Update markdown parsing library to github.com/gomarkdown/markdown (#944)

1 files changed, 1978 insertions, 0 deletions

diff --git a/vendor/github.com/gomarkdown/markdown/parser/block.go b/vendor/github.com/gomarkdown/markdown/parser/block.go
new file mode 100644
index 00000000..18a2dd89
--- /dev/null
+++ b/vendor/github.com/gomarkdown/markdown/parser/block.go
@@ -0,0 +1,1978 @@
+package parser
+
+import (
+	"bytes"
+	"html"
+	"regexp"
+	"strconv"
+	"unicode"
+
+	"github.com/gomarkdown/markdown/ast"
+)
+
+// Parsing block-level elements.
+
+const (
+	charEntity = "&(?:#x[a-f0-9]{1,8}|#[0-9]{1,8}|[a-z][a-z0-9]{1,31});"
+	escapable  = "[!\"#$%&'()*+,./:;<=>?@[\\\\\\]^_`{|}~-]"
+)
+
+var (
+	reBackslashOrAmp      = regexp.MustCompile("[\\&]")
+	reEntityOrEscapedChar = regexp.MustCompile("(?i)\\\\" + escapable + "|" + charEntity)
+
+	// blockTags is a set of tags that are recognized as HTML block tags.
+	// Any of these can be included in markdown text without special escaping.
+	blockTags = map[string]struct{}{
+		"blockquote": struct{}{},
+		"del":        struct{}{},
+		"div":        struct{}{},
+		"dl":         struct{}{},
+		"fieldset":   struct{}{},
+		"form":       struct{}{},
+		"h1":         struct{}{},
+		"h2":         struct{}{},
+		"h3":         struct{}{},
+		"h4":         struct{}{},
+		"h5":         struct{}{},
+		"h6":         struct{}{},
+		"iframe":     struct{}{},
+		"ins":        struct{}{},
+		"math":       struct{}{},
+		"noscript":   struct{}{},
+		"ol":         struct{}{},
+		"pre":        struct{}{},
+		"p":          struct{}{},
+		"script":     struct{}{},
+		"style":      struct{}{},
+		"table":      struct{}{},
+		"ul":         struct{}{},
+
+		// HTML5
+		"address":    struct{}{},
+		"article":    struct{}{},
+		"aside":      struct{}{},
+		"canvas":     struct{}{},
+		"figcaption": struct{}{},
+		"figure":     struct{}{},
+		"footer":     struct{}{},
+		"header":     struct{}{},
+		"hgroup":     struct{}{},
+		"main":       struct{}{},
+		"nav":        struct{}{},
+		"output":     struct{}{},
+		"progress":   struct{}{},
+		"section":    struct{}{},
+		"video":      struct{}{},
+	}
+)
+
+// sanitizeAnchorName returns a sanitized anchor name for the given text.
+// Taken from https://github.com/shurcooL/sanitized_anchor_name/blob/master/main.go#L14:1
+func sanitizeAnchorName(text string) string {
+	var anchorName []rune
+	var futureDash = false
+	for _, r := range text {
+		switch {
+		case unicode.IsLetter(r) || unicode.IsNumber(r):
+			if futureDash && len(anchorName) > 0 {
+				anchorName = append(anchorName, '-')
+			}
+			futureDash = false
+			anchorName = append(anchorName, unicode.ToLower(r))
+		default:
+			futureDash = true
+		}
+	}
+	return string(anchorName)
+}
+
+// Parse block-level data.
+// Note: this function and many that it calls assume that
+// the input buffer ends with a newline.
+func (p *Parser) block(data []byte) {
+	// this is called recursively: enforce a maximum depth
+	if p.nesting >= p.maxNesting {
+		return
+	}
+	p.nesting++
+
+	// parse out one block-level construct at a time
+	for len(data) > 0 {
+		// attributes that can be specific before a block element:
+		//
+		// {#id .class1 .class2 key="value"}
+		if p.extensions&Attributes != 0 {
+			data = p.attribute(data)
+		}
+
+		if p.extensions&Includes != 0 {
+			f := p.readInclude
+			path, address, consumed := p.isInclude(data)
+			if consumed == 0 {
+				path, address, consumed = p.isCodeInclude(data)
+				f = p.readCodeInclude
+			}
+			if consumed > 0 {
+				included := f(p.includeStack.Last(), path, address)
+				p.includeStack.Push(path)
+				p.block(included)
+				p.includeStack.Pop()
+				data = data[consumed:]
+				continue
+			}
+		}
+
+		// user supplied parser function
+		if p.Opts.ParserHook != nil {
+			node, blockdata, consumed := p.Opts.ParserHook(data)
+			if consumed > 0 {
+				data = data[consumed:]
+
+				if node != nil {
+					p.addBlock(node)
+					if blockdata != nil {
+						p.block(blockdata)
+						p.finalize(node)
+					}
+				}
+				continue
+			}
+		}
+
+		// prefixed heading:
+		//
+		// # Heading 1
+		// ## Heading 2
+		// ...
+		// ###### Heading 6
+		if p.isPrefixHeading(data) {
+			data = data[p.prefixHeading(data):]
+			continue
+		}
+
+		// prefixed special heading:
+		// (there are no levels.)
+		//
+		// .# Abstract
+		if p.isPrefixSpecialHeading(data) {
+			data = data[p.prefixSpecialHeading(data):]
+			continue
+		}
+
+		// block of preformatted HTML:
+		//
+		// <div>
+		//     ...
+		// </div>
+		if data[0] == '<' {
+			if i := p.html(data, true); i > 0 {
+				data = data[i:]
+				continue
+			}
+		}
+
+		// title block
+		//
+		// % stuff
+		// % more stuff
+		// % even more stuff
+		if p.extensions&Titleblock != 0 {
+			if data[0] == '%' {
+				if i := p.titleBlock(data, true); i > 0 {
+					data = data[i:]
+					continue
+				}
+			}
+		}
+
+		// blank lines.  note: returns the # of bytes to skip
+		if i := p.isEmpty(data); i > 0 {
+			data = data[i:]
+			continue
+		}
+
+		// indented code block:
+		//
+		//     func max(a, b int) int {
+		//         if a > b {
+		//             return a
+		//         }
+		//         return b
+		//      }
+		if p.codePrefix(data) > 0 {
+			data = data[p.code(data):]
+			continue
+		}
+
+		// fenced code block:
+		//
+		// ``` go
+		// func fact(n int) int {
+		//     if n <= 1 {
+		//         return n
+		//     }
+		//     return n * fact(n-1)
+		// }
+		// ```
+		if p.extensions&FencedCode != 0 {
+			if i := p.fencedCodeBlock(data, true); i > 0 {
+				data = data[i:]
+				continue
+			}
+		}
+
+		// horizontal rule:
+		//
+		// ------
+		// or
+		// ******
+		// or
+		// ______
+		if p.isHRule(data) {
+			p.addBlock(&ast.HorizontalRule{})
+			i := skipUntilChar(data, 0, '\n')
+			data = data[i:]
+			continue
+		}
+
+		// block quote:
+		//
+		// > A big quote I found somewhere
+		// > on the web
+		if p.quotePrefix(data) > 0 {
+			data = data[p.quote(data):]
+			continue
+		}
+
+		// aside:
+		//
+		// A> The proof is too large to fit
+		// A> in the margin.
+		if p.extensions&Mmark != 0 {
+			if p.asidePrefix(data) > 0 {
+				data = data[p.aside(data):]
+				continue
+			}
+		}
+
+		// figure block:
+		//
+		// !---
+		// ![Alt Text](img.jpg "This is an image")
+		// ![Alt Text](img2.jpg "This is a second image")
+		// !---
+		if p.extensions&Mmark != 0 {
+			if i := p.figureBlock(data, true); i > 0 {
+				data = data[i:]
+				continue
+			}
+		}
+
+		// table:
+		//
+		// Name  | Age | Phone
+		// ------|-----|---------
+		// Bob   | 31  | 555-1234
+		// Alice | 27  | 555-4321
+		if p.extensions&Tables != 0 {
+			if i := p.table(data); i > 0 {
+				data = data[i:]
+				continue
+			}
+		}
+
+		// an itemized/unordered list:
+		//
+		// * Item 1
+		// * Item 2
+		//
+		// also works with + or -
+		if p.uliPrefix(data) > 0 {
+			data = data[p.list(data, 0, 0):]
+			continue
+		}
+
+		// a numbered/ordered list:
+		//
+		// 1. Item 1
+		// 2. Item 2
+		if i := p.oliPrefix(data); i > 0 {
+			start := 0
+			if i > 2 && p.extensions&OrderedListStart != 0 {
+				s := string(data[:i-2])
+				start, _ = strconv.Atoi(s)
+				if start == 1 {
+					start = 0
+				}
+			}
+			data = data[p.list(data, ast.ListTypeOrdered, start):]
+			continue
+		}
+
+		// definition lists:
+		//
+		// Term 1
+		// :   Definition a
+		// :   Definition b
+		//
+		// Term 2
+		// :   Definition c
+		if p.extensions&DefinitionLists != 0 {
+			if p.dliPrefix(data) > 0 {
+				data = data[p.list(data, ast.ListTypeDefinition, 0):]
+				continue
+			}
+		}
+
+		if p.extensions&MathJax != 0 {
+			if i := p.blockMath(data); i > 0 {
+				data = data[i:]
+				continue
+			}
+		}
+
+		// document matters:
+		//
+		// {frontmatter}/{mainmatter}/{backmatter}
+		if p.extensions&Mmark != 0 {
+			if i := p.documentMatter(data); i > 0 {
+				data = data[i:]
+				continue
+			}
+		}
+
+		// anything else must look like a normal paragraph
+		// note: this finds underlined headings, too
+		idx := p.paragraph(data)
+		data = data[idx:]
+	}
+
+	p.nesting--
+}
+
+func (p *Parser) addBlock(n ast.Node) ast.Node {
+	p.closeUnmatchedBlocks()
+
+	if p.attr != nil {
+		if c := n.AsContainer(); c != nil {
+			c.Attribute = p.attr
+		}
+		if l := n.AsLeaf(); l != nil {
+			l.Attribute = p.attr
+		}
+		p.attr = nil
+	}
+	return p.addChild(n)
+}
+
+func (p *Parser) isPrefixHeading(data []byte) bool {
+	if data[0] != '#' {
+		return false
+	}
+
+	if p.extensions&SpaceHeadings != 0 {
+		level := skipCharN(data, 0, '#', 6)
+		if level == len(data) || data[level] != ' ' {
+			return false
+		}
+	}
+	return true
+}
+
+func (p *Parser) prefixHeading(data []byte) int {
+	level := skipCharN(data, 0, '#', 6)
+	i := skipChar(data, level, ' ')
+	end := skipUntilChar(data, i, '\n')
+	skip := end
+	id := ""
+	if p.extensions&HeadingIDs != 0 {
+		j, k := 0, 0
+		// find start/end of heading id
+		for j = i; j < end-1 && (data[j] != '{' || data[j+1] != '#'); j++ {
+		}
+		for k = j + 1; k < end && data[k] != '}'; k++ {
+		}
+		// extract heading id iff found
+		if j < end && k < end {
+			id = string(data[j+2 : k])
+			end = j
+			skip = k + 1
+			for end > 0 && data[end-1] == ' ' {
+				end--
+			}
+		}
+	}
+	for end > 0 && data[end-1] == '#' {
+		if isBackslashEscaped(data, end-1) {
+			break
+		}
+		end--
+	}
+	for end > 0 && data[end-1] == ' ' {
+		end--
+	}
+	if end > i {
+		if id == "" && p.extensions&AutoHeadingIDs != 0 {
+			id = sanitizeAnchorName(string(data[i:end]))
+		}
+		block := &ast.Heading{
+			HeadingID: id,
+			Level:     level,
+		}
+		block.Content = data[i:end]
+		p.addBlock(block)
+	}
+	return skip
+}
+
+func (p *Parser) isPrefixSpecialHeading(data []byte) bool {
+	if p.extensions|Mmark == 0 {
+		return false
+	}
+	if len(data) < 4 {
+		return false
+	}
+	if data[0] != '.' {
+		return false
+	}
+	if data[1] != '#' {
+		return false
+	}
+	if data[2] == '#' { // we don't support level, so nack this.
+		return false
+	}
+
+	if p.extensions&SpaceHeadings != 0 {
+		if data[2] != ' ' {
+			return false
+		}
+	}
+	return true
+}
+
+func (p *Parser) prefixSpecialHeading(data []byte) int {
+	i := skipChar(data, 2, ' ') // ".#" skipped
+	end := skipUntilChar(data, i, '\n')
+	skip := end
+	id := ""
+	if p.extensions&HeadingIDs != 0 {
+		j, k := 0, 0
+		// find start/end of heading id
+		for j = i; j < end-1 && (data[j] != '{' || data[j+1] != '#'); j++ {
+		}
+		for k = j + 1; k < end && data[k] != '}'; k++ {
+		}
+		// extract heading id iff found
+		if j < end && k < end {
+			id = string(data[j+2 : k])
+			end = j
+			skip = k + 1
+			for end > 0 && data[end-1] == ' ' {
+				end--
+			}
+		}
+	}
+	for end > 0 && data[end-1] == '#' {
+		if isBackslashEscaped(data, end-1) {
+			break
+		}
+		end--
+	}
+	for end > 0 && data[end-1] == ' ' {
+		end--
+	}
+	if end > i {
+		if id == "" && p.extensions&AutoHeadingIDs != 0 {
+			id = sanitizeAnchorName(string(data[i:end]))
+		}
+		block := &ast.Heading{
+			HeadingID: id,
+			IsSpecial: true,
+			Level:     1, // always level 1.
+		}
+		block.Literal = data[i:end]
+		block.Content = data[i:end]
+		p.addBlock(block)
+	}
+	return skip
+}
+
+func (p *Parser) isUnderlinedHeading(data []byte) int {
+	// test of level 1 heading
+	if data[0] == '=' {
+		i := skipChar(data, 1, '=')
+		i = skipChar(data, i, ' ')
+		if i < len(data) && data[i] == '\n' {
+			return 1
+		}
+		return 0
+	}
+
+	// test of level 2 heading
+	if data[0] == '-' {
+		i := skipChar(data, 1, '-')
+		i = skipChar(data, i, ' ')
+		if i < len(data) && data[i] == '\n' {
+			return 2
+		}
+		return 0
+	}
+
+	return 0
+}
+
+func (p *Parser) titleBlock(data []byte, doRender bool) int {
+	if data[0] != '%' {
+		return 0
+	}
+	splitData := bytes.Split(data, []byte("\n"))
+	var i int
+	for idx, b := range splitData {
+		if !bytes.HasPrefix(b, []byte("%")) {
+			i = idx // - 1
+			break
+		}
+	}
+
+	data = bytes.Join(splitData[0:i], []byte("\n"))
+	consumed := len(data)
+	data = bytes.TrimPrefix(data, []byte("% "))
+	data = bytes.Replace(data, []byte("\n% "), []byte("\n"), -1)
+	block := &ast.Heading{
+		Level:        1,
+		IsTitleblock: true,
+	}
+	block.Content = data
+	p.addBlock(block)
+
+	return consumed
+}
+
+func (p *Parser) html(data []byte, doRender bool) int {
+	var i, j int
+
+	// identify the opening tag
+	if data[0] != '<' {
+		return 0
+	}
+	curtag, tagfound := p.htmlFindTag(data[1:])
+
+	// handle special cases
+	if !tagfound {
+		// check for an HTML comment
+		if size := p.htmlComment(data, doRender); size > 0 {
+			return size
+		}
+
+		// check for an <hr> tag
+		if size := p.htmlHr(data, doRender); size > 0 {
+			return size
+		}
+
+		// no special case recognized
+		return 0
+	}
+
+	// look for an unindented matching closing tag
+	// followed by a blank line
+	found := false
+	/*
+		closetag := []byte("\n</" + curtag + ">")
+		j = len(curtag) + 1
+		for !found {
+			// scan for a closing tag at the beginning of a line
+			if skip := bytes.Index(data[j:], closetag); skip >= 0 {
+				j += skip + len(closetag)
+			} else {
+				break
+			}
+
+			// see if it is the only thing on the line
+			if skip := p.isEmpty(data[j:]); skip > 0 {
+				// see if it is followed by a blank line/eof
+				j += skip
+				if j >= len(data) {
+					found = true
+					i = j
+				} else {
+					if skip := p.isEmpty(data[j:]); skip > 0 {
+						j += skip
+						found = true
+						i = j
+					}
+				}
+			}
+		}
+	*/
+
+	// if not found, try a second pass looking for indented match
+	// but not if tag is "ins" or "del" (following original Markdown.pl)
+	if !found && curtag != "ins" && curtag != "del" {
+		i = 1
+		for i < len(data) {
+			i++
+			for i < len(data) && !(data[i-1] == '<' && data[i] == '/') {
+				i++
+			}
+
+			if i+2+len(curtag) >= len(data) {
+				break
+			}
+
+			j = p.htmlFindEnd(curtag, data[i-1:])
+
+			if j > 0 {
+				i += j - 1
+				found = true
+				break
+			}
+		}
+	}
+
+	if !found {
+		return 0
+	}
+
+	// the end of the block has been found
+	if doRender {
+		// trim newlines
+		end := backChar(data, i, '\n')
+		htmlBLock := &ast.HTMLBlock{ast.Leaf{Content: data[:end]}}
+		p.addBlock(htmlBLock)
+		finalizeHTMLBlock(htmlBLock)
+	}
+
+	return i
+}
+
+func finalizeHTMLBlock(block *ast.HTMLBlock) {
+	block.Literal = block.Content
+	block.Content = nil
+}
+
+// HTML comment, lax form
+func (p *Parser) htmlComment(data []byte, doRender bool) int {
+	i := p.inlineHTMLComment(data)
+	// needs to end with a blank line
+	if j := p.isEmpty(data[i:]); j > 0 {
+		size := i + j
+		if doRender {
+			// trim trailing newlines
+			end := backChar(data, size, '\n')
+			htmlBLock := &ast.HTMLBlock{ast.Leaf{Content: data[:end]}}
+			p.addBlock(htmlBLock)
+			finalizeHTMLBlock(htmlBLock)
+		}
+		return size
+	}
+	return 0
+}
+
+// HR, which is the only self-closing block tag considered
+func (p *Parser) htmlHr(data []byte, doRender bool) int {
+	if len(data) < 4 {
+		return 0
+	}
+	if data[0] != '<' || (data[1] != 'h' && data[1] != 'H') || (data[2] != 'r' && data[2] != 'R') {
+		return 0
+	}
+	if data[3] != ' ' && data[3] != '/' && data[3] != '>' {
+		// not an <hr> tag after all; at least not a valid one
+		return 0
+	}
+	i := 3
+	for i < len(data) && data[i] != '>' && data[i] != '\n' {
+		i++
+	}
+	if i < len(data) && data[i] == '>' {
+		i++
+		if j := p.isEmpty(data[i:]); j > 0 {
+			size := i + j
+			if doRender {
+				// trim newlines
+				end := backChar(data, size, '\n')
+				htmlBlock := &ast.HTMLBlock{ast.Leaf{Content: data[:end]}}
+				p.addBlock(htmlBlock)
+				finalizeHTMLBlock(htmlBlock)
+			}
+			return size
+		}
+	}
+	return 0
+}
+
+func (p *Parser) htmlFindTag(data []byte) (string, bool) {
+	i := skipAlnum(data, 0)
+	key := string(data[:i])
+	if _, ok := blockTags[key]; ok {
+		return key, true
+	}
+	return "", false
+}
+
+func (p *Parser) htmlFindEnd(tag string, data []byte) int {
+	// assume data[0] == '<' && data[1] == '/' already tested
+	if tag == "hr" {
+		return 2
+	}
+	// check if tag is a match
+	closetag := []byte("</" + tag + ">")
+	if !bytes.HasPrefix(data, closetag) {
+		return 0
+	}
+	i := len(closetag)
+
+	// check that the rest of the line is blank
+	skip := 0
+	if skip = p.isEmpty(data[i:]); skip == 0 {
+		return 0
+	}
+	i += skip
+	skip = 0
+
+	if i >= len(data) {
+		return i
+	}
+
+	if p.extensions&LaxHTMLBlocks != 0 {
+		return i
+	}
+	if skip = p.isEmpty(data[i:]); skip == 0 {
+		// following line must be blank
+		return 0
+	}
+
+	return i + skip
+}
+
+func (*Parser) isEmpty(data []byte) int {
+	// it is okay to call isEmpty on an empty buffer
+	if len(data) == 0 {
+		return 0
+	}
+
+	var i int
+	for i = 0; i < len(data) && data[i] != '\n'; i++ {
+		if data[i] != ' ' && data[i] != '\t' {
+			return 0
+		}
+	}
+	i = skipCharN(data, i, '\n', 1)
+	return i
+}
+
+func (*Parser) isHRule(data []byte) bool {
+	i := 0
+
+	// skip up to three spaces
+	for i < 3 && data[i] == ' ' {
+		i++
+	}
+
+	// look at the hrule char
+	if data[i] != '*' && data[i] != '-' && data[i] != '_' {
+		return false
+	}
+	c := data[i]
+
+	// the whole line must be the char or whitespace
+	n := 0
+	for i < len(data) && data[i] != '\n' {
+		switch {
+		case data[i] == c:
+			n++
+		case data[i] != ' ':
+			return false
+		}
+		i++
+	}
+
+	return n >= 3
+}
+
+// isFenceLine checks if there's a fence line (e.g., ``` or ``` go) at the beginning of data,
+// and returns the end index if so, or 0 otherwise. It also returns the marker found.
+// If syntax is not nil, it gets set to the syntax specified in the fence line.
+func isFenceLine(data []byte, syntax *string, oldmarker string) (end int, marker string) {
+	i, size := 0, 0
+
+	n := len(data)
+	// skip up to three spaces
+	for i < n && i < 3 && data[i] == ' ' {
+		i++
+	}
+
+	// check for the marker characters: ~ or `
+	if i >= n {
+		return 0, ""
+	}
+	if data[i] != '~' && data[i] != '`' {
+		return 0, ""
+	}
+
+	c := data[i]
+
+	// the whole line must be the same char or whitespace
+	for i < n && data[i] == c {
+		size++
+		i++
+	}
+
+	// the marker char must occur at least 3 times
+	if size < 3 {
+		return 0, ""
+	}
+	marker = string(data[i-size : i])
+
+	// if this is the end marker, it must match the beginning marker
+	if oldmarker != "" && marker != oldmarker {
+		return 0, ""
+	}
+
+	// TODO(shurcooL): It's probably a good idea to simplify the 2 code paths here
+	// into one, always get the syntax, and discard it if the caller doesn't care.
+	if syntax != nil {
+		syn := 0
+		i = skipChar(data, i, ' ')
+
+		if i >= n {
+			if i == n {
+				return i, marker
+			}
+			return 0, ""
+		}
+
+		syntaxStart := i
+
+		if data[i] == '{' {
+			i++
+			syntaxStart++
+
+			for i < n && data[i] != '}' && data[i] != '\n' {
+				syn++
+				i++
+			}
+
+			if i >= n || data[i] != '}' {
+				return 0, ""
+			}
+
+			// strip all whitespace at the beginning and the end
+			// of the {} block
+			for syn > 0 && isSpace(data[syntaxStart]) {
+				syntaxStart++
+				syn--
+			}
+
+			for syn > 0 && isSpace(data[syntaxStart+syn-1]) {
+				syn--
+			}
+
+			i++
+		} else {
+			for i < n && !isSpace(data[i]) {
+				syn++
+				i++
+			}
+		}
+
+		*syntax = string(data[syntaxStart : syntaxStart+syn])
+	}
+
+	i = skipChar(data, i, ' ')
+	if i >= n || data[i] != '\n' {
+		if i == n {
+			return i, marker
+		}
+		return 0, ""
+	}
+	return i + 1, marker // Take newline into account.
+}
+
+// fencedCodeBlock returns the end index if data contains a fenced code block at the beginning,
+// or 0 otherwise. It writes to out if doRender is true, otherwise it has no side effects.
+// If doRender is true, a final newline is mandatory to recognize the fenced code block.
+func (p *Parser) fencedCodeBlock(data []byte, doRender bool) int {
+	var syntax string
+	beg, marker := isFenceLine(data, &syntax, "")
+	if beg == 0 || beg >= len(data) {
+		return 0
+	}
+
+	var work bytes.Buffer
+	work.WriteString(syntax)
+	work.WriteByte('\n')
+
+	for {
+		// safe to assume beg < len(data)
+
+		// check for the end of the code block
+		fenceEnd, _ := isFenceLine(data[beg:], nil, marker)
+		if fenceEnd != 0 {
+			beg += fenceEnd
+			break
+		}
+
+		// copy the current line
+		end := skipUntilChar(data, beg, '\n') + 1
+
+		// did we reach the end of the buffer without a closing marker?
+		if end >= len(data) {
+			return 0
+		}
+
+		// verbatim copy to the working buffer
+		if doRender {
+			work.Write(data[beg:end])
+		}
+		beg = end
+	}
+
+	if doRender {
+		codeBlock := &ast.CodeBlock{
+			IsFenced: true,
+		}
+		codeBlock.Content = work.Bytes() // TODO: get rid of temp buffer
+
+		if p.extensions&Mmark == 0 {
+			p.addBlock(codeBlock)
+			finalizeCodeBlock(codeBlock)
+			return beg
+		}
+
+		// Check for caption and if found make it a figure.
+		if captionContent, id, consumed := p.caption(data[beg:], []byte("Figure: ")); consumed > 0 {
+			figure := &ast.CaptionFigure{}
+			caption := &ast.Caption{}
+			figure.HeadingID = id
+			p.Inline(caption, captionContent)
+
+			p.addBlock(figure)
+			codeBlock.AsLeaf().Attribute = figure.AsContainer().Attribute
+			p.addChild(codeBlock)
+			finalizeCodeBlock(codeBlock)
+			p.addChild(caption)
+			p.finalize(figure)
+
+			beg += consumed
+
+			return beg
+		}
+
+		// Still here, normal block
+		p.addBlock(codeBlock)
+		finalizeCodeBlock(codeBlock)
+	}
+
+	return beg
+}
+
+func unescapeChar(str []byte) []byte {
+	if str[0] == '\\' {
+		return []byte{str[1]}
+	}
+	return []byte(html.UnescapeString(string(str)))
+}
+
+func unescapeString(str []byte) []byte {
+	if reBackslashOrAmp.Match(str) {
+		return reEntityOrEscapedChar.ReplaceAllFunc(str, unescapeChar)
+	}
+	return str
+}
+
+func finalizeCodeBlock(code *ast.CodeBlock) {
+	c := code.Content
+	if code.IsFenced {
+		newlinePos := bytes.IndexByte(c, '\n')
+		firstLine := c[:newlinePos]
+		rest := c[newlinePos+1:]
+		code.Info = unescapeString(bytes.Trim(firstLine, "\n"))
+		code.Literal = rest
+	} else {
+		code.Literal = c
+	}
+	code.Content = nil
+}
+
+func (p *Parser) table(data []byte) int {
+	i, columns, table := p.tableHeader(data)
+	if i == 0 {
+		return 0
+	}
+
+	p.addBlock(&ast.TableBody{})
+
+	for i < len(data) {
+		pipes, rowStart := 0, i
+		for ; i < len(data) && data[i] != '\n'; i++ {
+			if data[i] == '|' {
+				pipes++
+			}
+		}
+
+		if pipes == 0 {
+			i = rowStart
+			break
+		}
+
+		// include the newline in data sent to tableRow
+		i = skipCharN(data, i, '\n', 1)
+
+		if p.tableFooter(data[rowStart:i]) {
+			continue
+		}
+
+		p.tableRow(data[rowStart:i], columns, false)
+	}
+	if captionContent, id, consumed := p.caption(data[i:], []byte("Table: ")); consumed > 0 {
+		caption := &ast.Caption{}
+		p.Inline(caption, captionContent)
+
+		// Some switcheroo to re-insert the parsed table as a child of the captionfigure.
+		figure := &ast.CaptionFigure{}
+		figure.HeadingID = id
+		table2 := &ast.Table{}
+		// Retain any block level attributes.
+		table2.AsContainer().Attribute = table.AsContainer().Attribute
+		children := table.GetChildren()
+		ast.RemoveFromTree(table)
+
+		table2.SetChildren(children)
+		ast.AppendChild(figure, table2)
+		ast.AppendChild(figure, caption)
+
+		p.addChild(figure)
+		p.finalize(figure)
+
+		i += consumed
+	}
+
+	return i
+}
+
+// check if the specified position is preceded by an odd number of backslashes
+func isBackslashEscaped(data []byte, i int) bool {
+	backslashes := 0
+	for i-backslashes-1 >= 0 && data[i-backslashes-1] == '\\' {
+		backslashes++
+	}
+	return backslashes&1 == 1
+}
+
+// tableHeaders parses the header. If recognized it will also add a table.
+func (p *Parser) tableHeader(data []byte) (size int, columns []ast.CellAlignFlags, table ast.Node) {
+	i := 0
+	colCount := 1
+	for i = 0; i < len(data) && data[i] != '\n'; i++ {
+		if data[i] == '|' && !isBackslashEscaped(data, i) {
+			colCount++
+		}
+	}
+
+	// doesn't look like a table header
+	if colCount == 1 {
+		return
+	}
+
+	// include the newline in the data sent to tableRow
+	j := skipCharN(data, i, '\n', 1)
+	header := data[:j]
+
+	// column count ignores pipes at beginning or end of line
+	if data[0] == '|' {
+		colCount--
+	}
+	if i > 2 && data[i-1] == '|' && !isBackslashEscaped(data, i-1) {
+		colCount--
+	}
+
+	columns = make([]ast.CellAlignFlags, colCount)
+
+	// move on to the header underline
+	i++
+	if i >= len(data) {
+		return
+	}
+
+	if data[i] == '|' && !isBackslashEscaped(data, i) {
+		i++
+	}
+	i = skipChar(data, i, ' ')
+
+	// each column header is of form: / *:?-+:? *|/ with # dashes + # colons >= 3
+	// and trailing | optional on last column
+	col := 0
+	n := len(data)
+	for i < n && data[i] != '\n' {
+		dashes := 0
+
+		if data[i] == ':' {
+			i++
+			columns[col] |= ast.TableAlignmentLeft
+			dashes++
+		}
+		for i < n && data[i] == '-' {
+			i++
+			dashes++
+		}
+		if i < n && data[i] == ':' {
+			i++
+			columns[col] |= ast.TableAlignmentRight
+			dashes++
+		}
+		for i < n && data[i] == ' ' {
+			i++
+		}
+		if i == n {
+			return
+		}
+		// end of column test is messy
+		switch {
+		case dashes < 3:
+			// not a valid column
+			return
+
+		case data[i] == '|' && !isBackslashEscaped(data, i):
+			// marker found, now skip past trailing whitespace
+			col++
+			i++
+			for i < n && data[i] == ' ' {
+				i++
+			}
+
+			// trailing junk found after last column
+			if col >= colCount && i < len(data) && data[i] != '\n' {
+				return
+			}
+
+		case (data[i] != '|' || isBackslashEscaped(data, i)) && col+1 < colCount:
+			// something else found where marker was required
+			return
+
+		case data[i] == '\n':
+			// marker is optional for the last column
+			col++
+
+		default:
+			// trailing junk found after last column
+			return
+		}
+	}
+	if col != colCount {
+		return
+	}
+
+	table = &ast.Table{}
+	p.addBlock(table)
+	p.addBlock(&ast.TableHeader{})
+	p.tableRow(header, columns, true)
+	size = skipCharN(data, i, '\n', 1)
+	return
+}
+
+func (p *Parser) tableRow(data []byte, columns []ast.CellAlignFlags, header bool) {
+	p.addBlock(&ast.TableRow{})
+	i, col := 0, 0
+
+	if data[i] == '|' && !isBackslashEscaped(data, i) {
+		i++
+	}
+
+	n := len(data)
+	for col = 0; col < len(columns) && i < n; col++ {
+		for i < n && data[i] == ' ' {
+			i++
+		}
+
+		cellStart := i
+
+		for i < n && (data[i] != '|' || isBackslashEscaped(data, i)) && data[i] != '\n' {
+			i++
+		}
+
+		cellEnd := i
+
+		// skip the end-of-cell marker, possibly taking us past end of buffer
+		i++
+
+		for cellEnd > cellStart && cellEnd-1 < n && data[cellEnd-1] == ' ' {
+			cellEnd--
+		}
+
+		block := &ast.TableCell{
+			IsHeader: header,
+			Align:    columns[col],
+		}
+		block.Content = data[cellStart:cellEnd]
+		p.addBlock(block)
+	}
+
+	// pad it out with empty columns to get the right number
+	for ; col < len(columns); col++ {
+		block := &ast.TableCell{
+			IsHeader: header,
+			Align:    columns[col],
+		}
+		p.addBlock(block)
+	}
+
+	// silently ignore rows with too many cells
+}
+
+// tableFooter parses the (optional) table footer.
+func (p *Parser) tableFooter(data []byte) bool {
+	colCount := 1
+	for i := 0; i < len(data) && data[i] != '\n'; i++ {
+		if data[i] == '|' && !isBackslashEscaped(data, i) {
+			colCount++
+			continue
+		}
+		// remaining data must be the = character
+		if data[i] != '=' {
+			return false
+		}
+	}
+
+	// doesn't look like a table footer
+	if colCount == 1 {
+		return false
+	}
+
+	p.addBlock(&ast.TableFooter{})
+
+	return true
+}
+
+// returns blockquote prefix length
+func (p *Parser) quotePrefix(data []byte) int {
+	i := 0
+	n := len(data)
+	for i < 3 && i < n && data[i] == ' ' {
+		i++
+	}
+	if i < n && data[i] == '>' {
+		if i+1 < n && data[i+1] == ' ' {
+			return i + 2
+		}
+		return i + 1
+	}
+	return 0
+}
+
+// blockquote ends with at least one blank line
+// followed by something without a blockquote prefix
+func (p *Parser) terminateBlockquote(data []byte, beg, end int) bool {
+	if p.isEmpty(data[beg:]) <= 0 {
+		return false
+	}
+	if end >= len(data) {
+		return true
+	}
+	return p.quotePrefix(data[end:]) == 0 && p.isEmpty(data[end:]) == 0
+}
+
+// parse a blockquote fragment
+func (p *Parser) quote(data []byte) int {
+	var raw bytes.Buffer
+	beg, end := 0, 0
+	for beg < len(data) {
+		end = beg
+		// Step over whole lines, collecting them. While doing that, check for
+		// fenced code and if one's found, incorporate it altogether,
+		// irregardless of any contents inside it
+		for end < len(data) && data[end] != '\n' {
+			if p.extensions&FencedCode != 0 {
+				if i := p.fencedCodeBlock(data[end:], false); i > 0 {
+					// -1 to compensate for the extra end++ after the loop:
+					end += i - 1
+					break
+				}
+			}
+			end++
+		}
+		end = skipCharN(data, end, '\n', 1)
+		if pre := p.quotePrefix(data[beg:]); pre > 0 {
+			// skip the prefix
+			beg += pre
+		} else if p.terminateBlockquote(data, beg, end) {
+			break
+		}
+		// this line is part of the blockquote
+		raw.Write(data[beg:end])
+		beg = end
+	}
+
+	if p.extensions&Mmark == 0 {
+		block := p.addBlock(&ast.BlockQuote{})
+		p.block(raw.Bytes())
+		p.finalize(block)
+		return end
+	}
+
+	if captionContent, id, consumed := p.caption(data[end:], []byte("Quote: ")); consumed > 0 {
+		figure := &ast.CaptionFigure{}
+		caption := &ast.Caption{}
+		figure.HeadingID = id
+		p.Inline(caption, captionContent)
+
+		p.addBlock(figure) // this discard any attributes
+		block := &ast.BlockQuote{}
+		block.AsContainer().Attribute = figure.AsContainer().Attribute
+		p.addChild(block)
+		p.block(raw.Bytes())
+		p.finalize(block)
+
+		p.addChild(caption)
+		p.finalize(figure)
+
+		end += consumed
+
+		return end
+	}
+
+	block := p.addBlock(&ast.BlockQuote{})
+	p.block(raw.Bytes())
+	p.finalize(block)
+
+	return end
+}
+
+// returns prefix length for block code
+func (p *Parser) codePrefix(data []byte) int {
+	n := len(data)
+	if n >= 1 && data[0] == '\t' {
+		return 1
+	}
+	if n >= 4 && data[3] == ' ' && data[2] == ' ' && data[1] == ' ' && data[0] == ' ' {
+		return 4
+	}
+	return 0
+}
+
+func (p *Parser) code(data []byte) int {
+	var work bytes.Buffer
+
+	i := 0
+	for i < len(data) {
+		beg := i
+
+		i = skipUntilChar(data, i, '\n')
+		i = skipCharN(data, i, '\n', 1)
+
+		blankline := p.isEmpty(data[beg:i]) > 0
+		if pre := p.codePrefix(data[beg:i]); pre > 0 {
+			beg += pre
+		} else if !blankline {
+			// non-empty, non-prefixed line breaks the pre
+			i = beg
+			break
+		}
+
+		// verbatim copy to the working buffer
+		if blankline {
+			work.WriteByte('\n')
+		} else {
+			work.Write(data[beg:i])
+		}
+	}
+
+	// trim all the \n off the end of work
+	workbytes := work.Bytes()
+
+	eol := backChar(workbytes, len(workbytes), '\n')
+
+	if eol != len(workbytes) {
+		work.Truncate(eol)
+	}
+
+	work.WriteByte('\n')
+
+	codeBlock := &ast.CodeBlock{
+		IsFenced: false,
+	}
+	// TODO: get rid of temp buffer
+	codeBlock.Content = work.Bytes()
+	p.addBlock(codeBlock)
+	finalizeCodeBlock(codeBlock)
+
+	return i
+}
+
+// returns unordered list item prefix
+func (p *Parser) uliPrefix(data []byte) int {
+	// start with up to 3 spaces
+	i := skipCharN(data, 0, ' ', 3)
+
+	if i >= len(data)-1 {
+		return 0
+	}
+	// need one of {'*', '+', '-'} followed by a space or a tab
+	if (data[i] != '*' && data[i] != '+' && data[i] != '-') ||
+		(data[i+1] != ' ' && data[i+1] != '\t') {
+		return 0
+	}
+	return i + 2
+}
+
+// returns ordered list item prefix
+func (p *Parser) oliPrefix(data []byte) int {
+	// start with up to 3 spaces
+	i := skipCharN(data, 0, ' ', 3)
+
+	// count the digits
+	start := i
+	for i < len(data) && data[i] >= '0' && data[i] <= '9' {
+		i++
+	}
+	if start == i || i >= len(data)-1 {
+		return 0
+	}
+
+	// we need >= 1 digits followed by a dot and a space or a tab
+	if data[i] != '.' || !(data[i+1] == ' ' || data[i+1] == '\t') {
+		return 0
+	}
+	return i + 2
+}
+
+// returns definition list item prefix
+func (p *Parser) dliPrefix(data []byte) int {
+	if len(data) < 2 {
+		return 0
+	}
+	// need a ':' followed by a space or a tab
+	if data[0] != ':' || !(data[1] == ' ' || data[1] == '\t') {
+		return 0
+	}
+	i := skipChar(data, 0, ' ')
+	return i + 2
+}
+
+// parse ordered or unordered list block
+func (p *Parser) list(data []byte, flags ast.ListType, start int) int {
+	i := 0
+	flags |= ast.ListItemBeginningOfList
+	list := &ast.List{
+		ListFlags: flags,
+		Tight:     true,
+		Start:     start,
+	}
+	block := p.addBlock(list)
+
+	for i < len(data) {
+		skip := p.listItem(data[i:], &flags)
+		if flags&ast.ListItemContainsBlock != 0 {
+			list.Tight = false
+		}
+		i += skip
+		if skip == 0 || flags&ast.ListItemEndOfList != 0 {
+			break
+		}
+		flags &= ^ast.ListItemBeginningOfList
+	}
+
+	above := block.GetParent()
+	finalizeList(list)
+	p.tip = above
+	return i
+}
+
+// Returns true if the list item is not the same type as its parent list
+func (p *Parser) listTypeChanged(data []byte, flags *ast.ListType) bool {
+	if p.dliPrefix(data) > 0 && *flags&ast.ListTypeDefinition == 0 {
+		return true
+	} else if p.oliPrefix(data) > 0 && *flags&ast.ListTypeOrdered == 0 {
+		return true
+	} else if p.uliPrefix(data) > 0 && (*flags&ast.ListTypeOrdered != 0 || *flags&ast.ListTypeDefinition != 0) {
+		return true
+	}
+	return false
+}
+
+// Returns true if block ends with a blank line, descending if needed
+// into lists and sublists.
+func endsWithBlankLine(block ast.Node) bool {
+	// TODO: figure this out. Always false now.
+	for block != nil {
+		//if block.lastLineBlank {
+		//return true
+		//}
+		switch block.(type) {
+		case *ast.List, *ast.ListItem:
+			block = ast.GetLastChild(block)
+		default:
+			return false
+		}
+	}
+	return false
+}
+
+func finalizeList(list *ast.List) {
+	items := list.Parent.GetChildren()
+	lastItemIdx := len(items) - 1
+	for i, item := range items {
+		isLastItem := i == lastItemIdx
+		// check for non-final list item ending with blank line:
+		if !isLastItem && endsWithBlankLine(item) {
+			list.Tight = false
+			break
+		}
+		// recurse into children of list item, to see if there are spaces
+		// between any of them:
+		subItems := item.GetParent().GetChildren()
+		lastSubItemIdx := len(subItems) - 1
+		for j, subItem := range subItems {
+			isLastSubItem := j == lastSubItemIdx
+			if (!isLastItem || !isLastSubItem) && endsWithBlankLine(subItem) {
+				list.Tight = false
+				break
+			}
+		}
+	}
+}
+
+// Parse a single list item.
+// Assumes initial prefix is already removed if this is a sublist.
+func (p *Parser) listItem(data []byte, flags *ast.ListType) int {
+	// keep track of the indentation of the first line
+	itemIndent := 0
+	if data[0] == '\t' {
+		itemIndent += 4
+	} else {
+		for itemIndent < 3 && data[itemIndent] == ' ' {
+			itemIndent++
+		}
+	}
+
+	var bulletChar byte = '*'
+	i := p.uliPrefix(data)
+	if i == 0 {
+		i = p.oliPrefix(data)
+	} else {
+		bulletChar = data[i-2]
+	}
+	if i == 0 {
+		i = p.dliPrefix(data)
+		// reset definition term flag
+		if i > 0 {
+			*flags &= ^ast.ListTypeTerm
+		}
+	}
+	if i == 0 {
+		// if in definition list, set term flag and continue
+		if *flags&ast.ListTypeDefinition != 0 {
+			*flags |= ast.ListTypeTerm
+		} else {
+			return 0
+		}
+	}
+
+	// skip leading whitespace on first line
+	i = skipChar(data, i, ' ')
+
+	// find the end of the line
+	line := i
+	for i > 0 && i < len(data) && data[i-1] != '\n' {
+		i++
+	}
+
+	// get working buffer
+	var raw bytes.Buffer
+
+	// put the first line into the working buffer
+	raw.Write(data[line:i])
+	line = i
+
+	// process the following lines
+	containsBlankLine := false
+	sublist := 0
+
+gatherlines:
+	for line < len(data) {
+		i++
+
+		// find the end of this line
+		for i < len(data) && data[i-1] != '\n' {
+			i++
+		}
+
+		// if it is an empty line, guess that it is part of this item
+		// and move on to the next line
+		if p.isEmpty(data[line:i]) > 0 {
+			containsBlankLine = true
+			line = i
+			continue
+		}
+
+		// calculate the indentation
+		indent := 0
+		indentIndex := 0
+		if data[line] == '\t' {
+			indentIndex++
+			indent += 4
+		} else {
+			for indent < 4 && line+indent < i && data[line+indent] == ' ' {
+				indent++
+				indentIndex++
+			}
+		}
+
+		chunk := data[line+indentIndex : i]
+
+		// evaluate how this line fits in
+		switch {
+		// is this a nested list item?
+		case (p.uliPrefix(chunk) > 0 && !p.isHRule(chunk)) || p.oliPrefix(chunk) > 0 || p.dliPrefix(chunk) > 0:
+
+			// to be a nested list, it must be indented more
+			// if not, it is either a different kind of list
+			// or the next item in the same list
+			if indent <= itemIndent {
+				if p.listTypeChanged(chunk, flags) {
+					*flags |= ast.ListItemEndOfList
+				} else if containsBlankLine {
+					*flags |= ast.ListItemContainsBlock
+				}
+
+				break gatherlines
+			}
+
+			if containsBlankLine {
+				*flags |= ast.ListItemContainsBlock
+			}
+
+			// is this the first item in the nested list?
+			if sublist == 0 {
+				sublist = raw.Len()
+				// in the case of dliPrefix we are too late and need to search back for the definition item, which
+				// should be on the previous line, we then adjust sublist to start there.
+				if p.dliPrefix(chunk) > 0 {
+					sublist = backUntilChar(raw.Bytes(), raw.Len()-1, '\n')
+				}
+			}
+
+			// is this a nested prefix heading?
+		case p.isPrefixHeading(chunk), p.isPrefixSpecialHeading(chunk):
+			// if the heading is not indented, it is not nested in the list
+			// and thus ends the list
+			if containsBlankLine && indent < 4 {
+				*flags |= ast.ListItemEndOfList
+				break gatherlines
+			}
+			*flags |= ast.ListItemContainsBlock
+
+		// anything following an empty line is only part
+		// of this item if it is indented 4 spaces
+		// (regardless of the indentation of the beginning of the item)
+		case containsBlankLine && indent < 4:
+			if *flags&ast.ListTypeDefinition != 0 && i < len(data)-1 {
+				// is the next item still a part of this list?
+				next := i
+				for next < len(data) && data[next] != '\n' {
+					next++
+				}
+				for next < len(data)-1 && data[next] == '\n' {
+					next++
+				}
+				if i < len(data)-1 && data[i] != ':' && next < len(data)-1 && data[next] != ':' {
+					*flags |= ast.ListItemEndOfList
+				}
+			} else {
+				*flags |= ast.ListItemEndOfList
+			}
+			break gatherlines
+
+		// a blank line means this should be parsed as a block
+		case containsBlankLine:
+			raw.WriteByte('\n')
+			*flags |= ast.ListItemContainsBlock
+		}
+
+		// if this line was preceded by one or more blanks,
+		// re-introduce the blank into the buffer
+		if containsBlankLine {
+			containsBlankLine = false
+			raw.WriteByte('\n')
+		}
+
+		// add the line into the working buffer without prefix
+		raw.Write(data[line+indentIndex : i])
+
+		line = i
+	}
+
+	rawBytes := raw.Bytes()
+
+	listItem := &ast.ListItem{
+		ListFlags:  *flags,
+		Tight:      false,
+		BulletChar: bulletChar,
+		Delimiter:  '.', // Only '.' is possible in Markdown, but ')' will also be possible in CommonMark
+	}
+	p.addBlock(listItem)
+
+	// render the contents of the list item
+	if *flags&ast.ListItemContainsBlock != 0 && *flags&ast.ListTypeTerm == 0 {
+		// intermediate render of block item, except for definition term
+		if sublist > 0 {
+			p.block(rawBytes[:sublist])
+			p.block(rawBytes[sublist:])
+		} else {
+			p.block(rawBytes)
+		}
+	} else {
+		// intermediate render of inline item
+		para := &ast.Paragraph{}
+		if sublist > 0 {
+			para.Content = rawBytes[:sublist]
+		} else {
+			para.Content = rawBytes
+		}
+		p.addChild(para)
+		if sublist > 0 {
+			p.block(rawBytes[sublist:])
+		}
+	}
+	return line
+}
+
+// render a single paragraph that has already been parsed out
+func (p *Parser) renderParagraph(data []byte) {
+	if len(data) == 0 {
+		return
+	}
+
+	// trim leading spaces
+	beg := skipChar(data, 0, ' ')
+
+	end := len(data)
+	// trim trailing newline
+	if data[len(data)-1] == '\n' {
+		end--
+	}
+
+	// trim trailing spaces
+	for end > beg && data[end-1] == ' ' {
+		end--
+	}
+	para := &ast.Paragraph{}
+	para.Content = data[beg:end]
+	p.addBlock(para)
+}
+
+// blockMath handle block surround with $$
+func (p *Parser) blockMath(data []byte) int {
+	if len(data) <= 4 || data[0] != '$' || data[1] != '$' || data[2] == '$' {
+		return 0
+	}
+
+	// find next $$
+	var end int
+	for end = 2; end+1 < len(data) && (data[end] != '$' || data[end+1] != '$'); end++ {
+	}
+
+	// $$ not match
+	if end+1 == len(data) {
+		return 0
+	}
+
+	// render the display math
+	mathBlock := &ast.MathBlock{}
+	mathBlock.Literal = data[2:end]
+	p.addBlock(mathBlock)
+
+	return end + 2
+}
+
+func (p *Parser) paragraph(data []byte) int {
+	// prev: index of 1st char of previous line
+	// line: index of 1st char of current line
+	// i: index of cursor/end of current line
+	var prev, line, i int
+	tabSize := tabSizeDefault
+	if p.extensions&TabSizeEight != 0 {
+		tabSize = tabSizeDouble
+	}
+	// keep going until we find something to mark the end of the paragraph
+	for i < len(data) {
+		// mark the beginning of the current line
+		prev = line
+		current := data[i:]
+		line = i
+
+		// did we find a reference or a footnote? If so, end a paragraph
+		// preceding it and report that we have consumed up to the end of that
+		// reference:
+		if refEnd := isReference(p, current, tabSize); refEnd > 0 {
+			p.renderParagraph(data[:i])
+			return i + refEnd
+		}
+
+		// did we find a blank line marking the end of the paragraph?
+		if n := p.isEmpty(current); n > 0 {
+			// did this blank line followed by a definition list item?
+			if p.extensions&DefinitionLists != 0 {
+				if i < len(data)-1 && data[i+1] == ':' {
+					listLen := p.list(data[prev:], ast.ListTypeDefinition, 0)
+					return prev + listLen
+				}
+			}
+
+			p.renderParagraph(data[:i])
+			return i + n
+		}
+
+		// an underline under some text marks a heading, so our paragraph ended on prev line
+		if i > 0 {
+			if level := p.isUnderlinedHeading(current); level > 0 {
+				// render the paragraph
+				p.renderParagraph(data[:prev])
+
+				// ignore leading and trailing whitespace
+				eol := i - 1
+				for prev < eol && data[prev] == ' ' {
+					prev++
+				}
+				for eol > prev && data[eol-1] == ' ' {
+					eol--
+				}
+
+				id := ""
+				if p.extensions&AutoHeadingIDs != 0 {
+					id = sanitizeAnchorName(string(data[prev:eol]))
+				}
+
+				block := &ast.Heading{
+					Level:     level,
+					HeadingID: id,
+				}
+				block.Content = data[prev:eol]
+				p.addBlock(block)
+
+				// find the end of the underline
+				return skipUntilChar(data, i, '\n')
+			}
+		}
+
+		// if the next line starts a block of HTML, then the paragraph ends here
+		if p.extensions&LaxHTMLBlocks != 0 {
+			if data[i] == '<' && p.html(current, false) > 0 {
+				// rewind to before the HTML block
+				p.renderParagraph(data[:i])
+				return i
+			}
+		}
+
+		// if there's a prefixed heading or a horizontal rule after this, paragraph is over
+		if p.isPrefixHeading(current) || p.isPrefixSpecialHeading(current) || p.isHRule(current) {
+			p.renderParagraph(data[:i])
+			return i
+		}
+
+		// if there's a fenced code block, paragraph is over
+		if p.extensions&FencedCode != 0 {
+			if p.fencedCodeBlock(current, false) > 0 {
+				p.renderParagraph(data[:i])
+				return i
+			}
+		}
+
+		// if there's a figure block, paragraph is over
+		if p.extensions&Mmark != 0 {
+			if p.figureBlock(current, false) > 0 {
+				p.renderParagraph(data[:i])
+				return i
+			}
+		}
+
+		// if there's a definition list item, prev line is a definition term
+		if p.extensions&DefinitionLists != 0 {
+			if p.dliPrefix(current) != 0 {
+				ret := p.list(data[prev:], ast.ListTypeDefinition, 0)
+				return ret + prev
+			}
+		}
+
+		// if there's a list after this, paragraph is over
+		if p.extensions&NoEmptyLineBeforeBlock != 0 {
+			if p.uliPrefix(current) != 0 ||
+				p.oliPrefix(current) != 0 ||
+				p.quotePrefix(current) != 0 ||
+				p.codePrefix(current) != 0 {
+				p.renderParagraph(data[:i])
+				return i
+			}
+		}
+
+		// otherwise, scan to the beginning of the next line
+		nl := bytes.IndexByte(data[i:], '\n')
+		if nl >= 0 {
+			i += nl + 1
+		} else {
+			i += len(data[i:])
+		}
+	}
+
+	p.renderParagraph(data[:i])
+	return i
+}
+
+// skipChar advances i as long as data[i] == c
+func skipChar(data []byte, i int, c byte) int {
+	n := len(data)
+	for i < n && data[i] == c {
+		i++
+	}
+	return i
+}
+
+// like skipChar but only skips up to max characters
+func skipCharN(data []byte, i int, c byte, max int) int {
+	n := len(data)
+	for i < n && max > 0 && data[i] == c {
+		i++
+		max--
+	}
+	return i
+}
+
+// skipUntilChar advances i as long as data[i] != c
+func skipUntilChar(data []byte, i int, c byte) int {
+	n := len(data)
+	for i < n && data[i] != c {
+		i++
+	}
+	return i
+}
+
+func skipAlnum(data []byte, i int) int {
+	n := len(data)
+	for i < n && isAlnum(data[i]) {
+		i++
+	}
+	return i
+}
+
+func skipSpace(data []byte, i int) int {
+	n := len(data)
+	for i < n && isSpace(data[i]) {
+		i++
+	}
+	return i
+}
+
+func backChar(data []byte, i int, c byte) int {
+	for i > 0 && data[i-1] == c {
+		i--
+	}
+	return i
+}
+
+func backUntilChar(data []byte, i int, c byte) int {
+	for i > 0 && data[i-1] != c {
+		i--
+	}
+	return i
+}