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//
// 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"
"strconv"
"strings"
)
const (
HTML_SKIP_HTML = 1 << iota
HTML_SKIP_STYLE
HTML_SKIP_IMAGES
HTML_SKIP_LINKS
HTML_SAFELINK
HTML_TOC
HTML_OMIT_CONTENTS
HTML_COMPLETE_PAGE
HTML_GITHUB_BLOCKCODE
HTML_USE_XHTML
HTML_USE_SMARTYPANTS
HTML_SMARTYPANTS_FRACTIONS
HTML_SMARTYPANTS_LATEX_DASHES
)
type Html struct {
flags int // HTML_* options
closeTag string // how to end singleton tags: either " />\n" or ">\n"
title string // document title
css string // optional css file url (used with HTML_COMPLETE_PAGE)
// table of contents data
tocMarker int
headerCount int
currentLevel int
toc *bytes.Buffer
smartypants *SmartypantsRenderer
}
const (
xhtmlClose = " />\n"
htmlClose = ">\n"
)
func HtmlRenderer(flags int, title string, css string) Renderer {
// configure the rendering engine
closeTag := htmlClose
if flags&HTML_USE_XHTML != 0 {
closeTag = xhtmlClose
}
return &Html{
flags: flags,
closeTag: closeTag,
title: title,
css: css,
headerCount: 0,
currentLevel: 0,
toc: new(bytes.Buffer),
smartypants: Smartypants(flags),
}
}
func attrEscape(out *bytes.Buffer, src []byte) {
org := 0
for i, ch := range src {
// using if statements is a bit faster than a switch statement.
// as the compiler improves, this should be unnecessary
// this is only worthwhile because attrEscape is the single
// largest CPU user in normal use
if ch == '"' {
if i > org {
// copy all the normal characters since the last escape
out.Write(src[org:i])
}
org = i + 1
out.WriteString("&quot;")
continue
}
if ch == '&' {
if i > org {
out.Write(src[org:i])
}
org = i + 1
out.WriteString("&amp;")
continue
}
if ch == '<' {
if i > org {
out.Write(src[org:i])
}
org = i + 1
out.WriteString("&lt;")
continue
}
if ch == '>' {
if i > org {
out.Write(src[org:i])
}
org = i + 1
out.WriteString("&gt;")
continue
}
}
if org < len(src) {
out.Write(src[org:])
}
}
func (options *Html) Header(out *bytes.Buffer, text func() bool, level int) {
marker := out.Len()
doubleSpace(out)
if options.flags&HTML_TOC != 0 {
// headerCount is incremented in htmlTocHeader
out.WriteString(fmt.Sprintf("<h%d id=\"toc_%d\">", level, options.headerCount))
} else {
out.WriteString(fmt.Sprintf("<h%d>", level))
}
tocMarker := out.Len()
if !text() {
out.Truncate(marker)
return
}
// are we building a table of contents?
if options.flags&HTML_TOC != 0 {
options.TocHeader(out.Bytes()[tocMarker:], level)
}
out.WriteString(fmt.Sprintf("</h%d>\n", level))
}
func (options *Html) BlockHtml(out *bytes.Buffer, text []byte) {
if options.flags&HTML_SKIP_HTML != 0 {
return
}
doubleSpace(out)
out.Write(text)
out.WriteByte('\n')
}
func (options *Html) HRule(out *bytes.Buffer) {
doubleSpace(out)
out.WriteString("<hr")
out.WriteString(options.closeTag)
}
func (options *Html) BlockCode(out *bytes.Buffer, text []byte, lang string) {
if options.flags&HTML_GITHUB_BLOCKCODE != 0 {
options.BlockCodeGithub(out, text, lang)
} else {
options.BlockCodeNormal(out, text, lang)
}
}
func (options *Html) BlockCodeNormal(out *bytes.Buffer, text []byte, lang string) {
doubleSpace(out)
// parse out the language names/classes
count := 0
for _, elt := range strings.Fields(lang) {
if elt[0] == '.' {
elt = elt[1:]
}
if len(elt) == 0 {
continue
}
if count == 0 {
out.WriteString("<pre><code class=\"")
} else {
out.WriteByte(' ')
}
attrEscape(out, []byte(elt))
count++
}
if count == 0 {
out.WriteString("<pre><code>")
} else {
out.WriteString("\">")
}
attrEscape(out, text)
out.WriteString("</code></pre>\n")
}
/*
* GitHub style code block:
*
* <pre lang="LANG"><code>
* ...
* </pre></code>
*
* Unlike other parsers, we store the language identifier in the <pre>,
* and don't let the user generate custom classes.
*
* The language identifier in the <pre> block gets postprocessed and all
* the code inside gets syntax highlighted with Pygments. This is much safer
* than letting the user specify a CSS class for highlighting.
*
* Note that we only generate HTML for the first specifier.
* E.g.
* ~~~~ {.python .numbered} => <pre lang="python"><code>
*/
func (options *Html) BlockCodeGithub(out *bytes.Buffer, text []byte, lang string) {
doubleSpace(out)
// parse out the language name
count := 0
for _, elt := range strings.Fields(lang) {
if elt[0] == '.' {
elt = elt[1:]
}
if len(elt) == 0 {
continue
}
out.WriteString("<pre lang=\"")
attrEscape(out, []byte(elt))
out.WriteString("\"><code>")
count++
break
}
if count == 0 {
out.WriteString("<pre><code>")
}
attrEscape(out, text)
out.WriteString("</code></pre>\n")
}
func (options *Html) BlockQuote(out *bytes.Buffer, text []byte) {
doubleSpace(out)
out.WriteString("<blockquote>\n")
out.Write(text)
out.WriteString("</blockquote>\n")
}
func (options *Html) Table(out *bytes.Buffer, header []byte, body []byte, columnData []int) {
doubleSpace(out)
out.WriteString("<table>\n<thead>\n")
out.Write(header)
out.WriteString("\n</thead>\n<tbody>\n")
out.Write(body)
out.WriteString("\n</tbody>\n</table>\n")
}
func (options *Html) TableRow(out *bytes.Buffer, text []byte) {
doubleSpace(out)
out.WriteString("<tr>\n")
out.Write(text)
out.WriteString("\n</tr>")
}
func (options *Html) TableCell(out *bytes.Buffer, text []byte, align int) {
doubleSpace(out)
switch align {
case TABLE_ALIGNMENT_LEFT:
out.WriteString("<td align=\"left\">")
case TABLE_ALIGNMENT_RIGHT:
out.WriteString("<td align=\"right\">")
case TABLE_ALIGNMENT_CENTER:
out.WriteString("<td align=\"center\">")
default:
out.WriteString("<td>")
}
out.Write(text)
out.WriteString("</td>")
}
func (options *Html) List(out *bytes.Buffer, text func() bool, flags int) {
marker := out.Len()
doubleSpace(out)
if flags&LIST_TYPE_ORDERED != 0 {
out.WriteString("<ol>")
} else {
out.WriteString("<ul>")
}
if !text() {
out.Truncate(marker)
return
}
if flags&LIST_TYPE_ORDERED != 0 {
out.WriteString("</ol>\n")
} else {
out.WriteString("</ul>\n")
}
}
func (options *Html) ListItem(out *bytes.Buffer, text []byte, flags int) {
if flags&LIST_ITEM_CONTAINS_BLOCK != 0 || flags&LIST_ITEM_BEGINNING_OF_LIST != 0 {
doubleSpace(out)
}
out.WriteString("<li>")
out.Write(text)
out.WriteString("</li>\n")
}
func (options *Html) Paragraph(out *bytes.Buffer, text func() bool) {
marker := out.Len()
doubleSpace(out)
out.WriteString("<p>")
if !text() {
out.Truncate(marker)
return
}
out.WriteString("</p>\n")
}
func (options *Html) AutoLink(out *bytes.Buffer, link []byte, kind int) {
if options.flags&HTML_SAFELINK != 0 && !isSafeLink(link) && kind != LINK_TYPE_EMAIL {
// mark it but don't link it if it is not a safe link: no smartypants
out.WriteString("<tt>")
attrEscape(out, link)
out.WriteString("</tt>")
return
}
out.WriteString("<a href=\"")
if kind == LINK_TYPE_EMAIL {
out.WriteString("mailto:")
}
attrEscape(out, link)
out.WriteString("\">")
// Pretty print: if we get an email address as
// an actual URI, e.g. `mailto:foo@bar.com`, we don't
// want to print the `mailto:` prefix
switch {
case bytes.HasPrefix(link, []byte("mailto://")):
attrEscape(out, link[len("mailto://"):])
case bytes.HasPrefix(link, []byte("mailto:")):
attrEscape(out, link[len("mailto:"):])
default:
attrEscape(out, link)
}
out.WriteString("</a>")
}
func (options *Html) CodeSpan(out *bytes.Buffer, text []byte) {
out.WriteString("<code>")
attrEscape(out, text)
out.WriteString("</code>")
}
func (options *Html) DoubleEmphasis(out *bytes.Buffer, text []byte) {
out.WriteString("<strong>")
out.Write(text)
out.WriteString("</strong>")
}
func (options *Html) Emphasis(out *bytes.Buffer, text []byte) {
if len(text) == 0 {
return
}
out.WriteString("<em>")
out.Write(text)
out.WriteString("</em>")
}
func (options *Html) Image(out *bytes.Buffer, link []byte, title []byte, alt []byte) {
if options.flags&HTML_SKIP_IMAGES != 0 {
return
}
out.WriteString("<img src=\"")
attrEscape(out, link)
out.WriteString("\" alt=\"")
if len(alt) > 0 {
attrEscape(out, alt)
}
if len(title) > 0 {
out.WriteString("\" title=\"")
attrEscape(out, title)
}
out.WriteByte('"')
out.WriteString(options.closeTag)
return
}
func (options *Html) LineBreak(out *bytes.Buffer) {
out.WriteString("<br")
out.WriteString(options.closeTag)
}
func (options *Html) Link(out *bytes.Buffer, link []byte, title []byte, content []byte) {
if options.flags&HTML_SKIP_LINKS != 0 {
// write the link text out but don't link it, just mark it with typewriter font
out.WriteString("<tt>")
attrEscape(out, content)
out.WriteString("</tt>")
return
}
if options.flags&HTML_SAFELINK != 0 && !isSafeLink(link) {
// write the link text out but don't link it, just mark it with typewriter font
out.WriteString("<tt>")
attrEscape(out, content)
out.WriteString("</tt>")
return
}
out.WriteString("<a href=\"")
attrEscape(out, link)
if len(title) > 0 {
out.WriteString("\" title=\"")
attrEscape(out, title)
}
out.WriteString("\">")
out.Write(content)
out.WriteString("</a>")
return
}
func (options *Html) RawHtmlTag(out *bytes.Buffer, text []byte) {
if options.flags&HTML_SKIP_HTML != 0 {
return
}
if options.flags&HTML_SKIP_STYLE != 0 && isHtmlTag(text, "style") {
return
}
if options.flags&HTML_SKIP_LINKS != 0 && isHtmlTag(text, "a") {
return
}
if options.flags&HTML_SKIP_IMAGES != 0 && isHtmlTag(text, "img") {
return
}
out.Write(text)
}
func (options *Html) TripleEmphasis(out *bytes.Buffer, text []byte) {
out.WriteString("<strong><em>")
out.Write(text)
out.WriteString("</em></strong>")
}
func (options *Html) StrikeThrough(out *bytes.Buffer, text []byte) {
out.WriteString("<del>")
out.Write(text)
out.WriteString("</del>")
}
func (options *Html) Entity(out *bytes.Buffer, entity []byte) {
out.Write(entity)
}
func (options *Html) NormalText(out *bytes.Buffer, text []byte) {
if options.flags&HTML_USE_SMARTYPANTS != 0 {
options.Smartypants(out, text)
} else {
attrEscape(out, text)
}
}
func (options *Html) Smartypants(out *bytes.Buffer, text []byte) {
smrt := smartypantsData{false, false}
// first do normal entity escaping
var escaped bytes.Buffer
attrEscape(&escaped, text)
text = escaped.Bytes()
mark := 0
for i := 0; i < len(text); i++ {
if action := options.smartypants[text[i]]; action != nil {
if i > mark {
out.Write(text[mark:i])
}
previousChar := byte(0)
if i > 0 {
previousChar = text[i-1]
}
i += action(out, &smrt, previousChar, text[i:])
mark = i + 1
}
}
if mark < len(text) {
out.Write(text[mark:])
}
}
func (options *Html) DocumentHeader(out *bytes.Buffer) {
if options.flags&HTML_COMPLETE_PAGE == 0 {
return
}
ending := ""
if options.flags&HTML_USE_XHTML != 0 {
out.WriteString("<!DOCTYPE html PUBLIC \"-//W3C//DTD XHTML 1.0 Transitional//EN\" ")
out.WriteString("\"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd\">\n")
out.WriteString("<html xmlns=\"http://www.w3.org/1999/xhtml\">\n")
ending = " /"
} else {
out.WriteString("<!DOCTYPE html PUBLIC \"-//W3C//DTD HTML 4.01//EN\" ")
out.WriteString("\"http://www.w3.org/TR/html4/strict.dtd\">\n")
out.WriteString("<html>\n")
}
out.WriteString("<head>\n")
out.WriteString(" <title>")
options.NormalText(out, []byte(options.title))
out.WriteString("</title>\n")
out.WriteString(" <meta name=\"GENERATOR\" content=\"Blackfriday Markdown Processor v")
out.WriteString(VERSION)
out.WriteString("\"")
out.WriteString(ending)
out.WriteString(">\n")
out.WriteString(" <meta http-equiv=\"Content-Type\" content=\"text/html; charset=utf-8\"")
out.WriteString(ending)
out.WriteString(">\n")
if options.css != "" {
out.WriteString(" <link rel=\"stylesheet\" type=\"text/css\" href=\"")
attrEscape(out, []byte(options.css))
out.WriteString("\"")
out.WriteString(ending)
out.WriteString(">\n")
}
out.WriteString("</head>\n")
out.WriteString("<body>\n")
options.tocMarker = out.Len()
}
func (options *Html) DocumentFooter(out *bytes.Buffer) {
// finalize and insert the table of contents
if options.flags&HTML_TOC != 0 {
options.TocFinalize()
// now we have to insert the table of contents into the document
var temp bytes.Buffer
// start by making a copy of everything after the document header
temp.Write(out.Bytes()[options.tocMarker:])
// now clear the copied material from the main output buffer
out.Truncate(options.tocMarker)
// corner case spacing issue
if options.flags&HTML_COMPLETE_PAGE != 0 {
out.WriteByte('\n')
}
// insert the table of contents
out.Write(options.toc.Bytes())
// corner case spacing issue
if options.flags&HTML_COMPLETE_PAGE == 0 && options.flags&HTML_OMIT_CONTENTS == 0 {
out.WriteByte('\n')
}
// write out everything that came after it
if options.flags&HTML_OMIT_CONTENTS == 0 {
out.Write(temp.Bytes())
}
}
if options.flags&HTML_COMPLETE_PAGE != 0 {
out.WriteString("\n</body>\n")
out.WriteString("</html>\n")
}
}
func (options *Html) TocHeader(text []byte, level int) {
for level > options.currentLevel {
switch {
case bytes.HasSuffix(options.toc.Bytes(), []byte("</li>\n")):
// this sublist can nest underneath a header
size := options.toc.Len()
options.toc.Truncate(size - len("</li>\n"))
case options.currentLevel > 0:
options.toc.WriteString("<li>")
}
if options.toc.Len() > 0 {
options.toc.WriteByte('\n')
}
options.toc.WriteString("<ul>\n")
options.currentLevel++
}
for level < options.currentLevel {
options.toc.WriteString("</ul>")
if options.currentLevel > 1 {
options.toc.WriteString("</li>\n")
}
options.currentLevel--
}
options.toc.WriteString("<li><a href=\"#toc_")
options.toc.WriteString(strconv.Itoa(options.headerCount))
options.toc.WriteString("\">")
options.headerCount++
options.toc.Write(text)
options.toc.WriteString("</a></li>\n")
}
func (options *Html) TocFinalize() {
for options.currentLevel > 1 {
options.toc.WriteString("</ul></li>\n")
options.currentLevel--
}
if options.currentLevel > 0 {
options.toc.WriteString("</ul>\n")
}
}
func isHtmlTag(tag []byte, tagname string) bool {
i := 0
if i < len(tag) && tag[0] != '<' {
return false
}
i++
for i < len(tag) && isspace(tag[i]) {
i++
}
if i < len(tag) && tag[i] == '/' {
i++
}
for i < len(tag) && isspace(tag[i]) {
i++
}
j := i
for ; i < len(tag); i, j = i+1, j+1 {
if j >= len(tagname) {
break
}
if tag[i] != tagname[j] {
return false
}
}
if i == len(tag) {
return false
}
return isspace(tag[i]) || tag[i] == '>'
}
func doubleSpace(out *bytes.Buffer) {
if out.Len() > 0 {
out.WriteByte('\n')
}
}
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