0.21.0
0.20.0

//-----------------------------------------------------------------------------
// Copyright (c) 2020-present Detlef Stern
//
// This file is part of Zettelstore.
//
// Zettelstore is licensed under the latest version of the EUPL (European Union
// Public License). Please see file LICENSE.txt for your rights and obligations
// under this license.
//
// SPDX-License-Identifier: EUPL-1.2
// SPDX-FileCopyrightText: 2020-present Detlef Stern
//-----------------------------------------------------------------------------

// Package ast provides the abstract syntax tree for parsed zettel content.
package ast

import (
	"net/url"

	"t73f.de/r/zsc/domain/id"
	"t73f.de/r/zsc/domain/meta"
	"zettelstore.de/z/zettel"
)

// ZettelNode is the root node of the abstract syntax tree.
// It is *not* part of the visitor pattern.
type ZettelNode struct {
	Meta      *meta.Meta     // Original metadata
	Content   zettel.Content // Original content
	Zid       id.Zid         // Zettel identification.
	InhMeta   *meta.Meta     // Metadata of the zettel, with inherited values.
	BlocksAST BlockSlice     // Zettel abstract syntax tree is a sequence of block nodes.
	Syntax    string         // Syntax / parser that produced the Ast
}

// Node is the interface, all nodes must implement.
type Node interface {
	WalkChildren(v Visitor)
}

// BlockNode is the interface that all block nodes must implement.
type BlockNode interface {
	Node
	blockNode()
}

// ItemNode is a node that can occur as a list item.
type ItemNode interface {
	BlockNode
	itemNode()
}

// ItemSlice is a slice of ItemNodes.
type ItemSlice []ItemNode

// DescriptionNode is a node that contains just textual description.
type DescriptionNode interface {
	ItemNode
	descriptionNode()
}

// DescriptionSlice is a slice of DescriptionNodes.
type DescriptionSlice []DescriptionNode

// InlineNode is the interface that all inline nodes must implement.
type InlineNode interface {
	Node
	inlineNode()
}

// Reference is a reference to external or internal material.
type Reference struct {
	URL   *url.URL
	Value string
	State RefState
}

// RefState indicates the state of the reference.
type RefState int

// Constants for RefState
const (
	RefStateInvalid  RefState = iota // Invalid Reference
	RefStateZettel                   // Reference to an internal zettel
	RefStateSelf                     // Reference to same zettel with a fragment
	RefStateFound                    // Reference to an existing internal zettel, URL is ajusted
	RefStateBroken                   // Reference to a non-existing internal zettel
	RefStateHosted                   // Reference to local hosted non-Zettel, without URL change
	RefStateBased                    // Reference to local non-Zettel, to be prefixed
	RefStateQuery                    // Reference to a zettel query
	RefStateExternal                 // Reference to external material
)

//-----------------------------------------------------------------------------
// Copyright (c) 2020-present Detlef Stern
//
// This file is part of Zettelstore.
//
// Zettelstore is licensed under the latest version of the EUPL (European Union
// Public License). Please see file LICENSE.txt for your rights and obligations
// under this license.
//
// SPDX-License-Identifier: EUPL-1.2
// SPDX-FileCopyrightText: 2020-present Detlef Stern
//-----------------------------------------------------------------------------

package ast

import "t73f.de/r/zsc/attrs"

// Definition of Block nodes.

// BlockSlice is a slice of BlockNodes.
type BlockSlice []BlockNode

func (*BlockSlice) blockNode() { /* Just a marker */ }

// WalkChildren walks down to the descriptions.
func (bs *BlockSlice) WalkChildren(v Visitor) {
	if bs != nil {
		for _, bn := range *bs {
			Walk(v, bn)
		}
	}
}

// FirstParagraphInlines returns the inline list of the first paragraph that
// contains a inline list.
func (bs BlockSlice) FirstParagraphInlines() InlineSlice {
	for _, bn := range bs {
		pn, ok := bn.(*ParaNode)
		if !ok {
			continue
		}
		if inl := pn.Inlines; len(inl) > 0 {
			return inl
		}
	}
	return nil
}

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

// ParaNode contains just a sequence of inline elements.
// Another name is "paragraph".
type ParaNode struct {
	Inlines InlineSlice
}

func (*ParaNode) blockNode()       { /* Just a marker */ }
func (*ParaNode) itemNode()        { /* Just a marker */ }
func (*ParaNode) descriptionNode() { /* Just a marker */ }

// CreateParaNode creates a parameter block from inline nodes.
func CreateParaNode(nodes ...InlineNode) *ParaNode { return &ParaNode{Inlines: nodes} }

// WalkChildren walks down the inline elements.
func (pn *ParaNode) WalkChildren(v Visitor) { Walk(v, &pn.Inlines) }

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

// VerbatimNode contains uninterpreted text
type VerbatimNode struct {
	Kind    VerbatimKind
	Attrs   attrs.Attributes
	Content []byte
}

// VerbatimKind specifies the format that is applied to code inline nodes.
type VerbatimKind int

// Constants for VerbatimCode
const (
	_               VerbatimKind = iota
	VerbatimZettel               // Zettel content
	VerbatimCode                 // Program code
	VerbatimEval                 // Code to be externally interpreted. Syntax is stored in default attribute.
	VerbatimComment              // Block comment
	VerbatimHTML                 // Block HTML, e.g. for Markdown
	VerbatimMath                 // Block math mode
)

func (*VerbatimNode) blockNode() { /* Just a marker */ }
func (*VerbatimNode) itemNode()  { /* Just a marker */ }

// WalkChildren does nothing.
func (*VerbatimNode) WalkChildren(Visitor) { /* No children*/ }

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

// RegionNode encapsulates a region of block nodes.
type RegionNode struct {
	Kind    RegionKind
	Attrs   attrs.Attributes
	Blocks  BlockSlice
	Inlines InlineSlice // Optional text at the end of the region
}

// RegionKind specifies the actual region type.
type RegionKind int

// Values for RegionCode
const (
	_           RegionKind = iota
	RegionSpan             // Just a span of blocks
	RegionQuote            // A longer quotation
	RegionVerse            // Line breaks matter
)

func (*RegionNode) blockNode() { /* Just a marker */ }
func (*RegionNode) itemNode()  { /* Just a marker */ }

// WalkChildren walks down the blocks and the text.
func (rn *RegionNode) WalkChildren(v Visitor) {
	Walk(v, &rn.Blocks)
	Walk(v, &rn.Inlines)
}

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

// HeadingNode stores the heading text and level.
type HeadingNode struct {
	Level    int
	Attrs    attrs.Attributes
	Slug     string      // Heading text, normalized
	Fragment string      // Heading text, suitable to be used as an unique URL fragment
	Inlines  InlineSlice // Heading text, possibly formatted
}

func (*HeadingNode) blockNode() { /* Just a marker */ }
func (*HeadingNode) itemNode()  { /* Just a marker */ }

// WalkChildren walks the heading text.
func (hn *HeadingNode) WalkChildren(v Visitor) { Walk(v, &hn.Inlines) }

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

// HRuleNode specifies a horizontal rule.
type HRuleNode struct {
	Attrs attrs.Attributes
}

func (*HRuleNode) blockNode() { /* Just a marker */ }
func (*HRuleNode) itemNode()  { /* Just a marker */ }

// WalkChildren does nothing.
func (*HRuleNode) WalkChildren(Visitor) { /* No children*/ }

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

// NestedListNode specifies a nestable list, either ordered or unordered.
type NestedListNode struct {
	Kind  NestedListKind
	Items []ItemSlice
	Attrs attrs.Attributes
}

// NestedListKind specifies the actual list type.
type NestedListKind uint8

// Values for ListCode
const (
	_                   NestedListKind = iota
	NestedListOrdered                  // Ordered list.
	NestedListUnordered                // Unordered list.
	NestedListQuote                    // Quote list.
)

func (*NestedListNode) blockNode() { /* Just a marker */ }
func (*NestedListNode) itemNode()  { /* Just a marker */ }

// WalkChildren walks down the items.
func (ln *NestedListNode) WalkChildren(v Visitor) {
	if items := ln.Items; items != nil {
		for _, item := range items {
			WalkItemSlice(v, item)
		}
	}
}

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

// DescriptionListNode specifies a description list.
type DescriptionListNode struct {
	Descriptions []Description
}

// Description is one element of a description list.
type Description struct {
	Term         InlineSlice
	Descriptions []DescriptionSlice
}

func (*DescriptionListNode) blockNode() { /* Just a marker */ }

// WalkChildren walks down to the descriptions.
func (dn *DescriptionListNode) WalkChildren(v Visitor) {
	if descrs := dn.Descriptions; descrs != nil {
		for i, desc := range descrs {
			if len(desc.Term) > 0 {
				Walk(v, &descrs[i].Term) // Otherwise, changes in desc.Term will not go back into AST
			}
			if dss := desc.Descriptions; dss != nil {
				for _, dns := range dss {
					WalkDescriptionSlice(v, dns)
				}
			}
		}
	}
}

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

// TableNode specifies a full table
type TableNode struct {
	Header TableRow    // The header row
	Align  []Alignment // Default column alignment
	Rows   []TableRow  // The slice of cell rows
}

// TableCell contains the data for one table cell
type TableCell struct {
	Align   Alignment   // Cell alignment
	Inlines InlineSlice // Cell content
}

// TableRow is a slice of cells.
type TableRow []*TableCell

// Alignment specifies text alignment.
// Currently only for tables.
type Alignment int

// Constants for Alignment.
const (
	_            Alignment = iota
	AlignDefault           // Default alignment, inherited
	AlignLeft              // Left alignment
	AlignCenter            // Center the content
	AlignRight             // Right alignment
)

func (*TableNode) blockNode() { /* Just a marker */ }

// WalkChildren walks down to the cells.
func (tn *TableNode) WalkChildren(v Visitor) {
	if header := tn.Header; header != nil {
		for i := range header {
			Walk(v, header[i]) // Otherwise changes will not go back
		}
	}
	if rows := tn.Rows; rows != nil {
		for _, row := range rows {
			for i := range row {
				Walk(v, &row[i].Inlines) // Otherwise changes will not go back
			}
		}
	}
}

// WalkChildren walks the list of inline elements.
func (cell *TableCell) WalkChildren(v Visitor) {
	Walk(v, &cell.Inlines) // Otherwise changes will not go back
}

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

// TranscludeNode specifies block content from other zettel to embedded in
// current zettel
type TranscludeNode struct {
	Attrs   attrs.Attributes
	Ref     *Reference
	Inlines InlineSlice // Optional text.
}

func (*TranscludeNode) blockNode() { /* Just a marker */ }

// WalkChildren walks the associated text.
func (tn *TranscludeNode) WalkChildren(v Visitor) { Walk(v, &tn.Inlines) }

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

// BLOBNode contains just binary data that must be interpreted according to
// a syntax.
type BLOBNode struct {
	Description InlineSlice
	Syntax      string
	Blob        []byte
}

func (*BLOBNode) blockNode() { /* Just a marker */ }

// WalkChildren does nothing.
func (*BLOBNode) WalkChildren(Visitor) { /* No children*/ }

//-----------------------------------------------------------------------------
// Copyright (c) 2020-present Detlef Stern
//
// This file is part of Zettelstore.
//
// Zettelstore is licensed under the latest version of the EUPL (European Union
// Public License). Please see file LICENSE.txt for your rights and obligations
// under this license.
//
// SPDX-License-Identifier: EUPL-1.2
// SPDX-FileCopyrightText: 2020-present Detlef Stern
//-----------------------------------------------------------------------------

package ast

import (
	"t73f.de/r/zsc/attrs"
)

// Definitions of inline nodes.

// InlineSlice is a list of BlockNodes.
type InlineSlice []InlineNode

func (*InlineSlice) inlineNode() { /* Just a marker */ }

// WalkChildren walks down to the list.
func (is *InlineSlice) WalkChildren(v Visitor) {
	if is != nil {
		for _, in := range *is {
			Walk(v, in)
		}
	}
}

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

// TextNode just contains some text.
type TextNode struct {
	Text string // The text itself.
}

func (*TextNode) inlineNode() { /* Just a marker */ }

// WalkChildren does nothing.
func (*TextNode) WalkChildren(Visitor) { /* No children*/ }

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

// BreakNode signals a new line that must / should be interpreted as a new line break.
type BreakNode struct {
	Hard bool // Hard line break?
}

func (*BreakNode) inlineNode() { /* Just a marker */ }

// WalkChildren does nothing.
func (*BreakNode) WalkChildren(Visitor) { /* No children*/ }

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

// LinkNode contains the specified link.
type LinkNode struct {
	Attrs   attrs.Attributes // Optional attributes
	Ref     *Reference
	Inlines InlineSlice // The text associated with the link.
}

func (*LinkNode) inlineNode() { /* Just a marker */ }

// WalkChildren walks to the link text.
func (ln *LinkNode) WalkChildren(v Visitor) {
	if len(ln.Inlines) > 0 {
		Walk(v, &ln.Inlines)
	}
}

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

// EmbedRefNode contains the specified embedded reference material.
type EmbedRefNode struct {
	Attrs   attrs.Attributes // Optional attributes
	Ref     *Reference       // The reference to be embedded.
	Syntax  string           // Syntax of referenced material, if known
	Inlines InlineSlice      // Optional text associated with the image.
}

func (*EmbedRefNode) inlineNode() { /* Just a marker */ }

// WalkChildren walks to the text that describes the embedded material.
func (en *EmbedRefNode) WalkChildren(v Visitor) { Walk(v, &en.Inlines) }

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

// EmbedBLOBNode contains the specified embedded BLOB material.
type EmbedBLOBNode struct {
	Attrs   attrs.Attributes // Optional attributes
	Syntax  string           // Syntax of Blob
	Blob    []byte           // BLOB data itself.
	Inlines InlineSlice      // Optional text associated with the image.
}

func (*EmbedBLOBNode) inlineNode() { /* Just a marker */ }

// WalkChildren walks to the text that describes the embedded material.
func (en *EmbedBLOBNode) WalkChildren(v Visitor) { Walk(v, &en.Inlines) }

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

// CiteNode contains the specified citation.
type CiteNode struct {
	Attrs   attrs.Attributes // Optional attributes
	Key     string           // The citation key
	Inlines InlineSlice      // Optional text associated with the citation.
}

func (*CiteNode) inlineNode() { /* Just a marker */ }

// WalkChildren walks to the cite text.
func (cn *CiteNode) WalkChildren(v Visitor) { Walk(v, &cn.Inlines) }

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

// MarkNode contains the specified merked position.
// It is a BlockNode too, because although it is typically parsed during inline
// mode, it is moved into block mode afterwards.
type MarkNode struct {
	Mark     string      // The mark text itself
	Slug     string      // Slugified form of Mark
	Fragment string      // Unique form of Slug
	Inlines  InlineSlice // Marked inline content
}

func (*MarkNode) inlineNode() { /* Just a marker */ }

// WalkChildren does nothing.
func (mn *MarkNode) WalkChildren(v Visitor) {
	if len(mn.Inlines) > 0 {
		Walk(v, &mn.Inlines)
	}
}

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

// FootnoteNode contains the specified footnote.
type FootnoteNode struct {
	Attrs   attrs.Attributes // Optional attributes
	Inlines InlineSlice      // The footnote text.
}

func (*FootnoteNode) inlineNode() { /* Just a marker */ }

// WalkChildren walks to the footnote text.
func (fn *FootnoteNode) WalkChildren(v Visitor) { Walk(v, &fn.Inlines) }

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

// FormatNode specifies some inline formatting.
type FormatNode struct {
	Kind    FormatKind
	Attrs   attrs.Attributes // Optional attributes.
	Inlines InlineSlice
}

// FormatKind specifies the format that is applied to the inline nodes.
type FormatKind int

// Constants for FormatCode
const (
	_            FormatKind = iota
	FormatEmph              // Emphasized text
	FormatStrong            // Strongly emphasized text
	FormatInsert            // Inserted text
	FormatDelete            // Deleted text
	FormatSuper             // Superscripted text
	FormatSub               // SubscriptedText
	FormatQuote             // Quoted text
	FormatMark              // Marked text
	FormatSpan              // Generic inline container
)

func (*FormatNode) inlineNode() { /* Just a marker */ }

// WalkChildren walks to the formatted text.
func (fn *FormatNode) WalkChildren(v Visitor) { Walk(v, &fn.Inlines) }

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

// LiteralNode specifies some uninterpreted text.
type LiteralNode struct {
	Kind    LiteralKind
	Attrs   attrs.Attributes // Optional attributes.
	Content []byte
}

// LiteralKind specifies the format that is applied to code inline nodes.
type LiteralKind int

// Constants for LiteralCode
const (
	_              LiteralKind = iota
	LiteralCode                // Inline program code
	LiteralInput               // Computer input, e.g. Keyboard strokes
	LiteralOutput              // Computer output
	LiteralComment             // Inline comment
	LiteralMath                // Inline math mode
)

func (*LiteralNode) inlineNode() { /* Just a marker */ }

// WalkChildren does nothing.
func (*LiteralNode) WalkChildren(Visitor) { /* No children*/ }

//-----------------------------------------------------------------------------
// Copyright (c) 2020-present Detlef Stern
//
// This file is part of Zettelstore.
//
// Zettelstore is licensed under the latest version of the EUPL (European Union
// Public License). Please see file LICENSE.txt for your rights and obligations
// under this license.
//
// SPDX-License-Identifier: EUPL-1.2
// SPDX-FileCopyrightText: 2020-present Detlef Stern
//-----------------------------------------------------------------------------

package ast

import (
	"net/url"
	"strings"

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

// QueryPrefix is the prefix that denotes a query expression.
const QueryPrefix = api.QueryPrefix

// ParseReference parses a string and returns a reference.
func ParseReference(s string) *Reference {
	if invalidReference(s) {
		return &Reference{URL: nil, Value: s, State: RefStateInvalid}
	}
	if strings.HasPrefix(s, QueryPrefix) {
		return &Reference{URL: nil, Value: s[len(QueryPrefix):], State: RefStateQuery}
	}
	if state, ok := localState(s); ok {
		if state == RefStateBased {
			s = s[1:]
		}
		u, err := url.Parse(s)
		if err == nil {
			return &Reference{URL: u, Value: s, State: state}
		}
	}
	u, err := url.Parse(s)
	if err != nil {
		return &Reference{URL: nil, Value: s, State: RefStateInvalid}
	}
	if !externalURL(u) {
		if _, err = id.Parse(u.Path); err == nil {
			return &Reference{URL: u, Value: s, State: RefStateZettel}
		}
		if u.Path == "" && u.Fragment != "" {
			return &Reference{URL: u, Value: s, State: RefStateSelf}
		}
	}
	return &Reference{URL: u, Value: s, State: RefStateExternal}
}

func invalidReference(s string) bool { return s == "" || s == "00000000000000" }
func externalURL(u *url.URL) bool {
	return u.Scheme != "" || u.Opaque != "" || u.Host != "" || u.User != nil
}

func localState(path string) (RefState, bool) {
	if len(path) > 0 && path[0] == '/' {
		if len(path) > 1 && path[1] == '/' {
			return RefStateBased, true
		}
		return RefStateHosted, true
	}
	if len(path) > 1 && path[0] == '.' {
		if len(path) > 2 && path[1] == '.' && path[2] == '/' {
			return RefStateHosted, true
		}
		return RefStateHosted, path[1] == '/'
	}
	return RefStateInvalid, false
}

// String returns the string representation of a reference.
func (r Reference) String() string {
	if r.State == RefStateQuery {
		return QueryPrefix + r.Value
	}
	if r.URL != nil {
		return r.URL.String()
	}
	return r.Value
}

// IsValid returns true if reference is valid
func (r *Reference) IsValid() bool { return r.State != RefStateInvalid }

// IsZettel returns true if it is a referencen to a local zettel.
func (r *Reference) IsZettel() bool {
	switch r.State {
	case RefStateZettel, RefStateSelf, RefStateFound, RefStateBroken:
		return true
	}
	return false
}

// IsLocal returns true if reference is local
func (r *Reference) IsLocal() bool {
	return r.State == RefStateHosted || r.State == RefStateBased
}

// IsExternal returns true if it is a referencen to external material.
func (r *Reference) IsExternal() bool { return r.State == RefStateExternal }

//-----------------------------------------------------------------------------
// Copyright (c) 2020-present Detlef Stern
//
// This file is part of Zettelstore.
//
// Zettelstore is licensed under the latest version of the EUPL (European Union
// Public License). Please see file LICENSE.txt for your rights and obligations
// under this license.
//
// SPDX-License-Identifier: EUPL-1.2
// SPDX-FileCopyrightText: 2020-present Detlef Stern
//-----------------------------------------------------------------------------

package ast_test

import (
	"testing"

	"zettelstore.de/z/ast"
)

func TestParseReference(t *testing.T) {
	t.Parallel()
	testcases := []struct {
		link string
		err  bool
		exp  string
	}{
		{"", true, ""},
		{"123", false, "123"},
		{",://", true, ""},
	}

	for i, tc := range testcases {
		got := ast.ParseReference(tc.link)
		if got.IsValid() == tc.err {
			t.Errorf(
				"TC=%d, expected parse error of %q: %v, but got %q", i, tc.link, tc.err, got)
		}
		if got.IsValid() && got.String() != tc.exp {
			t.Errorf("TC=%d, Reference of %q is %q, but got %q", i, tc.link, tc.exp, got)
		}
	}
}

func TestReferenceIsZettelMaterial(t *testing.T) {
	t.Parallel()
	testcases := []struct {
		link       string
		isZettel   bool
		isExternal bool
		isLocal    bool
	}{
		{"", false, false, false},
		{"00000000000000", false, false, false},
		{"http://zettelstore.de/z/ast", false, true, false},
		{"12345678901234", true, false, false},
		{"12345678901234#local", true, false, false},
		{"http://12345678901234", false, true, false},
		{"http://zettelstore.de/z/12345678901234", false, true, false},
		{"http://zettelstore.de/12345678901234", false, true, false},
		{"/12345678901234", false, false, true},
		{"//12345678901234", false, false, true},
		{"./12345678901234", false, false, true},
		{"../12345678901234", false, false, true},
		{".../12345678901234", false, true, false},
	}

	for i, tc := range testcases {
		ref := ast.ParseReference(tc.link)
		isZettel := ref.IsZettel()
		if isZettel != tc.isZettel {
			t.Errorf(
				"TC=%d, Reference %q isZettel=%v expected, but got %v",
				i,
				tc.link,
				tc.isZettel,
				isZettel)
		}
		isLocal := ref.IsLocal()
		if isLocal != tc.isLocal {
			t.Errorf(
				"TC=%d, Reference %q isLocal=%v expected, but got %v",
				i,
				tc.link,
				tc.isLocal, isLocal)
		}
		isExternal := ref.IsExternal()
		if isExternal != tc.isExternal {
			t.Errorf(
				"TC=%d, Reference %q isExternal=%v expected, but got %v",
				i,
				tc.link,
				tc.isExternal,
				isExternal)
		}
	}
}

//-----------------------------------------------------------------------------
// Copyright (c) 2025-present Detlef Stern
//
// This file is part of Zettelstore.
//
// Zettelstore is licensed under the latest version of the EUPL (European Union
// Public License). Please see file LICENSE.txt for your rights and obligations
// under this license.
//
// SPDX-License-Identifier: EUPL-1.2
// SPDX-FileCopyrightText: 2025-present Detlef Stern
//-----------------------------------------------------------------------------

// Package sztrans allows to transform a sz representation of text into an
// abstract syntax tree.
package sztrans

import (
	"fmt"
	"log"

	"t73f.de/r/sx"
	"t73f.de/r/zsc/sz"
	"zettelstore.de/z/ast"
)

type transformer struct{}

// GetBlockSlice returns the sz representations as a AST BlockSlice
func GetBlockSlice(pair *sx.Pair) (ast.BlockSlice, error) {
	if pair == nil {
		return nil, nil
	}
	var t transformer
	if obj := sz.Walk(&t, pair, nil); !obj.IsNil() {
		if sxn, isNode := obj.(sxNode); isNode {
			if bs, ok := sxn.node.(*ast.BlockSlice); ok {
				return *bs, nil
			}
			return nil, fmt.Errorf("no BlockSlice AST: %T/%v for %v", sxn.node, sxn.node, pair)
		}
		return nil, fmt.Errorf("no AST for %v: %v", pair, obj)
	}
	return nil, fmt.Errorf("error walking %v", pair)
}

func (t *transformer) VisitBefore(pair *sx.Pair, _ *sx.Pair) (sx.Object, bool) {
	if sym, isSymbol := sx.GetSymbol(pair.Car()); isSymbol {
		switch sym {
		case sz.SymText:
			if p := pair.Tail(); p != nil {
				if s, isString := sx.GetString(p.Car()); isString {
					return sxNode{&ast.TextNode{Text: s.GetValue()}}, true
				}
			}
		case sz.SymSoft:
			return sxNode{&ast.BreakNode{Hard: false}}, true
		case sz.SymHard:
			return sxNode{&ast.BreakNode{Hard: true}}, true
		case sz.SymLiteralCode:
			return handleLiteral(ast.LiteralCode, pair.Tail())
		case sz.SymLiteralComment:
			return handleLiteral(ast.LiteralComment, pair.Tail())
		case sz.SymLiteralInput:
			return handleLiteral(ast.LiteralInput, pair.Tail())
		case sz.SymLiteralMath:
			return handleLiteral(ast.LiteralMath, pair.Tail())
		case sz.SymLiteralOutput:
			return handleLiteral(ast.LiteralOutput, pair.Tail())
		case sz.SymThematic:
			return sxNode{&ast.HRuleNode{Attrs: sz.GetAttributes(pair.Tail().Head())}}, true
		case sz.SymVerbatimComment:
			return handleVerbatim(ast.VerbatimComment, pair.Tail())
		case sz.SymVerbatimEval:
			return handleVerbatim(ast.VerbatimEval, pair.Tail())
		case sz.SymVerbatimHTML:
			return handleVerbatim(ast.VerbatimHTML, pair.Tail())
		case sz.SymVerbatimMath:
			return handleVerbatim(ast.VerbatimMath, pair.Tail())
		case sz.SymVerbatimCode:
			return handleVerbatim(ast.VerbatimCode, pair.Tail())
		case sz.SymVerbatimZettel:
			return handleVerbatim(ast.VerbatimZettel, pair.Tail())
		}
	}
	return sx.Nil(), false
}

func handleLiteral(kind ast.LiteralKind, rest *sx.Pair) (sx.Object, bool) {
	if rest != nil {
		attrs := sz.GetAttributes(rest.Head())
		if curr := rest.Tail(); curr != nil {
			if s, isString := sx.GetString(curr.Car()); isString {
				return sxNode{&ast.LiteralNode{
					Kind:    kind,
					Attrs:   attrs,
					Content: []byte(s.GetValue())}}, true
			}
		}
	}
	return nil, false
}

func handleVerbatim(kind ast.VerbatimKind, rest *sx.Pair) (sx.Object, bool) {
	if rest != nil {
		attrs := sz.GetAttributes(rest.Head())
		if curr := rest.Tail(); curr != nil {
			if s, isString := sx.GetString(curr.Car()); isString {
				return sxNode{&ast.VerbatimNode{
					Kind:    kind,
					Attrs:   attrs,
					Content: []byte(s.GetValue()),
				}}, true
			}
		}
	}
	return nil, false
}

func (t *transformer) VisitAfter(pair *sx.Pair, _ *sx.Pair) sx.Object {
	if sym, isSymbol := sx.GetSymbol(pair.Car()); isSymbol {
		switch sym {
		case sz.SymBlock:
			bns := collectBlocks(pair.Tail())
			return sxNode{&bns}
		case sz.SymPara:
			return sxNode{&ast.ParaNode{Inlines: collectInlines(pair.Tail())}}
		case sz.SymHeading:
			return handleHeading(pair.Tail())
		case sz.SymListOrdered:
			return sxNode{&ast.NestedListNode{
				Kind:  ast.NestedListOrdered,
				Items: collectItemSlices(pair.Tail()),
				Attrs: nil}}
		case sz.SymListUnordered:
			return sxNode{&ast.NestedListNode{
				Kind:  ast.NestedListUnordered,
				Items: collectItemSlices(pair.Tail()),
				Attrs: nil}}
		case sz.SymListQuote:
			return sxNode{&ast.NestedListNode{
				Kind:  ast.NestedListQuote,
				Items: collectItemSlices(pair.Tail()),
				Attrs: nil}}
		case sz.SymDescription:
			return handleDescription(pair.Tail())
		case sz.SymTable:
			return handleTable(pair.Tail())
		case sz.SymCell:
			return handleCell(ast.AlignDefault, pair.Tail())
		case sz.SymCellCenter:
			return handleCell(ast.AlignCenter, pair.Tail())
		case sz.SymCellLeft:
			return handleCell(ast.AlignLeft, pair.Tail())
		case sz.SymCellRight:
			return handleCell(ast.AlignRight, pair.Tail())
		case sz.SymRegionBlock:
			return handleRegion(ast.RegionSpan, pair.Tail())
		case sz.SymRegionQuote:
			return handleRegion(ast.RegionQuote, pair.Tail())
		case sz.SymRegionVerse:
			return handleRegion(ast.RegionVerse, pair.Tail())
		case sz.SymTransclude:
			return handleTransclude(pair.Tail())

		case sz.SymLinkHosted:
			return handleLink(ast.RefStateHosted, pair.Tail())
		case sz.SymLinkInvalid:
			return handleLink(ast.RefStateInvalid, pair.Tail())
		case sz.SymLinkZettel:
			return handleLink(ast.RefStateZettel, pair.Tail())
		case sz.SymLinkSelf:
			return handleLink(ast.RefStateSelf, pair.Tail())
		case sz.SymLinkFound:
			return handleLink(ast.RefStateFound, pair.Tail())
		case sz.SymLinkBroken:
			return handleLink(ast.RefStateBroken, pair.Tail())
		case sz.SymLinkHosted:
			return handleLink(ast.RefStateHosted, pair.Tail())
		case sz.SymLinkBased:
			return handleLink(ast.RefStateBased, pair.Tail())
		case sz.SymLinkQuery:
			return handleLink(ast.RefStateQuery, pair.Tail())
		case sz.SymLinkExternal:
			return handleLink(ast.RefStateExternal, pair.Tail())
		case sz.SymEmbed:
			return handleEmbed(pair.Tail())
		case sz.SymCite:
			return handleCite(pair.Tail())
		case sz.SymMark:
			return handleMark(pair.Tail())
		case sz.SymEndnote:
			return handleEndnote(pair.Tail())
		case sz.SymFormatDelete:
			return handleFormat(ast.FormatDelete, pair.Tail())
		case sz.SymFormatEmph:
			return handleFormat(ast.FormatEmph, pair.Tail())
		case sz.SymFormatInsert:
			return handleFormat(ast.FormatInsert, pair.Tail())
		case sz.SymFormatMark:
			return handleFormat(ast.FormatMark, pair.Tail())
		case sz.SymFormatQuote:
			return handleFormat(ast.FormatQuote, pair.Tail())
		case sz.SymFormatSpan:
			return handleFormat(ast.FormatSpan, pair.Tail())
		case sz.SymFormatSub:
			return handleFormat(ast.FormatSub, pair.Tail())
		case sz.SymFormatSuper:
			return handleFormat(ast.FormatSuper, pair.Tail())
		case sz.SymFormatStrong:
			return handleFormat(ast.FormatStrong, pair.Tail())
		}
		log.Println("MISS", pair)
	}
	return pair
}

func collectBlocks(lst *sx.Pair) (result ast.BlockSlice) {
	for val := range lst.Values() {
		if sxn, isNode := val.(sxNode); isNode {
			if bn, isInline := sxn.node.(ast.BlockNode); isInline {
				result = append(result, bn)
			}
		}
	}
	return result
}

func collectInlines(lst *sx.Pair) (result ast.InlineSlice) {
	for val := range lst.Values() {
		if sxn, isNode := val.(sxNode); isNode {
			if in, isInline := sxn.node.(ast.InlineNode); isInline {
				result = append(result, in)
			}
		}
	}
	return result
}

func handleHeading(rest *sx.Pair) sx.Object {
	if rest != nil {
		if num, isNumber := rest.Car().(sx.Int64); isNumber && num > 0 && num < 6 {
			if curr := rest.Tail(); curr != nil {
				attrs := sz.GetAttributes(curr.Head())
				if curr = curr.Tail(); curr != nil {
					if sSlug, isSlug := sx.GetString(curr.Car()); isSlug {
						if curr = curr.Tail(); curr != nil {
							if sUniq, isUniq := sx.GetString(curr.Car()); isUniq {
								return sxNode{&ast.HeadingNode{
									Level:    int(num),
									Attrs:    attrs,
									Slug:     sSlug.GetValue(),
									Fragment: sUniq.GetValue(),
									Inlines:  collectInlines(curr.Tail()),
								}}
							}
						}
					}
				}
			}
		}
	}
	log.Println("HEAD", rest)
	return rest
}

func collectItemSlices(lst *sx.Pair) (result []ast.ItemSlice) {
	for val := range lst.Values() {
		if sxn, isNode := val.(sxNode); isNode {
			if bns, isBlockSlice := sxn.node.(*ast.BlockSlice); isBlockSlice {
				items := make(ast.ItemSlice, len(*bns))
				for i, bn := range *bns {
					if it, ok := bn.(ast.ItemNode); ok {
						items[i] = it
					}
				}
				result = append(result, items)
			}
			if ins, isInline := sxn.node.(*ast.InlineSlice); isInline {
				items := make(ast.ItemSlice, len(*ins))
				for i, bn := range *ins {
					if it, ok := bn.(ast.ItemNode); ok {
						items[i] = it
					}
				}
				result = append(result, items)
			}
		}
	}
	return result
}

func handleDescription(rest *sx.Pair) sx.Object {
	var descs []ast.Description
	for curr := rest; curr != nil; {
		term := collectInlines(curr.Head())
		curr = curr.Tail()
		if curr == nil {
			descr := ast.Description{Term: term, Descriptions: nil}
			descs = append(descs, descr)
			break
		}

		car := curr.Car()
		if sx.IsNil(car) {
			descs = append(descs, ast.Description{Term: term, Descriptions: nil})
			curr = curr.Tail()
			continue
		}

		sxn, isNode := car.(sxNode)
		if !isNode {
			descs = nil
			break
		}
		blocks, isBlocks := sxn.node.(*ast.BlockSlice)
		if !isBlocks {
			descs = nil
			break
		}

		descSlice := make([]ast.DescriptionSlice, 0, len(*blocks))
		for _, bn := range *blocks {
			bns, isBns := bn.(*ast.BlockSlice)
			if !isBns {
				continue
			}
			ds := make(ast.DescriptionSlice, 0, len(*bns))
			for _, b := range *bns {
				if defNode, isDef := b.(ast.DescriptionNode); isDef {
					ds = append(ds, defNode)
				}
			}
			descSlice = append(descSlice, ds)
		}

		descr := ast.Description{Term: term, Descriptions: descSlice}
		descs = append(descs, descr)

		curr = curr.Tail()
	}
	if len(descs) > 0 {
		return sxNode{&ast.DescriptionListNode{Descriptions: descs}}
	}
	log.Println("DESC", rest)
	return rest
}

func handleTable(rest *sx.Pair) sx.Object {
	if rest != nil {
		header := collectRow(rest.Head())
		cols := len(header)

		var rows []ast.TableRow
		for curr := range rest.Tail().Pairs() {
			row := collectRow(curr.Head())
			rows = append(rows, row)
			cols = max(cols, len(row))
		}
		align := make([]ast.Alignment, cols)
		for i := range cols {
			align[i] = ast.AlignDefault
		}

		return sxNode{&ast.TableNode{
			Header: header,
			Align:  align,
			Rows:   rows,
		}}
	}
	log.Println("TABL", rest)
	return rest
}

func collectRow(lst *sx.Pair) (row ast.TableRow) {
	for curr := range lst.Values() {
		if sxn, isNode := curr.(sxNode); isNode {
			if cell, isCell := sxn.node.(*ast.TableCell); isCell {
				row = append(row, cell)
			}
		}
	}
	return row
}

func handleCell(align ast.Alignment, rest *sx.Pair) sx.Object {
	return sxNode{&ast.TableCell{
		Align:   align,
		Inlines: collectInlines(rest),
	}}
}

func handleRegion(kind ast.RegionKind, rest *sx.Pair) sx.Object {
	if rest != nil {
		attrs := sz.GetAttributes(rest.Head())
		if curr := rest.Tail(); curr != nil {
			if blockList := curr.Head(); blockList != nil {
				return sxNode{&ast.RegionNode{
					Kind:    kind,
					Attrs:   attrs,
					Blocks:  collectBlocks(blockList),
					Inlines: collectInlines(curr.Tail()),
				}}
			}
		}
	}
	log.Println("REGI", rest)
	return rest
}

func handleTransclude(rest *sx.Pair) sx.Object {
	if rest != nil {
		attrs := sz.GetAttributes(rest.Head())
		if curr := rest.Tail(); curr != nil {
			ref := collectReference(curr.Head())
			return sxNode{&ast.TranscludeNode{
				Attrs:   attrs,
				Ref:     ref,
				Inlines: collectInlines(curr.Tail()),
			}}
		}
	}
	log.Println("TRAN", rest)
	return rest
}

func handleLink(state ast.RefState, rest *sx.Pair) sx.Object {
	if rest != nil {
		attrs := sz.GetAttributes(rest.Head())
		if curr := rest.Tail(); curr != nil {
			if sref, isString := sx.GetString(curr.Car()); isString {
				ref := ast.ParseReference(sref.GetValue())
				ref.State = state
				ins := collectInlines(curr.Tail())
				return sxNode{&ast.LinkNode{
					Attrs:   attrs,
					Ref:     ref,
					Inlines: ins,
				}}
			}
		}
	}
	log.Println("LINK", state, rest)
	return rest
}

func handleEmbed(rest *sx.Pair) sx.Object {
	if rest != nil {
		attrs := sz.GetAttributes(rest.Head())
		if curr := rest.Tail(); curr != nil {
			if ref := collectReference(curr.Head()); ref != nil {
				if curr = curr.Tail(); curr != nil {
					if syntax, isString := sx.GetString(curr.Car()); isString {
						return sxNode{&ast.EmbedRefNode{
							Attrs:   attrs,
							Ref:     ref,
							Syntax:  syntax.GetValue(),
							Inlines: collectInlines(curr.Tail()),
						}}
					}
				}
			}
		}
	}
	log.Println("EMBE", rest)
	return rest
}

func collectReference(pair *sx.Pair) *ast.Reference {
	if pair != nil {
		if sym, isSymbol := sx.GetSymbol(pair.Car()); isSymbol {
			if next := pair.Tail(); next != nil {
				if sRef, isString := sx.GetString(next.Car()); isString {
					ref := ast.ParseReference(sRef.GetValue())
					switch sym {
					case sz.SymRefStateInvalid:
						ref.State = ast.RefStateInvalid
					case sz.SymRefStateZettel:
						ref.State = ast.RefStateZettel
					case sz.SymRefStateSelf:
						ref.State = ast.RefStateSelf
					case sz.SymRefStateFound:
						ref.State = ast.RefStateFound
					case sz.SymRefStateBroken:
						ref.State = ast.RefStateBroken
					case sz.SymRefStateHosted:
						ref.State = ast.RefStateHosted
					case sz.SymRefStateBased:
						ref.State = ast.RefStateBased
					case sz.SymRefStateQuery:
						ref.State = ast.RefStateQuery
					case sz.SymRefStateExternal:
						ref.State = ast.RefStateExternal
					}
					return ref
				}
			}
		}
	}
	return nil
}

func handleCite(rest *sx.Pair) sx.Object {
	if rest != nil {
		attrs := sz.GetAttributes(rest.Head())
		if curr := rest.Tail(); curr != nil {
			if sKey, isString := sx.GetString(curr.Car()); isString {
				return sxNode{&ast.CiteNode{
					Attrs:   attrs,
					Key:     sKey.GetValue(),
					Inlines: collectInlines(curr.Tail()),
				}}
			}
		}
	}
	log.Println("CITE", rest)
	return rest
}

func handleMark(rest *sx.Pair) sx.Object {
	if rest != nil {
		if sMark, isMarkS := sx.GetString(rest.Car()); isMarkS {
			if curr := rest.Tail(); curr != nil {
				if sSlug, isSlug := sx.GetString(curr.Car()); isSlug {
					if curr = curr.Tail(); curr != nil {
						if sUniq, isUniq := sx.GetString(curr.Car()); isUniq {
							return sxNode{&ast.MarkNode{
								Mark:     sMark.GetValue(),
								Slug:     sSlug.GetValue(),
								Fragment: sUniq.GetValue(),
								Inlines:  collectInlines(curr.Tail()),
							}}
						}
					}
				}
			}
		}
	}
	log.Println("MARK", rest)
	return rest
}

func handleEndnote(rest *sx.Pair) sx.Object {
	if rest != nil {
		attrs := sz.GetAttributes(rest.Head())
		return sxNode{&ast.FootnoteNode{
			Attrs:   attrs,
			Inlines: collectInlines(rest.Tail()),
		}}
	}
	log.Println("ENDN", rest)
	return rest
}

func handleFormat(kind ast.FormatKind, rest *sx.Pair) sx.Object {
	if rest != nil {
		attrs := sz.GetAttributes(rest.Head())
		return sxNode{&ast.FormatNode{
			Kind:    kind,
			Attrs:   attrs,
			Inlines: collectInlines(rest.Tail()),
		}}
	}
	log.Println("FORM", kind, rest)
	return rest
}

type sxNode struct {
	node ast.Node
}

func (sxNode) IsNil() bool        { return false }
func (sxNode) IsAtom() bool       { return true }
func (n sxNode) String() string   { return fmt.Sprintf("%T/%v", n.node, n.node) }
func (n sxNode) GoString() string { return n.String() }
func (n sxNode) IsEqual(other sx.Object) bool {
	return n.String() == other.String()
}

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

package ast

// Visitor is a visitor for walking the AST.
type Visitor interface {
	Visit(node Node) Visitor
}

// Walk traverses the AST.
func Walk(v Visitor, node Node) {
	if v = v.Visit(node); v == nil {
		return
	}

	// Implementation note:
	// It is much faster to use interface dispatching than to use a switch statement.
	// On my "cpu: Intel(R) Core(TM) i7-6820HQ CPU @ 2.70GHz", a switch statement
	// implementation tooks approx 940-980 ns/op. Interface dispatching is in the
	// range of 900-930 ns/op.
	node.WalkChildren(v)
	v.Visit(nil)
}

// WalkItemSlice traverses an item slice.
func WalkItemSlice(v Visitor, ins ItemSlice) {
	for _, in := range ins {
		Walk(v, in)
	}
}

// WalkDescriptionSlice traverses an item slice.
func WalkDescriptionSlice(v Visitor, dns DescriptionSlice) {
	for _, dn := range dns {
		Walk(v, dn)
	}
}

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

package ast_test

import (
	"testing"

	"t73f.de/r/zsc/attrs"
	"zettelstore.de/z/ast"
)

func BenchmarkWalk(b *testing.B) {
	root := ast.BlockSlice{
		&ast.HeadingNode{
			Inlines: ast.InlineSlice{&ast.TextNode{Text: "A Simple Heading"}},
		},
		&ast.ParaNode{
			Inlines: ast.InlineSlice{&ast.TextNode{Text: "This is the introduction."}},
		},
		&ast.NestedListNode{
			Kind: ast.NestedListUnordered,
			Items: []ast.ItemSlice{
				[]ast.ItemNode{
					&ast.ParaNode{
						Inlines: ast.InlineSlice{&ast.TextNode{Text: "Item 1"}},
					},
				},
				[]ast.ItemNode{
					&ast.ParaNode{
						Inlines: ast.InlineSlice{&ast.TextNode{Text: "Item 2"}},
					},
				},
			},
		},
		&ast.ParaNode{
			Inlines: ast.InlineSlice{&ast.TextNode{Text: "This is some intermediate text."}},
		},
		ast.CreateParaNode(
			&ast.FormatNode{
				Kind: ast.FormatEmph,
				Attrs: attrs.Attributes(map[string]string{
					"":      "class",
					"color": "green",
				}),
				Inlines: ast.InlineSlice{&ast.TextNode{Text: "This is some emphasized text."}},
			},
			&ast.TextNode{Text: " "},
			&ast.LinkNode{
				Ref:     &ast.Reference{Value: "http://zettelstore.de"},
				Inlines: ast.InlineSlice{&ast.TextNode{Text: "URL text."}},
			},
		),
	}
	v := benchVisitor{}

	for b.Loop() {
		ast.Walk(&v, &root)
	}
}

type benchVisitor struct{}

func (bv *benchVisitor) Visit(ast.Node) ast.Visitor { return bv }

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

// Package auth provides services for authentification / authorization.
package auth

import (
	"time"

	"t73f.de/r/zsc/domain/id"
	"t73f.de/r/zsc/domain/meta"
	"zettelstore.de/z/box"
	"zettelstore.de/z/config"
)

// BaseManager allows to check some base auth modes.
type BaseManager interface {
	// IsReadonly returns true, if the systems is configured to run in read-only-mode.
	IsReadonly() bool
}

// TokenManager provides methods to create authentication
type TokenManager interface {

	// GetToken produces a authentication token.
	GetToken(ident *meta.Meta, d time.Duration, kind TokenKind) ([]byte, error)

	// CheckToken checks the validity of the token and returns relevant data.
	CheckToken(token []byte, k TokenKind) (TokenData, error)
}

// TokenKind specifies for which application / usage a token is/was requested.
type TokenKind int

// Allowed values of token kind
const (
	_ TokenKind = iota
	KindAPI
	KindwebUI
)

// TokenData contains some important elements from a token.
type TokenData struct {
	Token   []byte
	Now     time.Time
	Issued  time.Time
	Expires time.Time
	Ident   string
	Zid     id.Zid
}

// AuthzManager provides methods for authorization.
type AuthzManager interface {
	BaseManager

	// Owner returns the zettel identifier of the owner.
	Owner() id.Zid

	// IsOwner returns true, if the given zettel identifier is that of the owner.
	IsOwner(zid id.Zid) bool

	// Returns true if authentication is enabled.
	WithAuth() bool

	// GetUserRole role returns the user role of the given user zettel.
	GetUserRole(user *meta.Meta) meta.UserRole
}

// Manager is the main interface for providing the service.
type Manager interface {
	TokenManager
	AuthzManager

	BoxWithPolicy(unprotectedBox box.Box, rtConfig config.Config) (box.Box, Policy)
}

// Policy is an interface for checking access authorization.
type Policy interface {
	// User is allowed to create a new zettel.
	CanCreate(user, newMeta *meta.Meta) bool

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

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

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

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

//-----------------------------------------------------------------------------
// Copyright (c) 2020-present Detlef Stern
//
// This file is part of Zettelstore.
//
// Zettelstore is licensed under the latest version of the EUPL (European Union
// Public License). Please see file LICENSE.txt for your rights and obligations
// under this license.
//
// SPDX-License-Identifier: EUPL-1.2
// SPDX-FileCopyrightText: 2020-present Detlef Stern
//-----------------------------------------------------------------------------

// Package cred provides some function for handling credentials.
package cred

import (
	"bytes"

	"golang.org/x/crypto/bcrypt"

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

// HashCredential returns a hashed vesion of the given credential
func HashCredential(zid id.Zid, ident, credential string) (string, error) {
	fullCredential := createFullCredential(zid, ident, credential)
	res, err := bcrypt.GenerateFromPassword(fullCredential, bcrypt.DefaultCost)
	if err != nil {
		return "", err
	}
	return string(res), nil
}

// CompareHashAndCredential checks, whether the hashed credential is a possible
// value when hashing the credential.
func CompareHashAndCredential(hashed string, zid id.Zid, ident, credential string) (bool, error) {
	fullCredential := createFullCredential(zid, ident, credential)
	err := bcrypt.CompareHashAndPassword([]byte(hashed), fullCredential)
	if err == nil {
		return true, nil
	}
	if err == bcrypt.ErrMismatchedHashAndPassword {
		return false, nil
	}
	return false, err
}

func createFullCredential(zid id.Zid, ident, credential string) []byte {
	var buf bytes.Buffer
	buf.Write(zid.Bytes())
	buf.WriteByte(' ')
	buf.WriteString(ident)
	buf.WriteByte(' ')
	buf.WriteString(credential)
	return buf.Bytes()
}

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

package impl

import (
	"bytes"
	"crypto"
	"crypto/hmac"
	"encoding/base64"

	"t73f.de/r/sx"
	"t73f.de/r/sx/sxreader"
)

var encoding = base64.RawURLEncoding

const digestAlg = crypto.SHA384

func sign(claim sx.Object, secret []byte) ([]byte, error) {
	var buf bytes.Buffer
	_, err := sx.Print(&buf, claim)
	if err != nil {
		return nil, err
	}
	token := make([]byte, encoding.EncodedLen(buf.Len()))
	encoding.Encode(token, buf.Bytes())

	digest := hmac.New(digestAlg.New, secret)
	_, err = digest.Write(buf.Bytes())
	if err != nil {
		return nil, err
	}
	dig := digest.Sum(nil)
	encDig := make([]byte, encoding.EncodedLen(len(dig)))
	encoding.Encode(encDig, dig)

	token = append(token, '.')
	token = append(token, encDig...)
	return token, nil
}

func check(token []byte, secret []byte) (sx.Object, error) {
	i := bytes.IndexByte(token, '.')
	if i <= 0 || 1024 < i {
		return nil, ErrMalformedToken
	}
	buf := make([]byte, len(token))
	n, err := encoding.Decode(buf, token[:i])
	if err != nil {
		return nil, err
	}
	rdr := sxreader.MakeReader(bytes.NewReader(buf[:n]))
	obj, err := rdr.Read()
	if err != nil {
		return nil, err
	}

	var objBuf bytes.Buffer
	_, err = sx.Print(&objBuf, obj)
	if err != nil {
		return nil, err
	}

	digest := hmac.New(digestAlg.New, secret)
	_, err = digest.Write(objBuf.Bytes())
	if err != nil {
		return nil, err
	}

	n, err = encoding.Decode(buf, token[i+1:])
	if err != nil {
		return nil, err
	}
	if !hmac.Equal(buf[:n], digest.Sum(nil)) {
		return nil, ErrMalformedToken
	}
	return obj, nil
}

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

// Package impl provides services for authentification / authorization.
package impl

import (
	"errors"
	"hash/fnv"
	"io"
	"time"

	"t73f.de/r/sx"
	"t73f.de/r/zsc/domain/id"
	"t73f.de/r/zsc/domain/meta"
	"t73f.de/r/zsc/sexp"
	"zettelstore.de/z/auth"
	"zettelstore.de/z/auth/policy"
	"zettelstore.de/z/box"
	"zettelstore.de/z/config"
	"zettelstore.de/z/kernel"
)

type myAuth struct {
	readonly bool
	owner    id.Zid
	secret   []byte
}

// New creates a new auth object.
func New(readonly bool, owner id.Zid, extSecret string) auth.Manager {
	return &myAuth{
		readonly: readonly,
		owner:    owner,
		secret:   calcSecret(extSecret),
	}
}

var configKeys = []string{
	kernel.CoreProgname,
	kernel.CoreGoVersion,
	kernel.CoreHostname,
	kernel.CoreGoOS,
	kernel.CoreGoArch,
	kernel.CoreVersion,
}

func calcSecret(extSecret string) []byte {
	h := fnv.New128()
	if extSecret != "" {
		io.WriteString(h, extSecret)
	}
	for _, key := range configKeys {
		io.WriteString(h, kernel.Main.GetConfig(kernel.CoreService, key).(string))
	}
	return h.Sum(nil)
}

// IsReadonly returns true, if the systems is configured to run in read-only-mode.
func (a *myAuth) IsReadonly() bool { return a.readonly }

// ErrMalformedToken signals a broken token.
var ErrMalformedToken = errors.New("auth: malformed token")

// ErrNoIdent signals that the 'ident' key is missing.
var ErrNoIdent = errors.New("auth: missing ident")

// ErrOtherKind signals that the token was defined for another token kind.
var ErrOtherKind = errors.New("auth: wrong token kind")

// ErrNoZid signals that the 'zid' key is missing.
var ErrNoZid = errors.New("auth: missing zettel id")

// GetToken returns a token to be used for authentification.
func (a *myAuth) GetToken(ident *meta.Meta, d time.Duration, kind auth.TokenKind) ([]byte, error) {
	subject, ok := ident.Get(meta.KeyUserID)
	if !ok || subject == "" {
		return nil, ErrNoIdent
	}

	now := time.Now().Round(time.Second)
	sClaim := sx.MakeList(
		sx.Int64(kind),
		sx.MakeString(string(subject)),
		sx.Int64(now.Unix()),
		sx.Int64(now.Add(d).Unix()),
		sx.Int64(ident.Zid),
	)
	return sign(sClaim, a.secret)
}

// ErrTokenExpired signals an exired token
var ErrTokenExpired = errors.New("auth: token expired")

// CheckToken checks the validity of the token and returns relevant data.
func (a *myAuth) CheckToken(tok []byte, k auth.TokenKind) (auth.TokenData, error) {
	var tokenData auth.TokenData

	obj, err := check(tok, a.secret)
	if err != nil {
		return tokenData, err
	}

	tokenData.Token = tok
	err = setupTokenData(obj, k, &tokenData)
	return tokenData, err
}

func setupTokenData(obj sx.Object, k auth.TokenKind, tokenData *auth.TokenData) error {
	vals, err := sexp.ParseList(obj, "isiii")
	if err != nil {
		return ErrMalformedToken
	}
	if auth.TokenKind(vals[0].(sx.Int64)) != k {
		return ErrOtherKind
	}
	ident := vals[1].(sx.String).GetValue()
	if ident == "" {
		return ErrNoIdent
	}
	issued := time.Unix(int64(vals[2].(sx.Int64)), 0)
	expires := time.Unix(int64(vals[3].(sx.Int64)), 0)
	now := time.Now().Round(time.Second)
	if expires.Before(now) {
		return ErrTokenExpired
	}
	zid := id.Zid(vals[4].(sx.Int64))
	if !zid.IsValid() {
		return ErrNoZid
	}

	tokenData.Ident = string(ident)
	tokenData.Issued = issued
	tokenData.Now = now
	tokenData.Expires = expires
	tokenData.Zid = zid
	return nil
}

func (a *myAuth) Owner() id.Zid { return a.owner }

func (a *myAuth) IsOwner(zid id.Zid) bool {
	return zid.IsValid() && zid == a.owner
}

func (a *myAuth) WithAuth() bool { return a.owner != id.Invalid }

// GetUserRole role returns the user role of the given user zettel.
func (a *myAuth) GetUserRole(user *meta.Meta) meta.UserRole {
	if user == nil {
		if a.WithAuth() {
			return meta.UserRoleUnknown
		}
		return meta.UserRoleOwner
	}
	if a.IsOwner(user.Zid) {
		return meta.UserRoleOwner
	}
	if val, ok := user.Get(meta.KeyUserRole); ok {
		if ur := val.AsUserRole(); ur != meta.UserRoleUnknown {
			return ur
		}
	}
	return meta.UserRoleReader
}

func (a *myAuth) BoxWithPolicy(unprotectedBox box.Box, rtConfig config.Config) (box.Box, auth.Policy) {
	return policy.BoxWithPolicy(a, unprotectedBox, rtConfig)
}