blackfriday/markdown.go
Dmitri Shuralyov 8df342acd5 Fix bug where newlines were inserted inside fenced code blocks.
Change firstPass() code that checks for fenced code blocks to check all
of them and properly keep track of lastFencedCodeBlockEnd.
This way, it won't misinterpret the end of a fenced code block as a
beginning of a new one.
2014-04-11 21:27:28 -07:00

837 lines
21 KiB
Go

//
// 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.
//
//
//
// Markdown parsing and processing
//
//
// Blackfriday markdown processor.
//
// Translates plain text with simple formatting rules into HTML or LaTeX.
package blackfriday
import (
"bytes"
"unicode/utf8"
)
const VERSION = "1.1"
// These are the supported markdown parsing extensions.
// OR these values together to select multiple extensions.
const (
EXTENSION_NO_INTRA_EMPHASIS = 1 << iota // ignore emphasis markers inside words
EXTENSION_TABLES // render tables
EXTENSION_FENCED_CODE // render fenced code blocks
EXTENSION_AUTOLINK // detect embedded URLs that are not explicitly marked
EXTENSION_STRIKETHROUGH // strikethrough text using ~~test~~
EXTENSION_LAX_HTML_BLOCKS // loosen up HTML block parsing rules
EXTENSION_SPACE_HEADERS // be strict about prefix header rules
EXTENSION_HARD_LINE_BREAK // translate newlines into line breaks
EXTENSION_TAB_SIZE_EIGHT // expand tabs to eight spaces instead of four
EXTENSION_FOOTNOTES // Pandoc-style footnotes
EXTENSION_NO_EMPTY_LINE_BEFORE_BLOCK // No need to insert an empty line to start a (code, quote, order list, unorder list)block
EXTENSION_HEADER_IDS // specify header IDs with {#id}
)
// These are the possible flag values for the link renderer.
// Only a single one of these values will be used; they are not ORed together.
// These are mostly of interest if you are writing a new output format.
const (
LINK_TYPE_NOT_AUTOLINK = iota
LINK_TYPE_NORMAL
LINK_TYPE_EMAIL
)
// These are the possible flag values for the ListItem renderer.
// Multiple flag values may be ORed together.
// These are mostly of interest if you are writing a new output format.
const (
LIST_TYPE_ORDERED = 1 << iota
LIST_ITEM_CONTAINS_BLOCK
LIST_ITEM_BEGINNING_OF_LIST
LIST_ITEM_END_OF_LIST
)
// These are the possible flag values for the table cell renderer.
// Only a single one of these values will be used; they are not ORed together.
// These are mostly of interest if you are writing a new output format.
const (
TABLE_ALIGNMENT_LEFT = 1 << iota
TABLE_ALIGNMENT_RIGHT
TABLE_ALIGNMENT_CENTER = (TABLE_ALIGNMENT_LEFT | TABLE_ALIGNMENT_RIGHT)
)
// The size of a tab stop.
const (
TAB_SIZE_DEFAULT = 4
TAB_SIZE_EIGHT = 8
)
// These are the tags that are recognized as HTML block tags.
// Any of these can be included in markdown text without special escaping.
var blockTags = map[string]bool{
"p": true,
"dl": true,
"h1": true,
"h2": true,
"h3": true,
"h4": true,
"h5": true,
"h6": true,
"ol": true,
"ul": true,
"del": true,
"div": true,
"ins": true,
"pre": true,
"form": true,
"math": true,
"table": true,
"iframe": true,
"script": true,
"fieldset": true,
"noscript": true,
"blockquote": true,
// HTML5
"video": true,
"aside": true,
"canvas": true,
"figure": true,
"footer": true,
"header": true,
"hgroup": true,
"output": true,
"article": true,
"section": true,
"progress": true,
"figcaption": true,
}
// Renderer is the rendering interface.
// This is mostly of interest if you are implementing a new rendering format.
//
// When a byte slice is provided, it contains the (rendered) contents of the
// element.
//
// When a callback is provided instead, it will write the contents of the
// respective element directly to the output buffer and return true on success.
// If the callback returns false, the rendering function should reset the
// output buffer as though it had never been called.
//
// Currently Html and Latex implementations are provided
type Renderer interface {
// block-level callbacks
BlockCode(out *bytes.Buffer, text []byte, lang string)
BlockQuote(out *bytes.Buffer, text []byte)
BlockHtml(out *bytes.Buffer, text []byte)
Header(out *bytes.Buffer, text func() bool, level int, id string)
HRule(out *bytes.Buffer)
List(out *bytes.Buffer, text func() bool, flags int)
ListItem(out *bytes.Buffer, text []byte, flags int)
Paragraph(out *bytes.Buffer, text func() bool)
Table(out *bytes.Buffer, header []byte, body []byte, columnData []int)
TableRow(out *bytes.Buffer, text []byte)
TableHeaderCell(out *bytes.Buffer, text []byte, flags int)
TableCell(out *bytes.Buffer, text []byte, flags int)
Footnotes(out *bytes.Buffer, text func() bool)
FootnoteItem(out *bytes.Buffer, name, text []byte, flags int)
// Span-level callbacks
AutoLink(out *bytes.Buffer, link []byte, kind int)
CodeSpan(out *bytes.Buffer, text []byte)
DoubleEmphasis(out *bytes.Buffer, text []byte)
Emphasis(out *bytes.Buffer, text []byte)
Image(out *bytes.Buffer, link []byte, title []byte, alt []byte)
LineBreak(out *bytes.Buffer)
Link(out *bytes.Buffer, link []byte, title []byte, content []byte)
RawHtmlTag(out *bytes.Buffer, tag []byte)
TripleEmphasis(out *bytes.Buffer, text []byte)
StrikeThrough(out *bytes.Buffer, text []byte)
FootnoteRef(out *bytes.Buffer, ref []byte, id int)
// Low-level callbacks
Entity(out *bytes.Buffer, entity []byte)
NormalText(out *bytes.Buffer, text []byte)
// Header and footer
DocumentHeader(out *bytes.Buffer)
DocumentFooter(out *bytes.Buffer)
GetFlags() int
}
// Callback functions for inline parsing. One such function is defined
// for each character that triggers a response when parsing inline data.
type inlineParser func(p *parser, out *bytes.Buffer, data []byte, offset int) int
// Parser holds runtime state used by the parser.
// This is constructed by the Markdown function.
type parser struct {
r Renderer
refs map[string]*reference
inlineCallback [256]inlineParser
flags int
nesting int
maxNesting int
insideLink bool
// Footnotes need to be ordered as well as available to quickly check for
// presence. If a ref is also a footnote, it's stored both in refs and here
// in notes. Slice is nil if footnotes not enabled.
notes []*reference
}
//
//
// Public interface
//
//
// MarkdownBasic is a convenience function for simple rendering.
// It processes markdown input with no extensions enabled.
func MarkdownBasic(input []byte) []byte {
// set up the HTML renderer
htmlFlags := HTML_USE_XHTML
renderer := HtmlRenderer(htmlFlags, "", "")
// set up the parser
extensions := 0
return Markdown(input, renderer, extensions)
}
// Call Markdown with most useful extensions enabled
// MarkdownCommon is a convenience function for simple rendering.
// It processes markdown input with common extensions enabled, including:
//
// * Smartypants processing with smart fractions and LaTeX dashes
//
// * Intra-word emphasis suppression
//
// * Tables
//
// * Fenced code blocks
//
// * Autolinking
//
// * Strikethrough support
//
// * Strict header parsing
//
// * Custom Header IDs
func MarkdownCommon(input []byte) []byte {
// set up the HTML renderer
htmlFlags := 0
htmlFlags |= HTML_USE_XHTML
htmlFlags |= HTML_USE_SMARTYPANTS
htmlFlags |= HTML_SMARTYPANTS_FRACTIONS
htmlFlags |= HTML_SMARTYPANTS_LATEX_DASHES
htmlFlags |= HTML_SANITIZE_OUTPUT
renderer := HtmlRenderer(htmlFlags, "", "")
// set up the parser
extensions := 0
extensions |= EXTENSION_NO_INTRA_EMPHASIS
extensions |= EXTENSION_TABLES
extensions |= EXTENSION_FENCED_CODE
extensions |= EXTENSION_AUTOLINK
extensions |= EXTENSION_STRIKETHROUGH
extensions |= EXTENSION_SPACE_HEADERS
extensions |= EXTENSION_HEADER_IDS
return Markdown(input, renderer, extensions)
}
// Markdown is the main rendering function.
// It parses and renders a block of markdown-encoded text.
// The supplied Renderer is used to format the output, and extensions dictates
// which non-standard extensions are enabled.
//
// To use the supplied Html or LaTeX renderers, see HtmlRenderer and
// LatexRenderer, respectively.
func Markdown(input []byte, renderer Renderer, extensions int) []byte {
// no point in parsing if we can't render
if renderer == nil {
return nil
}
// fill in the render structure
p := new(parser)
p.r = renderer
p.flags = extensions
p.refs = make(map[string]*reference)
p.maxNesting = 16
p.insideLink = false
// register inline parsers
p.inlineCallback['*'] = emphasis
p.inlineCallback['_'] = emphasis
if extensions&EXTENSION_STRIKETHROUGH != 0 {
p.inlineCallback['~'] = emphasis
}
p.inlineCallback['`'] = codeSpan
p.inlineCallback['\n'] = lineBreak
p.inlineCallback['['] = link
p.inlineCallback['<'] = leftAngle
p.inlineCallback['\\'] = escape
p.inlineCallback['&'] = entity
if extensions&EXTENSION_AUTOLINK != 0 {
p.inlineCallback[':'] = autoLink
}
if extensions&EXTENSION_FOOTNOTES != 0 {
p.notes = make([]*reference, 0)
}
first := firstPass(p, input)
second := secondPass(p, first)
if renderer.GetFlags()&HTML_SANITIZE_OUTPUT != 0 {
second = sanitizeHtml(second)
}
return second
}
// first pass:
// - extract references
// - expand tabs
// - normalize newlines
// - copy everything else
// - add missing newlines before fenced code blocks
func firstPass(p *parser, input []byte) []byte {
var out bytes.Buffer
tabSize := TAB_SIZE_DEFAULT
if p.flags&EXTENSION_TAB_SIZE_EIGHT != 0 {
tabSize = TAB_SIZE_EIGHT
}
beg, end := 0, 0
lastLineWasBlank := false
lastFencedCodeBlockEnd := 0
for beg < len(input) { // iterate over lines
if end = isReference(p, input[beg:], tabSize); end > 0 {
beg += end
} else { // skip to the next line
end = beg
for end < len(input) && input[end] != '\n' && input[end] != '\r' {
end++
}
if p.flags&EXTENSION_FENCED_CODE != 0 {
// when last line was none blank and a fenced code block comes after
if beg >= lastFencedCodeBlockEnd {
if i := p.fencedCode(&out, append(input[beg:], '\n'), false); i > 0 {
if !lastLineWasBlank {
out.WriteByte('\n') // need to inject additional linebreak
}
lastFencedCodeBlockEnd = beg + i
}
}
lastLineWasBlank = end == beg
}
// add the line body if present
if end > beg {
expandTabs(&out, input[beg:end], tabSize)
}
out.WriteByte('\n')
if end < len(input) && input[end] == '\r' {
end++
}
if end < len(input) && input[end] == '\n' {
end++
}
beg = end
}
}
// empty input?
if out.Len() == 0 {
out.WriteByte('\n')
}
return out.Bytes()
}
// second pass: actual rendering
func secondPass(p *parser, input []byte) []byte {
var output bytes.Buffer
p.r.DocumentHeader(&output)
p.block(&output, input)
if p.flags&EXTENSION_FOOTNOTES != 0 && len(p.notes) > 0 {
p.r.Footnotes(&output, func() bool {
flags := LIST_ITEM_BEGINNING_OF_LIST
for _, ref := range p.notes {
var buf bytes.Buffer
if ref.hasBlock {
flags |= LIST_ITEM_CONTAINS_BLOCK
p.block(&buf, ref.title)
} else {
p.inline(&buf, ref.title)
}
p.r.FootnoteItem(&output, ref.link, buf.Bytes(), flags)
flags &^= LIST_ITEM_BEGINNING_OF_LIST | LIST_ITEM_CONTAINS_BLOCK
}
return true
})
}
p.r.DocumentFooter(&output)
if p.nesting != 0 {
panic("Nesting level did not end at zero")
}
return output.Bytes()
}
//
// Link references
//
// This section implements support for references that (usually) appear
// as footnotes in a document, and can be referenced anywhere in the document.
// The basic format is:
//
// [1]: http://www.google.com/ "Google"
// [2]: http://www.github.com/ "Github"
//
// Anywhere in the document, the reference can be linked by referring to its
// label, i.e., 1 and 2 in this example, as in:
//
// This library is hosted on [Github][2], a git hosting site.
//
// Actual footnotes as specified in Pandoc and supported by some other Markdown
// libraries such as php-markdown are also taken care of. They look like this:
//
// This sentence needs a bit of further explanation.[^note]
//
// [^note]: This is the explanation.
//
// Footnotes should be placed at the end of the document in an ordered list.
// Inline footnotes such as:
//
// Inline footnotes^[Not supported.] also exist.
//
// are not yet supported.
// References are parsed and stored in this struct.
type reference struct {
link []byte
title []byte
noteId int // 0 if not a footnote ref
hasBlock bool
}
// Check whether or not data starts with a reference link.
// If so, it is parsed and stored in the list of references
// (in the render struct).
// Returns the number of bytes to skip to move past it,
// or zero if the first line is not a reference.
func isReference(p *parser, data []byte, tabSize int) int {
// up to 3 optional leading spaces
if len(data) < 4 {
return 0
}
i := 0
for i < 3 && data[i] == ' ' {
i++
}
noteId := 0
// id part: anything but a newline between brackets
if data[i] != '[' {
return 0
}
i++
if p.flags&EXTENSION_FOOTNOTES != 0 {
if data[i] == '^' {
// we can set it to anything here because the proper noteIds will
// be assigned later during the second pass. It just has to be != 0
noteId = 1
i++
}
}
idOffset := i
for i < len(data) && data[i] != '\n' && data[i] != '\r' && data[i] != ']' {
i++
}
if i >= len(data) || data[i] != ']' {
return 0
}
idEnd := i
// spacer: colon (space | tab)* newline? (space | tab)*
i++
if i >= len(data) || data[i] != ':' {
return 0
}
i++
for i < len(data) && (data[i] == ' ' || data[i] == '\t') {
i++
}
if i < len(data) && (data[i] == '\n' || data[i] == '\r') {
i++
if i < len(data) && data[i] == '\n' && data[i-1] == '\r' {
i++
}
}
for i < len(data) && (data[i] == ' ' || data[i] == '\t') {
i++
}
if i >= len(data) {
return 0
}
var (
linkOffset, linkEnd int
titleOffset, titleEnd int
lineEnd int
raw []byte
hasBlock bool
)
if p.flags&EXTENSION_FOOTNOTES != 0 && noteId != 0 {
linkOffset, linkEnd, raw, hasBlock = scanFootnote(p, data, i, tabSize)
lineEnd = linkEnd
} else {
linkOffset, linkEnd, titleOffset, titleEnd, lineEnd = scanLinkRef(p, data, i)
}
if lineEnd == 0 {
return 0
}
// a valid ref has been found
ref := &reference{
noteId: noteId,
hasBlock: hasBlock,
}
if noteId > 0 {
// reusing the link field for the id since footnotes don't have links
ref.link = data[idOffset:idEnd]
// if footnote, it's not really a title, it's the contained text
ref.title = raw
} else {
ref.link = data[linkOffset:linkEnd]
ref.title = data[titleOffset:titleEnd]
}
// id matches are case-insensitive
id := string(bytes.ToLower(data[idOffset:idEnd]))
p.refs[id] = ref
return lineEnd
}
func scanLinkRef(p *parser, data []byte, i int) (linkOffset, linkEnd, titleOffset, titleEnd, lineEnd int) {
// link: whitespace-free sequence, optionally between angle brackets
if data[i] == '<' {
i++
}
linkOffset = i
for i < len(data) && data[i] != ' ' && data[i] != '\t' && data[i] != '\n' && data[i] != '\r' {
i++
}
linkEnd = i
if data[linkOffset] == '<' && data[linkEnd-1] == '>' {
linkOffset++
linkEnd--
}
// optional spacer: (space | tab)* (newline | '\'' | '"' | '(' )
for i < len(data) && (data[i] == ' ' || data[i] == '\t') {
i++
}
if i < len(data) && data[i] != '\n' && data[i] != '\r' && data[i] != '\'' && data[i] != '"' && data[i] != '(' {
return
}
// compute end-of-line
if i >= len(data) || data[i] == '\r' || data[i] == '\n' {
lineEnd = i
}
if i+1 < len(data) && data[i] == '\r' && data[i+1] == '\n' {
lineEnd++
}
// optional (space|tab)* spacer after a newline
if lineEnd > 0 {
i = lineEnd + 1
for i < len(data) && (data[i] == ' ' || data[i] == '\t') {
i++
}
}
// optional title: any non-newline sequence enclosed in '"() alone on its line
if i+1 < len(data) && (data[i] == '\'' || data[i] == '"' || data[i] == '(') {
i++
titleOffset = i
// look for EOL
for i < len(data) && data[i] != '\n' && data[i] != '\r' {
i++
}
if i+1 < len(data) && data[i] == '\n' && data[i+1] == '\r' {
titleEnd = i + 1
} else {
titleEnd = i
}
// step back
i--
for i > titleOffset && (data[i] == ' ' || data[i] == '\t') {
i--
}
if i > titleOffset && (data[i] == '\'' || data[i] == '"' || data[i] == ')') {
lineEnd = titleEnd
titleEnd = i
}
}
return
}
// The first bit of this logic is the same as (*parser).listItem, but the rest
// is much simpler. This function simply finds the entire block and shifts it
// over by one tab if it is indeed a block (just returns the line if it's not).
// blockEnd is the end of the section in the input buffer, and contents is the
// extracted text that was shifted over one tab. It will need to be rendered at
// the end of the document.
func scanFootnote(p *parser, data []byte, i, indentSize int) (blockStart, blockEnd int, contents []byte, hasBlock bool) {
if i == 0 || len(data) == 0 {
return
}
// skip leading whitespace on first line
for i < len(data) && data[i] == ' ' {
i++
}
blockStart = i
// find the end of the line
blockEnd = i
for 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[blockEnd:i])
blockEnd = i
// process the following lines
containsBlankLine := false
gatherLines:
for blockEnd < 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[blockEnd:i]) > 0 {
containsBlankLine = true
blockEnd = i
continue
}
n := 0
if n = isIndented(data[blockEnd:i], indentSize); n == 0 {
// this is the end of the block.
// we don't want to include this last line in the index.
break gatherLines
}
// if there were blank lines before this one, insert a new one now
if containsBlankLine {
raw.WriteByte('\n')
containsBlankLine = false
}
// get rid of that first tab, write to buffer
raw.Write(data[blockEnd+n : i])
hasBlock = true
blockEnd = i
}
if data[blockEnd-1] != '\n' {
raw.WriteByte('\n')
}
contents = raw.Bytes()
return
}
//
//
// Miscellaneous helper functions
//
//
// Test if a character is a punctuation symbol.
// Taken from a private function in regexp in the stdlib.
func ispunct(c byte) bool {
for _, r := range []byte("!\"#$%&'()*+,-./:;<=>?@[\\]^_`{|}~") {
if c == r {
return true
}
}
return false
}
// Test if a character is a whitespace character.
func isspace(c byte) bool {
return c == ' ' || c == '\t' || c == '\n' || c == '\r' || c == '\f' || c == '\v'
}
// Test if a character is letter.
func isletter(c byte) bool {
return (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z')
}
// Test if a character is a letter or a digit.
// TODO: check when this is looking for ASCII alnum and when it should use unicode
func isalnum(c byte) bool {
return (c >= '0' && c <= '9') || isletter(c)
}
// Replace tab characters with spaces, aligning to the next TAB_SIZE column.
// always ends output with a newline
func expandTabs(out *bytes.Buffer, line []byte, tabSize int) {
// first, check for common cases: no tabs, or only tabs at beginning of line
i, prefix := 0, 0
slowcase := false
for i = 0; i < len(line); i++ {
if line[i] == '\t' {
if prefix == i {
prefix++
} else {
slowcase = true
break
}
}
}
// no need to decode runes if all tabs are at the beginning of the line
if !slowcase {
for i = 0; i < prefix*tabSize; i++ {
out.WriteByte(' ')
}
out.Write(line[prefix:])
return
}
// the slow case: we need to count runes to figure out how
// many spaces to insert for each tab
column := 0
i = 0
for i < len(line) {
start := i
for i < len(line) && line[i] != '\t' {
_, size := utf8.DecodeRune(line[i:])
i += size
column++
}
if i > start {
out.Write(line[start:i])
}
if i >= len(line) {
break
}
for {
out.WriteByte(' ')
column++
if column%tabSize == 0 {
break
}
}
i++
}
}
// Find if a line counts as indented or not.
// Returns number of characters the indent is (0 = not indented).
func isIndented(data []byte, indentSize int) int {
if len(data) == 0 {
return 0
}
if data[0] == '\t' {
return 1
}
if len(data) < indentSize {
return 0
}
for i := 0; i < indentSize; i++ {
if data[i] != ' ' {
return 0
}
}
return indentSize
}
// Create a url-safe slug for fragments
func slugify(in []byte) []byte {
if len(in) == 0 {
return in
}
out := make([]byte, 0, len(in))
sym := false
for _, ch := range in {
if isalnum(ch) {
sym = false
out = append(out, ch)
} else if sym {
continue
} else {
out = append(out, '-')
sym = true
}
}
var a, b int
var ch byte
for a, ch = range out {
if ch != '-' {
break
}
}
for b = len(out) - 1; b > 0; b-- {
if out[b] != '-' {
break
}
}
return out[a : b+1]
}