// // Blackfriday Markdown Processor // Available at http://github.com/russross/blackfriday // // Copyright © 2011 Russ Ross <russ@russross.com>. // Distributed under the Simplified BSD License. // See README.md for details. // // // // HTML rendering backend // // package blackfriday import ( "bytes" "fmt" "io" "regexp" "strings" ) // HTMLFlags control optional behavior of HTML renderer. type HTMLFlags int // HTML renderer configuration options. const ( HTMLFlagsNone HTMLFlags = 0 SkipHTML HTMLFlags = 1 << iota // Skip preformatted HTML blocks SkipImages // Skip embedded images SkipLinks // Skip all links Safelink // Only link to trusted protocols NofollowLinks // Only link with rel="nofollow" NoreferrerLinks // Only link with rel="noreferrer" NoopenerLinks // Only link with rel="noopener" HrefTargetBlank // Add a blank target CompletePage // Generate a complete HTML page UseXHTML // Generate XHTML output instead of HTML FootnoteReturnLinks // Generate a link at the end of a footnote to return to the source Smartypants // Enable smart punctuation substitutions SmartypantsFractions // Enable smart fractions (with Smartypants) SmartypantsDashes // Enable smart dashes (with Smartypants) SmartypantsLatexDashes // Enable LaTeX-style dashes (with Smartypants) SmartypantsAngledQuotes // Enable angled double quotes (with Smartypants) for double quotes rendering SmartypantsQuotesNBSP // Enable « French guillemets » (with Smartypants) TOC // Generate a table of contents ) var ( htmlTagRe = regexp.MustCompile("(?i)^" + htmlTag) ) const ( htmlTag = "(?:" + openTag + "|" + closeTag + "|" + htmlComment + "|" + processingInstruction + "|" + declaration + "|" + cdata + ")" closeTag = "</" + tagName + "\\s*[>]" openTag = "<" + tagName + attribute + "*" + "\\s*/?>" attribute = "(?:" + "\\s+" + attributeName + attributeValueSpec + "?)" attributeValue = "(?:" + unquotedValue + "|" + singleQuotedValue + "|" + doubleQuotedValue + ")" attributeValueSpec = "(?:" + "\\s*=" + "\\s*" + attributeValue + ")" attributeName = "[a-zA-Z_:][a-zA-Z0-9:._-]*" cdata = "<!\\[CDATA\\[[\\s\\S]*?\\]\\]>" declaration = "<![A-Z]+" + "\\s+[^>]*>" doubleQuotedValue = "\"[^\"]*\"" htmlComment = "<!---->|<!--(?:-?[^>-])(?:-?[^-])*-->" processingInstruction = "[<][?].*?[?][>]" singleQuotedValue = "'[^']*'" tagName = "[A-Za-z][A-Za-z0-9-]*" unquotedValue = "[^\"'=<>`\\x00-\\x20]+" ) // HTMLRendererParameters is a collection of supplementary parameters tweaking // the behavior of various parts of HTML renderer. type HTMLRendererParameters struct { // Prepend this text to each relative URL. AbsolutePrefix string // Add this text to each footnote anchor, to ensure uniqueness. FootnoteAnchorPrefix string // Show this text inside the <a> tag for a footnote return link, if the // HTML_FOOTNOTE_RETURN_LINKS flag is enabled. If blank, the string // <sup>[return]</sup> is used. FootnoteReturnLinkContents string // If set, add this text to the front of each Heading ID, to ensure // uniqueness. HeadingIDPrefix string // If set, add this text to the back of each Heading ID, to ensure uniqueness. HeadingIDSuffix string // Increase heading levels: if the offset is 1, <h1> becomes <h2> etc. // Negative offset is also valid. // Resulting levels are clipped between 1 and 6. HeadingLevelOffset int Title string // Document title (used if CompletePage is set) CSS string // Optional CSS file URL (used if CompletePage is set) Icon string // Optional icon file URL (used if CompletePage is set) Flags HTMLFlags // Flags allow customizing this renderer's behavior } // HTMLRenderer is a type that implements the Renderer interface for HTML output. // // Do not create this directly, instead use the NewHTMLRenderer function. type HTMLRenderer struct { HTMLRendererParameters closeTag string // how to end singleton tags: either " />" or ">" // Track heading IDs to prevent ID collision in a single generation. headingIDs map[string]int lastOutputLen int disableTags int sr *SPRenderer } const ( xhtmlClose = " />" htmlClose = ">" ) // NewHTMLRenderer creates and configures an HTMLRenderer object, which // satisfies the Renderer interface. func NewHTMLRenderer(params HTMLRendererParameters) *HTMLRenderer { // configure the rendering engine closeTag := htmlClose if params.Flags&UseXHTML != 0 { closeTag = xhtmlClose } if params.FootnoteReturnLinkContents == "" { // U+FE0E is VARIATION SELECTOR-15. // It suppresses automatic emoji presentation of the preceding // U+21A9 LEFTWARDS ARROW WITH HOOK on iOS and iPadOS. params.FootnoteReturnLinkContents = "<span aria-label='Return'>↩\ufe0e</span>" } return &HTMLRenderer{ HTMLRendererParameters: params, closeTag: closeTag, headingIDs: make(map[string]int), sr: NewSmartypantsRenderer(params.Flags), } } func isHTMLTag(tag []byte, tagname string) bool { found, _ := findHTMLTagPos(tag, tagname) return found } // Look for a character, but ignore it when it's in any kind of quotes, it // might be JavaScript func skipUntilCharIgnoreQuotes(html []byte, start int, char byte) int { inSingleQuote := false inDoubleQuote := false inGraveQuote := false i := start for i < len(html) { switch { case html[i] == char && !inSingleQuote && !inDoubleQuote && !inGraveQuote: return i case html[i] == '\'': inSingleQuote = !inSingleQuote case html[i] == '"': inDoubleQuote = !inDoubleQuote case html[i] == '`': inGraveQuote = !inGraveQuote } i++ } return start } func findHTMLTagPos(tag []byte, tagname string) (bool, int) { i := 0 if i < len(tag) && tag[0] != '<' { return false, -1 } i++ i = skipSpace(tag, i) if i < len(tag) && tag[i] == '/' { i++ } i = skipSpace(tag, i) j := 0 for ; i < len(tag); i, j = i+1, j+1 { if j >= len(tagname) { break } if strings.ToLower(string(tag[i]))[0] != tagname[j] { return false, -1 } } if i == len(tag) { return false, -1 } rightAngle := skipUntilCharIgnoreQuotes(tag, i, '>') if rightAngle >= i { return true, rightAngle } return false, -1 } func skipSpace(tag []byte, i int) int { for i < len(tag) && isspace(tag[i]) { i++ } return i } func isRelativeLink(link []byte) (yes bool) { // a tag begin with '#' if link[0] == '#' { return true } // link begin with '/' but not '//', the second maybe a protocol relative link if len(link) >= 2 && link[0] == '/' && link[1] != '/' { return true } // only the root '/' if len(link) == 1 && link[0] == '/' { return true } // current directory : begin with "./" if bytes.HasPrefix(link, []byte("./")) { return true } // parent directory : begin with "../" if bytes.HasPrefix(link, []byte("../")) { return true } return false } func (r *HTMLRenderer) ensureUniqueHeadingID(id string) string { for count, found := r.headingIDs[id]; found; count, found = r.headingIDs[id] { tmp := fmt.Sprintf("%s-%d", id, count+1) if _, tmpFound := r.headingIDs[tmp]; !tmpFound { r.headingIDs[id] = count + 1 id = tmp } else { id = id + "-1" } } if _, found := r.headingIDs[id]; !found { r.headingIDs[id] = 0 } return id } func (r *HTMLRenderer) addAbsPrefix(link []byte) []byte { if r.AbsolutePrefix != "" && isRelativeLink(link) && link[0] != '.' { newDest := r.AbsolutePrefix if link[0] != '/' { newDest += "/" } newDest += string(link) return []byte(newDest) } return link } func appendLinkAttrs(attrs []string, flags HTMLFlags, link []byte) []string { if isRelativeLink(link) { return attrs } val := []string{} if flags&NofollowLinks != 0 { val = append(val, "nofollow") } if flags&NoreferrerLinks != 0 { val = append(val, "noreferrer") } if flags&NoopenerLinks != 0 { val = append(val, "noopener") } if flags&HrefTargetBlank != 0 { attrs = append(attrs, "target=\"_blank\"") } if len(val) == 0 { return attrs } attr := fmt.Sprintf("rel=%q", strings.Join(val, " ")) return append(attrs, attr) } func isMailto(link []byte) bool { return bytes.HasPrefix(link, []byte("mailto:")) } func needSkipLink(flags HTMLFlags, dest []byte) bool { if flags&SkipLinks != 0 { return true } return flags&Safelink != 0 && !isSafeLink(dest) && !isMailto(dest) } func isSmartypantable(node *Node) bool { pt := node.Parent.Type return pt != Link && pt != CodeBlock && pt != Code } func appendLanguageAttr(attrs []string, info []byte) []string { if len(info) == 0 { return attrs } endOfLang := bytes.IndexAny(info, "\t ") if endOfLang < 0 { endOfLang = len(info) } return append(attrs, fmt.Sprintf("class=\"language-%s\"", info[:endOfLang])) } func (r *HTMLRenderer) tag(w io.Writer, name []byte, attrs []string) { w.Write(name) if len(attrs) > 0 { w.Write(spaceBytes) w.Write([]byte(strings.Join(attrs, " "))) } w.Write(gtBytes) r.lastOutputLen = 1 } func footnoteRef(prefix string, node *Node) []byte { urlFrag := prefix + string(slugify(node.Destination)) anchor := fmt.Sprintf(`<a href="#fn:%s">%d</a>`, urlFrag, node.NoteID) return []byte(fmt.Sprintf(`<sup class="footnote-ref" id="fnref:%s">%s</sup>`, urlFrag, anchor)) } func footnoteItem(prefix string, slug []byte) []byte { return []byte(fmt.Sprintf(`<li id="fn:%s%s">`, prefix, slug)) } func footnoteReturnLink(prefix, returnLink string, slug []byte) []byte { const format = ` <a class="footnote-return" href="#fnref:%s%s">%s</a>` return []byte(fmt.Sprintf(format, prefix, slug, returnLink)) } func itemOpenCR(node *Node) bool { if node.Prev == nil { return false } ld := node.Parent.ListData return !ld.Tight && ld.ListFlags&ListTypeDefinition == 0 } func skipParagraphTags(node *Node) bool { grandparent := node.Parent.Parent if grandparent == nil || grandparent.Type != List { return false } tightOrTerm := grandparent.Tight || node.Parent.ListFlags&ListTypeTerm != 0 return grandparent.Type == List && tightOrTerm } func cellAlignment(align CellAlignFlags) string { switch align { case TableAlignmentLeft: return "left" case TableAlignmentRight: return "right" case TableAlignmentCenter: return "center" default: return "" } } func (r *HTMLRenderer) out(w io.Writer, text []byte) { if r.disableTags > 0 { w.Write(htmlTagRe.ReplaceAll(text, []byte{})) } else { w.Write(text) } r.lastOutputLen = len(text) } func (r *HTMLRenderer) cr(w io.Writer) { if r.lastOutputLen > 0 { r.out(w, nlBytes) } } var ( nlBytes = []byte{'\n'} gtBytes = []byte{'>'} spaceBytes = []byte{' '} ) var ( brTag = []byte("<br>") brXHTMLTag = []byte("<br />") emTag = []byte("<em>") emCloseTag = []byte("</em>") strongTag = []byte("<strong>") strongCloseTag = []byte("</strong>") delTag = []byte("<del>") delCloseTag = []byte("</del>") ttTag = []byte("<tt>") ttCloseTag = []byte("</tt>") aTag = []byte("<a") aCloseTag = []byte("</a>") preTag = []byte("<pre>") preCloseTag = []byte("</pre>") codeTag = []byte("<code>") codeCloseTag = []byte("</code>") pTag = []byte("<p>") pCloseTag = []byte("</p>") blockquoteTag = []byte("<blockquote>") blockquoteCloseTag = []byte("</blockquote>") hrTag = []byte("<hr>") hrXHTMLTag = []byte("<hr />") ulTag = []byte("<ul>") ulCloseTag = []byte("</ul>") olTag = []byte("<ol>") olCloseTag = []byte("</ol>") dlTag = []byte("<dl>") dlCloseTag = []byte("</dl>") liTag = []byte("<li>") liCloseTag = []byte("</li>") ddTag = []byte("<dd>") ddCloseTag = []byte("</dd>") dtTag = []byte("<dt>") dtCloseTag = []byte("</dt>") tableTag = []byte("<table>") tableCloseTag = []byte("</table>") tdTag = []byte("<td") tdCloseTag = []byte("</td>") thTag = []byte("<th") thCloseTag = []byte("</th>") theadTag = []byte("<thead>") theadCloseTag = []byte("</thead>") tbodyTag = []byte("<tbody>") tbodyCloseTag = []byte("</tbody>") trTag = []byte("<tr>") trCloseTag = []byte("</tr>") h1Tag = []byte("<h1") h1CloseTag = []byte("</h1>") h2Tag = []byte("<h2") h2CloseTag = []byte("</h2>") h3Tag = []byte("<h3") h3CloseTag = []byte("</h3>") h4Tag = []byte("<h4") h4CloseTag = []byte("</h4>") h5Tag = []byte("<h5") h5CloseTag = []byte("</h5>") h6Tag = []byte("<h6") h6CloseTag = []byte("</h6>") footnotesDivBytes = []byte("\n<div class=\"footnotes\">\n\n") footnotesCloseDivBytes = []byte("\n</div>\n") ) func headingTagsFromLevel(level int) ([]byte, []byte) { if level <= 1 { return h1Tag, h1CloseTag } switch level { case 2: return h2Tag, h2CloseTag case 3: return h3Tag, h3CloseTag case 4: return h4Tag, h4CloseTag case 5: return h5Tag, h5CloseTag } return h6Tag, h6CloseTag } func (r *HTMLRenderer) outHRTag(w io.Writer) { if r.Flags&UseXHTML == 0 { r.out(w, hrTag) } else { r.out(w, hrXHTMLTag) } } // RenderNode is a default renderer of a single node of a syntax tree. For // block nodes it will be called twice: first time with entering=true, second // time with entering=false, so that it could know when it's working on an open // tag and when on close. It writes the result to w. // // The return value is a way to tell the calling walker to adjust its walk // pattern: e.g. it can terminate the traversal by returning Terminate. Or it // can ask the walker to skip a subtree of this node by returning SkipChildren. // The typical behavior is to return GoToNext, which asks for the usual // traversal to the next node. func (r *HTMLRenderer) RenderNode(w io.Writer, node *Node, entering bool) WalkStatus { attrs := []string{} switch node.Type { case Text: if r.Flags&Smartypants != 0 { var tmp bytes.Buffer escapeHTML(&tmp, node.Literal) r.sr.Process(w, tmp.Bytes()) } else { if node.Parent.Type == Link { escLink(w, node.Literal) } else { escapeHTML(w, node.Literal) } } case Softbreak: r.cr(w) // TODO: make it configurable via out(renderer.softbreak) case Hardbreak: if r.Flags&UseXHTML == 0 { r.out(w, brTag) } else { r.out(w, brXHTMLTag) } r.cr(w) case Emph: if entering { r.out(w, emTag) } else { r.out(w, emCloseTag) } case Strong: if entering { r.out(w, strongTag) } else { r.out(w, strongCloseTag) } case Del: if entering { r.out(w, delTag) } else { r.out(w, delCloseTag) } case HTMLSpan: if r.Flags&SkipHTML != 0 { break } r.out(w, node.Literal) case Link: // mark it but don't link it if it is not a safe link: no smartypants dest := node.LinkData.Destination if needSkipLink(r.Flags, dest) { if entering { r.out(w, ttTag) } else { r.out(w, ttCloseTag) } } else { if entering { dest = r.addAbsPrefix(dest) var hrefBuf bytes.Buffer hrefBuf.WriteString("href=\"") escLink(&hrefBuf, dest) hrefBuf.WriteByte('"') attrs = append(attrs, hrefBuf.String()) if node.NoteID != 0 { r.out(w, footnoteRef(r.FootnoteAnchorPrefix, node)) break } attrs = appendLinkAttrs(attrs, r.Flags, dest) if len(node.LinkData.Title) > 0 { var titleBuff bytes.Buffer titleBuff.WriteString("title=\"") escapeHTML(&titleBuff, node.LinkData.Title) titleBuff.WriteByte('"') attrs = append(attrs, titleBuff.String()) } r.tag(w, aTag, attrs) } else { if node.NoteID != 0 { break } r.out(w, aCloseTag) } } case Image: if r.Flags&SkipImages != 0 { return SkipChildren } if entering { dest := node.LinkData.Destination dest = r.addAbsPrefix(dest) if r.disableTags == 0 { //if options.safe && potentiallyUnsafe(dest) { //out(w, `<img src="" alt="`) //} else { r.out(w, []byte(`<img src="`)) escLink(w, dest) r.out(w, []byte(`" alt="`)) //} } r.disableTags++ } else { r.disableTags-- if r.disableTags == 0 { if node.LinkData.Title != nil { r.out(w, []byte(`" title="`)) escapeHTML(w, node.LinkData.Title) } r.out(w, []byte(`" />`)) } } case Code: r.out(w, codeTag) escapeAllHTML(w, node.Literal) r.out(w, codeCloseTag) case Document: break case Paragraph: if skipParagraphTags(node) { break } if entering { // TODO: untangle this clusterfuck about when the newlines need // to be added and when not. if node.Prev != nil { switch node.Prev.Type { case HTMLBlock, List, Paragraph, Heading, CodeBlock, BlockQuote, HorizontalRule: r.cr(w) } } if node.Parent.Type == BlockQuote && node.Prev == nil { r.cr(w) } r.out(w, pTag) } else { r.out(w, pCloseTag) if !(node.Parent.Type == Item && node.Next == nil) { r.cr(w) } } case BlockQuote: if entering { r.cr(w) r.out(w, blockquoteTag) } else { r.out(w, blockquoteCloseTag) r.cr(w) } case HTMLBlock: if r.Flags&SkipHTML != 0 { break } r.cr(w) r.out(w, node.Literal) r.cr(w) case Heading: headingLevel := r.HTMLRendererParameters.HeadingLevelOffset + node.Level openTag, closeTag := headingTagsFromLevel(headingLevel) if entering { if node.IsTitleblock { attrs = append(attrs, `class="title"`) } if node.HeadingID != "" { id := r.ensureUniqueHeadingID(node.HeadingID) if r.HeadingIDPrefix != "" { id = r.HeadingIDPrefix + id } if r.HeadingIDSuffix != "" { id = id + r.HeadingIDSuffix } attrs = append(attrs, fmt.Sprintf(`id="%s"`, id)) } r.cr(w) r.tag(w, openTag, attrs) } else { r.out(w, closeTag) if !(node.Parent.Type == Item && node.Next == nil) { r.cr(w) } } case HorizontalRule: r.cr(w) r.outHRTag(w) r.cr(w) case List: openTag := ulTag closeTag := ulCloseTag if node.ListFlags&ListTypeOrdered != 0 { openTag = olTag closeTag = olCloseTag } if node.ListFlags&ListTypeDefinition != 0 { openTag = dlTag closeTag = dlCloseTag } if entering { if node.IsFootnotesList { r.out(w, footnotesDivBytes) r.outHRTag(w) r.cr(w) } r.cr(w) if node.Parent.Type == Item && node.Parent.Parent.Tight { r.cr(w) } r.tag(w, openTag[:len(openTag)-1], attrs) r.cr(w) } else { r.out(w, closeTag) //cr(w) //if node.parent.Type != Item { // cr(w) //} if node.Parent.Type == Item && node.Next != nil { r.cr(w) } if node.Parent.Type == Document || node.Parent.Type == BlockQuote { r.cr(w) } if node.IsFootnotesList { r.out(w, footnotesCloseDivBytes) } } case Item: openTag := liTag closeTag := liCloseTag if node.ListFlags&ListTypeDefinition != 0 { openTag = ddTag closeTag = ddCloseTag } if node.ListFlags&ListTypeTerm != 0 { openTag = dtTag closeTag = dtCloseTag } if entering { if itemOpenCR(node) { r.cr(w) } if node.ListData.RefLink != nil { slug := slugify(node.ListData.RefLink) r.out(w, footnoteItem(r.FootnoteAnchorPrefix, slug)) break } r.out(w, openTag) } else { if node.ListData.RefLink != nil { slug := slugify(node.ListData.RefLink) if r.Flags&FootnoteReturnLinks != 0 { r.out(w, footnoteReturnLink(r.FootnoteAnchorPrefix, r.FootnoteReturnLinkContents, slug)) } } r.out(w, closeTag) r.cr(w) } case CodeBlock: attrs = appendLanguageAttr(attrs, node.Info) r.cr(w) r.out(w, preTag) r.tag(w, codeTag[:len(codeTag)-1], attrs) escapeAllHTML(w, node.Literal) r.out(w, codeCloseTag) r.out(w, preCloseTag) if node.Parent.Type != Item { r.cr(w) } case Table: if entering { r.cr(w) r.out(w, tableTag) } else { r.out(w, tableCloseTag) r.cr(w) } case TableCell: openTag := tdTag closeTag := tdCloseTag if node.IsHeader { openTag = thTag closeTag = thCloseTag } if entering { align := cellAlignment(node.Align) if align != "" { attrs = append(attrs, fmt.Sprintf(`align="%s"`, align)) } if node.Prev == nil { r.cr(w) } r.tag(w, openTag, attrs) } else { r.out(w, closeTag) r.cr(w) } case TableHead: if entering { r.cr(w) r.out(w, theadTag) } else { r.out(w, theadCloseTag) r.cr(w) } case TableBody: if entering { r.cr(w) r.out(w, tbodyTag) // XXX: this is to adhere to a rather silly test. Should fix test. if node.FirstChild == nil { r.cr(w) } } else { r.out(w, tbodyCloseTag) r.cr(w) } case TableRow: if entering { r.cr(w) r.out(w, trTag) } else { r.out(w, trCloseTag) r.cr(w) } default: panic("Unknown node type " + node.Type.String()) } return GoToNext } // RenderHeader writes HTML document preamble and TOC if requested. func (r *HTMLRenderer) RenderHeader(w io.Writer, ast *Node) { r.writeDocumentHeader(w) if r.Flags&TOC != 0 { r.writeTOC(w, ast) } } // RenderFooter writes HTML document footer. func (r *HTMLRenderer) RenderFooter(w io.Writer, ast *Node) { if r.Flags&CompletePage == 0 { return } io.WriteString(w, "\n</body>\n</html>\n") } func (r *HTMLRenderer) writeDocumentHeader(w io.Writer) { if r.Flags&CompletePage == 0 { return } ending := "" if r.Flags&UseXHTML != 0 { io.WriteString(w, "<!DOCTYPE html PUBLIC \"-//W3C//DTD XHTML 1.0 Transitional//EN\" ") io.WriteString(w, "\"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd\">\n") io.WriteString(w, "<html xmlns=\"http://www.w3.org/1999/xhtml\">\n") ending = " /" } else { io.WriteString(w, "<!DOCTYPE html>\n") io.WriteString(w, "<html>\n") } io.WriteString(w, "<head>\n") io.WriteString(w, " <title>") if r.Flags&Smartypants != 0 { r.sr.Process(w, []byte(r.Title)) } else { escapeHTML(w, []byte(r.Title)) } io.WriteString(w, "</title>\n") io.WriteString(w, " <meta name=\"GENERATOR\" content=\"Blackfriday Markdown Processor v") io.WriteString(w, Version) io.WriteString(w, "\"") io.WriteString(w, ending) io.WriteString(w, ">\n") io.WriteString(w, " <meta charset=\"utf-8\"") io.WriteString(w, ending) io.WriteString(w, ">\n") if r.CSS != "" { io.WriteString(w, " <link rel=\"stylesheet\" type=\"text/css\" href=\"") escapeHTML(w, []byte(r.CSS)) io.WriteString(w, "\"") io.WriteString(w, ending) io.WriteString(w, ">\n") } if r.Icon != "" { io.WriteString(w, " <link rel=\"icon\" type=\"image/x-icon\" href=\"") escapeHTML(w, []byte(r.Icon)) io.WriteString(w, "\"") io.WriteString(w, ending) io.WriteString(w, ">\n") } io.WriteString(w, "</head>\n") io.WriteString(w, "<body>\n\n") } func (r *HTMLRenderer) writeTOC(w io.Writer, ast *Node) { buf := bytes.Buffer{} inHeading := false tocLevel := 0 headingCount := 0 ast.Walk(func(node *Node, entering bool) WalkStatus { if node.Type == Heading && !node.HeadingData.IsTitleblock { inHeading = entering if entering { node.HeadingID = fmt.Sprintf("toc_%d", headingCount) if node.Level == tocLevel { buf.WriteString("</li>\n\n<li>") } else if node.Level < tocLevel { for node.Level < tocLevel { tocLevel-- buf.WriteString("</li>\n</ul>") } buf.WriteString("</li>\n\n<li>") } else { for node.Level > tocLevel { tocLevel++ buf.WriteString("\n<ul>\n<li>") } } fmt.Fprintf(&buf, `<a href="#toc_%d">`, headingCount) headingCount++ } else { buf.WriteString("</a>") } return GoToNext } if inHeading { return r.RenderNode(&buf, node, entering) } return GoToNext }) for ; tocLevel > 0; tocLevel-- { buf.WriteString("</li>\n</ul>") } if buf.Len() > 0 { io.WriteString(w, "<nav>\n") w.Write(buf.Bytes()) io.WriteString(w, "\n\n</nav>\n") } r.lastOutputLen = buf.Len() }