc.exp {
			t.Errorf("%d: %v.ContainsOrNil(%v) == %v, but got %v", i, tc.s, tc.zid, tc.exp, got)
		}
	}
}

func TestSetAdd(t *testing.T) {
	t.Parallel()
	testcases := []struct {
		s1, s2 *idset.Set
		exp    []id.Zid
	}{
		{nil, nil, nil},
		{idset.New(), nil, nil},
		{idset.New(), idset.New(), nil},
		{nil, idset.New(1), []id.Zid{1}},
		{idset.New(1), nil, []id.Zid{1}},
		{idset.New(1), idset.New(), []id.Zid{1}},
		{idset.New(1), idset.New(2), []id.Zid{1, 2}},
		{idset.New(1), idset.New(1), []id.Zid{1}},
	}
	for i, tc := range testcases {
		sl1 := tc.s1.SafeSorted()
		sl2 := tc.s2.SafeSorted()
		got := tc.s1.IUnion(tc.s2).SafeSorted()
		if !slices.Equal(got, tc.exp) {
			t.Errorf("%d: %v.Add(%v) should be %v, but got %v", i, sl1, sl2, tc.exp, got)
		}
	}
}

func TestSetSafeSorted(t *testing.T) {
	t.Parallel()
	testcases := []struct {
		set *idset.Set
		exp []id.Zid
	}{
		{nil, nil},
		{idset.New(), nil},
		{idset.New(9, 4, 6, 1, 7), []id.Zid{1, 4, 6, 7, 9}},
	}
	for i, tc := range testcases {
		got := tc.set.SafeSorted()
		if !slices.Equal(got, tc.exp) {
			t.Errorf("%d: %v.SafeSorted() should be %v, but got %v", i, tc.set, tc.exp, got)
		}
	}
}

func TestSetIntersectOrSet(t *testing.T) {
	t.Parallel()
	testcases := []struct {
		s1, s2 *idset.Set
		exp    []id.Zid
	}{
		{nil, nil, nil},
		{idset.New(), nil, nil},
		{nil, idset.New(), nil},
		{idset.New(), idset.New(), nil},
		{idset.New(1), nil, nil},
		{nil, idset.New(1), []id.Zid{1}},
		{idset.New(1), idset.New(), nil},
		{idset.New(), idset.New(1), nil},
		{idset.New(1), idset.New(2), nil},
		{idset.New(2), idset.New(1), nil},
		{idset.New(1), idset.New(1), []id.Zid{1}},
	}
	for i, tc := range testcases {
		sl1 := tc.s1.SafeSorted()
		sl2 := tc.s2.SafeSorted()
		got := tc.s1.IntersectOrSet(tc.s2).SafeSorted()
		if !slices.Equal(got, tc.exp) {
			t.Errorf("%d: %v.IntersectOrSet(%v) should be %v, but got %v", i, sl1, sl2, tc.exp, got)
		}
	}
}

func TestSetIUnion(t *testing.T) {
	t.Parallel()
	testcases := []struct {
		s1, s2 *idset.Set
		exp    *idset.Set
	}{
		{nil, nil, nil},
		{idset.New(), nil, nil},
		{nil, idset.New(), nil},
		{idset.New(), idset.New(), nil},
		{idset.New(1), nil, idset.New(1)},
		{nil, idset.New(1), idset.New(1)},
		{idset.New(1), idset.New(), idset.New(1)},
		{idset.New(), idset.New(1), idset.New(1)},
		{idset.New(1), idset.New(2), idset.New(1, 2)},
		{idset.New(2), idset.New(1), idset.New(2, 1)},
		{idset.New(1), idset.New(1), idset.New(1)},
		{idset.New(1, 2, 3), idset.New(2, 3, 4), idset.New(1, 2, 3, 4)},
	}
	for i, tc := range testcases {
		s1 := tc.s1.Clone()
		sl1 := s1.SafeSorted()
		sl2 := tc.s2.SafeSorted()
		got := s1.IUnion(tc.s2)
		if !got.Equal(tc.exp) {
			t.Errorf("%d: %v.IUnion(%v) should be %v, but got %v", i, sl1, sl2, tc.exp, got)
		}
	}
}

func TestSetISubtract(t *testing.T) {
	t.Parallel()
	testcases := []struct {
		s1, s2 *idset.Set
		exp    []id.Zid
	}{
		{nil, nil, nil},
		{idset.New(), nil, nil},
		{nil, idset.New(), nil},
		{idset.New(), idset.New(), nil},
		{idset.New(1), nil, []id.Zid{1}},
		{nil, idset.New(1), nil},
		{idset.New(1), idset.New(), []id.Zid{1}},
		{idset.New(), idset.New(1), nil},
		{idset.New(1), idset.New(2), []id.Zid{1}},
		{idset.New(2), idset.New(1), []id.Zid{2}},
		{idset.New(1), idset.New(1), nil},
		{idset.New(1, 2, 3), idset.New(1), []id.Zid{2, 3}},
		{idset.New(1, 2, 3), idset.New(2), []id.Zid{1, 3}},
		{idset.New(1, 2, 3), idset.New(3), []id.Zid{1, 2}},
		{idset.New(1, 2, 3), idset.New(1, 2), []id.Zid{3}},
		{idset.New(1, 2, 3), idset.New(1, 3), []id.Zid{2}},
		{idset.New(1, 2, 3), idset.New(2, 3), []id.Zid{1}},
	}
	for i, tc := range testcases {
		s1 := tc.s1.Clone()
		sl1 := s1.SafeSorted()
		sl2 := tc.s2.SafeSorted()
		s1.ISubstract(tc.s2)
		got := s1.SafeSorted()
		if !slices.Equal(got, tc.exp) {
			t.Errorf("%d: %v.ISubstract(%v) should be %v, but got %v", i, sl1, sl2, tc.exp, got)
		}
	}
}

func TestSetDiff(t *testing.T) {
	t.Parallel()
	testcases := []struct {
		in1, in2   *idset.Set
		exp1, exp2 *idset.Set
	}{
		{nil, nil, nil, nil},
		{idset.New(1), nil, nil, idset.New(1)},
		{nil, idset.New(1), idset.New(1), nil},
		{idset.New(1), idset.New(1), nil, nil},
		{idset.New(1, 2), idset.New(1), nil, idset.New(2)},
		{idset.New(1), idset.New(1, 2), idset.New(2), nil},
		{idset.New(1, 2), idset.New(1, 3), idset.New(3), idset.New(2)},
		{idset.New(1, 2, 3), idset.New(2, 3, 4), idset.New(4), idset.New(1)},
		{idset.New(2, 3, 4), idset.New(1, 2, 3), idset.New(1), idset.New(4)},
	}
	for i, tc := range testcases {
		gotN, gotO := tc.in1.Diff(tc.in2)
		if !tc.exp1.Equal(gotN) {
			t.Errorf("%d: expected %v, but got: %v", i, tc.exp1, gotN)
		}
		if !tc.exp2.Equal(gotO) {
			t.Errorf("%d: expected %v, but got: %v", i, tc.exp2, gotO)
		}
	}
}

func TestSetRemove(t *testing.T) {
	t.Parallel()
	testcases := []struct {
		s1, s2 *idset.Set
		exp    []id.Zid
	}{
		{nil, nil, nil},
		{idset.New(), nil, nil},
		{idset.New(), idset.New(), nil},
		{idset.New(1), nil, []id.Zid{1}},
		{idset.New(1), idset.New(), []id.Zid{1}},
		{idset.New(1), idset.New(2), []id.Zid{1}},
		{idset.New(1), idset.New(1), []id.Zid{}},
	}
	for i, tc := range testcases {
		sl1 := tc.s1.SafeSorted()
		sl2 := tc.s2.SafeSorted()
		newS1 := idset.New(sl1...)
		newS1.ISubstract(tc.s2)
		got := newS1.SafeSorted()
		if !slices.Equal(got, tc.exp) {
			t.Errorf("%d: %v.Remove(%v) should be %v, but got %v", i, sl1, sl2, tc.exp, got)
		}
	}
}

func BenchmarkSet(b *testing.B) {
	s := idset.NewCap(b.N)
	for i := range b.N {
		s.Add(id.Zid(i))
	}
}

//-----------------------------------------------------------------------------
// Copyright (c) 2022-present Detlef Stern
//
// This file is part of zettelstore-client.
//
// Zettelstore Client 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: 2022-present Detlef Stern
//-----------------------------------------------------------------------------

package meta

import (
	"slices"
	"strings"
)

// Arrangement stores metadata within its categories.
// Typecally a category might be a tag name, a role name, a syntax value.
type Arrangement map[string][]*Meta

// CreateArrangement by inspecting a given key and use the found
// value as a category.
func CreateArrangement(metaList []*Meta, key string) Arrangement {
	if len(metaList) == 0 {
		return nil
	}
	descr := Type(key)
	if descr == nil {
		return nil
	}
	if descr.IsSet {
		return createSetArrangement(metaList, key)
	}
	return createSimplearrangement(metaList, key)
}

func createSetArrangement(metaList []*Meta, key string) Arrangement {
	a := make(Arrangement)
	for _, m := range metaList {
		for val := range m.GetFields(key) {
			a[val] = append(a[val], m)
		}
	}
	return a
}

func createSimplearrangement(metaList []*Meta, key string) Arrangement {
	a := make(Arrangement)
	for _, m := range metaList {
		if val, ok := m.Get(key); ok && val != "" {
			a[string(val)] = append(a[string(val)], m)
		}
	}
	return a
}

// Counted returns the list of categories, together with the number of
// metadata for each category.
func (a Arrangement) Counted() CountedCategories {
	if len(a) == 0 {
		return nil
	}
	result := make(CountedCategories, 0, len(a))
	for cat, metas := range a {
		result = append(result, CountedCategory{Name: cat, Count: len(metas)})
	}
	return result
}

// CountedCategory contains of a name and the number how much this name occured
// somewhere.
type CountedCategory struct {
	Name  string
	Count int
}

// CountedCategories is the list of CountedCategories.
// Every name must occur only once.
type CountedCategories []CountedCategory

// SortByName sorts the list by the name attribute.
// Since each name must occur only once, two CountedCategories cannot have
// the same name.
func (ccs CountedCategories) SortByName() {
	slices.SortFunc(ccs, func(i, j CountedCategory) int { return strings.Compare(i.Name, j.Name) })
}

// SortByCount sorts the list by the count attribute, descending.
// If two counts are equal, elements are sorted by name.
func (ccs CountedCategories) SortByCount() {
	slices.SortFunc(ccs, func(i, j CountedCategory) int {
		iCount, jCount := i.Count, j.Count
		if iCount > jCount {
			return -1
		}
		if iCount == jCount {
			return strings.Compare(i.Name, j.Name)
		}
		return 1
	})
}

// Categories returns just the category names.
func (ccs CountedCategories) Categories() []string {
	result := make([]string, len(ccs))
	for i, cc := range ccs {
		result[i] = cc.Name
	}
	return result
}

//-----------------------------------------------------------------------------
// Copyright (c) 2020-present Detlef Stern
//
// This file is part of zettelstore-client.
//
// Zettelstore Client 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: 2020-present Detlef Stern
//-----------------------------------------------------------------------------

// Package meta provides the zettel specific type 'meta'.
package meta

import (
	"iter"
	"maps"
	"regexp"
	"slices"
	"strings"
	"unicode"
	"unicode/utf8"

	"t73f.de/r/zero/set"
	"t73f.de/r/zsc/domain/id"
)

type keyUsage int

const (
	_             keyUsage = iota
	usageUser              // Key will be manipulated by the user
	usageComputed          // Key is computed by zettelstore
	usageProperty          // Key is computed and not stored by zettelstore
)

// DescriptionKey formally describes each supported metadata key.
type DescriptionKey struct {
	Name    string
	Type    *DescriptionType
	usage   keyUsage
	Inverse string
}

// IsComputed returns true, if metadata is computed and not set by the user.
func (kd *DescriptionKey) IsComputed() bool { return kd.usage >= usageComputed }

// IsProperty returns true, if metadata is a computed property.
func (kd *DescriptionKey) IsProperty() bool { return kd.usage >= usageProperty }

var registeredKeys = make(map[string]*DescriptionKey)

func registerKey(name string, t *DescriptionType, usage keyUsage, inverse string) {
	if _, ok := registeredKeys[name]; ok {
		panic("Key '" + name + "' already defined")
	}
	if inverse != "" {
		if t != TypeID && t != TypeIDSet {
			panic("Inversable key '" + name + "' is not identifier type, but " + t.String())
		}
		inv, ok := registeredKeys[inverse]
		if !ok {
			panic("Inverse Key '" + inverse + "' not found")
		}
		if !inv.IsComputed() {
			panic("Inverse Key '" + inverse + "' is not computed.")
		}
		if inv.Type != TypeIDSet {
			panic("Inverse Key '" + inverse + "' is not an identifier set, but " + inv.Type.String())
		}
	}
	registeredKeys[name] = &DescriptionKey{name, t, usage, inverse}
}

// IsComputed returns true, if key denotes a computed metadata key.
func IsComputed(name string) bool {
	if kd, ok := registeredKeys[name]; ok {
		return kd.IsComputed()
	}
	return false
}

// IsProperty returns true, if key denotes a property metadata value.
func IsProperty(name string) bool {
	if kd, ok := registeredKeys[name]; ok {
		return kd.IsProperty()
	}
	return false
}

// Inverse returns the name of the inverse key.
func Inverse(name string) string {
	if kd, ok := registeredKeys[name]; ok {
		return kd.Inverse
	}
	return ""
}

// GetDescription returns the key description object of the given key name.
func GetDescription(name string) DescriptionKey {
	if d, ok := registeredKeys[name]; ok {
		return *d
	}
	return DescriptionKey{Type: Type(name)}
}

// GetSortedKeyDescriptions delivers all metadata key descriptions as a slice, sorted by name.
func GetSortedKeyDescriptions() []*DescriptionKey {
	keys := slices.Sorted(maps.Keys(registeredKeys))
	result := make([]*DescriptionKey, 0, len(keys))
	for _, n := range keys {
		result = append(result, registeredKeys[n])
	}
	return result
}

// Key is the type of metadata keys.
type Key = string

// Predefined / supported metadata keys.
//
// See [Supported Metadata Keys].
//
// [Supported Metadata Keys]: https://zettelstore.de/manual/h/00001006020000
const (
	KeyID           = "id"
	KeyTitle        = "title"
	KeyRole         = "role"
	KeyTags         = "tags"
	KeySyntax       = "syntax"
	KeyAuthor       = "author"
	KeyBack         = "back"
	KeyBackward     = "backward"
	KeyBoxNumber    = "box-number"
	KeyCopyright    = "copyright"
	KeyCreated      = "created"
	KeyCredential   = "credential"
	KeyDead         = "dead"
	KeyExpire       = "expire"
	KeyFolge        = "folge"
	KeyFolgeRole    = "folge-role"
	KeyForward      = "forward"
	KeyLang         = "lang"
	KeyLicense      = "license"
	KeyModified     = "modified"
	KeyPrecursor    = "precursor"
	KeyPredecessor  = "predecessor"
	KeyPrequel      = "prequel"
	KeyPublished    = "published"
	KeyQuery        = "query"
	KeyReadOnly     = "read-only"
	KeySequel       = "sequel"
	KeySubordinates = "subordinates"
	KeySuccessors   = "successors"
	KeySummary      = "summary"
	KeySuperior     = "superior"
	KeyURL          = "url"
	KeyUselessFiles = "useless-files"
	KeyUserID       = "user-id"
	KeyUserRole     = "user-role"
	KeyVisibility   = "visibility"
)

// Supported keys.
func init() {
	registerKey(KeyID, TypeID, usageComputed, "")
	registerKey(KeyTitle, TypeEmpty, usageUser, "")
	registerKey(KeyRole, TypeWord, usageUser, "")
	registerKey(KeyTags, TypeTagSet, usageUser, "")
	registerKey(KeySyntax, TypeWord, usageUser, "")

	// Properties that are inverse keys
	registerKey(KeyFolge, TypeIDSet, usageProperty, "")
	registerKey(KeySequel, TypeIDSet, usageProperty, "")
	registerKey(KeySuccessors, TypeIDSet, usageProperty, "")
	registerKey(KeySubordinates, TypeIDSet, usageProperty, "")

	// Non-inverse keys
	registerKey(KeyAuthor, TypeString, usageUser, "")
	registerKey(KeyBack, TypeIDSet, usageProperty, "")
	registerKey(KeyBackward, TypeIDSet, usageProperty, "")
	registerKey(KeyBoxNumber, TypeNumber, usageProperty, "")
	registerKey(KeyCopyright, TypeString, usageUser, "")
	registerKey(KeyCreated, TypeTimestamp, usageComputed, "")
	registerKey(KeyCredential, TypeCredential, usageUser, "")
	registerKey(KeyDead, TypeIDSet, usageProperty, "")
	registerKey(KeyExpire, TypeTimestamp, usageUser, "")
	registerKey(KeyFolgeRole, TypeWord, usageUser, "")
	registerKey(KeyForward, TypeIDSet, usageProperty, "")
	registerKey(KeyLang, TypeWord, usageUser, "")
	registerKey(KeyLicense, TypeEmpty, usageUser, "")
	registerKey(KeyModified, TypeTimestamp, usageComputed, "")
	registerKey(KeyPrecursor, TypeIDSet, usageUser, KeyFolge)
	registerKey(KeyPredecessor, TypeID, usageUser, KeySuccessors)
	registerKey(KeyPrequel, TypeIDSet, usageUser, KeySequel)
	registerKey(KeyPublished, TypeTimestamp, usageProperty, "")
	registerKey(KeyQuery, TypeEmpty, usageUser, "")
	registerKey(KeyReadOnly, TypeWord, usageUser, "")
	registerKey(KeySummary, TypeString, usageUser, "")
	registerKey(KeySuperior, TypeIDSet, usageUser, KeySubordinates)
	registerKey(KeyURL, TypeURL, usageUser, "")
	registerKey(KeyUselessFiles, TypeString, usageProperty, "")
	registerKey(KeyUserID, TypeWord, usageUser, "")
	registerKey(KeyUserRole, TypeWord, usageUser, "")
	registerKey(KeyVisibility, TypeWord, usageUser, "")
}

// NewPrefix is the prefix for metadata keys in template zettel for creating new zettel.
const NewPrefix = "new-"

// Meta contains all meta-data of a zettel.
type Meta struct {
	Zid     id.Zid
	pairs   map[Key]Value
	YamlSep bool
}

// New creates a new chunk for storing metadata.
func New(zid id.Zid) *Meta {
	return &Meta{Zid: zid, pairs: make(map[Key]Value, 5)}
}

// NewWithData creates metadata object with given data.
func NewWithData(zid id.Zid, data map[string]string) *Meta {
	pairs := make(map[Key]Value, len(data))
	for k, v := range data {
		pairs[k] = Value(v)
	}
	return &Meta{Zid: zid, pairs: pairs}
}

// ByteSize returns the number of bytes stored for the metadata.
func (m *Meta) ByteSize() int {
	if m == nil {
		return 0
	}
	result := 6 // storage needed for Zid
	for k, v := range m.pairs {
		result += len(k) + len(v) + 1 // 1 because separator
	}
	return result
}

// Clone returns a new copy of the metadata.
func (m *Meta) Clone() *Meta {
	return &Meta{
		Zid:     m.Zid,
		pairs:   maps.Clone(m.pairs),
		YamlSep: m.YamlSep,
	}
}

// Map returns a copy of the meta data as a string map.
func (m *Meta) Map() map[string]string {
	pairs := make(map[string]string, len(m.pairs))
	for k, v := range m.pairs {
		pairs[k] = string(v)
	}
	return pairs
}

var reKey = regexp.MustCompile("^[0-9a-z][-0-9a-z]{0,254}$")

// KeyIsValid returns true, if the string is a valid metadata key.
func KeyIsValid(s string) bool { return reKey.MatchString(s) }

var firstKeys = []string{KeyTitle, KeyRole, KeyTags, KeySyntax}

// Set stores the given string value under the given key.
func (m *Meta) Set(key string, value Value) {
	if key != KeyID {
		m.pairs[key] = value.TrimSpace()
	}
}

// SetNonEmpty stores the given value under the given key, if the value is non-empty.
// An empty value will delete the previous association.
func (m *Meta) SetNonEmpty(key string, value Value) {
	if value == "" {
		delete(m.pairs, key) // TODO: key != KeyID
	} else {
		m.Set(key, value.TrimSpace())
	}
}

// Get retrieves the string value of a given key. The bool value signals,
// whether there was a value stored or not.
func (m *Meta) Get(key string) (Value, bool) {
	if m == nil {
		return "", false
	}
	if key == KeyID {
		return Value(m.Zid.String()), true
	}
	value, ok := m.pairs[key]
	return value, ok
}

// GetDefault retrieves the string value of the given key. If no value was
// stored, the given default value is returned.
func (m *Meta) GetDefault(key string, def Value) Value {
	if value, found := m.Get(key); found {
		return value
	}
	return def
}

// GetTitle returns the title of the metadata. It is the only key that has a
// defined default value: the string representation of the zettel identifier.
func (m *Meta) GetTitle() string {
	if title, found := m.Get(KeyTitle); found {
		return string(title)
	}
	return m.Zid.String()
}

// All returns an iterator over all key/value pairs, except the zettel identifier
// and computed values.
func (m *Meta) All() iter.Seq2[Key, Value] {
	return func(yield func(Key, Value) bool) {
		m.firstKeys()(yield)
		m.restKeys(notComputedKey)(yield)
	}
}

// Computed returns an iterator over all key/value pairs, except the zettel identifier.
func (m *Meta) Computed() iter.Seq2[Key, Value] {
	return func(yield func(Key, Value) bool) {
		m.firstKeys()(yield)
		m.restKeys(anyKey)(yield)
	}
}

// Rest returns an iterator over all key/value pairs, except the zettel identifier,
// the main keys, and computed values.
func (m *Meta) Rest() iter.Seq2[Key, Value] {
	return func(yield func(Key, Value) bool) {
		m.restKeys(notComputedKey)(yield)
	}
}

// ComputedRest returns an iterator over all key/value pairs, except the zettel identifier,
// and the main keys.
func (m *Meta) ComputedRest() iter.Seq2[Key, Value] {
	return func(yield func(Key, Value) bool) {
		m.restKeys(anyKey)(yield)
	}
}

func (m *Meta) firstKeys() iter.Seq2[Key, Value] {
	return func(yield func(Key, Value) bool) {
		for _, key := range firstKeys {
			if val, ok := m.pairs[key]; ok {
				if !yield(key, val) {
					return
				}
			}
		}
	}
}

func (m *Meta) restKeys(addKeyPred func(Key) bool) iter.Seq2[Key, Value] {
	return func(yield func(Key, Value) bool) {
		keys := slices.Sorted(maps.Keys(m.pairs))
		for _, key := range keys {
			if !slices.Contains(firstKeys, key) && addKeyPred(key) {
				if !yield(key, m.pairs[key]) {
					return
				}
			}
		}
	}
}

func notComputedKey(key string) bool { return !IsComputed(key) }
func anyKey(string) bool             { return true }

// Delete removes a key from the data.
func (m *Meta) Delete(key string) {
	if key != KeyID {
		delete(m.pairs, key)
	}
}

// Equal compares to metas for equality.
func (m *Meta) Equal(o *Meta, allowComputed bool) bool {
	if m == nil && o == nil {
		return true
	}
	if m == nil || o == nil || m.Zid != o.Zid {
		return false
	}
	tested := set.New[string]()
	for k, v := range m.pairs {
		tested.Add(k)
		if !equalValue(k, v, o, allowComputed) {
			return false
		}
	}
	for k, v := range o.pairs {
		if !tested.Contains(k) && !equalValue(k, v, m, allowComputed) {
			return false
		}
	}
	return true
}

func equalValue(key string, val Value, other *Meta, allowComputed bool) bool {
	if allowComputed || !IsComputed(key) {
		if valO, found := other.pairs[key]; !found || val != valO {
			return false
		}
	}
	return true
}

// Sanitize all metadata keys and values, so that they can be written safely into a file.
func (m *Meta) Sanitize() {
	if m == nil {
		return
	}
	for key, val := range m.pairs {
		newKey := RemoveNonGraphic(key)
		if key == newKey {
			m.pairs[key] = Value(RemoveNonGraphic(string(val)))
		} else {
			delete(m.pairs, key)
			m.pairs[newKey] = Value(RemoveNonGraphic(string(val)))
		}
	}
}

// RemoveNonGraphic changes the given string not to include non-graphical characters.
// It is needed to sanitize meta data.
func RemoveNonGraphic(s string) string {
	if s == "" {
		return ""
	}
	pos := 0
	var sb strings.Builder
	for pos < len(s) {
		nextPos := strings.IndexFunc(s[pos:], func(r rune) bool { return !unicode.IsGraphic(r) })
		if nextPos < 0 {
			break
		}
		sb.WriteString(s[pos:nextPos])
		sb.WriteByte(' ')
		_, size := utf8.DecodeRuneInString(s[nextPos:])
		pos = nextPos + size
	}
	if pos == 0 {
		return strings.TrimSpace(s)
	}
	sb.WriteString(s[pos:])
	return strings.TrimSpace(sb.String())
}

//-----------------------------------------------------------------------------
// Copyright (c) 2020-present Detlef Stern
//
// This file is part of zettelstore-client.
//
// Zettelstore Client 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: 2020-present Detlef Stern
//-----------------------------------------------------------------------------

package meta

import (
	"iter"
	"slices"
	"strings"
	"testing"

	"t73f.de/r/zsc/domain/id"
)

const testID = id.Zid(98765432101234)

func TestKeyIsValid(t *testing.T) {
	t.Parallel()
	validKeys := []string{"0", "a", "0-", "title", "title-----", strings.Repeat("r", 255)}
	for _, key := range validKeys {
		if !KeyIsValid(key) {
			t.Errorf("Key %q wrongly identified as invalid key", key)
		}
	}
	invalidKeys := []string{"", "-", "-a", "Title", "a_b", strings.Repeat("e", 256)}
	for _, key := range invalidKeys {
		if KeyIsValid(key) {
			t.Errorf("Key %q wrongly identified as valid key", key)
		}
	}
}

func TestTitleHeader(t *testing.T) {
	t.Parallel()
	m := New(testID)
	if got, ok := m.Get(KeyTitle); ok && got != "" {
		t.Errorf("Title is not empty, but %q", got)
	}
	addToMeta(m, KeyTitle, " ")
	if got, ok := m.Get(KeyTitle); ok && got != "" {
		t.Errorf("Title is not empty, but %q", got)
	}
	const st = "A simple text"
	addToMeta(m, KeyTitle, " "+st+"  ")
	if got, ok := m.Get(KeyTitle); !ok || got != st {
		t.Errorf("Title is not %q, but %q", st, got)
	}
	addToMeta(m, KeyTitle, "  "+st+"\t")
	const exp = st + " " + st
	if got, ok := m.Get(KeyTitle); !ok || got != exp {
		t.Errorf("Title is not %q, but %q", exp, got)
	}

	m = New(testID)
	const at = "A Title"
	addToMeta(m, KeyTitle, at)
	addToMeta(m, KeyTitle, " ")
	if got, ok := m.Get(KeyTitle); !ok || got != at {
		t.Errorf("Title is not %q, but %q", at, got)
	}
}

func checkTags(t *testing.T, exp []string, m *Meta) {
	t.Helper()
	got := slices.Collect(m.GetFields(KeyTags))
	for i, tag := range exp {
		if i < len(got) {
			if tag != got[i] {
				t.Errorf("Pos=%d, expected %q, got %q", i, exp[i], got[i])
			}
		} else {
			t.Errorf("Expected %q, but is missing", exp[i])
		}
	}
	if len(exp) < len(got) {
		t.Errorf("Extra tags: %q", got[len(exp):])
	}
}

func TestTagsHeader(t *testing.T) {
	t.Parallel()
	m := New(testID)
	checkTags(t, []string{}, m)

	addToMeta(m, KeyTags, "")
	checkTags(t, []string{}, m)

	addToMeta(m, KeyTags, "  #t1 #t2  #t3 #t4  ")
	checkTags(t, []string{"#t1", "#t2", "#t3", "#t4"}, m)

	addToMeta(m, KeyTags, "#t5")
	checkTags(t, []string{"#t1", "#t2", "#t3", "#t4", "#t5"}, m)

	addToMeta(m, KeyTags, "t6")
	checkTags(t, []string{"#t1", "#t2", "#t3", "#t4", "#t5"}, m)
}

func TestSyntax(t *testing.T) {
	t.Parallel()
	m := New(testID)
	if got, ok := m.Get(KeySyntax); ok || got != "" {
		t.Errorf("Syntax is not %q, but %q", "", got)
	}
	addToMeta(m, KeySyntax, " ")
	if got, _ := m.Get(KeySyntax); got != "" {
		t.Errorf("Syntax is not %q, but %q", "", got)
	}
	addToMeta(m, KeySyntax, "MarkDown")
	const exp = "markdown"
	if got, ok := m.Get(KeySyntax); !ok || got != exp {
		t.Errorf("Syntax is not %q, but %q", exp, got)
	}
	addToMeta(m, KeySyntax, " ")
	if got, _ := m.Get(KeySyntax); got != "" {
		t.Errorf("Syntax is not %q, but %q", "", got)
	}
}

func checkHeader(t *testing.T, exp map[string]string, gotI iter.Seq2[Key, Value]) {
	t.Helper()
	got := make(map[string]string)
	gotI(func(key Key, val Value) bool {
		got[key] = string(val)
		if _, ok := exp[key]; !ok {
			t.Errorf("Key %q is not expected, but has value %q", key, val)
		}
		return true
	})
	for k, v := range exp {
		if gv, ok := got[k]; !ok || v != gv {
			if ok {
				t.Errorf("Key %q is not %q, but %q", k, v, got[k])
			} else {
				t.Errorf("Key %q missing, should have value %q", k, v)
			}
		}
	}
}

func TestDefaultHeader(t *testing.T) {
	t.Parallel()
	m := New(testID)
	addToMeta(m, "h1", "d1")
	addToMeta(m, "H2", "D2")
	addToMeta(m, "H1", "D1.1")
	exp := map[string]string{"h1": "d1 D1.1", "h2": "D2"}
	checkHeader(t, exp, m.All())
	addToMeta(m, "", "d0")
	checkHeader(t, exp, m.All())
	addToMeta(m, "h3", "")
	exp["h3"] = ""
	checkHeader(t, exp, m.All())
	addToMeta(m, "h3", "  ")
	checkHeader(t, exp, m.All())
	addToMeta(m, "h4", " ")
	exp["h4"] = ""
	checkHeader(t, exp, m.All())
}

func TestDelete(t *testing.T) {
	t.Parallel()
	m := New(testID)
	m.Set("key", "val")
	if got, ok := m.Get("key"); !ok || got != "val" {
		t.Errorf("Value != %q, got: %v/%q", "val", ok, got)
	}
	m.Set("key", "")
	if got, ok := m.Get("key"); !ok || got != "" {
		t.Errorf("Value != %q, got: %v/%q", "", ok, got)
	}
	m.Delete("key")
	if got, ok := m.Get("key"); ok || got != "" {
		t.Errorf("Value != %q, got: %v/%q", "", ok, got)
	}
}

func TestEqual(t *testing.T) {
	t.Parallel()
	testcases := []struct {
		pairs1, pairs2 []string
		allowComputed  bool
		exp            bool
	}{
		{nil, nil, true, true},
		{nil, nil, false, true},
		{[]string{"a", "a"}, nil, false, false},
		{[]string{"a", "a"}, nil, true, false},
		{[]string{KeyFolge, "0"}, nil, true, false},
		{[]string{KeyFolge, "0"}, nil, false, true},
		{[]string{KeyFolge, "0"}, []string{KeyFolge, "0"}, true, true},
		{[]string{KeyFolge, "0"}, []string{KeyFolge, "0"}, false, true},
	}
	for i, tc := range testcases {
		m1 := pairs2meta(tc.pairs1)
		m2 := pairs2meta(tc.pairs2)
		got := m1.Equal(m2, tc.allowComputed)
		if tc.exp != got {
			t.Errorf("%d: %v =?= %v: expected=%v, but got=%v", i, tc.pairs1, tc.pairs2, tc.exp, got)
		}
		got = m2.Equal(m1, tc.allowComputed)
		if tc.exp != got {
			t.Errorf("%d: %v =!= %v: expected=%v, but got=%v", i, tc.pairs1, tc.pairs2, tc.exp, got)
		}
	}

	// Pathologic cases
	var m1, m2 *Meta
	if !m1.Equal(m2, true) {
		t.Error("Nil metas should be treated equal")
	}
	m1 = New(testID)
	if m1.Equal(m2, true) {
		t.Error("Empty meta should not be equal to nil")
	}
	if m2.Equal(m1, true) {
		t.Error("Nil meta should should not be equal to empty")
	}
	m2 = New(testID + 1)
	if m1.Equal(m2, true) {
		t.Error("Different ID should differentiate")
	}
	if m2.Equal(m1, true) {
		t.Error("Different ID should differentiate")
	}
}

func pairs2meta(pairs []string) *Meta {
	m := New(testID)
	for i := 0; i < len(pairs); i += 2 {
		m.Set(pairs[i], Value(pairs[i+1]))
	}
	return m
}

func TestRemoveNonGraphic(t *testing.T) {
	testCases := []struct {
		inp string
		exp string
	}{
		{"", ""},
		{" ", ""},
		{"a", "a"},
		{"a ", "a"},
		{"a b", "a b"},
		{"\n", ""},
		{"a\n", "a"},
		{"a\nb", "a b"},
		{"a\tb", "a b"},
	}
	for i, tc := range testCases {
		got := RemoveNonGraphic(tc.inp)
		if tc.exp != got {
			t.Errorf("%q/%d: expected %q, but got %q", tc.inp, i, tc.exp, got)
		}
	}
}

//-----------------------------------------------------------------------------
// Copyright (c) 2020-present Detlef Stern
//
// This file is part of zettelstore-client.
//
// Zettelstore Client 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: 2020-present Detlef Stern
//-----------------------------------------------------------------------------

package meta

import (
	"iter"
	"slices"
	"strings"

	"t73f.de/r/zero/set"
	"t73f.de/r/zsc/domain/id"
	"t73f.de/r/zsx/input"
)

// NewFromInput parses the meta data of a zettel.
func NewFromInput(zid id.Zid, inp *input.Input) *Meta {
	if inp.Ch == '-' && inp.PeekN(0) == '-' && inp.PeekN(1) == '-' {
		skipToEOL(inp)
		inp.EatEOL()
	}
	meta := New(zid)
	for {
		inp.SkipSpace()
		switch inp.Ch {
		case '\r':
			if inp.Peek() == '\n' {
				inp.Next()
			}
			fallthrough
		case '\n':
			inp.Next()
			return meta
		case input.EOS:
			return meta
		case '%':
			skipToEOL(inp)
			inp.EatEOL()
			continue
		}
		parseHeader(meta, inp)
		if inp.Ch == '-' && inp.PeekN(0) == '-' && inp.PeekN(1) == '-' {
			skipToEOL(inp)
			inp.EatEOL()
			meta.YamlSep = true
			return meta
		}
	}
}

func parseHeader(m *Meta, inp *input.Input) {
	pos := inp.Pos
	for isHeader(inp.Ch) {
		inp.Next()
	}
	key := inp.Src[pos:inp.Pos]
	inp.SkipSpace()
	if inp.Ch == ':' {
		inp.Next()
	}
	var val []byte
	for {
		inp.SkipSpace()
		pos = inp.Pos
		skipToEOL(inp)
		val = append(val, inp.Src[pos:inp.Pos]...)
		inp.EatEOL()
		if !inp.IsSpace() {
			break
		}
		val = append(val, ' ')
	}
	addToMeta(m, string(key), Value(val))
}

func skipToEOL(inp *input.Input) {
	for {
		switch inp.Ch {
		case '\n', '\r', input.EOS:
			return
		}
		inp.Next()
	}
}

// Return true iff rune is valid for header key.
func isHeader(ch rune) bool {
	return ('a' <= ch && ch <= 'z') ||
		('0' <= ch && ch <= '9') ||
		ch == '-' ||
		('A' <= ch && ch <= 'Z')
}

type predValidElem func(string) bool

func addToSet(set *set.Set[string], it iter.Seq[string], useElem predValidElem) {
	for e := range it {
		if len(e) > 0 && useElem(e) {
			set.Add(e)
		}
	}
}

func addSet(m *Meta, key string, val Value, useElem predValidElem) {
	newElems := val.Fields()
	oldElems := m.GetFields(key)

	s := set.New[string]()
	addToSet(s, newElems, useElem)
	if s.Length() == 0 {
		// Nothing to add. Maybe because of rejected elements.
		return
	}
	addToSet(s, oldElems, useElem)
	m.SetList(key, slices.Sorted(s.Values()))
}

func addData(m *Meta, k string, v Value) {
	if o, ok := m.Get(k); !ok || o == "" {
		m.Set(k, v)
	} else if v != "" {
		m.Set(k, o+" "+v)
	}
}

func addToMeta(m *Meta, key string, val Value) {
	v := val.TrimSpace()
	key = strings.ToLower(key)
	if !KeyIsValid(key) {
		return
	}
	switch key {
	case "", KeyID:
		// Empty key and 'id' key will be ignored
		return
	}

	switch Type(key) {
	case TypeTagSet:
		addSet(m, key, v.ToLower(), func(s string) bool { return s[0] == '#' && len(s) > 1 })
	case TypeWord:
		m.Set(key, v.ToLower())
	case TypeID:
		if _, err := id.Parse(string(v)); err == nil {
			m.Set(key, v)
		}
	case TypeIDSet:
		addSet(m, key, v, func(s string) bool {
			_, err := id.Parse(s)
			return err == nil
		})
	case TypeTimestamp:
		if _, ok := v.AsTime(); ok {
			m.Set(key, v)
		}
	default:
		addData(m, key, v)
	}
}

//-----------------------------------------------------------------------------
// Copyright (c) 2020-present Detlef Stern
//
// This file is part of zettelstore-client.
//
// Zettelstore Client 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: 2020-present Detlef Stern
//-----------------------------------------------------------------------------

package meta_test

import (
	"iter"
	"slices"
	"strings"
	"testing"

	"t73f.de/r/zsc/domain/meta"
	"t73f.de/r/zsx/input"
)

func parseMetaStr(src string) *meta.Meta {
	return meta.NewFromInput(testID, input.NewInput([]byte(src)))
}

func TestEmpty(t *testing.T) {
	t.Parallel()
	m := parseMetaStr("")
	if got, ok := m.Get(meta.KeySyntax); ok || got != "" {
		t.Errorf("Syntax is not %q, but %q", "", got)
	}
	if got := slices.Collect(m.GetDefault(meta.KeyTags, "").Fields()); len(got) > 0 {
		t.Errorf("Tags are not nil, but %v", got)
	}
}

func TestTitle(t *testing.T) {
	t.Parallel()
	td := []struct {
		s string
		e meta.Value
	}{
		{meta.KeyTitle + ": a title", "a title"},
		{meta.KeyTitle + ": a\n\t title", "a title"},
		{meta.KeyTitle + ": a\n\t title\r\n  x", "a title x"},
		{meta.KeyTitle + " AbC", "AbC"},
		{meta.KeyTitle + " AbC\n ded", "AbC ded"},
		{meta.KeyTitle + ": o\ntitle: p", "o p"},
		{meta.KeyTitle + ": O\n\ntitle: P", "O"},
		{meta.KeyTitle + ": b\r\ntitle: c", "b c"},
		{meta.KeyTitle + ": B\r\n\r\ntitle: C", "B"},
		{meta.KeyTitle + ": r\rtitle: q", "r q"},
		{meta.KeyTitle + ": R\r\rtitle: Q", "R"},
	}
	for i, tc := range td {
		m := parseMetaStr(tc.s)
		if got, ok := m.Get(meta.KeyTitle); !ok || got != tc.e {
			t.Log(m)
			t.Errorf("TC=%d: expected %q, got %q", i, tc.e, got)
		}
	}
}

func TestTags(t *testing.T) {
	t.Parallel()
	testcases := []struct {
		src string
		exp string
	}{
		{"", ""},
		{meta.KeyTags + ":", ""},
		{meta.KeyTags + ": c", ""},
		{meta.KeyTags + ": #", ""},
		{meta.KeyTags + ": #c", "c"},
		{meta.KeyTags + ": #c #", "c"},
		{meta.KeyTags + ": #c #b", "b c"},
		{meta.KeyTags + ": #c # #", "c"},
		{meta.KeyTags + ": #c # #b", "b c"},
	}
	for i, tc := range testcases {
		m := parseMetaStr(tc.src)
		tagsString, found := m.Get(meta.KeyTags)
		if !found {
			if tc.exp != "" {
				t.Errorf("%d / %q: no %s found", i, tc.src, meta.KeyTags)
			}
			continue
		}
		tags := tagsString.AsTags()
		if tc.exp == "" && len(tags) > 0 {
			t.Errorf("%d / %q: expected no %s, but got %v", i, tc.src, meta.KeyTags, tags)
			continue
		}
		got := strings.Join(tags, " ")
		if tc.exp != got {
			t.Errorf("%d / %q: expected %q, got: %q", i, tc.src, tc.exp, got)
		}
	}
}

func TestNewFromInput(t *testing.T) {
	t.Parallel()
	testcases := []struct {
		input string
		exp   []pair
	}{
		{"", []pair{}},
		{" a:b", []pair{{"a", "b"}}},
		{"%a:b", []pair{}},
		{"a:b\r\n\r\nc:d", []pair{{"a", "b"}}},
		{"a:b\r\n%c:d", []pair{{"a", "b"}}},
		{"% a:b\r\n c:d", []pair{{"c", "d"}}},
		{"---\r\na:b\r\n", []pair{{"a", "b"}}},
		{"---\r\na:b\r\n--\r\nc:d", []pair{{"a", "b"}, {"c", "d"}}},
		{"---\r\na:b\r\n---\r\nc:d", []pair{{"a", "b"}}},
		{"---\r\na:b\r\n----\r\nc:d", []pair{{"a", "b"}}},
		{"new-title:\nnew-url:", []pair{{"new-title", ""}, {"new-url", ""}}},
	}
	for i, tc := range testcases {
		meta := parseMetaStr(tc.input)
		if got := iter2pairs(meta.All()); !equalPairs(tc.exp, got) {
			t.Errorf("TC=%d: expected=%v, got=%v", i, tc.exp, got)
		}
	}

	// Test, whether input position is correct.
	inp := input.NewInput([]byte("---\na:b\n---\nX"))
	m := meta.NewFromInput(testID, inp)
	exp := []pair{{"a", "b"}}
	if got := iter2pairs(m.All()); !equalPairs(exp, got) {
		t.Errorf("Expected=%v, got=%v", exp, got)
	}
	expCh := 'X'
	if gotCh := inp.Ch; gotCh != expCh {
		t.Errorf("Expected=%v, got=%v", expCh, gotCh)
	}
}

type pair struct {
	key meta.Key
	val meta.Value
}

func iter2pairs(it iter.Seq2[meta.Key, meta.Value]) (result []pair) {
	it(func(key meta.Key, val meta.Value) bool {
		result = append(result, pair{key, val})
		return true
	})
	return result
}

func equalPairs(one, two []pair) bool {
	if len(one) != len(two) {
		return false
	}
	for i := range len(one) {
		if one[i].key != two[i].key || one[i].val != two[i].val {
			return false
		}
	}
	return true
}

func TestPrecursorIDSet(t *testing.T) {
	t.Parallel()
	var testdata = []struct {
		inp string
		exp meta.Value
	}{
		{"", ""},
		{"123", ""},
		{"12345678901234", "12345678901234"},
		{"123 12345678901234", "12345678901234"},
		{"12345678901234 123", "12345678901234"},
		{"01234567890123 123 12345678901234", "01234567890123 12345678901234"},
		{"12345678901234 01234567890123", "01234567890123 12345678901234"},
	}
	for i, tc := range testdata {
		m := parseMetaStr(meta.KeyPrecursor + ": " + tc.inp)
		if got, ok := m.Get(meta.KeyPrecursor); (!ok && tc.exp != "") || tc.exp != got {
			t.Errorf("TC=%d: expected %q, but got %q when parsing %q", i, tc.exp, got, tc.inp)
		}
	}
}

//-----------------------------------------------------------------------------
// Copyright (c) 2020-present Detlef Stern
//
// This file is part of zettelstore-client.
//
// Zettelstore Client 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: 2020-present Detlef Stern
//-----------------------------------------------------------------------------

package meta

import (
	"iter"
	"strconv"
	"strings"
	"sync"
	"time"

	zeroiter "t73f.de/r/zero/iter"
	"t73f.de/r/zsc/domain/id"
)

// DescriptionType is a description of a specific key type.
type DescriptionType struct {
	Name  string
	IsSet bool
}

// String returns the string representation of the given type
func (t DescriptionType) String() string { return t.Name }

var registeredTypes = make(map[string]*DescriptionType)

func registerType(name string, isSet bool) *DescriptionType {
	if _, ok := registeredTypes[name]; ok {
		panic("Type '" + name + "' already registered")
	}
	t := &DescriptionType{name, isSet}
	registeredTypes[name] = t
	return t
}

// Values of the metadata key/value types.
//
// See [Supported Key Types].
//
// [Supported Key Types]: https://zettelstore.de/manual/h/00001006030000
const (
	MetaCredential = "Credential"
	MetaEmpty      = "EString"
	MetaID         = "Identifier"
	MetaIDSet      = "IdentifierSet"
	MetaNumber     = "Number"
	MetaString     = "String"
	MetaTagSet     = "TagSet"
	MetaTimestamp  = "Timestamp"
	MetaURL        = "URL"
	MetaWord       = "Word"
)

// Supported key types.
var (
	TypeCredential = registerType(MetaCredential, false)
	TypeEmpty      = registerType(MetaEmpty, false)
	TypeID         = registerType(MetaID, false)
	TypeIDSet      = registerType(MetaIDSet, true)
	TypeNumber     = registerType(MetaNumber, false)
	TypeString     = registerType(MetaString, false)
	TypeTagSet     = registerType(MetaTagSet, true)
	TypeTimestamp  = registerType(MetaTimestamp, false)
	TypeURL        = registerType(MetaURL, false)
	TypeWord       = registerType(MetaWord, false)
)

// Type returns a type hint for the given key. If no type hint is specified,
// TypeUnknown is returned.
func (*Meta) Type(key string) *DescriptionType {
	return Type(key)
}

// Some constants for key suffixes that determine a type.
const (
	SuffixKeyRole = "-role"
	SuffixKeyURL  = "-url"
)

var (
	cachedTypedKeys = make(map[string]*DescriptionType)
	mxTypedKey      sync.RWMutex
	suffixTypes     = map[string]*DescriptionType{
		"-date":       TypeTimestamp,
		"-number":     TypeNumber,
		SuffixKeyRole: TypeWord,
		"-time":       TypeTimestamp,
		SuffixKeyURL:  TypeURL,
		"-zettel":     TypeID,
		"-zid":        TypeID,
		"-zids":       TypeIDSet,
	}
)

// Type returns a type hint for the given key. If no type hint is specified,
// TypeEmpty is returned.
func Type(key string) *DescriptionType {
	if k, ok := registeredKeys[key]; ok {
		return k.Type
	}
	mxTypedKey.RLock()
	k, found := cachedTypedKeys[key]
	mxTypedKey.RUnlock()
	if found {
		return k
	}

	for suffix, t := range suffixTypes {
		if strings.HasSuffix(key, suffix) {
			mxTypedKey.Lock()
			defer mxTypedKey.Unlock()
			// Double check to avoid races
			if _, found = cachedTypedKeys[key]; !found {
				cachedTypedKeys[key] = t
			}
			return t
		}
	}
	return TypeEmpty
}

// SetList stores the given string list value under the given key.
func (m *Meta) SetList(key string, values []string) {
	if key != KeyID {
		for i, val := range values {
			values[i] = string(Value(val).TrimSpace())
		}
		m.pairs[key] = Value(strings.Join(values, " "))
	}
}

// SetWord stores the given word under the given key.
func (m *Meta) SetWord(key, word string) {
	for val := range Value(word).Elems() {
		m.Set(key, val)
		return
	}
}

// SetNow stores the current timestamp under the given key.
func (m *Meta) SetNow(key string) {
	m.Set(key, Value(time.Now().Local().Format(id.TimestampLayout)))
}

// GetBool returns the boolean value of the given key.
func (m *Meta) GetBool(key string) bool {
	if val, ok := m.Get(key); ok {
		return val.AsBool()
	}
	return false
}

// GetFields returns the metadata value as a sequence of string. The bool value
// signals, whether there was a value stored or not.
func (m *Meta) GetFields(key Key) iter.Seq[string] {
	if val, ok := m.Get(key); ok {
		return val.Fields()
	}
	return zeroiter.EmptySeq[string]()
}

// GetNumber retrieves the numeric value of a given key.
func (m *Meta) GetNumber(key string, def int64) int64 {
	if value, ok := m.Get(key); ok {
		if num, err := strconv.ParseInt(string(value), 10, 64); err == nil {
			return num
		}
	}
	return def
}

//-----------------------------------------------------------------------------
// Copyright (c) 2020-present Detlef Stern
//
// This file is part of zettelstore-client.
//
// Zettelstore Client 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: 2020-present Detlef Stern
//-----------------------------------------------------------------------------

package meta_test

import (
	"strconv"
	"testing"
	"time"

	"t73f.de/r/zsc/domain/id"
	"t73f.de/r/zsc/domain/meta"
)

func TestNow(t *testing.T) {
	t.Parallel()
	m := meta.New(id.Invalid)
	m.SetNow("key")
	val, ok := m.Get("key")
	if !ok {
		t.Error("Unable to get value of key")
	}
	if len(val) != 14 {
		t.Errorf("Value is not 14 digits long: %q", val)
	}
	if _, err := strconv.ParseInt(string(val), 10, 64); err != nil {
		t.Errorf("Unable to parse %q as an int64: %v", val, err)
	}
	if _, ok = val.AsTime(); !ok {
		t.Errorf("Unable to get time from value %q", val)
	}
}

func TestTimeValue(t *testing.T) {
	t.Parallel()
	testCases := []struct {
		value meta.Value
		valid bool
		exp   time.Time
	}{
		{"", false, time.Time{}},
		{"1", false, time.Time{}},
		{"00000000000000", false, time.Time{}},
		{"98765432109876", false, time.Time{}},
		{"20201221111905", true, time.Date(2020, time.December, 21, 11, 19, 5, 0, time.UTC)},
		{"2023", true, time.Date(2023, time.January, 1, 0, 0, 0, 0, time.UTC)},
		{"20231", false, time.Time{}},
		{"202310", true, time.Date(2023, time.October, 1, 0, 0, 0, 0, time.UTC)},
		{"2023103", false, time.Time{}},
		{"20231030", true, time.Date(2023, time.October, 30, 0, 0, 0, 0, time.UTC)},
		{"202310301", false, time.Time{}},
		{"2023103016", true, time.Date(2023, time.October, 30, 16, 0, 0, 0, time.UTC)},
		{"20231030165", false, time.Time{}},
		{"202310301654", true, time.Date(2023, time.October, 30, 16, 54, 0, 0, time.UTC)},
		{"2023103016541", false, time.Time{}},
		{"20231030165417", true, time.Date(2023, time.October, 30, 16, 54, 17, 0, time.UTC)},
		{"2023103916541700", false, time.Time{}},
	}
	for i, tc := range testCases {
		got, ok := tc.value.AsTime()
		if ok != tc.valid {
			t.Errorf("%d: parsing of %q should be %v, but got %v", i, tc.value, tc.valid, ok)
			continue
		}
		if got != tc.exp {
			t.Errorf("%d: parsing of %q should return %v, but got %v", i, tc.value, tc.exp, got)
		}
	}
}

//-----------------------------------------------------------------------------
// Copyright (c) 2020-present Detlef Stern
//
// This file is part of zettelstore-client.
//
// Zettelstore Client 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: 2020-present Detlef Stern
//-----------------------------------------------------------------------------

package meta

import (
	"fmt"
	"iter"
	"slices"
	"strings"
	"time"

	zeroiter "t73f.de/r/zero/iter"
	"t73f.de/r/zsc/domain/id"
	"t73f.de/r/zsx/input"
)

// Value ist a single metadata value.
type Value string

// AsBool returns the value interpreted as a bool.
func (val Value) AsBool() bool {
	if len(val) > 0 {
		switch val[0] {
		case '0', 'f', 'F', 'n', 'N':
			return false
		}
	}
	return true
}

// AsTime returns the time value of the given value.
func (val Value) AsTime() (time.Time, bool) {
	if t, err := time.Parse(id.TimestampLayout, ExpandTimestamp(val)); err == nil {
		return t, true
	}
	return time.Time{}, false
}

// ExpandTimestamp makes a short-form timestamp larger.
func ExpandTimestamp(val Value) string {
	switch l := len(val); l {
	case 4: // YYYY
		return string(val) + "0101000000"
	case 6: // YYYYMM
		return string(val) + "01000000"
	case 8, 10, 12: // YYYYMMDD, YYYYMMDDhh, YYYYMMDDhhmm
		return string(val) + "000000"[:14-l]
	case 14: // YYYYMMDDhhmmss
		return string(val)
	default:
		if l > 14 {
			return string(val[:14])
		}
		return string(val)
	}
}

// Fields iterates over the value as a list/set of strings.
func (val Value) Fields() iter.Seq[string] {
	return strings.FieldsSeq(string(val))
}

// Elems iterates over the value as a list/set of values.
func (val Value) Elems() iter.Seq[Value] {
	return zeroiter.MapSeq(val.Fields(), func(s string) Value { return Value(s) })
}

// AsSlice transforms a value into a slice of strings.
func (val Value) AsSlice() []string {
	return strings.Fields(string(val))
}

// ToLower maps the value to lowercase runes.
func (val Value) ToLower() Value { return Value(strings.ToLower(string(val))) }

// TrimSpace removes all leading and remaining space from value
func (val Value) TrimSpace() Value {
	return Value(strings.TrimFunc(string(val), input.IsSpace))
}

// AsTags returns the value as a sequence of normalized tags.
func (val Value) AsTags() []string {
	return slices.Collect(zeroiter.MapSeq(
		val.Fields(),
		func(e string) string { return string(Value(e).ToLower().CleanTag()) }))
}

// CleanTag removes the number character ('#') from a tag value.
func (val Value) CleanTag() Value {
	if len(val) > 1 && val[0] == '#' {
		return val[1:]
	}
	return val
}

// NormalizeTag adds a missing prefix "#" to the tag
func (val Value) NormalizeTag() Value {
	if len(val) > 0 && val[0] == '#' {
		return val
	}
	return "#" + val
}

// Predefined metadata values.
const (
	ValueFalse             = "false"
	ValueTrue              = "true"
	ValueLangEN            = "en"            // Default for "lang"
	ValueRoleConfiguration = "configuration" // A role for internal zettel
	ValueRoleTag           = "tag"           // A role for tag zettel
	ValueRoleRole          = "role"          // A role for role zettel
	ValueRoleZettel        = "zettel"        // A role for zettel
	ValueSyntaxCSS         = "css"           // Syntax: CSS
	ValueSyntaxDraw        = "draw"          // Syntax: Drawing
	ValueSyntaxGif         = "gif"           // Syntax: GIF image
	ValueSyntaxHTML        = "html"          // Syntax: HTML
	ValueSyntaxJPEG        = "jpeg"          // Syntax: JPEG image
	ValueSyntaxJPG         = "jpg"           // Syntax: PEG image
	ValueSyntaxMarkdown    = "markdown"      // Syntax: Markdown / CommonMark
	ValueSyntaxMD          = "md"            // Syntax: Markdown / CommonMark
	ValueSyntaxNone        = "none"          // Syntax: no syntax / content, just metadata
	ValueSyntaxPlain       = "plain"         // Syntax: plain text
	ValueSyntaxPNG         = "png"           // Syntax: PNG image
	ValueSyntaxSVG         = "svg"           // Syntax: SVG
	ValueSyntaxSxn         = "sxn"           // Syntax: S-Expression
	ValueSyntaxText        = "text"          // Syntax: plain text
	ValueSyntaxTxt         = "txt"           // Syntax: plain text
	ValueSyntaxWebp        = "webp"          // Syntax: WEBP image
	ValueSyntaxZmk         = "zmk"           // Syntax: Zettelmarkup
	ValueUserRoleCreator   = "creator"
	ValueUserRoleOwner     = "owner"
	ValueUserRoleReader    = "reader"
	ValueUserRoleWriter    = "writer"
	ValueVisibilityCreator = "creator"
	ValueVisibilityExpert  = "expert"
	ValueVisibilityLogin   = "login"
	ValueVisibilityOwner   = "owner"
	ValueVisibilityPublic  = "public"
)

// DefaultSyntax is the default value for metadata 'syntax'.
const DefaultSyntax = ValueSyntaxPlain

// Visibility enumerates the variations of the 'visibility' meta key.
type Visibility int

// Supported values for visibility.
const (
	_ Visibility = iota
	VisibilityUnknown
	VisibilityPublic
	VisibilityCreator
	VisibilityLogin
	VisibilityOwner
	VisibilityExpert
)

var visMap = map[Value]Visibility{
	ValueVisibilityPublic:  VisibilityPublic,
	ValueVisibilityCreator: VisibilityCreator,
	ValueVisibilityLogin:   VisibilityLogin,
	ValueVisibilityOwner:   VisibilityOwner,
	ValueVisibilityExpert:  VisibilityExpert,
}
var revVisMap = map[Visibility]Value{}

func init() {
	for k, v := range visMap {
		revVisMap[v] = k
	}
}

// AsVisibility returns the visibility value of the given value string
func (val Value) AsVisibility() Visibility {
	if vis, ok := visMap[val]; ok {
		return vis
	}
	return VisibilityUnknown
}

func (v Visibility) String() string {
	if s, ok := revVisMap[v]; ok {
		return string(s)
	}
	return fmt.Sprintf("Unknown (%d)", v)
}

// UserRole enumerates the supported values of meta key 'user-role'.
type UserRole int

// Supported values for user roles.
const (
	_ UserRole = iota
	UserRoleUnknown
	UserRoleCreator
	UserRoleReader
	UserRoleWriter
	UserRoleOwner
)

var urMap = map[Value]UserRole{
	ValueUserRoleCreator: UserRoleCreator,
	ValueUserRoleReader:  UserRoleReader,
	ValueUserRoleWriter:  UserRoleWriter,
	ValueUserRoleOwner:   UserRoleOwner,
}

// AsUserRole role returns the user role of the given string.
func (val Value) AsUserRole() UserRole {
	if ur, ok := urMap[val]; ok {
		return ur
	}
	return UserRoleUnknown
}

//-----------------------------------------------------------------------------
// Copyright (c) 2020-present Detlef Stern
//
// This file is part of zettelstore-client.
//
// Zettelstore Client 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: 2020-present Detlef Stern
//-----------------------------------------------------------------------------

package meta

import "io"

// Write writes metadata to a writer, excluding computed and propery values.
func (m *Meta) Write(w io.Writer) (int, error) {
	return m.doWrite(w, IsComputed)
}

// WriteComputed writes metadata to a writer, including computed values,
// but excluding property values.
func (m *Meta) WriteComputed(w io.Writer) (int, error) {
	return m.doWrite(w, IsProperty)
}

func (m *Meta) doWrite(w io.Writer, ignoreKeyPred func(string) bool) (length int, err error) {
	for key, val := range m.Computed() {
		if ignoreKeyPred(key) {
			continue
		}
		if err != nil {
			break
		}
		var l int
		l, err = io.WriteString(w, key)
		length += l
		if err == nil {
			l, err = w.Write(colonSpace)
			length += l
		}
		if err == nil {
			l, err = io.WriteString(w, string(val))
			length += l
		}
		if err == nil {
			l, err = w.Write(newline)
			length += l
		}
	}
	return length, err
}

var (
	colonSpace = []byte{':', ' '}
	newline    = []byte{'\n'}
)

//-----------------------------------------------------------------------------
// Copyright (c) 2020-present Detlef Stern
//
// This file is part of zettelstore-client.
//
// Zettelstore Client 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: 2020-present Detlef Stern
//-----------------------------------------------------------------------------

package meta_test

import (
	"strings"
	"testing"

	"t73f.de/r/zsc/domain/id"
	"t73f.de/r/zsc/domain/meta"
)

const testID = id.Zid(98765432101234)

func newMeta(title string, tags []string, syntax string) *meta.Meta {
	m := meta.New(testID)
	if title != "" {
		m.Set(meta.KeyTitle, meta.Value(title))
	}
	if tags != nil {
		m.Set(meta.KeyTags, meta.Value(strings.Join(tags, " ")))
	}
	if syntax != "" {
		m.Set(meta.KeySyntax, meta.Value(syntax))
	}
	return m
}
func assertWriteMeta(t *testing.T, m *meta.Meta, expected string) {
	t.Helper()
	var sb strings.Builder
	_, _ = m.Write(&sb)
	if got := sb.String(); got != expected {
		t.Errorf("\nExp: %q\ngot: %q", expected, got)
	}
}

func TestWriteMeta(t *testing.T) {
	t.Parallel()
	assertWriteMeta(t, newMeta("", nil, ""), "")

	m := newMeta("TITLE", []string{"#t1", "#t2"}, "syntax")
	assertWriteMeta(t, m, "title: TITLE\ntags: #t1 #t2\nsyntax: syntax\n")

	m = newMeta("TITLE", nil, "")
	m.Set("user", "zettel")
	m.Set("auth", "basic")
	assertWriteMeta(t, m, "title: TITLE\nauth: basic\nuser: zettel\n")
}

module t73f.de/r/zsc

go 1.24

require (
	t73f.de/r/sx v0.0.0-20250415161954-42ed9c4d6abc
	t73f.de/r/sxwebs v0.0.0-20250415162443-110f49c5a1ae
	t73f.de/r/webs v0.0.0-20250311182734-f263a38b32d5
	t73f.de/r/zero v0.0.0-20250226205915-c4194684acb7
	t73f.de/r/zsx v0.0.0-20250415162540-fc13b286b6ce
)

t73f.de/r/sx v0.0.0-20250415161954-42ed9c4d6abc h1:tlsP+47Rf8i9Zv1TqRnwfbQx3nN/F/92RkT6iCA6SVA=
t73f.de/r/sx v0.0.0-20250415161954-42ed9c4d6abc/go.mod h1:hzg05uSCMk3D/DWaL0pdlowfL2aWQeGIfD1S04vV+Xg=
t73f.de/r/sxwebs v0.0.0-20250415162443-110f49c5a1ae h1:K6nxN/bb0BCSiDffwNPGTF2uf5WcTdxcQXzByXNuJ7M=
t73f.de/r/sxwebs v0.0.0-20250415162443-110f49c5a1ae/go.mod h1:0LQ9T1svSg9ADY/6vQLKNUu6LqpPi8FGr7fd2qDT5H8=
t73f.de/r/webs v0.0.0-20250311182734-f263a38b32d5 h1:nnKfs/2i9n3S5VjbSj98odcwZKGcL96qPSIUATT/2P8=
t73f.de/r/webs v0.0.0-20250311182734-f263a38b32d5/go.mod h1:zk92hSKB4iWyT290+163seNzu350TA9XLATC9kOldqo=
t73f.de/r/zero v0.0.0-20250226205915-c4194684acb7 h1:OuzHSfniY8UzLmo5zp1w23Kd9h7x9CSXP2jQ+kppeqU=
t73f.de/r/zero v0.0.0-20250226205915-c4194684acb7/go.mod h1:T1vFcHoymUQcr7+vENBkS1yryZRZ3YB8uRtnMy8yRBA=
t73f.de/r/zsx v0.0.0-20250415162540-fc13b286b6ce h1:R9rtg4ecx4YYixsMmsh+wdcqLdY9GxoC5HZ9mMS33to=
t73f.de/r/zsx v0.0.0-20250415162540-fc13b286b6ce/go.mod h1:tXOlmsQBoY4mY7Plu0LCCMZNSJZJbng98fFarZXAWvM=

//-----------------------------------------------------------------------------
// Copyright (c) 2023-present Detlef Stern
//
// This file is part of zettelstore-client.
//
// Zettelstore client 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
//-----------------------------------------------------------------------------

// Package sexp contains helper function to work with s-expression in an alien
// environment.
package sexp

import (
	"errors"
	"fmt"
	"sort"

	"t73f.de/r/sx"
	"t73f.de/r/zsc/api"
)

// EncodeZettel transforms zettel data into a sx object.
func EncodeZettel(zettel api.ZettelData) sx.Object {

	return sx.MakeList(
		sx.MakeSymbol("zettel"),
		meta2sz(zettel.Meta),
		sx.MakeList(sx.MakeSymbol("rights"), sx.Int64(int64(zettel.Rights))),
		sx.MakeList(sx.MakeSymbol("encoding"), sx.MakeString(zettel.Encoding)),
		sx.MakeList(sx.MakeSymbol("content"), sx.MakeString(zettel.Content)),
	)
}

// ParseZettel parses an object to contain all needed data for a zettel.
func ParseZettel(obj sx.Object) (api.ZettelData, error) {
	vals, err := ParseList(obj, "ypppp")
	if err != nil {
		return api.ZettelData{}, err
	}
	if errSym := CheckSymbol(vals[0], "zettel"); errSym != nil {
		return api.ZettelData{}, errSym

	if errSym := CheckSymbol(contentVals[0], "content"); errSym != nil {
		return api.ZettelData{}, errSym
	}

	return api.ZettelData{
		Meta:     meta,
		Rights:   rights,
		Encoding: encVals[1].(sx.String).GetValue(),
		Content:  contentVals[1].(sx.String).GetValue(),
	}, nil
}

// EncodeMetaRights translates metadata/rights into a sx object.
func EncodeMetaRights(mr api.MetaRights) *sx.Pair {

	return sx.MakeList(
		sx.SymbolList,
		meta2sz(mr.Meta),
		sx.MakeList(sx.MakeSymbol("rights"), sx.Int64(int64(mr.Rights))),
	)
}

func meta2sz(m api.ZettelMeta) sx.Object {
	var result sx.ListBuilder
	result.Add(sx.MakeSymbol("meta"))
	keys := make([]string, 0, len(m))
	for k := range m {
		keys = append(keys, k)
	}
	sort.Strings(keys)
	for _, k := range keys {
		val := sx.MakeList(sx.MakeSymbol(k), sx.MakeString(m[k]))
		result.Add(val)
	}
	return result.List()
}

// ParseMeta translates the given list to metadata.
func ParseMeta(pair *sx.Pair) (api.ZettelMeta, error) {
	if err := CheckSymbol(pair.Car(), "meta"); err != nil {
		return nil, err
	}
	res := api.ZettelMeta{}
	for obj := range pair.Tail().Values() {
		mVals, err := ParseList(obj, "ys")
		if err != nil {
			return nil, err
		}
		res[(mVals[0].(*sx.Symbol)).GetValue()] = mVals[1].(sx.String).GetValue()
	}
	return res, nil
}

// ParseRights returns the rights values of the given object.
func ParseRights(obj sx.Object) (api.ZettelRights, error) {
	rVals, err := ParseList(obj, "yi")

	if i64 < 0 && i64 >= int64(api.ZettelMaxRight) {
		return api.ZettelMaxRight, fmt.Errorf("invalid zettel right value: %v", i64)
	}
	return api.ZettelRights(i64), nil
}

// ParseList parses the given object as a proper list, based on a type specification.
//
// 'b' expects a boolean, 'i' an int64, 'o' any object, 'p' a pair, 's' a string,
// and 'y' expects a symbol. A 'r' as the last type spracification matches all
// remaining values, including a non existent object.
func ParseList(obj sx.Object, spec string) (sx.Vector, error) {
	pair, isPair := sx.GetPair(obj)
	if !isPair {
		return nil, fmt.Errorf("not a list: %T/%v", obj, obj)
	}
	if pair == nil {
		if spec == "r" {
			return sx.Vector{sx.Nil()}, nil
		}
		if spec == "" {
			return nil, nil
		}
		return nil, ErrElementsMissing
	}

	specLen := len(spec)
	result := make(sx.Vector, 0, specLen)
	node, i := pair, 0
loop:
	for ; node != nil; i++ {
		if i >= specLen {
			return nil, ErrNoSpec
		}
		var val sx.Object
		var ok bool
		car := node.Car()
		switch spec[i] {
		case 'b':
			val, ok = sx.MakeBoolean(!sx.IsNil(car)), true
		case 'i':
			val, ok = car.(sx.Int64)
		case 'o':
			val, ok = car, true
		case 'p':
			val, ok = sx.GetPair(car)
		case 'r':
			if i < specLen-1 {
				return nil, fmt.Errorf("spec 'r' must be the last: %v", spec)
			}
			result = append(result, node)
			i++
			break loop
		case 's':
			val, ok = sx.GetString(car)
		case 'y':
			val, ok = sx.GetSymbol(car)
		default:
			return nil, fmt.Errorf("unknown spec '%c'", spec[i])
		}
		if !ok {
			return nil, fmt.Errorf("does not match spec '%v': %v", spec[i], car)
		}
		result = append(result, val)
		next, isNextPair := sx.GetPair(node.Cdr())
		if !isNextPair {
			return nil, sx.ErrImproper{Pair: pair}
		}
		node = next
	}
	if i < specLen {
		if lastSpec := specLen - 1; i < lastSpec || spec[lastSpec] != 'r' {
			return nil, ErrElementsMissing
		}
		result = append(result, sx.Nil())
	}
	return result, nil
}

// ErrElementsMissing is returned,
// if ParseList is called with a list smaller than the number of type specifications.
var ErrElementsMissing = errors.New("spec contains more data")

// ErrNoSpec is returned,
// if ParseList if called with a list greater than the number of type specifications.
var ErrNoSpec = errors.New("no spec for elements")

// CheckSymbol ensures that the given object is a symbol with the given name.
func CheckSymbol(obj sx.Object, name string) error {
	sym, isSymbol := sx.GetSymbol(obj)
	if !isSymbol {
		return fmt.Errorf("object %v/%T is not a symbol", obj, obj)
	}
	if got := sym.GetValue(); got != name {
		return fmt.Errorf("symbol %q expected, but got: %q", name, got)
	}
	return nil
}

//-----------------------------------------------------------------------------
// Copyright (c) 2023-present Detlef Stern
//
// This file is part of zettelstore-client.
//
// Zettelstore client 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
//-----------------------------------------------------------------------------

package sexp_test

import (
	"testing"

	"t73f.de/r/sx"
	"t73f.de/r/zsc/sexp"
)

func TestParseObject(t *testing.T) {
	if elems, err := sexp.ParseList(sx.MakeString("a"), "s"); err == nil {
		t.Error("expected an error, but got: ", elems)
	}
	if elems, err := sexp.ParseList(sx.Nil(), ""); err != nil {

	if elems, err := sexp.ParseList(sx.MakeList(sx.MakeString("a")), "ss"); err == nil {
		t.Error("expected error, but got: ", elems)
	}
	if elems, err := sexp.ParseList(sx.MakeList(sx.MakeString("a")), ""); err == nil {
		t.Error("expected error, but got: ", elems)
	}
	if _, err := sexp.ParseList(sx.MakeList(sx.MakeString("a")), "b"); err != nil {
		t.Error("expected [1], but got error: ", err)
	}
	if elems, err := sexp.ParseList(sx.Cons(sx.Nil(), sx.MakeString("a")), "ps"); err == nil {
		t.Error("expected error, but got: ", elems)
	}

	if elems, err := sexp.ParseList(sx.MakeList(sx.MakeString("a")), "s"); err != nil {
		t.Error(err)
	} else if len(elems) != 1 {
		t.Error("length == 1, but got: ", elems)
	} else {
		_ = elems[0].(sx.String)
	}

	if elems, err := sexp.ParseList(sx.Nil(), "r"); err != nil {
		t.Error(err)
	} else if len(elems) != 1 {
		t.Error("length == 1, but got: ", elems)
	} else if !sx.IsNil(elems[0]) {
		t.Error("must be nil, but got:", elems[0])
	}
	if elems, err := sexp.ParseList(sx.MakeList(sx.MakeString("a")), "r"); err != nil {
		t.Error(err)
	} else if len(elems) != 1 {
		t.Error("length == 1, but got: ", elems)
	} else if !elems[0].IsEqual(sx.MakeList(sx.MakeString("a"))) {
		t.Error("must be (\"a\"), but got:", elems[0])
	}
	if elems, err := sexp.ParseList(sx.MakeList(sx.MakeString("a")), "sr"); err != nil {
		t.Error(err)
	} else if len(elems) != 2 {
		t.Error("length == 2, but got: ", elems)
	} else if !elems[0].IsEqual(sx.MakeString("a")) {
		t.Error("0-th must be \"a\", but got:", elems[0])
	} else if !sx.IsNil(elems[1]) {
		t.Error("must be nil, but got:", elems[1])
	}
	if elems, err := sexp.ParseList(sx.MakeList(sx.MakeString("a"), sx.MakeString("b"), sx.MakeString("c")), "sr"); err != nil {
		t.Error(err)
	} else if len(elems) != 2 {
		t.Error("length == 2, but got: ", elems)
	} else if !elems[0].IsEqual(sx.MakeString("a")) {
		t.Error("0-th must be \"a\", but got:", elems[0])
	} else if !elems[1].IsEqual(sx.MakeList(sx.MakeString("b"), sx.MakeString("c"))) {
		t.Error("must be nil, but got:", elems[1])
	}
}

//-----------------------------------------------------------------------------
// Copyright (c) 2024-present Detlef Stern
//
// This file is part of zettelstore-client.
//
// Zettelstore client 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 shtml

import "t73f.de/r/sx"

// Symbols for HTML header tags
var (
	SymBody   = sx.MakeSymbol("body")
	SymHead   = sx.MakeSymbol("head")
	SymHTML   = sx.MakeSymbol("html")
	SymMeta   = sx.MakeSymbol("meta")
	SymScript = sx.MakeSymbol("script")
	SymTitle  = sx.MakeSymbol("title")
)

// Symbols for HTML body tags
var (
	SymA          = sx.MakeSymbol("a")
	SymASIDE      = sx.MakeSymbol("aside")
	symBLOCKQUOTE = sx.MakeSymbol("blockquote")
	symBR         = sx.MakeSymbol("br")
	symCITE       = sx.MakeSymbol("cite")
	symCODE       = sx.MakeSymbol("code")
	symDD         = sx.MakeSymbol("dd")
	symDEL        = sx.MakeSymbol("del")
	SymDIV        = sx.MakeSymbol("div")
	symDL         = sx.MakeSymbol("dl")
	symDT         = sx.MakeSymbol("dt")
	symEM         = sx.MakeSymbol("em")
	SymEMBED      = sx.MakeSymbol("embed")
	SymFIGURE     = sx.MakeSymbol("figure")
	SymH1         = sx.MakeSymbol("h1")
	SymH2         = sx.MakeSymbol("h2")
	SymHR         = sx.MakeSymbol("hr")
	SymIMG        = sx.MakeSymbol("img")
	symINS        = sx.MakeSymbol("ins")
	symKBD        = sx.MakeSymbol("kbd")
	SymLI         = sx.MakeSymbol("li")
	symMARK       = sx.MakeSymbol("mark")
	SymOL         = sx.MakeSymbol("ol")
	SymP          = sx.MakeSymbol("p")
	symPRE        = sx.MakeSymbol("pre")
	symSAMP       = sx.MakeSymbol("samp")
	SymSPAN       = sx.MakeSymbol("span")
	SymSTRONG     = sx.MakeSymbol("strong")
	symSUB        = sx.MakeSymbol("sub")
	symSUP        = sx.MakeSymbol("sup")
	symTABLE      = sx.MakeSymbol("table")
	symTBODY      = sx.MakeSymbol("tbody")
	symTHEAD      = sx.MakeSymbol("thead")
	symTD         = sx.MakeSymbol("td")
	symTH         = sx.MakeSymbol("th")
	symTR         = sx.MakeSymbol("tr")
	SymUL         = sx.MakeSymbol("ul")
)

// Symbols for HTML attribute keys
var (
	SymAttrClass  = sx.MakeSymbol("class")
	SymAttrHref   = sx.MakeSymbol("href")
	SymAttrID     = sx.MakeSymbol("id")
	SymAttrLang   = sx.MakeSymbol("lang")
	SymAttrOpen   = sx.MakeSymbol("open")
	SymAttrRel    = sx.MakeSymbol("rel")
	SymAttrRole   = sx.MakeSymbol("role")
	SymAttrSrc    = sx.MakeSymbol("src")
	SymAttrTarget = sx.MakeSymbol("target")
	SymAttrTitle  = sx.MakeSymbol("title")
	SymAttrType   = sx.MakeSymbol("type")
	SymAttrValue  = sx.MakeSymbol("value")
)

//-----------------------------------------------------------------------------
// Copyright (c) 2023-present Detlef Stern
//
// This file is part of zettelstore-client.
//
// Zettelstore client 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
//-----------------------------------------------------------------------------

package shtml

import (
	"strings"

	"t73f.de/r/zsc/domain/meta"
)

// LangStack is a stack to store the nesting of "lang" attribute values.
// It is used to generate typographically correct quotes.
type LangStack []string

// NewLangStack creates a new language stack.
func NewLangStack(lang string) LangStack {
	ls := make([]string, 1, 16)
	ls[0] = lang
	return ls
}

// Reset restores the language stack to its initial value.
func (ls *LangStack) Reset() {
	*ls = (*ls)[0:1]
}

// Push adds a new language value.
func (ls *LangStack) Push(lang string) {
	*ls = append(*ls, lang)
}

// Pop removes the topmost language value.
func (ls *LangStack) Pop() {
	*ls = (*ls)[0 : len(*ls)-1]
}

// Top returns the topmost language value.
func (ls *LangStack) Top() string {
	return (*ls)[len(*ls)-1]
}

// Dup duplicates the topmost language value.
func (ls *LangStack) Dup() {
	*ls = append(*ls, (*ls)[len(*ls)-1])
}

// QuoteInfo contains language specific data about quotes.
type QuoteInfo struct {
	primLeft, primRight string
	secLeft, secRight   string
	nbsp                bool
}

// GetPrimary returns the primary left and right quote entity.
func (qi *QuoteInfo) GetPrimary() (string, string) {
	return qi.primLeft, qi.primRight
}

// GetSecondary returns the secondary left and right quote entity.
func (qi *QuoteInfo) GetSecondary() (string, string) {
	return qi.secLeft, qi.secRight
}

// GetQuotes returns quotes based on a nesting level.
func (qi *QuoteInfo) GetQuotes(level uint) (string, string) {
	if level%2 == 0 {
		return qi.GetPrimary()
	}
	return qi.GetSecondary()
}

// GetNBSp returns true, if there must be a non-breaking space between the
// quote entities and the quoted text.
func (qi *QuoteInfo) GetNBSp() bool { return qi.nbsp }

var langQuotes = map[string]*QuoteInfo{
	"":               {""", """, """, """, false},
	meta.ValueLangEN: {"“", "”", "‘", "’", false},
	"de":             {"„", "“", "‚", "‘", false},
	"fr":             {"«", "»", "‹", "›", true},
}

// GetQuoteInfo returns language specific data about quotes.
func GetQuoteInfo(lang string) *QuoteInfo {
	langFields := strings.FieldsFunc(lang, func(r rune) bool { return r == '-' || r == '_' })
	for len(langFields) > 0 {
		langSup := strings.Join(langFields, "-")
		quotes, ok := langQuotes[langSup]
		if ok {
			return quotes
		}
		langFields = langFields[0 : len(langFields)-1]
	}
	return langQuotes[""]
}

//-----------------------------------------------------------------------------
// Copyright (c) 2023-present Detlef Stern
//
// This file is part of zettelstore-client.
//
// Zettelstore client 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
//-----------------------------------------------------------------------------

// Package shtml transforms a s-expr encoded zettel AST into a s-expr representation of HTML.
package shtml

import (
	"fmt"
	"net/url"
	"strconv"
	"strings"

	"t73f.de/r/sx"

	"t73f.de/r/sxwebs/sxhtml"
	"t73f.de/r/zsc/api"
	"t73f.de/r/zsc/domain/meta"

	"t73f.de/r/zsc/sz"
	"t73f.de/r/zsx"
)

// Evaluator will transform a s-expression that encodes the zettel AST into an s-expression
// that represents HTML.
type Evaluator struct {


	headingOffset int64
	unique        string

	noLinks       bool // true iff output must not include links






	fns     map[string]EvalFn
	minArgs map[string]int



}

// NewEvaluator creates a new Evaluator object.
func NewEvaluator(headingOffset int) *Evaluator {
	ev := &Evaluator{





		headingOffset: int64(headingOffset),






		fns:     make(map[string]EvalFn, 128),
		minArgs: make(map[string]int, 128),
	}
	ev.bindMetadata()
	ev.bindBlocks()
	ev.bindInlines()
	return ev
}



// SetUnique sets a prefix to make several HTML ids unique.
func (ev *Evaluator) SetUnique(s string) { ev.unique = s }

// IsValidName returns true, if name is a valid symbol name.
func isValidName(s string) bool { return s != "" }










// EvaluateAttributes transforms the given attributes into a HTML s-expression.
func EvaluateAttributes(a zsx.Attributes) *sx.Pair {
	if len(a) == 0 {
		return nil
	}
	plist := sx.Nil()
	keys := a.Keys()
	for i := len(keys) - 1; i >= 0; i-- {
		key := keys[i]
		if key != zsx.DefaultAttribute && isValidName(key) {
			plist = plist.Cons(sx.Cons(sx.MakeSymbol(key), sx.MakeString(a[key])))
		}
	}
	if plist == nil {
		return nil
	}
	return plist.Cons(sxhtml.SymAttr)
}

// Evaluate a metadata s-expression into a list of HTML s-expressions.
func (ev *Evaluator) Evaluate(lst *sx.Pair, env *Environment) (*sx.Pair, error) {
	result := ev.Eval(lst, env)
	if err := env.err; err != nil {
		return nil, err
	}
	pair, isPair := sx.GetPair(result)
	if !isPair {
		return nil, fmt.Errorf("evaluation does not result in a pair, but %T/%v", result, result)
	}

	for i := 0; i < len(env.endnotes); i++ {
		// May extend tr.endnotes -> do not use for i := range len(...)!!!

		if env.endnotes[i].noteHx != nil {
			continue
		}


		noteHx, _ := ev.EvaluateList(env.endnotes[i].noteAST, env)
		env.endnotes[i].noteHx = noteHx


	}










	return pair, nil

}




// EvaluateList will evaluate all list elements separately and returns them as a sx.Pair list
func (ev *Evaluator) EvaluateList(lst sx.Vector, env *Environment) (*sx.Pair, error) {
	var result sx.ListBuilder
	for _, elem := range lst {
		p := ev.Eval(elem, env)
		result.Add(p)
	}

	if err := env.err; err != nil {
		return nil, err
	}








	return result.List(), nil









}

// Endnotes returns a SHTML object with all collected endnotes.
func Endnotes(env *Environment) *sx.Pair {
	if env.err != nil || len(env.endnotes) == 0 {
		return nil
	}

	var result sx.ListBuilder
	result.AddN(
		SymOL,
		sx.Nil().Cons(sx.Cons(SymAttrClass, sx.MakeString("zs-endnotes"))).Cons(sxhtml.SymAttr),
	)
	for i, fni := range env.endnotes {
		noteNum := strconv.Itoa(i + 1)


		attrs := fni.attrs.Cons(sx.Cons(SymAttrClass, sx.MakeString("zs-endnote"))).
			Cons(sx.Cons(SymAttrValue, sx.MakeString(noteNum))).
			Cons(sx.Cons(SymAttrID, sx.MakeString("fn:"+fni.noteID))).
			Cons(sx.Cons(SymAttrRole, sx.MakeString("doc-endnote"))).
			Cons(sxhtml.SymAttr)

		backref := sx.Nil().Cons(sx.MakeString("\u21a9\ufe0e")).
			Cons(sx.Nil().
				Cons(sx.Cons(SymAttrClass, sx.MakeString("zs-endnote-backref"))).
				Cons(sx.Cons(SymAttrHref, sx.MakeString("#fnref:"+fni.noteID))).
				Cons(sx.Cons(SymAttrRole, sx.MakeString("doc-backlink"))).
				Cons(sxhtml.SymAttr)).
			Cons(SymA)

		var li sx.ListBuilder
		li.AddN(SymLI, attrs)
		li.ExtendBang(fni.noteHx)
		li.AddN(sx.MakeString(" "), backref)
		result.Add(li.List())
	}

	return result.List()
}

// Environment where sz objects are evaluated to shtml objects
type Environment struct {
	err          error
	langStack    LangStack
	endnotes     []endnoteInfo
	quoteNesting uint
}
type endnoteInfo struct {
	noteID  string    // link id
	noteAST sx.Vector // Endnote as list of AST inline elements
	attrs   *sx.Pair  // attrs a-list
	noteHx  *sx.Pair  // Endnote as SxHTML
}

// MakeEnvironment builds a new evaluation environment.
func MakeEnvironment(lang string) Environment {



	return Environment{
		err:          nil,


		langStack:    NewLangStack(lang),
		endnotes:     nil,


		quoteNesting: 0,
	}
}

// GetError returns the last error found.
func (env *Environment) GetError() error { return env.err }

// Reset the environment.
func (env *Environment) Reset() {
	env.langStack.Reset()
	env.endnotes = nil
	env.quoteNesting = 0
}

// pushAttribute adds the current attributes to the environment.
func (env *Environment) pushAttributes(a zsx.Attributes) {
	if value, ok := a.Get("lang"); ok {
		env.langStack.Push(value)
	} else {
		env.langStack.Dup()
	}
}

// popAttributes removes the current attributes from the envrionment.
func (env *Environment) popAttributes() { env.langStack.Pop() }

// getLanguage returns the current language.
func (env *Environment) getLanguage() string { return env.langStack.Top() }

func (env *Environment) getQuotes() (string, string, bool) {
	qi := GetQuoteInfo(env.getLanguage())
	leftQ, rightQ := qi.GetQuotes(env.quoteNesting)
	return leftQ, rightQ, qi.GetNBSp()
}

// EvalFn is a function to be called for evaluation.
type EvalFn func(sx.Vector, *Environment) sx.Object

func (ev *Evaluator) bind(sym *sx.Symbol, minArgs int, fn EvalFn) {
	symVal := sym.GetValue()
	ev.fns[symVal] = fn
	if minArgs > 0 {
		ev.minArgs[symVal] = minArgs
	}
}

// ResolveBinding returns the function bound to the given name.
func (ev *Evaluator) ResolveBinding(sym *sx.Symbol) EvalFn {
	if fn, found := ev.fns[sym.GetValue()]; found {
		return fn
	}






	return nil
}

// Rebind overwrites a binding, but leaves the minimum number of arguments intact.
func (ev *Evaluator) Rebind(sym *sx.Symbol, fn EvalFn) {
	symVal := sym.GetValue()
	if _, found := ev.fns[symVal]; !found {
		panic(sym)
	}
	ev.fns[symVal] = fn
}

func (ev *Evaluator) bindMetadata() {
	ev.bind(sz.SymMeta, 0, ev.evalList)
	evalMetaString := func(args sx.Vector, env *Environment) sx.Object {
		a := make(zsx.Attributes, 2).
			Set("name", getSymbol(args[0], env).GetValue()).
			Set("content", getString(args[1], env).GetValue())
		return ev.EvaluateMeta(a)
	}
	ev.bind(sz.SymTypeCredential, 2, evalMetaString)
	ev.bind(sz.SymTypeEmpty, 2, evalMetaString)
	ev.bind(sz.SymTypeID, 2, evalMetaString)
	ev.bind(sz.SymTypeNumber, 2, evalMetaString)
	ev.bind(sz.SymTypeString, 2, evalMetaString)
	ev.bind(sz.SymTypeTimestamp, 2, evalMetaString)
	ev.bind(sz.SymTypeURL, 2, evalMetaString)
	ev.bind(sz.SymTypeWord, 2, evalMetaString)

	evalMetaSet := func(args sx.Vector, env *Environment) sx.Object {
		var sb strings.Builder
		for obj := range getList(args[1], env).Values() {
			sb.WriteByte(' ')
			sb.WriteString(getString(obj, env).GetValue())
		}
		s := sb.String()
		if len(s) > 0 {
			s = s[1:]
		}
		a := make(zsx.Attributes, 2).
			Set("name", getSymbol(args[0], env).GetValue()).
			Set("content", s)
		return ev.EvaluateMeta(a)
	}
	ev.bind(sz.SymTypeIDSet, 2, evalMetaSet)
	ev.bind(sz.SymTypeTagSet, 2, evalMetaSet)
}

// EvaluateMeta returns HTML meta object for an attribute.
func (ev *Evaluator) EvaluateMeta(a zsx.Attributes) *sx.Pair {
	return sx.Nil().Cons(EvaluateAttributes(a)).Cons(SymMeta)
}

func (ev *Evaluator) bindBlocks() {
	ev.bind(zsx.SymBlock, 0, ev.evalList)
	ev.bind(zsx.SymPara, 0, func(args sx.Vector, env *Environment) sx.Object {






		return ev.evalSlice(args, env).Cons(SymP)
	})
	ev.bind(zsx.SymHeading, 5, func(args sx.Vector, env *Environment) sx.Object {
		nLevel := getInt64(args[0], env)
		if nLevel <= 0 {
			env.err = fmt.Errorf("%v is a negative heading level", nLevel)
			return sx.Nil()
		}
		level := strconv.FormatInt(nLevel+ev.headingOffset, 10)
		headingSymbol := sx.MakeSymbol("h" + level)

		a := GetAttributes(args[1], env)
		env.pushAttributes(a)
		defer env.popAttributes()
		if fragment := getString(args[3], env).GetValue(); fragment != "" {
			a = a.Set("id", ev.unique+fragment)
		}

		if result, _ := ev.EvaluateList(args[4:], env); result != nil {
			if len(a) > 0 {
				result = result.Cons(EvaluateAttributes(a))
			}
			return result.Cons(headingSymbol)
		}
		return sx.MakeList(headingSymbol, sx.MakeString("<MISSING TEXT>"))
	})
	ev.bind(zsx.SymThematic, 0, func(args sx.Vector, env *Environment) sx.Object {
		result := sx.Nil()
		if len(args) > 0 {
			if attrList := getList(args[0], env); attrList != nil {
				result = result.Cons(EvaluateAttributes(zsx.GetAttributes(attrList)))
			}
		}
		return result.Cons(SymHR)
	})

	ev.bind(zsx.SymListOrdered, 1, ev.makeListFn(SymOL))
	ev.bind(zsx.SymListUnordered, 1, ev.makeListFn(SymUL))
	ev.bind(zsx.SymListQuote, 1, func(args sx.Vector, env *Environment) sx.Object {
		if len(args) == 1 {
			return sx.Nil()
		}
		var result sx.ListBuilder
		result.Add(symBLOCKQUOTE)
		if attrs := EvaluateAttributes(GetAttributes(args[0], env)); attrs != nil {
			result.Add(attrs)
		}
		for _, elem := range args[1:] {
			if quote, isPair := sx.GetPair(ev.Eval(elem, env)); isPair {
				result.Add(quote.Cons(sxhtml.SymListSplice))
			}
		}
		return result.List()
	})

	ev.bind(zsx.SymDescription, 1, func(args sx.Vector, env *Environment) sx.Object {
		if len(args) == 1 {
			return sx.Nil()
		}
		var result sx.ListBuilder
		result.Add(symDL)
		if attrs := EvaluateAttributes(GetAttributes(args[0], env)); attrs != nil {
			result.Add(attrs)
		}
		for pos := 1; pos < len(args); pos++ {
			term := ev.evalDescriptionTerm(getList(args[pos], env), env)
			result.Add(term.Cons(symDT))
			pos++
			if pos >= len(args) {
				break
			}
			ddBlock := getList(ev.Eval(args[pos], env), env)
			if ddBlock == nil {

				continue
			}
			for ddlst := range ddBlock.Values() {
				dditem := getList(ddlst, env)





				result.Add(dditem.Cons(symDD))



			}





		}

		return result.List()
	})

	ev.bind(zsx.SymTable, 1, func(args sx.Vector, env *Environment) sx.Object {
		thead := sx.Nil()
		if header := getList(args[0], env); !sx.IsNil(header) {
			thead = sx.Nil().Cons(ev.evalTableRow(symTH, header, env)).Cons(symTHEAD)
		}

		var tbody sx.ListBuilder
		if len(args) > 1 {

			tbody.Add(symTBODY)
			for _, row := range args[1:] {
				tbody.Add(ev.evalTableRow(symTD, getList(row, env), env))
			}
		}

		table := sx.Nil()
		if !tbody.IsEmpty() {
			table = table.Cons(tbody.List())
		}
		if thead != nil {
			table = table.Cons(thead)
		}
		if table == nil {
			return sx.Nil()
		}
		return table.Cons(symTABLE)
	})
	ev.bind(zsx.SymCell, 1, func(args sx.Vector, env *Environment) sx.Object {
		tdata := ev.evalSlice(args[1:], env)
		pattrs := getList(args[0], env)
		if alignPairs := pattrs.Assoc(zsx.SymAttrAlign); alignPairs != nil {
			if salign, isString := sx.GetString(alignPairs.Cdr()); isString {
				a := zsx.GetAttributes(pattrs.RemoveAssoc(zsx.SymAttrAlign))
				// Since in Sz there are attributes of align:center|left|right, we can reuse the values.
				a = a.AddClass(salign.GetValue())
				tdata = tdata.Cons(EvaluateAttributes(a))
			}
		}
		return tdata
	})

	ev.bind(zsx.SymRegionBlock, 2, ev.makeRegionFn(SymDIV, true))
	ev.bind(zsx.SymRegionQuote, 2, ev.makeRegionFn(symBLOCKQUOTE, false))
	ev.bind(zsx.SymRegionVerse, 2, ev.makeRegionFn(SymDIV, false))

	ev.bind(zsx.SymVerbatimComment, 1, func(args sx.Vector, env *Environment) sx.Object {
		if GetAttributes(args[0], env).HasDefault() {
			if len(args) > 1 {
				if s := getString(args[1], env); s.GetValue() != "" {

					return sx.Nil().Cons(s).Cons(sxhtml.SymBlockComment)
				}
			}
		}
		return nil
	})

	ev.bind(zsx.SymVerbatimEval, 2, func(args sx.Vector, env *Environment) sx.Object {
		return evalVerbatim(GetAttributes(args[0], env).AddClass("zs-eval"), getString(args[1], env))
	})
	ev.bind(zsx.SymVerbatimHTML, 2, ev.evalHTML)
	ev.bind(zsx.SymVerbatimMath, 2, func(args sx.Vector, env *Environment) sx.Object {
		return evalVerbatim(GetAttributes(args[0], env).AddClass("zs-math"), getString(args[1], env))
	})
	ev.bind(zsx.SymVerbatimCode, 2, func(args sx.Vector, env *Environment) sx.Object {
		a := GetAttributes(args[0], env)
		content := getString(args[1], env)
		if a.HasDefault() {
			content = sx.MakeString(visibleReplacer.Replace(content.GetValue()))
		}
		return evalVerbatim(a, content)
	})
	ev.bind(zsx.SymVerbatimZettel, 0, nilFn)
	ev.bind(zsx.SymBLOB, 4, func(args sx.Vector, env *Environment) sx.Object {
		a := GetAttributes(args[0], env)
		return evalBLOB(a, getList(args[1], env), getString(args[2], env), getString(args[3], env))
	})

	ev.bind(zsx.SymTransclude, 2, func(args sx.Vector, env *Environment) sx.Object {
		if refSym, refValue := GetReference(args[1], env); refSym != nil {








			if refSym.IsEqualSymbol(zsx.SymRefStateExternal) {
				a := GetAttributes(args[0], env).Set("src", refValue).AddClass("external")
				// TODO: if len(args) > 2, add "alt" attr based on args[2:], as in SymEmbed
				return sx.Nil().Cons(sx.Nil().Cons(EvaluateAttributes(a)).Cons(SymIMG)).Cons(SymP)
			}
			return sx.MakeList(
				sxhtml.SymInlineComment,
				sx.MakeString("transclude"),
				refSym,
				sx.MakeString("->"),
				sx.MakeString(refValue),
			)
		}
		return ev.evalSlice(args, env)
	})
}

func (ev *Evaluator) makeListFn(sym *sx.Symbol) EvalFn {

	return func(args sx.Vector, env *Environment) sx.Object {
		var result sx.ListBuilder
		result.Add(sym)
		if attrs := EvaluateAttributes(GetAttributes(args[0], env)); attrs != nil {
			result.Add(attrs)
		}
		if len(args) > 1 {
			for _, elem := range args[1:] {
				item := sx.Nil().Cons(SymLI)
				if res, isPair := sx.GetPair(ev.Eval(elem, env)); isPair {
					item.ExtendBang(res)
				}
				result.Add(item)
			}
		}
		return result.List()
	}
}

func (ev *Evaluator) evalDescriptionTerm(term *sx.Pair, env *Environment) *sx.Pair {
	var result sx.ListBuilder
	for obj := range term.Values() {
		elem := ev.Eval(obj, env)
		result.Add(elem)
	}
	return result.List()
}

func (ev *Evaluator) evalTableRow(sym *sx.Symbol, pairs *sx.Pair, env *Environment) *sx.Pair {
	if pairs == nil {
		return nil
	}
	var row sx.ListBuilder
	row.Add(symTR)
	for obj := range pairs.Values() {
		row.Add(sx.Cons(sym, ev.Eval(obj, env)))
	}
	return row.List()
}











func (ev *Evaluator) makeRegionFn(sym *sx.Symbol, genericToClass bool) EvalFn {
	return func(args sx.Vector, env *Environment) sx.Object {
		a := GetAttributes(args[0], env)
		env.pushAttributes(a)
		defer env.popAttributes()
		if genericToClass {
			if val, found := a.Get(""); found {
				a = a.Remove("").AddClass(val)
			}
		}
		var result sx.ListBuilder
		result.Add(sym)
		if len(a) > 0 {
			result.Add(EvaluateAttributes(a))
		}


		if region, isPair := sx.GetPair(args[1]); isPair {
			if evalRegion := ev.EvalPairList(region, env); evalRegion != nil {
				result.ExtendBang(evalRegion)
			}
		}
		if len(args) > 2 {
			if cite, _ := ev.EvaluateList(args[2:], env); cite != nil {
				result.Add(cite.Cons(symCITE))
			}
		}
		return result.List()
	}
}

func evalVerbatim(a zsx.Attributes, s sx.String) sx.Object {
	a = setProgLang(a)
	code := sx.Nil().Cons(s)
	if al := EvaluateAttributes(a); al != nil {
		code = code.Cons(al)
	}
	code = code.Cons(symCODE)
	return sx.Nil().Cons(code).Cons(symPRE)
}

func (ev *Evaluator) bindInlines() {
	ev.bind(zsx.SymInline, 0, ev.evalList)
	ev.bind(zsx.SymText, 1, func(args sx.Vector, env *Environment) sx.Object { return getString(args[0], env) })


	ev.bind(zsx.SymSoft, 0, func(sx.Vector, *Environment) sx.Object { return sx.MakeString(" ") })
	ev.bind(zsx.SymHard, 0, func(sx.Vector, *Environment) sx.Object { return sx.Nil().Cons(symBR) })

	ev.bind(zsx.SymLink, 2, func(args sx.Vector, env *Environment) sx.Object {
		a := GetAttributes(args[0], env)
		env.pushAttributes(a)
		defer env.popAttributes()
		refSym, refValue := GetReference(args[1], env)
		switch refSym {
		case sz.SymRefStateZettel, zsx.SymRefStateSelf, sz.SymRefStateFound, zsx.SymRefStateHosted, sz.SymRefStateBased:
			return ev.evalLink(a.Set("href", refValue), refValue, args[2:], env)

		case zsx.SymRefStateExternal:
			return ev.evalLink(a.Set("href", refValue).Add("rel", "external"), refValue, args[2:], env)

		case sz.SymRefStateQuery:
			query := "?" + api.QueryKeyQuery + "=" + url.QueryEscape(refValue)
			return ev.evalLink(a.Set("href", query), refValue, args[2:], env)

		case sz.SymRefStateBroken:
			return ev.evalLink(a.AddClass("broken"), refValue, args[2:], env)
		}


		// sz.SymRefStateInvalid or unknown
		var inline *sx.Pair
		if len(args) > 2 {
			inline = ev.evalSlice(args[2:], env)
		}
		if inline == nil {
			inline = sx.Nil().Cons(sx.MakeString(refValue))
		}
		return inline.Cons(SymSPAN)
	})



























	ev.bind(zsx.SymEmbed, 3, func(args sx.Vector, env *Environment) sx.Object {
		_, refValue := GetReference(args[1], env)















		a := GetAttributes(args[0], env).Set("src", refValue)

		if len(args) > 3 {
			var sb strings.Builder
			flattenText(&sb, sx.MakeList(args[3:]...))
			if d := sb.String(); d != "" {
				a = a.Set("alt", d)
			}
		}
		return sx.MakeList(SymIMG, EvaluateAttributes(a))
	})
	ev.bind(zsx.SymEmbedBLOB, 3, func(args sx.Vector, env *Environment) sx.Object {
		a, syntax, data := GetAttributes(args[0], env), getString(args[1], env), getString(args[2], env)
		summary, hasSummary := a.Get(meta.KeySummary)
		if !hasSummary {
			summary = ""
		}
		return evalBLOB(
			a,
			sx.MakeList(sxhtml.SymListSplice, sx.MakeString(summary)),
			syntax,
			data,
		)
	})

	ev.bind(zsx.SymCite, 2, func(args sx.Vector, env *Environment) sx.Object {
		a := GetAttributes(args[0], env)
		env.pushAttributes(a)
		defer env.popAttributes()
		result := sx.Nil()
		if key := getString(args[1], env); key.GetValue() != "" {
			if len(args) > 2 {
				result = ev.evalSlice(args[2:], env).Cons(sx.MakeString(", "))
			}
			result = result.Cons(key)
		}
		if len(a) > 0 {
			result = result.Cons(EvaluateAttributes(a))
		}
		if result == nil {
			return nil
		}
		return result.Cons(SymSPAN)
	})
	ev.bind(zsx.SymMark, 3, func(args sx.Vector, env *Environment) sx.Object {

		result := ev.evalSlice(args[3:], env)
		if !ev.noLinks {
			if fragment := getString(args[2], env).GetValue(); fragment != "" {
				a := zsx.Attributes{"id": fragment + ev.unique}
				return result.Cons(EvaluateAttributes(a)).Cons(SymA)
			}
		}
		return result.Cons(SymSPAN)
	})
	ev.bind(zsx.SymEndnote, 1, func(args sx.Vector, env *Environment) sx.Object {
		a := GetAttributes(args[0], env)
		env.pushAttributes(a)
		defer env.popAttributes()
		attrPlist := sx.Nil()
		if len(a) > 0 {
			if attrs := EvaluateAttributes(a); attrs != nil {
				attrPlist = attrs.Tail()
			}
		}






		noteNum := strconv.Itoa(len(env.endnotes) + 1)
		noteID := ev.unique + noteNum
		env.endnotes = append(env.endnotes, endnoteInfo{
			noteID: noteID, noteAST: args[1:], noteHx: nil, attrs: attrPlist})
		hrefAttr := sx.Nil().Cons(sx.Cons(SymAttrRole, sx.MakeString("doc-noteref"))).
			Cons(sx.Cons(SymAttrHref, sx.MakeString("#fn:"+noteID))).
			Cons(sx.Cons(SymAttrClass, sx.MakeString("zs-noteref"))).
			Cons(sxhtml.SymAttr)
		href := sx.Nil().Cons(sx.MakeString(noteNum)).Cons(hrefAttr).Cons(SymA)
		supAttr := sx.Nil().Cons(sx.Cons(SymAttrID, sx.MakeString("fnref:"+noteID))).Cons(sxhtml.SymAttr)
		return sx.Nil().Cons(href).Cons(supAttr).Cons(symSUP)
	})

	ev.bind(zsx.SymFormatDelete, 1, ev.makeFormatFn(symDEL))
	ev.bind(zsx.SymFormatEmph, 1, ev.makeFormatFn(symEM))
	ev.bind(zsx.SymFormatInsert, 1, ev.makeFormatFn(symINS))
	ev.bind(zsx.SymFormatMark, 1, ev.makeFormatFn(symMARK))
	ev.bind(zsx.SymFormatQuote, 1, ev.evalQuote)
	ev.bind(zsx.SymFormatSpan, 1, ev.makeFormatFn(SymSPAN))
	ev.bind(zsx.SymFormatStrong, 1, ev.makeFormatFn(SymSTRONG))
	ev.bind(zsx.SymFormatSub, 1, ev.makeFormatFn(symSUB))
	ev.bind(zsx.SymFormatSuper, 1, ev.makeFormatFn(symSUP))

	ev.bind(zsx.SymLiteralComment, 1, func(args sx.Vector, env *Environment) sx.Object {
		if GetAttributes(args[0], env).HasDefault() {
			if len(args) > 1 {
				if s := getString(ev.Eval(args[1], env), env); s.GetValue() != "" {
					return sx.Nil().Cons(s).Cons(sxhtml.SymInlineComment)
				}
			}
		}
		return sx.Nil()
	})


	ev.bind(zsx.SymLiteralInput, 2, func(args sx.Vector, env *Environment) sx.Object {
		return evalLiteral(args, nil, symKBD, env)
	})

	ev.bind(zsx.SymLiteralMath, 2, func(args sx.Vector, env *Environment) sx.Object {
		a := GetAttributes(args[0], env).AddClass("zs-math")
		return evalLiteral(args, a, symCODE, env)
	})

	ev.bind(zsx.SymLiteralOutput, 2, func(args sx.Vector, env *Environment) sx.Object {
		return evalLiteral(args, nil, symSAMP, env)
	})
	ev.bind(zsx.SymLiteralCode, 2, func(args sx.Vector, env *Environment) sx.Object {
		return evalLiteral(args, nil, symCODE, env)
	})
}

func (ev *Evaluator) makeFormatFn(sym *sx.Symbol) EvalFn {
	return func(args sx.Vector, env *Environment) sx.Object {
		a := GetAttributes(args[0], env)
		env.pushAttributes(a)
		defer env.popAttributes()
		if val, hasClass := a.Get(""); hasClass {
			a = a.Remove("").AddClass(val)
		}
		res := ev.evalSlice(args[1:], env)
		if len(a) > 0 {
			res = res.Cons(EvaluateAttributes(a))
		}

		return res.Cons(sym)
	}
}

func (ev *Evaluator) evalQuote(args sx.Vector, env *Environment) sx.Object {
	a := GetAttributes(args[0], env)
	env.pushAttributes(a)
	defer env.popAttributes()

	if val, hasClass := a.Get(""); hasClass {
		a = a.Remove("").AddClass(val)
	}
	leftQ, rightQ, withNbsp := env.getQuotes()



	env.quoteNesting++
	res := ev.evalSlice(args[1:], env)
	env.quoteNesting--

	lastPair := res.LastPair()
	if lastPair.IsNil() {
		res = sx.Cons(sx.MakeList(sxhtml.SymNoEscape, sx.MakeString(leftQ), sx.MakeString(rightQ)), sx.Nil())
	} else {




		if withNbsp {
			lastPair.AppendBang(sx.MakeList(sxhtml.SymNoEscape, sx.MakeString("&nbsp;"), sx.MakeString(rightQ)))
			res = res.Cons(sx.MakeList(sxhtml.SymNoEscape, sx.MakeString(leftQ), sx.MakeString("&nbsp;")))
		} else {
			lastPair.AppendBang(sx.MakeList(sxhtml.SymNoEscape, sx.MakeString(rightQ)))
			res = res.Cons(sx.MakeList(sxhtml.SymNoEscape, sx.MakeString(leftQ)))
		}

	}
	if len(a) > 0 {
		res = res.Cons(EvaluateAttributes(a))

		return res.Cons(SymSPAN)


	}
	return res.Cons(sxhtml.SymListSplice)
}

var visibleReplacer = strings.NewReplacer(" ", "\u2423")

func evalLiteral(args sx.Vector, a zsx.Attributes, sym *sx.Symbol, env *Environment) sx.Object {
	if a == nil {
		a = GetAttributes(args[0], env)
	}
	a = setProgLang(a)
	literal := getString(args[1], env).GetValue()
	if a.HasDefault() {
		a = a.RemoveDefault()
		literal = visibleReplacer.Replace(literal)
	}
	res := sx.Nil().Cons(sx.MakeString(literal))
	if len(a) > 0 {
		res = res.Cons(EvaluateAttributes(a))
	}
	return res.Cons(sym)
}

func setProgLang(a zsx.Attributes) zsx.Attributes {
	if val, found := a.Get(""); found {
		a = a.AddClass("language-" + val).Remove("")
	}
	return a
}

func (ev *Evaluator) evalHTML(args sx.Vector, env *Environment) sx.Object {
	if s := getString(ev.Eval(args[1], env), env); s.GetValue() != "" && IsSafe(s.GetValue()) {
		return sx.Nil().Cons(s).Cons(sxhtml.SymNoEscape)
	}
	return nil
}

func evalBLOB(a zsx.Attributes, description *sx.Pair, syntax, data sx.String) sx.Object {
	if data.GetValue() == "" {
		return sx.Nil()
	}
	switch syntax.GetValue() {
	case "":
		return sx.Nil()
	case meta.ValueSyntaxSVG:
		return sx.Nil().Cons(sx.Nil().Cons(data).Cons(sxhtml.SymNoEscape)).Cons(SymP)
	default:
		a = a.Add("src", "data:image/"+syntax.GetValue()+";base64,"+data.GetValue())
		var sb strings.Builder
		flattenText(&sb, description)
		if d := sb.String(); d != "" {
			a = a.Add("alt", d)
		}
		return sx.Nil().Cons(sx.Nil().Cons(EvaluateAttributes(a)).Cons(SymIMG)).Cons(SymP)
	}
}

func flattenText(sb *strings.Builder, lst *sx.Pair) {
	for elem := range lst.Values() {
		switch obj := elem.(type) {
		case sx.String:
			sb.WriteString(obj.GetValue())
		case *sx.Pair:
			flattenText(sb, obj)
		}
	}
}

func (ev *Evaluator) evalList(args sx.Vector, env *Environment) sx.Object {
	return ev.evalSlice(args, env)
}
func nilFn(sx.Vector, *Environment) sx.Object { return sx.Nil() }

// Eval evaluates an object in an environment.
func (ev *Evaluator) Eval(obj sx.Object, env *Environment) sx.Object {
	if env.err != nil {

		return sx.Nil()

	}
	if sx.IsNil(obj) {
		return obj
	}
	lst, isLst := sx.GetPair(obj)
	if !isLst {
		return obj
	}
	sym, found := sx.GetSymbol(lst.Car())
	if !found {
		env.err = fmt.Errorf("symbol expected, but got %T/%v", lst.Car(), lst.Car())
		return sx.Nil()
	}
	symVal := sym.GetValue()
	fn, found := ev.fns[symVal]
	if !found {
		env.err = fmt.Errorf("symbol %q not bound", sym)
		return sx.Nil()
	}
	var args sx.Vector
	for cdr := lst.Cdr(); !sx.IsNil(cdr); {
		pair, isPair := sx.GetPair(cdr)
		if !isPair {
			break
		}


		args = append(args, pair.Car())

		cdr = pair.Cdr()
	}
	if minArgs, hasMinArgs := ev.minArgs[symVal]; hasMinArgs {
		if minArgs > len(args) {
			env.err = fmt.Errorf("%v needs at least %d arguments, but got only %d", sym, minArgs, len(args))
			return sx.Nil()
		}
	}
	result := fn(args, env)
	if env.err != nil {
		return sx.Nil()
	}
	return result

}


func (ev *Evaluator) evalSlice(args sx.Vector, env *Environment) *sx.Pair {
	var result sx.ListBuilder
	for _, arg := range args {
		elem := ev.Eval(arg, env)


		result.Add(elem)
	}

	if env.err == nil {
		return result.List()
	}
	return nil
}

// EvalPairList evaluates a list of lists.
func (ev *Evaluator) EvalPairList(pair *sx.Pair, env *Environment) *sx.Pair {
	var result sx.ListBuilder
	for obj := range pair.Values() {
		elem := ev.Eval(obj, env)
		result.Add(elem)
	}
	if env.err == nil {
		return result.List()

	}
	return nil
}

func (ev *Evaluator) evalLink(a zsx.Attributes, refValue string, inline sx.Vector, env *Environment) sx.Object {
	result := ev.evalSlice(inline, env)
	if len(inline) == 0 {
		result = sx.Nil().Cons(sx.MakeString(refValue))
	}


	if ev.noLinks {
		return result.Cons(SymSPAN)
	}
	return result.Cons(EvaluateAttributes(a)).Cons(SymA)
}

func getSymbol(obj sx.Object, env *Environment) *sx.Symbol {
	if env.err == nil {
		if sym, ok := sx.GetSymbol(obj); ok {
			return sym
		}
		env.err = fmt.Errorf("%v/%T is not a symbol", obj, obj)
	}
	return sx.MakeSymbol("???")
}
func getString(val sx.Object, env *Environment) sx.String {
	if env.err == nil {
		if s, ok := sx.GetString(val); ok {
			return s
		}
		env.err = fmt.Errorf("%v/%T is not a string", val, val)
	}
	return sx.MakeString("")
}
func getList(val sx.Object, env *Environment) *sx.Pair {
	if env.err == nil {
		if res, isPair := sx.GetPair(val); isPair {
			return res
		}
		env.err = fmt.Errorf("%v/%T is not a list", val, val)
	}
	return nil
}
func getInt64(val sx.Object, env *Environment) int64 {
	if env.err != nil {
		return -1017
	}
	if num, ok := sx.GetNumber(val); ok {
		return int64(num.(sx.Int64))
	}
	env.err = fmt.Errorf("%v/%T is not a number", val, val)
	return -1017
}







// GetAttributes evaluates the given arg in the given environment and returns

// the contained attributes.
func GetAttributes(arg sx.Object, env *Environment) zsx.Attributes {
	return zsx.GetAttributes(getList(arg, env))
}

// GetReference returns the reference symbol and the reference value of a reference pair.
func GetReference(val sx.Object, env *Environment) (*sx.Symbol, string) {

	if env.err == nil {
		if p := getList(val, env); env.err == nil {
			sym, val := sz.GetReference(p)

			if sym != nil {
				return sym, val
			}


			env.err = fmt.Errorf("%v/%T is not a reference", val, val)


		}
	}

	return nil, ""
}

var unsafeSnippets = []string{
	"<script", "</script",
	"<iframe", "</iframe",
}