Source: parser.go in package github.com/yuin/goldmark/parser

Package parser contains stuff that are related to parsing a Markdown text.

package parser

import (
	"fmt"
	"strings"
	"sync"

	"github.com/yuin/goldmark/ast"
	"github.com/yuin/goldmark/text"
	"github.com/yuin/goldmark/util"
)

A Reference interface represents a link reference in Markdown text.

String implements Stringer.

	String() string

Label returns a label of the reference.

	Label() []byte

Destination returns a destination(URL) of the reference.

	Destination() []byte

Title returns a title of the reference.

	Title() []byte
}

type reference struct {
	label       []byte
	destination []byte
	title       []byte
}

NewReference returns a new Reference.

func NewReference(label, destination, title []byte) Reference {
	return &reference{label, destination, title}
}

func (r *reference) Label() []byte {
	return r.label
}

func (r *reference) Destination() []byte {
	return r.destination
}

func (r *reference) Title() []byte {
	return r.title
}

func (r *reference) String() string {
	return fmt.Sprintf("Reference{Label:%s, Destination:%s, Title:%s}", r.label, r.destination, r.title)
}

An IDs interface is a collection of the element ids.

Generate generates a new element id.

	Generate(value []byte, kind ast.NodeKind) []byte

Put puts a given element id to the used ids table.

	Put(value []byte)
}

type ids struct {
	values map[string]bool
}

func newIDs() IDs {
	return &ids{
		values: map[string]bool{},
	}
}

func (s *ids) Generate(value []byte, kind ast.NodeKind) []byte {
	value = util.TrimLeftSpace(value)
	value = util.TrimRightSpace(value)
	result := []byte{}
	for i := 0; i < len(value); {
		v := value[i]
		l := util.UTF8Len(v)
		i += int(l)
		if l != 1 {
			continue
		}
		if util.IsAlphaNumeric(v) {
			if 'A' <= v && v <= 'Z' {
				v += 'a' - 'A'
			}
			result = append(result, v)
		} else if util.IsSpace(v) || v == '-' || v == '_' {
			result = append(result, '-')
		}
	}
	if len(result) == 0 {
		if kind == ast.KindHeading {
			result = []byte("heading")
		} else {
			result = []byte("id")
		}
	}
	if _, ok := s.values[util.BytesToReadOnlyString(result)]; !ok {
		s.values[util.BytesToReadOnlyString(result)] = true
		return result
	}
	for i := 1; ; i++ {
		newResult := fmt.Sprintf("%s-%d", result, i)
		if _, ok := s.values[newResult]; !ok {
			s.values[newResult] = true
			return []byte(newResult)
		}

	}
}

func (s *ids) Put(value []byte) {
	s.values[util.BytesToReadOnlyString(value)] = true
}

ContextKey is a key that is used to set arbitrary values to the context.

type ContextKey int

ContextKeyMax is a maximum value of the ContextKey.

var ContextKeyMax ContextKey

NewContextKey return a new ContextKey value.

func NewContextKey() ContextKey {
	ContextKeyMax++
	return ContextKeyMax
}

A Context interface holds a information that are necessary to parse Markdown text.

String implements Stringer.

	String() string

Get returns a value associated with the given key.

	Get(ContextKey) interface{}

ComputeIfAbsent computes a value if a value associated with the given key is absent and returns the value.

	ComputeIfAbsent(ContextKey, func() interface{}) interface{}

Set sets the given value to the context.

	Set(ContextKey, interface{})

AddReference adds the given reference to this context.

	AddReference(Reference)

Reference returns (a reference, true) if a reference associated with the given label exists, otherwise (nil, false).

	Reference(label string) (Reference, bool)

References returns a list of references.

	References() []Reference

IDs returns a collection of the element ids.

	IDs() IDs

BlockOffset returns a first non-space character position on current line. This value is valid only for BlockParser.Open. BlockOffset returns -1 if current line is blank.

	BlockOffset() int

BlockOffset sets a first non-space character position on current line. This value is valid only for BlockParser.Open.

	SetBlockOffset(int)

BlockIndent returns an indent width on current line. This value is valid only for BlockParser.Open. BlockIndent returns -1 if current line is blank.

	BlockIndent() int

BlockIndent sets an indent width on current line. This value is valid only for BlockParser.Open.

	SetBlockIndent(int)

FirstDelimiter returns a first delimiter of the current delimiter list.

	FirstDelimiter() *Delimiter

LastDelimiter returns a last delimiter of the current delimiter list.

	LastDelimiter() *Delimiter

PushDelimiter appends the given delimiter to the tail of the current delimiter list.

	PushDelimiter(delimiter *Delimiter)

RemoveDelimiter removes the given delimiter from the current delimiter list.

	RemoveDelimiter(d *Delimiter)

ClearDelimiters clears the current delimiter list.

	ClearDelimiters(bottom ast.Node)

OpenedBlocks returns a list of nodes that are currently in parsing.

	OpenedBlocks() []Block

SetOpenedBlocks sets a list of nodes that are currently in parsing.

	SetOpenedBlocks([]Block)

LastOpenedBlock returns a last node that is currently in parsing.

	LastOpenedBlock() Block

IsInLinkLabel returns true if current position seems to be in link label.

	IsInLinkLabel() bool
}

A ContextConfig struct is a data structure that holds configuration of the Context.

type ContextConfig struct {
	IDs IDs
}

An ContextOption is a functional option type for the Context.

type ContextOption func(*ContextConfig)

WithIDs is a functional option for the Context.

func WithIDs(ids IDs) ContextOption {
	return func(c *ContextConfig) {
		c.IDs = ids
	}
}

type parseContext struct {
	store         []interface{}
	ids           IDs
	refs          map[string]Reference
	blockOffset   int
	blockIndent   int
	delimiters    *Delimiter
	lastDelimiter *Delimiter
	openedBlocks  []Block
}

NewContext returns a new Context.

func NewContext(options ...ContextOption) Context {
	cfg := &ContextConfig{
		IDs: newIDs(),
	}
	for _, option := range options {
		option(cfg)
	}

	return &parseContext{
		store:         make([]interface{}, ContextKeyMax+1),
		refs:          map[string]Reference{},
		ids:           cfg.IDs,
		blockOffset:   -1,
		blockIndent:   -1,
		delimiters:    nil,
		lastDelimiter: nil,
		openedBlocks:  []Block{},
	}
}

func (p *parseContext) Get(key ContextKey) interface{} {
	return p.store[key]
}

func (p *parseContext) ComputeIfAbsent(key ContextKey, f func() interface{}) interface{} {
	v := p.store[key]
	if v == nil {
		v = f()
		p.store[key] = v
	}
	return v
}

func (p *parseContext) Set(key ContextKey, value interface{}) {
	p.store[key] = value
}

func (p *parseContext) IDs() IDs {
	return p.ids
}

func (p *parseContext) BlockOffset() int {
	return p.blockOffset
}

func (p *parseContext) SetBlockOffset(v int) {
	p.blockOffset = v
}

func (p *parseContext) BlockIndent() int {
	return p.blockIndent
}

func (p *parseContext) SetBlockIndent(v int) {
	p.blockIndent = v
}

func (p *parseContext) LastDelimiter() *Delimiter {
	return p.lastDelimiter
}

func (p *parseContext) FirstDelimiter() *Delimiter {
	return p.delimiters
}

func (p *parseContext) PushDelimiter(d *Delimiter) {
	if p.delimiters == nil {
		p.delimiters = d
		p.lastDelimiter = d
	} else {
		l := p.lastDelimiter
		p.lastDelimiter = d
		l.NextDelimiter = d
		d.PreviousDelimiter = l
	}
}

func (p *parseContext) RemoveDelimiter(d *Delimiter) {
	if d.PreviousDelimiter == nil {
		p.delimiters = d.NextDelimiter
	} else {
		d.PreviousDelimiter.NextDelimiter = d.NextDelimiter
		if d.NextDelimiter != nil {
			d.NextDelimiter.PreviousDelimiter = d.PreviousDelimiter
		}
	}
	if d.NextDelimiter == nil {
		p.lastDelimiter = d.PreviousDelimiter
	}
	if p.delimiters != nil {
		p.delimiters.PreviousDelimiter = nil
	}
	if p.lastDelimiter != nil {
		p.lastDelimiter.NextDelimiter = nil
	}
	d.NextDelimiter = nil
	d.PreviousDelimiter = nil
	if d.Length != 0 {
		ast.MergeOrReplaceTextSegment(d.Parent(), d, d.Segment)
	} else {
		d.Parent().RemoveChild(d.Parent(), d)
	}
}

func (p *parseContext) ClearDelimiters(bottom ast.Node) {
	if p.lastDelimiter == nil {
		return
	}
	var c ast.Node
	for c = p.lastDelimiter; c != nil && c != bottom; {
		prev := c.PreviousSibling()
		if d, ok := c.(*Delimiter); ok {
			p.RemoveDelimiter(d)
		}
		c = prev
	}
}

func (p *parseContext) AddReference(ref Reference) {
	key := util.ToLinkReference(ref.Label())
	if _, ok := p.refs[key]; !ok {
		p.refs[key] = ref
	}
}

func (p *parseContext) Reference(label string) (Reference, bool) {
	v, ok := p.refs[label]
	return v, ok
}

func (p *parseContext) References() []Reference {
	ret := make([]Reference, 0, len(p.refs))
	for _, v := range p.refs {
		ret = append(ret, v)
	}
	return ret
}

func (p *parseContext) String() string {
	refs := []string{}
	for _, r := range p.refs {
		refs = append(refs, r.String())
	}

	return fmt.Sprintf("Context{Store:%#v, Refs:%s}", p.store, strings.Join(refs, ","))
}

func (p *parseContext) OpenedBlocks() []Block {
	return p.openedBlocks
}

func (p *parseContext) SetOpenedBlocks(v []Block) {
	p.openedBlocks = v
}

func (p *parseContext) LastOpenedBlock() Block {
	if l := len(p.openedBlocks); l != 0 {
		return p.openedBlocks[l-1]
	}
	return Block{}
}

func (p *parseContext) IsInLinkLabel() bool {
	tlist := p.Get(linkLabelStateKey)
	return tlist != nil
}

State represents parser's state. State is designed to use as a bit flag.

type State int

const (
	none State = 1 << iota

Continue indicates parser can continue parsing.

	Continue

Close indicates parser cannot parse anymore.

	Close

HasChildren indicates parser may have child blocks.

	HasChildren

NoChildren indicates parser does not have child blocks.

	NoChildren

RequireParagraph indicates parser requires that the last node must be a paragraph and is not converted to other nodes by ParagraphTransformers.

	RequireParagraph
)

A Config struct is a data structure that holds configuration of the Parser.

type Config struct {
	Options               map[OptionName]interface{}
	BlockParsers          util.PrioritizedSlice /*<BlockParser>*/
	InlineParsers         util.PrioritizedSlice /*<InlineParser>*/
	ParagraphTransformers util.PrioritizedSlice /*<ParagraphTransformer>*/
	ASTTransformers       util.PrioritizedSlice /*<ASTTransformer>*/
}

NewConfig returns a new Config.

func NewConfig() *Config {
	return &Config{
		Options:               map[OptionName]interface{}{},
		BlockParsers:          util.PrioritizedSlice{},
		InlineParsers:         util.PrioritizedSlice{},
		ParagraphTransformers: util.PrioritizedSlice{},
		ASTTransformers:       util.PrioritizedSlice{},
	}
}

An Option interface is a functional option type for the Parser.

type Option interface {
	SetParserOption(*Config)
}

OptionName is a name of parser options.

type OptionName string

Attribute is an option name that spacify attributes of elements.

const optAttribute OptionName = "Attribute"

type withAttribute struct {
}

func (o *withAttribute) SetParserOption(c *Config) {
	c.Options[optAttribute] = true
}

WithAttribute is a functional option that enables custom attributes.

func WithAttribute() Option {
	return &withAttribute{}
}

A Parser interface parses Markdown text into AST nodes.

Parse parses the given Markdown text into AST nodes.

	Parse(reader text.Reader, opts ...ParseOption) ast.Node

AddOption adds the given option to this parser.

	AddOptions(...Option)
}

A SetOptioner interface sets the given option to the object.

SetOption sets the given option to the object. Unacceptable options may be passed. Thus implementations must ignore unacceptable options.

	SetOption(name OptionName, value interface{})
}

A BlockParser interface parses a block level element like Paragraph, List, Blockquote etc.

Trigger returns a list of characters that triggers Parse method of this parser. If Trigger returns a nil, Open will be called with any lines.

	Trigger() []byte

Open parses the current line and returns a result of parsing. Open must not parse beyond the current line. If Open has been able to parse the current line, Open must advance a reader position by consumed byte length. If Open has not been able to parse the current line, Open should returns (nil, NoChildren). If Open has been able to parse the current line, Open should returns a new Block node and returns HasChildren or NoChildren.

	Open(parent ast.Node, reader text.Reader, pc Context) (ast.Node, State)

Continue parses the current line and returns a result of parsing. Continue must not parse beyond the current line. If Continue has been able to parse the current line, Continue must advance a reader position by consumed byte length. If Continue has not been able to parse the current line, Continue should returns Close. If Continue has been able to parse the current line, Continue should returns (Continue | NoChildren) or (Continue | HasChildren)

	Continue(node ast.Node, reader text.Reader, pc Context) State

Close will be called when the parser returns Close.

	Close(node ast.Node, reader text.Reader, pc Context)

CanInterruptParagraph returns true if the parser can interrupt paragraphs, otherwise false.

	CanInterruptParagraph() bool

CanAcceptIndentedLine returns true if the parser can open new node when the given line is being indented more than 3 spaces.

	CanAcceptIndentedLine() bool
}

An InlineParser interface parses an inline level element like CodeSpan, Link etc.

Trigger returns a list of characters that triggers Parse method of this parser. Trigger characters must be a punctuation or a halfspace. Halfspaces triggers this parser when character is any spaces characters or a head of line

	Trigger() []byte

Parse parse the given block into an inline node. Parse can parse beyond the current line. If Parse has been able to parse the current line, it must advance a reader position by consumed byte length.

	Parse(parent ast.Node, block text.Reader, pc Context) ast.Node
}

A CloseBlocker interface is a callback function that will be called when block is closed in the inline parsing.

CloseBlock will be called when a block is closed.

	CloseBlock(parent ast.Node, block text.Reader, pc Context)
}

A ParagraphTransformer transforms parsed Paragraph nodes. For example, link references are searched in parsed Paragraphs.

Transform transforms the given paragraph.

	Transform(node *ast.Paragraph, reader text.Reader, pc Context)
}

ASTTransformer transforms entire Markdown document AST tree.

Transform transforms the given AST tree.

	Transform(node *ast.Document, reader text.Reader, pc Context)
}

DefaultBlockParsers returns a new list of default BlockParsers. Priorities of default BlockParsers are: SetextHeadingParser, 100 ThematicBreakParser, 200 ListParser, 300 ListItemParser, 400 CodeBlockParser, 500 ATXHeadingParser, 600 FencedCodeBlockParser, 700 BlockquoteParser, 800 HTMLBlockParser, 900 ParagraphParser, 1000

func DefaultBlockParsers() []util.PrioritizedValue {
	return []util.PrioritizedValue{
		util.Prioritized(NewSetextHeadingParser(), 100),
		util.Prioritized(NewThematicBreakParser(), 200),
		util.Prioritized(NewListParser(), 300),
		util.Prioritized(NewListItemParser(), 400),
		util.Prioritized(NewCodeBlockParser(), 500),
		util.Prioritized(NewATXHeadingParser(), 600),
		util.Prioritized(NewFencedCodeBlockParser(), 700),
		util.Prioritized(NewBlockquoteParser(), 800),
		util.Prioritized(NewHTMLBlockParser(), 900),
		util.Prioritized(NewParagraphParser(), 1000),
	}
}

DefaultInlineParsers returns a new list of default InlineParsers. Priorities of default InlineParsers are: CodeSpanParser, 100 LinkParser, 200 AutoLinkParser, 300 RawHTMLParser, 400 EmphasisParser, 500

func DefaultInlineParsers() []util.PrioritizedValue {
	return []util.PrioritizedValue{
		util.Prioritized(NewCodeSpanParser(), 100),
		util.Prioritized(NewLinkParser(), 200),
		util.Prioritized(NewAutoLinkParser(), 300),
		util.Prioritized(NewRawHTMLParser(), 400),
		util.Prioritized(NewEmphasisParser(), 500),
	}
}

DefaultParagraphTransformers returns a new list of default ParagraphTransformers. Priorities of default ParagraphTransformers are: LinkReferenceParagraphTransformer, 100

func DefaultParagraphTransformers() []util.PrioritizedValue {
	return []util.PrioritizedValue{
		util.Prioritized(LinkReferenceParagraphTransformer, 100),
	}
}

A Block struct holds a node and correspond parser pair.

Node is a BlockNode.

Parser is a BlockParser.

	Parser BlockParser
}

type parser struct {
	options               map[OptionName]interface{}
	blockParsers          [256][]BlockParser
	freeBlockParsers      []BlockParser
	inlineParsers         [256][]InlineParser
	closeBlockers         []CloseBlocker
	paragraphTransformers []ParagraphTransformer
	astTransformers       []ASTTransformer
	config                *Config
	initSync              sync.Once
}

type withBlockParsers struct {
	value []util.PrioritizedValue
}

func (o *withBlockParsers) SetParserOption(c *Config) {
	c.BlockParsers = append(c.BlockParsers, o.value...)
}

WithBlockParsers is a functional option that allow you to add BlockParsers to the parser.

func WithBlockParsers(bs ...util.PrioritizedValue) Option {
	return &withBlockParsers{bs}
}

type withInlineParsers struct {
	value []util.PrioritizedValue
}

func (o *withInlineParsers) SetParserOption(c *Config) {
	c.InlineParsers = append(c.InlineParsers, o.value...)
}

WithInlineParsers is a functional option that allow you to add InlineParsers to the parser.

func WithInlineParsers(bs ...util.PrioritizedValue) Option {
	return &withInlineParsers{bs}
}

type withParagraphTransformers struct {
	value []util.PrioritizedValue
}

func (o *withParagraphTransformers) SetParserOption(c *Config) {
	c.ParagraphTransformers = append(c.ParagraphTransformers, o.value...)
}

WithParagraphTransformers is a functional option that allow you to add ParagraphTransformers to the parser.

func WithParagraphTransformers(ps ...util.PrioritizedValue) Option {
	return &withParagraphTransformers{ps}
}

type withASTTransformers struct {
	value []util.PrioritizedValue
}

func (o *withASTTransformers) SetParserOption(c *Config) {
	c.ASTTransformers = append(c.ASTTransformers, o.value...)
}

WithASTTransformers is a functional option that allow you to add ASTTransformers to the parser.

func WithASTTransformers(ps ...util.PrioritizedValue) Option {
	return &withASTTransformers{ps}
}

type withOption struct {
	name  OptionName
	value interface{}
}

func (o *withOption) SetParserOption(c *Config) {
	c.Options[o.name] = o.value
}

WithOption is a functional option that allow you to set an arbitrary option to the parser.

func WithOption(name OptionName, value interface{}) Option {
	return &withOption{name, value}
}

NewParser returns a new Parser with given options.

func NewParser(options ...Option) Parser {
	config := NewConfig()
	for _, opt := range options {
		opt.SetParserOption(config)
	}

	p := &parser{
		options: map[OptionName]interface{}{},
		config:  config,
	}

	return p
}

func (p *parser) AddOptions(opts ...Option) {
	for _, opt := range opts {
		opt.SetParserOption(p.config)
	}
}

func (p *parser) addBlockParser(v util.PrioritizedValue, options map[OptionName]interface{}) {
	bp, ok := v.Value.(BlockParser)
	if !ok {
		panic(fmt.Sprintf("%v is not a BlockParser", v.Value))
	}
	tcs := bp.Trigger()
	so, ok := v.Value.(SetOptioner)
	if ok {
		for oname, ovalue := range options {
			so.SetOption(oname, ovalue)
		}
	}
	if tcs == nil {
		p.freeBlockParsers = append(p.freeBlockParsers, bp)
	} else {
		for _, tc := range tcs {
			if p.blockParsers[tc] == nil {
				p.blockParsers[tc] = []BlockParser{}
			}
			p.blockParsers[tc] = append(p.blockParsers[tc], bp)
		}
	}
}

func (p *parser) addInlineParser(v util.PrioritizedValue, options map[OptionName]interface{}) {
	ip, ok := v.Value.(InlineParser)
	if !ok {
		panic(fmt.Sprintf("%v is not a InlineParser", v.Value))
	}
	tcs := ip.Trigger()
	so, ok := v.Value.(SetOptioner)
	if ok {
		for oname, ovalue := range options {
			so.SetOption(oname, ovalue)
		}
	}
	if cb, ok := ip.(CloseBlocker); ok {
		p.closeBlockers = append(p.closeBlockers, cb)
	}
	for _, tc := range tcs {
		if p.inlineParsers[tc] == nil {
			p.inlineParsers[tc] = []InlineParser{}
		}
		p.inlineParsers[tc] = append(p.inlineParsers[tc], ip)
	}
}

func (p *parser) addParagraphTransformer(v util.PrioritizedValue, options map[OptionName]interface{}) {
	pt, ok := v.Value.(ParagraphTransformer)
	if !ok {
		panic(fmt.Sprintf("%v is not a ParagraphTransformer", v.Value))
	}
	so, ok := v.Value.(SetOptioner)
	if ok {
		for oname, ovalue := range options {
			so.SetOption(oname, ovalue)
		}
	}
	p.paragraphTransformers = append(p.paragraphTransformers, pt)
}

func (p *parser) addASTTransformer(v util.PrioritizedValue, options map[OptionName]interface{}) {
	at, ok := v.Value.(ASTTransformer)
	if !ok {
		panic(fmt.Sprintf("%v is not a ASTTransformer", v.Value))
	}
	so, ok := v.Value.(SetOptioner)
	if ok {
		for oname, ovalue := range options {
			so.SetOption(oname, ovalue)
		}
	}
	p.astTransformers = append(p.astTransformers, at)
}

A ParseConfig struct is a data structure that holds configuration of the Parser.Parse.

type ParseConfig struct {
	Context Context
}

A ParseOption is a functional option type for the Parser.Parse.

type ParseOption func(c *ParseConfig)

WithContext is a functional option that allow you to override a default context.

func WithContext(context Context) ParseOption {
	return func(c *ParseConfig) {
		c.Context = context
	}
}

func (p *parser) Parse(reader text.Reader, opts ...ParseOption) ast.Node {
	p.initSync.Do(func() {
		p.config.BlockParsers.Sort()
		for _, v := range p.config.BlockParsers {
			p.addBlockParser(v, p.config.Options)
		}
		for i := range p.blockParsers {
			if p.blockParsers[i] != nil {
				p.blockParsers[i] = append(p.blockParsers[i], p.freeBlockParsers...)
			}
		}

		p.config.InlineParsers.Sort()
		for _, v := range p.config.InlineParsers {
			p.addInlineParser(v, p.config.Options)
		}
		p.config.ParagraphTransformers.Sort()
		for _, v := range p.config.ParagraphTransformers {
			p.addParagraphTransformer(v, p.config.Options)
		}
		p.config.ASTTransformers.Sort()
		for _, v := range p.config.ASTTransformers {
			p.addASTTransformer(v, p.config.Options)
		}
		p.config = nil
	})
	c := &ParseConfig{}
	for _, opt := range opts {
		opt(c)
	}
	if c.Context == nil {
		c.Context = NewContext()
	}
	pc := c.Context
	root := ast.NewDocument()
	p.parseBlocks(root, reader, pc)

	blockReader := text.NewBlockReader(reader.Source(), nil)
	p.walkBlock(root, func(node ast.Node) {
		p.parseBlock(blockReader, node, pc)
	})
	for _, at := range p.astTransformers {
		at.Transform(root, reader, pc)

root.Dump(reader.Source(), 0)

	return root
}

func (p *parser) transformParagraph(node *ast.Paragraph, reader text.Reader, pc Context) bool {
	for _, pt := range p.paragraphTransformers {
		pt.Transform(node, reader, pc)
		if node.Parent() == nil {
			return true
		}
	}
	return false
}

func (p *parser) closeBlocks(from, to int, reader text.Reader, pc Context) {
	blocks := pc.OpenedBlocks()
	for i := from; i >= to; i-- {
		node := blocks[i].Node
		blocks[i].Parser.Close(blocks[i].Node, reader, pc)
		paragraph, ok := node.(*ast.Paragraph)
		if ok && node.Parent() != nil {
			p.transformParagraph(paragraph, reader, pc)
		}
	}
	if from == len(blocks)-1 {
		blocks = blocks[0:to]
	} else {
		blocks = append(blocks[0:to], blocks[from+1:]...)
	}
	pc.SetOpenedBlocks(blocks)
}

type blockOpenResult int

const (
	paragraphContinuation blockOpenResult = iota + 1
	newBlocksOpened
	noBlocksOpened
)

func (p *parser) openBlocks(parent ast.Node, blankLine bool, reader text.Reader, pc Context) blockOpenResult {
	result := blockOpenResult(noBlocksOpened)
	continuable := false
	lastBlock := pc.LastOpenedBlock()
	if lastBlock.Node != nil {
		continuable = ast.IsParagraph(lastBlock.Node)
	}
retry:
	var bps []BlockParser
	line, _ := reader.PeekLine()
	w, pos := util.IndentWidth(line, reader.LineOffset())
	if w >= len(line) {
		pc.SetBlockOffset(-1)
		pc.SetBlockIndent(-1)
	} else {
		pc.SetBlockOffset(pos)
		pc.SetBlockIndent(w)
	}
	if line == nil || line[0] == '\n' {
		goto continuable
	}
	bps = p.freeBlockParsers
	if pos < len(line) {
		bps = p.blockParsers[line[pos]]
		if bps == nil {
			bps = p.freeBlockParsers
		}
	}
	if bps == nil {
		goto continuable
	}

	for _, bp := range bps {
		if continuable && result == noBlocksOpened && !bp.CanInterruptParagraph() {
			continue
		}
		if w > 3 && !bp.CanAcceptIndentedLine() {
			continue
		}
		lastBlock = pc.LastOpenedBlock()
		last := lastBlock.Node
		node, state := bp.Open(parent, reader, pc)

Parser requires last node to be a paragraph. With table extension: 0 -: - '-' on 3rd line seems a Setext heading because 1st and 2nd lines are being paragraph when the Settext heading parser tries to parse the 3rd line. But 1st line and 2nd line are a table. Thus this paragraph will be transformed by a paragraph transformer. So this text should be converted to a table and an empty list.

			if state&RequireParagraph != 0 {

Opened paragraph may be transformed by ParagraphTransformers in closeBlocks().

					lastBlock.Parser.Close(last, reader, pc)
					blocks := pc.OpenedBlocks()
					pc.SetOpenedBlocks(blocks[0 : len(blocks)-1])

Paragraph has been transformed. So this parser is considered as failing.

						continuable = false
						goto retry
					}
				}
			}
			node.SetBlankPreviousLines(blankLine)
			if last != nil && last.Parent() == nil {
				lastPos := len(pc.OpenedBlocks()) - 1
				p.closeBlocks(lastPos, lastPos, reader, pc)
			}
			parent.AppendChild(parent, node)
			result = newBlocksOpened
			be := Block{node, bp}
			pc.SetOpenedBlocks(append(pc.OpenedBlocks(), be))
			if state&HasChildren != 0 {
				parent = node
				goto retry // try child block
			}
			break // no children, can not open more blocks on this line
		}
	}

continuable:
	if result == noBlocksOpened && continuable {
		state := lastBlock.Parser.Continue(lastBlock.Node, reader, pc)
		if state&Continue != 0 {
			result = paragraphContinuation
		}
	}
	return result
}

type lineStat struct {
	lineNum int
	level   int
	isBlank bool
}

func isBlankLine(lineNum, level int, stats []lineStat) bool {
	ret := true
	for i := len(stats) - 1 - level; i >= 0; i-- {
		ret = false
		s := stats[i]
		if s.lineNum == lineNum {
			if s.level < level && s.isBlank {
				return true
			} else if s.level == level {
				return s.isBlank
			}
		}
		if s.lineNum < lineNum {
			return ret
		}
	}
	return ret
}

func (p *parser) parseBlocks(parent ast.Node, reader text.Reader, pc Context) {
	pc.SetOpenedBlocks([]Block{})
	blankLines := make([]lineStat, 0, 128)
	isBlank := false
	for { // process blocks separated by blank lines
		_, lines, ok := reader.SkipBlankLines()
		if !ok {
			return
		}
		lineNum, _ := reader.Position()
		if lines != 0 {
			blankLines = blankLines[0:0]
			l := len(pc.OpenedBlocks())
			for i := 0; i < l; i++ {
				blankLines = append(blankLines, lineStat{lineNum - 1, i, lines != 0})
			}
		}

first, we try to open blocks

		if p.openBlocks(parent, isBlank, reader, pc) != newBlocksOpened {
			return
		}
		reader.AdvanceLine()
		for { // process opened blocks line by line
			openedBlocks := pc.OpenedBlocks()
			l := len(openedBlocks)
			if l == 0 {
				break
			}
			lastIndex := l - 1
			for i := 0; i < l; i++ {
				be := openedBlocks[i]
				line, _ := reader.PeekLine()
				if line == nil {
					p.closeBlocks(lastIndex, 0, reader, pc)
					reader.AdvanceLine()
					return
				}
				lineNum, _ := reader.Position()

If node is a paragraph, p.openBlocks determines whether it is continuable. So we do not process paragraphs here.

				if !ast.IsParagraph(be.Node) {
					state := be.Parser.Continue(be.Node, reader, pc)

When current node is a container block and has no children, we try to open new child nodes

						if state&HasChildren != 0 && i == lastIndex {
							isBlank = isBlankLine(lineNum-1, i, blankLines)
							p.openBlocks(be.Node, isBlank, reader, pc)
							break
						}
						continue
					}

current node may be closed or lazy continuation

				isBlank = isBlankLine(lineNum-1, i, blankLines)
				thisParent := parent
				if i != 0 {
					thisParent = openedBlocks[i-1].Node
				}
				lastNode := openedBlocks[lastIndex].Node
				result := p.openBlocks(thisParent, isBlank, reader, pc)

lastNode is a paragraph and was transformed by the paragraph transformers.

					if openedBlocks[lastIndex].Node != lastNode {
						lastIndex--
					}
					p.closeBlocks(lastIndex, i, reader, pc)
				}
				break
			}

			reader.AdvanceLine()
		}
	}
}

func (p *parser) walkBlock(block ast.Node, cb func(node ast.Node)) {
	for c := block.FirstChild(); c != nil; c = c.NextSibling() {
		p.walkBlock(c, cb)
	}
	cb(block)
}

func (p *parser) parseBlock(block text.BlockReader, parent ast.Node, pc Context) {
	if parent.IsRaw() {
		return
	}
	escaped := false
	source := block.Source()
	block.Reset(parent.Lines())
	for {
	retry:
		line, _ := block.PeekLine()
		if line == nil {
			break
		}
		lineLength := len(line)
		hardlineBreak := false
		softLinebreak := line[lineLength-1] == '\n'
		if lineLength >= 2 && line[lineLength-2] == '\\' && softLinebreak { // ends with \\n
			lineLength -= 2
			hardlineBreak = true

		} else if lineLength >= 3 && line[lineLength-3] == '\\' && line[lineLength-2] == '\r' && softLinebreak { // ends with \\r\n
			lineLength -= 3
			hardlineBreak = true
		} else if lineLength >= 3 && line[lineLength-3] == ' ' && line[lineLength-2] == ' ' && softLinebreak { // ends with [space][space]\n
			lineLength -= 3
			hardlineBreak = true
		} else if lineLength >= 4 && line[lineLength-4] == ' ' && line[lineLength-3] == ' ' && line[lineLength-2] == '\r' && softLinebreak { // ends with [space][space]\r\n
			lineLength -= 4
			hardlineBreak = true
		}

		l, startPosition := block.Position()
		n := 0
		for i := 0; i < lineLength; i++ {
			c := line[i]
			if c == '\n' {
				break
			}
			isSpace := util.IsSpace(c)
			isPunct := util.IsPunct(c)
			if (isPunct && !escaped) || isSpace || i == 0 {
				parserChar := c
				if isSpace || (i == 0 && !isPunct) {
					parserChar = ' '
				}
				ips := p.inlineParsers[parserChar]
				if ips != nil {
					block.Advance(n)
					n = 0
					savedLine, savedPosition := block.Position()
					if i != 0 {
						_, currentPosition := block.Position()
						ast.MergeOrAppendTextSegment(parent, startPosition.Between(currentPosition))
						_, startPosition = block.Position()
					}
					var inlineNode ast.Node
					for _, ip := range ips {
						inlineNode = ip.Parse(parent, block, pc)
						if inlineNode != nil {
							break
						}
						block.SetPosition(savedLine, savedPosition)
					}
					if inlineNode != nil {
						parent.AppendChild(parent, inlineNode)
						goto retry
					}
				}
			}
			if escaped {
				escaped = false
				n++
				continue
			}

			if c == '\\' {
				escaped = true
				n++
				continue
			}

			escaped = false
			n++
		}
		if n != 0 {
			block.Advance(n)
		}
		currentL, currentPosition := block.Position()
		if l != currentL {
			continue
		}
		diff := startPosition.Between(currentPosition)
		stop := diff.Stop
		rest := diff.WithStop(stop)
		text := ast.NewTextSegment(rest.TrimRightSpace(source))
		text.SetSoftLineBreak(softLinebreak)
		text.SetHardLineBreak(hardlineBreak)
		parent.AppendChild(parent, text)
		block.AdvanceLine()
	}

	ProcessDelimiters(nil, pc)
	for _, ip := range p.closeBlockers {
		ip.CloseBlock(parent, block, pc)
	}