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(`^(]+")?\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
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 ret + 1, 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 brace := 0 // look for link end: ' " ) findlinkend: for i < len(data) { switch { case data[i] == '\\': i += 2 case data[i] == '(': brace++ i++ case data[i] == ')': if brace <= 0 { break findlinkend } brace-- i++ case 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 titleEndCharFound := false findtitleend: for i < len(data) { switch { case data[i] == '\\': i++ case data[i] == data[titleB-1]: // matching title delimiter titleEndCharFound = true case titleEndCharFound && data[i] == ')': break findtitleend } 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 if len(lr.text) > 0 { altContent = lr.text } } // 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 & escaping or it will be converted to &amp; by another // escaper in the renderer if bytes.Equal(ent, []byte("&")) { return end, newTextNode([]byte{'&'}) } if len(ent) < 4 { return end, newTextNode(ent) } // if ent consists solely out of numbers (hex or decimal) convert that unicode codepoint to actual rune codepoint := uint64(0) var err error if ent[2] == 'x' || ent[2] == 'X' { // hexadecimal codepoint, err = strconv.ParseUint(string(ent[3:len(ent)-1]), 16, 64) } else { codepoint, err = strconv.ParseUint(string(ent[2:len(ent)-1]), 10, 64) } if err == nil { // only if conversion was valid return here. return end, newTextNode([]byte(string(codepoint))) } 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{Leaf: ast.Leaf{Literal: d}} } func normalizeURI(s []byte) []byte { return s // TODO: implement }