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

1 files changed, 1284 insertions, 0 deletions

diff --git a/vendor/github.com/gomarkdown/markdown/parser/inline.go b/vendor/github.com/gomarkdown/markdown/parser/inline.go
new file mode 100644
index 00000000..81766b85
--- /dev/null
+++ b/vendor/github.com/gomarkdown/markdown/parser/inline.go
@@ -0,0 +1,1284 @@
+package parser
+
+import (
+	"bytes"
+	"regexp"
+	"strconv"
+
+	"github.com/gomarkdown/markdown/ast"
+)
+
+// Parsing of inline elements
+
+var (
+	urlRe    = `((https?|ftp):\/\/|\/)[-A-Za-z0-9+&@#\/%?=~_|!:,.;\(\)]+`
+	anchorRe = regexp.MustCompile(`^(<a\shref="` + urlRe + `"(\stitle="[^"<>]+")?\s?>` + urlRe + `<\/a>)`)
+
+	// TODO: improve this regexp to catch all possible entities:
+	htmlEntityRe = regexp.MustCompile(`&[a-z]{2,5};`)
+)
+
+// Inline parses text within a block.
+// Each function returns the number of consumed chars.
+func (p *Parser) Inline(currBlock ast.Node, data []byte) {
+	// handlers might call us recursively: enforce a maximum depth
+	if p.nesting >= p.maxNesting || len(data) == 0 {
+		return
+	}
+	p.nesting++
+	beg, end := 0, 0
+
+	n := len(data)
+	for end < n {
+		handler := p.inlineCallback[data[end]]
+		if handler == nil {
+			end++
+			continue
+		}
+		consumed, node := handler(p, data, end)
+		if consumed == 0 {
+			// no action from the callback
+			end++
+			continue
+		}
+		// copy inactive chars into the output
+		ast.AppendChild(currBlock, newTextNode(data[beg:end]))
+		if node != nil {
+			ast.AppendChild(currBlock, node)
+		}
+		beg = end + consumed
+		end = beg
+	}
+
+	if beg < n {
+		if data[end-1] == '\n' {
+			end--
+		}
+		ast.AppendChild(currBlock, newTextNode(data[beg:end]))
+	}
+	p.nesting--
+}
+
+// single and double emphasis parsing
+func emphasis(p *Parser, data []byte, offset int) (int, ast.Node) {
+	data = data[offset:]
+	c := data[0]
+
+	n := len(data)
+	if n > 2 && data[1] != c {
+		// whitespace cannot follow an opening emphasis;
+		// strikethrough only takes two characters '~~'
+		if isSpace(data[1]) {
+			return 0, nil
+		}
+		if p.extensions&SuperSubscript != 0 && c == '~' {
+			// potential subscript, no spaces, except when escaped, helperEmphasis does
+			// not check that for us, so walk the bytes and check.
+			ret := skipUntilChar(data[1:], 0, c)
+			if ret == 0 {
+				return 0, nil
+			}
+			ret++ // we started with data[1:] above.
+			for i := 1; i < ret; i++ {
+				if isSpace(data[i]) && !isEscape(data, i) {
+					return 0, nil
+				}
+			}
+			sub := &ast.Subscript{}
+			sub.Literal = data[1:ret]
+			return ret + 1, sub
+		}
+		ret, node := helperEmphasis(p, data[1:], c)
+		if ret == 0 {
+			return 0, nil
+		}
+
+		return ret + 1, node
+	}
+
+	if n > 3 && data[1] == c && data[2] != c {
+		if isSpace(data[2]) {
+			return 0, nil
+		}
+		ret, node := helperDoubleEmphasis(p, data[2:], c)
+		if ret == 0 {
+			return 0, nil
+		}
+
+		return ret + 2, node
+	}
+
+	if n > 4 && data[1] == c && data[2] == c && data[3] != c {
+		if c == '~' || isSpace(data[3]) {
+			return 0, nil
+		}
+		ret, node := helperTripleEmphasis(p, data, 3, c)
+		if ret == 0 {
+			return 0, nil
+		}
+
+		return ret + 3, node
+	}
+
+	return 0, nil
+}
+
+func codeSpan(p *Parser, data []byte, offset int) (int, ast.Node) {
+	data = data[offset:]
+
+	// count the number of backticks in the delimiter
+	nb := skipChar(data, 0, '`')
+
+	// find the next delimiter
+	i, end := 0, 0
+	for end = nb; end < len(data) && i < nb; end++ {
+		if data[end] == '`' {
+			i++
+		} else {
+			i = 0
+		}
+	}
+
+	// no matching delimiter?
+	if i < nb && end >= len(data) {
+		return 0, nil
+	}
+
+	// trim outside whitespace
+	fBegin := nb
+	for fBegin < end && data[fBegin] == ' ' {
+		fBegin++
+	}
+
+	fEnd := end - nb
+	for fEnd > fBegin && data[fEnd-1] == ' ' {
+		fEnd--
+	}
+
+	// render the code span
+	if fBegin != fEnd {
+		code := &ast.Code{}
+		code.Literal = data[fBegin:fEnd]
+		return end, code
+	}
+
+	return end, nil
+}
+
+// newline preceded by two spaces becomes <br>
+func maybeLineBreak(p *Parser, data []byte, offset int) (int, ast.Node) {
+	origOffset := offset
+	offset = skipChar(data, offset, ' ')
+
+	if offset < len(data) && data[offset] == '\n' {
+		if offset-origOffset >= 2 {
+			return offset - origOffset + 1, &ast.Hardbreak{}
+		}
+		return offset - origOffset, nil
+	}
+	return 0, nil
+}
+
+// newline without two spaces works when HardLineBreak is enabled
+func lineBreak(p *Parser, data []byte, offset int) (int, ast.Node) {
+	if p.extensions&HardLineBreak != 0 {
+		return 1, &ast.Hardbreak{}
+	}
+	return 0, nil
+}
+
+type linkType int
+
+const (
+	linkNormal linkType = iota
+	linkImg
+	linkDeferredFootnote
+	linkInlineFootnote
+	linkCitation
+)
+
+func isReferenceStyleLink(data []byte, pos int, t linkType) bool {
+	if t == linkDeferredFootnote {
+		return false
+	}
+	return pos < len(data)-1 && data[pos] == '[' && data[pos+1] != '^'
+}
+
+func maybeImage(p *Parser, data []byte, offset int) (int, ast.Node) {
+	if offset < len(data)-1 && data[offset+1] == '[' {
+		return link(p, data, offset)
+	}
+	return 0, nil
+}
+
+func maybeInlineFootnoteOrSuper(p *Parser, data []byte, offset int) (int, ast.Node) {
+	if offset < len(data)-1 && data[offset+1] == '[' {
+		return link(p, data, offset)
+	}
+
+	if p.extensions&SuperSubscript != 0 {
+		ret := skipUntilChar(data[offset:], 1, '^')
+		if ret == 0 {
+			return 0, nil
+		}
+		for i := offset; i < offset+ret; i++ {
+			if isSpace(data[i]) && !isEscape(data, i) {
+				return 0, nil
+			}
+		}
+		sup := &ast.Superscript{}
+		sup.Literal = data[offset+1 : offset+ret]
+		return offset + ret, sup
+	}
+
+	return 0, nil
+}
+
+// '[': parse a link or an image or a footnote or a citation
+func link(p *Parser, data []byte, offset int) (int, ast.Node) {
+	// no links allowed inside regular links, footnote, and deferred footnotes
+	if p.insideLink && (offset > 0 && data[offset-1] == '[' || len(data)-1 > offset && data[offset+1] == '^') {
+		return 0, nil
+	}
+
+	var t linkType
+	switch {
+	// special case: ![^text] == deferred footnote (that follows something with
+	// an exclamation point)
+	case p.extensions&Footnotes != 0 && len(data)-1 > offset && data[offset+1] == '^':
+		t = linkDeferredFootnote
+	// ![alt] == image
+	case offset >= 0 && data[offset] == '!':
+		t = linkImg
+		offset++
+	// [@citation], [@-citation], [@?citation], [@!citation]
+	case p.extensions&Mmark != 0 && len(data)-1 > offset && data[offset+1] == '@':
+		t = linkCitation
+	// [text] == regular link
+	// ^[text] == inline footnote
+	// [^refId] == deferred footnote
+	case p.extensions&Footnotes != 0:
+		if offset >= 0 && data[offset] == '^' {
+			t = linkInlineFootnote
+			offset++
+		} else if len(data)-1 > offset && data[offset+1] == '^' {
+			t = linkDeferredFootnote
+		}
+	default:
+		t = linkNormal
+	}
+
+	data = data[offset:]
+
+	if t == linkCitation {
+		return citation(p, data, 0)
+	}
+
+	var (
+		i                               = 1
+		noteID                          int
+		title, link, linkID, altContent []byte
+		textHasNl                       = false
+	)
+
+	if t == linkDeferredFootnote {
+		i++
+	}
+
+	// look for the matching closing bracket
+	for level := 1; level > 0 && i < len(data); i++ {
+		switch {
+		case data[i] == '\n':
+			textHasNl = true
+
+		case data[i-1] == '\\':
+			continue
+
+		case data[i] == '[':
+			level++
+
+		case data[i] == ']':
+			level--
+			if level <= 0 {
+				i-- // compensate for extra i++ in for loop
+			}
+		}
+	}
+
+	if i >= len(data) {
+		return 0, nil
+	}
+
+	txtE := i
+	i++
+	var footnoteNode ast.Node
+
+	// skip any amount of whitespace or newline
+	// (this is much more lax than original markdown syntax)
+	i = skipSpace(data, i)
+
+	// inline style link
+	switch {
+	case i < len(data) && data[i] == '(':
+		// skip initial whitespace
+		i++
+
+		i = skipSpace(data, i)
+
+		linkB := i
+
+		// look for link end: ' " )
+	findlinkend:
+		for i < len(data) {
+			switch {
+			case data[i] == '\\':
+				i += 2
+
+			case data[i] == ')' || data[i] == '\'' || data[i] == '"':
+				break findlinkend
+
+			default:
+				i++
+			}
+		}
+
+		if i >= len(data) {
+			return 0, nil
+		}
+		linkE := i
+
+		// look for title end if present
+		titleB, titleE := 0, 0
+		if data[i] == '\'' || data[i] == '"' {
+			i++
+			titleB = i
+
+		findtitleend:
+			for i < len(data) {
+				switch {
+				case data[i] == '\\':
+					i += 2
+
+				case data[i] == ')':
+					break findtitleend
+
+				default:
+					i++
+				}
+			}
+
+			if i >= len(data) {
+				return 0, nil
+			}
+
+			// skip whitespace after title
+			titleE = i - 1
+			for titleE > titleB && isSpace(data[titleE]) {
+				titleE--
+			}
+
+			// check for closing quote presence
+			if data[titleE] != '\'' && data[titleE] != '"' {
+				titleB, titleE = 0, 0
+				linkE = i
+			}
+		}
+
+		// remove whitespace at the end of the link
+		for linkE > linkB && isSpace(data[linkE-1]) {
+			linkE--
+		}
+
+		// remove optional angle brackets around the link
+		if data[linkB] == '<' {
+			linkB++
+		}
+		if data[linkE-1] == '>' {
+			linkE--
+		}
+
+		// build escaped link and title
+		if linkE > linkB {
+			link = data[linkB:linkE]
+		}
+
+		if titleE > titleB {
+			title = data[titleB:titleE]
+		}
+
+		i++
+
+	// reference style link
+	case isReferenceStyleLink(data, i, t):
+		var id []byte
+		altContentConsidered := false
+
+		// look for the id
+		i++
+		linkB := i
+		i = skipUntilChar(data, i, ']')
+
+		if i >= len(data) {
+			return 0, nil
+		}
+		linkE := i
+
+		// find the reference
+		if linkB == linkE {
+			if textHasNl {
+				var b bytes.Buffer
+
+				for j := 1; j < txtE; j++ {
+					switch {
+					case data[j] != '\n':
+						b.WriteByte(data[j])
+					case data[j-1] != ' ':
+						b.WriteByte(' ')
+					}
+				}
+
+				id = b.Bytes()
+			} else {
+				id = data[1:txtE]
+				altContentConsidered = true
+			}
+		} else {
+			id = data[linkB:linkE]
+		}
+
+		// find the reference with matching id
+		lr, ok := p.getRef(string(id))
+		if !ok {
+			return 0, nil
+		}
+
+		// keep link and title from reference
+		linkID = id
+		link = lr.link
+		title = lr.title
+		if altContentConsidered {
+			altContent = lr.text
+		}
+		i++
+
+	// shortcut reference style link or reference or inline footnote
+	default:
+		var id []byte
+
+		// craft the id
+		if textHasNl {
+			var b bytes.Buffer
+
+			for j := 1; j < txtE; j++ {
+				switch {
+				case data[j] != '\n':
+					b.WriteByte(data[j])
+				case data[j-1] != ' ':
+					b.WriteByte(' ')
+				}
+			}
+
+			id = b.Bytes()
+		} else {
+			if t == linkDeferredFootnote {
+				id = data[2:txtE] // get rid of the ^
+			} else {
+				id = data[1:txtE]
+			}
+		}
+
+		footnoteNode = &ast.ListItem{}
+		if t == linkInlineFootnote {
+			// create a new reference
+			noteID = len(p.notes) + 1
+
+			var fragment []byte
+			if len(id) > 0 {
+				if len(id) < 16 {
+					fragment = make([]byte, len(id))
+				} else {
+					fragment = make([]byte, 16)
+				}
+				copy(fragment, slugify(id))
+			} else {
+				fragment = append([]byte("footnote-"), []byte(strconv.Itoa(noteID))...)
+			}
+
+			ref := &reference{
+				noteID:   noteID,
+				hasBlock: false,
+				link:     fragment,
+				title:    id,
+				footnote: footnoteNode,
+			}
+
+			p.notes = append(p.notes, ref)
+			p.refsRecord[string(ref.link)] = struct{}{}
+
+			link = ref.link
+			title = ref.title
+		} else {
+			// find the reference with matching id
+			lr, ok := p.getRef(string(id))
+			if !ok {
+				return 0, nil
+			}
+
+			if t == linkDeferredFootnote && !p.isFootnote(lr) {
+				lr.noteID = len(p.notes) + 1
+				lr.footnote = footnoteNode
+				p.notes = append(p.notes, lr)
+				p.refsRecord[string(lr.link)] = struct{}{}
+			}
+
+			// keep link and title from reference
+			link = lr.link
+			// if inline footnote, title == footnote contents
+			title = lr.title
+			noteID = lr.noteID
+		}
+
+		// rewind the whitespace
+		i = txtE + 1
+	}
+
+	var uLink []byte
+	if t == linkNormal || t == linkImg {
+		if len(link) > 0 {
+			var uLinkBuf bytes.Buffer
+			unescapeText(&uLinkBuf, link)
+			uLink = uLinkBuf.Bytes()
+		}
+
+		// links need something to click on and somewhere to go
+		if len(uLink) == 0 || (t == linkNormal && txtE <= 1) {
+			return 0, nil
+		}
+	}
+
+	// call the relevant rendering function
+	switch t {
+	case linkNormal:
+		link := &ast.Link{
+			Destination: normalizeURI(uLink),
+			Title:       title,
+			DeferredID:  linkID,
+		}
+		if len(altContent) > 0 {
+			ast.AppendChild(link, newTextNode(altContent))
+		} else {
+			// links cannot contain other links, so turn off link parsing
+			// temporarily and recurse
+			insideLink := p.insideLink
+			p.insideLink = true
+			p.Inline(link, data[1:txtE])
+			p.insideLink = insideLink
+		}
+		return i, link
+
+	case linkImg:
+		image := &ast.Image{
+			Destination: uLink,
+			Title:       title,
+		}
+		ast.AppendChild(image, newTextNode(data[1:txtE]))
+		return i + 1, image
+
+	case linkInlineFootnote, linkDeferredFootnote:
+		link := &ast.Link{
+			Destination: link,
+			Title:       title,
+			NoteID:      noteID,
+			Footnote:    footnoteNode,
+		}
+		if t == linkDeferredFootnote {
+			link.DeferredID = data[2:txtE]
+		}
+		if t == linkInlineFootnote {
+			i++
+		}
+		return i, link
+
+	default:
+		return 0, nil
+	}
+}
+
+func (p *Parser) inlineHTMLComment(data []byte) int {
+	if len(data) < 5 {
+		return 0
+	}
+	if data[0] != '<' || data[1] != '!' || data[2] != '-' || data[3] != '-' {
+		return 0
+	}
+	i := 5
+	// scan for an end-of-comment marker, across lines if necessary
+	for i < len(data) && !(data[i-2] == '-' && data[i-1] == '-' && data[i] == '>') {
+		i++
+	}
+	// no end-of-comment marker
+	if i >= len(data) {
+		return 0
+	}
+	return i + 1
+}
+
+func stripMailto(link []byte) []byte {
+	if bytes.HasPrefix(link, []byte("mailto://")) {
+		return link[9:]
+	} else if bytes.HasPrefix(link, []byte("mailto:")) {
+		return link[7:]
+	} else {
+		return link
+	}
+}
+
+// autolinkType specifies a kind of autolink that gets detected.
+type autolinkType int
+
+// These are the possible flag values for the autolink renderer.
+const (
+	notAutolink autolinkType = iota
+	normalAutolink
+	emailAutolink
+)
+
+// '<' when tags or autolinks are allowed
+func leftAngle(p *Parser, data []byte, offset int) (int, ast.Node) {
+	data = data[offset:]
+
+	if p.extensions&Mmark != 0 {
+		id, consumed := IsCallout(data)
+		if consumed > 0 {
+			node := &ast.Callout{}
+			node.ID = id
+			return consumed, node
+		}
+	}
+
+	altype, end := tagLength(data)
+	if size := p.inlineHTMLComment(data); size > 0 {
+		end = size
+	}
+	if end <= 2 {
+		return end, nil
+	}
+	if altype == notAutolink {
+		htmlTag := &ast.HTMLSpan{}
+		htmlTag.Literal = data[:end]
+		return end, htmlTag
+	}
+
+	var uLink bytes.Buffer
+	unescapeText(&uLink, data[1:end+1-2])
+	if uLink.Len() <= 0 {
+		return end, nil
+	}
+	link := uLink.Bytes()
+	node := &ast.Link{
+		Destination: link,
+	}
+	if altype == emailAutolink {
+		node.Destination = append([]byte("mailto:"), link...)
+	}
+	ast.AppendChild(node, newTextNode(stripMailto(link)))
+	return end, node
+}
+
+// '\\' backslash escape
+var escapeChars = []byte("\\`*_{}[]()#+-.!:|&<>~")
+
+func escape(p *Parser, data []byte, offset int) (int, ast.Node) {
+	data = data[offset:]
+
+	if len(data) <= 1 {
+		return 2, nil
+	}
+
+	if p.extensions&NonBlockingSpace != 0 && data[1] == ' ' {
+		return 2, &ast.NonBlockingSpace{}
+	}
+
+	if p.extensions&BackslashLineBreak != 0 && data[1] == '\n' {
+		return 2, &ast.Hardbreak{}
+	}
+
+	if bytes.IndexByte(escapeChars, data[1]) < 0 {
+		return 0, nil
+	}
+
+	return 2, newTextNode(data[1:2])
+}
+
+func unescapeText(ob *bytes.Buffer, src []byte) {
+	i := 0
+	for i < len(src) {
+		org := i
+		for i < len(src) && src[i] != '\\' {
+			i++
+		}
+
+		if i > org {
+			ob.Write(src[org:i])
+		}
+
+		if i+1 >= len(src) {
+			break
+		}
+
+		ob.WriteByte(src[i+1])
+		i += 2
+	}
+}
+
+// '&' escaped when it doesn't belong to an entity
+// valid entities are assumed to be anything matching &#?[A-Za-z0-9]+;
+func entity(p *Parser, data []byte, offset int) (int, ast.Node) {
+	data = data[offset:]
+
+	end := skipCharN(data, 1, '#', 1)
+	end = skipAlnum(data, end)
+
+	if end < len(data) && data[end] == ';' {
+		end++ // real entity
+	} else {
+		return 0, nil // lone '&'
+	}
+
+	ent := data[:end]
+	// undo &amp; escaping or it will be converted to &amp;amp; by another
+	// escaper in the renderer
+	if bytes.Equal(ent, []byte("&amp;")) {
+		ent = []byte{'&'}
+	}
+
+	return end, newTextNode(ent)
+}
+
+func linkEndsWithEntity(data []byte, linkEnd int) bool {
+	entityRanges := htmlEntityRe.FindAllIndex(data[:linkEnd], -1)
+	return entityRanges != nil && entityRanges[len(entityRanges)-1][1] == linkEnd
+}
+
+// hasPrefixCaseInsensitive is a custom implementation of
+//     strings.HasPrefix(strings.ToLower(s), prefix)
+// we rolled our own because ToLower pulls in a huge machinery of lowercasing
+// anything from Unicode and that's very slow. Since this func will only be
+// used on ASCII protocol prefixes, we can take shortcuts.
+func hasPrefixCaseInsensitive(s, prefix []byte) bool {
+	if len(s) < len(prefix) {
+		return false
+	}
+	delta := byte('a' - 'A')
+	for i, b := range prefix {
+		if b != s[i] && b != s[i]+delta {
+			return false
+		}
+	}
+	return true
+}
+
+var protocolPrefixes = [][]byte{
+	[]byte("http://"),
+	[]byte("https://"),
+	[]byte("ftp://"),
+	[]byte("file://"),
+	[]byte("mailto:"),
+}
+
+const shortestPrefix = 6 // len("ftp://"), the shortest of the above
+
+func maybeAutoLink(p *Parser, data []byte, offset int) (int, ast.Node) {
+	// quick check to rule out most false hits
+	if p.insideLink || len(data) < offset+shortestPrefix {
+		return 0, nil
+	}
+	for _, prefix := range protocolPrefixes {
+		endOfHead := offset + 8 // 8 is the len() of the longest prefix
+		if endOfHead > len(data) {
+			endOfHead = len(data)
+		}
+		if hasPrefixCaseInsensitive(data[offset:endOfHead], prefix) {
+			return autoLink(p, data, offset)
+		}
+	}
+	return 0, nil
+}
+
+func autoLink(p *Parser, data []byte, offset int) (int, ast.Node) {
+	// Now a more expensive check to see if we're not inside an anchor element
+	anchorStart := offset
+	offsetFromAnchor := 0
+	for anchorStart > 0 && data[anchorStart] != '<' {
+		anchorStart--
+		offsetFromAnchor++
+	}
+
+	anchorStr := anchorRe.Find(data[anchorStart:])
+	if anchorStr != nil {
+		anchorClose := &ast.HTMLSpan{}
+		anchorClose.Literal = anchorStr[offsetFromAnchor:]
+		return len(anchorStr) - offsetFromAnchor, anchorClose
+	}
+
+	// scan backward for a word boundary
+	rewind := 0
+	for offset-rewind > 0 && rewind <= 7 && isLetter(data[offset-rewind-1]) {
+		rewind++
+	}
+	if rewind > 6 { // longest supported protocol is "mailto" which has 6 letters
+		return 0, nil
+	}
+
+	origData := data
+	data = data[offset-rewind:]
+
+	if !isSafeLink(data) {
+		return 0, nil
+	}
+
+	linkEnd := 0
+	for linkEnd < len(data) && !isEndOfLink(data[linkEnd]) {
+		linkEnd++
+	}
+
+	// Skip punctuation at the end of the link
+	if (data[linkEnd-1] == '.' || data[linkEnd-1] == ',') && data[linkEnd-2] != '\\' {
+		linkEnd--
+	}
+
+	// But don't skip semicolon if it's a part of escaped entity:
+	if data[linkEnd-1] == ';' && data[linkEnd-2] != '\\' && !linkEndsWithEntity(data, linkEnd) {
+		linkEnd--
+	}
+
+	// See if the link finishes with a punctuation sign that can be closed.
+	var copen byte
+	switch data[linkEnd-1] {
+	case '"':
+		copen = '"'
+	case '\'':
+		copen = '\''
+	case ')':
+		copen = '('
+	case ']':
+		copen = '['
+	case '}':
+		copen = '{'
+	default:
+		copen = 0
+	}
+
+	if copen != 0 {
+		bufEnd := offset - rewind + linkEnd - 2
+
+		openDelim := 1
+
+		/* Try to close the final punctuation sign in this same line;
+		 * if we managed to close it outside of the URL, that means that it's
+		 * not part of the URL. If it closes inside the URL, that means it
+		 * is part of the URL.
+		 *
+		 * Examples:
+		 *
+		 *      foo http://www.pokemon.com/Pikachu_(Electric) bar
+		 *              => http://www.pokemon.com/Pikachu_(Electric)
+		 *
+		 *      foo (http://www.pokemon.com/Pikachu_(Electric)) bar
+		 *              => http://www.pokemon.com/Pikachu_(Electric)
+		 *
+		 *      foo http://www.pokemon.com/Pikachu_(Electric)) bar
+		 *              => http://www.pokemon.com/Pikachu_(Electric))
+		 *
+		 *      (foo http://www.pokemon.com/Pikachu_(Electric)) bar
+		 *              => foo http://www.pokemon.com/Pikachu_(Electric)
+		 */
+
+		for bufEnd >= 0 && origData[bufEnd] != '\n' && openDelim != 0 {
+			if origData[bufEnd] == data[linkEnd-1] {
+				openDelim++
+			}
+
+			if origData[bufEnd] == copen {
+				openDelim--
+			}
+
+			bufEnd--
+		}
+
+		if openDelim == 0 {
+			linkEnd--
+		}
+	}
+
+	var uLink bytes.Buffer
+	unescapeText(&uLink, data[:linkEnd])
+
+	if uLink.Len() > 0 {
+		node := &ast.Link{
+			Destination: uLink.Bytes(),
+		}
+		ast.AppendChild(node, newTextNode(uLink.Bytes()))
+		return linkEnd, node
+	}
+
+	return linkEnd, nil
+}
+
+func isEndOfLink(char byte) bool {
+	return isSpace(char) || char == '<'
+}
+
+var validUris = [][]byte{[]byte("http://"), []byte("https://"), []byte("ftp://"), []byte("mailto://")}
+var validPaths = [][]byte{[]byte("/"), []byte("./"), []byte("../")}
+
+func isSafeLink(link []byte) bool {
+	nLink := len(link)
+	for _, path := range validPaths {
+		nPath := len(path)
+		linkPrefix := link[:nPath]
+		if nLink >= nPath && bytes.Equal(linkPrefix, path) {
+			if nLink == nPath {
+				return true
+			} else if isAlnum(link[nPath]) {
+				return true
+			}
+		}
+	}
+
+	for _, prefix := range validUris {
+		// TODO: handle unicode here
+		// case-insensitive prefix test
+		nPrefix := len(prefix)
+		if nLink > nPrefix {
+			linkPrefix := bytes.ToLower(link[:nPrefix])
+			if bytes.Equal(linkPrefix, prefix) && isAlnum(link[nPrefix]) {
+				return true
+			}
+		}
+	}
+
+	return false
+}
+
+// return the length of the given tag, or 0 is it's not valid
+func tagLength(data []byte) (autolink autolinkType, end int) {
+	var i, j int
+
+	// a valid tag can't be shorter than 3 chars
+	if len(data) < 3 {
+		return notAutolink, 0
+	}
+
+	// begins with a '<' optionally followed by '/', followed by letter or number
+	if data[0] != '<' {
+		return notAutolink, 0
+	}
+	if data[1] == '/' {
+		i = 2
+	} else {
+		i = 1
+	}
+
+	if !isAlnum(data[i]) {
+		return notAutolink, 0
+	}
+
+	// scheme test
+	autolink = notAutolink
+
+	// try to find the beginning of an URI
+	for i < len(data) && (isAlnum(data[i]) || data[i] == '.' || data[i] == '+' || data[i] == '-') {
+		i++
+	}
+
+	if i > 1 && i < len(data) && data[i] == '@' {
+		if j = isMailtoAutoLink(data[i:]); j != 0 {
+			return emailAutolink, i + j
+		}
+	}
+
+	if i > 2 && i < len(data) && data[i] == ':' {
+		autolink = normalAutolink
+		i++
+	}
+
+	// complete autolink test: no whitespace or ' or "
+	switch {
+	case i >= len(data):
+		autolink = notAutolink
+	case autolink != notAutolink:
+		j = i
+
+		for i < len(data) {
+			if data[i] == '\\' {
+				i += 2
+			} else if data[i] == '>' || data[i] == '\'' || data[i] == '"' || isSpace(data[i]) {
+				break
+			} else {
+				i++
+			}
+
+		}
+
+		if i >= len(data) {
+			return autolink, 0
+		}
+		if i > j && data[i] == '>' {
+			return autolink, i + 1
+		}
+
+		// one of the forbidden chars has been found
+		autolink = notAutolink
+	}
+	i += bytes.IndexByte(data[i:], '>')
+	if i < 0 {
+		return autolink, 0
+	}
+	return autolink, i + 1
+}
+
+// look for the address part of a mail autolink and '>'
+// this is less strict than the original markdown e-mail address matching
+func isMailtoAutoLink(data []byte) int {
+	nb := 0
+
+	// address is assumed to be: [-@._a-zA-Z0-9]+ with exactly one '@'
+	for i, c := range data {
+		if isAlnum(c) {
+			continue
+		}
+
+		switch c {
+		case '@':
+			nb++
+
+		case '-', '.', '_':
+			break
+
+		case '>':
+			if nb == 1 {
+				return i + 1
+			}
+			return 0
+		default:
+			return 0
+		}
+	}
+
+	return 0
+}
+
+// look for the next emph char, skipping other constructs
+func helperFindEmphChar(data []byte, c byte) int {
+	i := 0
+
+	for i < len(data) {
+		for i < len(data) && data[i] != c && data[i] != '`' && data[i] != '[' {
+			i++
+		}
+		if i >= len(data) {
+			return 0
+		}
+		// do not count escaped chars
+		if i != 0 && data[i-1] == '\\' {
+			i++
+			continue
+		}
+		if data[i] == c {
+			return i
+		}
+
+		if data[i] == '`' {
+			// skip a code span
+			tmpI := 0
+			i++
+			for i < len(data) && data[i] != '`' {
+				if tmpI == 0 && data[i] == c {
+					tmpI = i
+				}
+				i++
+			}
+			if i >= len(data) {
+				return tmpI
+			}
+			i++
+		} else if data[i] == '[' {
+			// skip a link
+			tmpI := 0
+			i++
+			for i < len(data) && data[i] != ']' {
+				if tmpI == 0 && data[i] == c {
+					tmpI = i
+				}
+				i++
+			}
+			i++
+			for i < len(data) && (data[i] == ' ' || data[i] == '\n') {
+				i++
+			}
+			if i >= len(data) {
+				return tmpI
+			}
+			if data[i] != '[' && data[i] != '(' { // not a link
+				if tmpI > 0 {
+					return tmpI
+				}
+				continue
+			}
+			cc := data[i]
+			i++
+			for i < len(data) && data[i] != cc {
+				if tmpI == 0 && data[i] == c {
+					return i
+				}
+				i++
+			}
+			if i >= len(data) {
+				return tmpI
+			}
+			i++
+		}
+	}
+	return 0
+}
+
+func helperEmphasis(p *Parser, data []byte, c byte) (int, ast.Node) {
+	i := 0
+
+	// skip one symbol if coming from emph3
+	if len(data) > 1 && data[0] == c && data[1] == c {
+		i = 1
+	}
+
+	for i < len(data) {
+		length := helperFindEmphChar(data[i:], c)
+		if length == 0 {
+			return 0, nil
+		}
+		i += length
+		if i >= len(data) {
+			return 0, nil
+		}
+
+		if i+1 < len(data) && data[i+1] == c {
+			i++
+			continue
+		}
+
+		if data[i] == c && !isSpace(data[i-1]) {
+
+			if p.extensions&NoIntraEmphasis != 0 {
+				if !(i+1 == len(data) || isSpace(data[i+1]) || isPunctuation(data[i+1])) {
+					continue
+				}
+			}
+
+			emph := &ast.Emph{}
+			p.Inline(emph, data[:i])
+			return i + 1, emph
+		}
+	}
+
+	return 0, nil
+}
+
+func helperDoubleEmphasis(p *Parser, data []byte, c byte) (int, ast.Node) {
+	i := 0
+
+	for i < len(data) {
+		length := helperFindEmphChar(data[i:], c)
+		if length == 0 {
+			return 0, nil
+		}
+		i += length
+
+		if i+1 < len(data) && data[i] == c && data[i+1] == c && i > 0 && !isSpace(data[i-1]) {
+			var node ast.Node = &ast.Strong{}
+			if c == '~' {
+				node = &ast.Del{}
+			}
+			p.Inline(node, data[:i])
+			return i + 2, node
+		}
+		i++
+	}
+	return 0, nil
+}
+
+func helperTripleEmphasis(p *Parser, data []byte, offset int, c byte) (int, ast.Node) {
+	i := 0
+	origData := data
+	data = data[offset:]
+
+	for i < len(data) {
+		length := helperFindEmphChar(data[i:], c)
+		if length == 0 {
+			return 0, nil
+		}
+		i += length
+
+		// skip whitespace preceded symbols
+		if data[i] != c || isSpace(data[i-1]) {
+			continue
+		}
+
+		switch {
+		case i+2 < len(data) && data[i+1] == c && data[i+2] == c:
+			// triple symbol found
+			strong := &ast.Strong{}
+			em := &ast.Emph{}
+			ast.AppendChild(strong, em)
+			p.Inline(em, data[:i])
+			return i + 3, strong
+		case i+1 < len(data) && data[i+1] == c:
+			// double symbol found, hand over to emph1
+			length, node := helperEmphasis(p, origData[offset-2:], c)
+			if length == 0 {
+				return 0, nil
+			}
+			return length - 2, node
+		default:
+			// single symbol found, hand over to emph2
+			length, node := helperDoubleEmphasis(p, origData[offset-1:], c)
+			if length == 0 {
+				return 0, nil
+			}
+			return length - 1, node
+		}
+	}
+	return 0, nil
+}
+
+// math handle inline math wrapped with '$'
+func math(p *Parser, data []byte, offset int) (int, ast.Node) {
+	data = data[offset:]
+
+	// too short, or block math
+	if len(data) <= 2 || data[1] == '$' {
+		return 0, nil
+	}
+
+	// find next '$'
+	var end int
+	for end = 1; end < len(data) && data[end] != '$'; end++ {
+	}
+
+	// $ not match
+	if end == len(data) {
+		return 0, nil
+	}
+
+	// create inline math node
+	math := &ast.Math{}
+	math.Literal = data[1:end]
+	return end + 1, math
+}
+
+func newTextNode(d []byte) *ast.Text {
+	return &ast.Text{ast.Leaf{Literal: d}}
+}
+
+func normalizeURI(s []byte) []byte {
+	return s // TODO: implement
+}