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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.
//
//
// Functions to parse inline elements.
//
package blackfriday
import (
"bytes"
)
// Functions to parse text within a block
// Each function returns the number of chars taken care of
// data is the complete block being rendered
// offset is the number of valid chars before the current cursor
func (p *parser) inline(out *bytes.Buffer, data []byte) {
// this is called recursively: enforce a maximum depth
if p.nesting >= p.maxNesting {
return
}
p.nesting++
i, end := 0, 0
for i < len(data) {
// copy inactive chars into the output
for end < len(data) && p.inlineCallback[data[end]] == nil {
end++
}
p.r.NormalText(out, data[i:end])
if end >= len(data) {
break
}
i = end
// call the trigger
handler := p.inlineCallback[data[end]]
if consumed := handler(p, out, data, i); consumed == 0 {
// no action from the callback; buffer the byte for later
end = i + 1
} else {
// skip past whatever the callback used
i += consumed
end = i
}
}
p.nesting--
}
// single and double emphasis parsing
func emphasis(p *parser, out *bytes.Buffer, data []byte, offset int) int {
data = data[offset:]
c := data[0]
ret := 0
if len(data) > 2 && data[1] != c {
// whitespace cannot follow an opening emphasis;
// strikethrough only takes two characters '~~'
if c == '~' || isspace(data[1]) {
return 0
}
if ret = helperEmphasis(p, out, data[1:], c); ret == 0 {
return 0
}
return ret + 1
}
if len(data) > 3 && data[1] == c && data[2] != c {
if isspace(data[2]) {
return 0
}
if ret = helperDoubleEmphasis(p, out, data[2:], c); ret == 0 {
return 0
}
return ret + 2
}
if len(data) > 4 && data[1] == c && data[2] == c && data[3] != c {
if c == '~' || isspace(data[3]) {
return 0
}
if ret = helperTripleEmphasis(p, out, data, 3, c); ret == 0 {
return 0
}
return ret + 3
}
return 0
}
func codeSpan(p *parser, out *bytes.Buffer, data []byte, offset int) int {
data = data[offset:]
nb := 0
// count the number of backticks in the delimiter
for nb < len(data) && data[nb] == '`' {
nb++
}
// 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
}
// 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 {
p.r.CodeSpan(out, data[fBegin:fEnd])
}
return end
}
// newline preceded by two spaces becomes <br>
// newline without two spaces works when EXTENSION_HARD_LINE_BREAK is enabled
func lineBreak(p *parser, out *bytes.Buffer, data []byte, offset int) int {
// remove trailing spaces from out
outBytes := out.Bytes()
end := len(outBytes)
eol := end
for eol > 0 && outBytes[eol-1] == ' ' {
eol--
}
out.Truncate(eol)
// should there be a hard line break here?
if p.flags&EXTENSION_HARD_LINE_BREAK == 0 && end-eol < 2 {
return 0
}
p.r.LineBreak(out)
return 1
}
// '[': parse a link or an image
func link(p *parser, out *bytes.Buffer, data []byte, offset int) int {
isImg := offset > 0 && data[offset-1] == '!'
data = data[offset:]
i := 1
var title, link []byte
textHasNl := false
// 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
}
txtE := i
i++
// skip any amount of whitespace or newline
// (this is much more lax than original markdown syntax)
for i < len(data) && isspace(data[i]) {
i++
}
// inline style link
switch {
case i < len(data) && data[i] == '(':
// skip initial whitespace
i++
for i < len(data) && isspace(data[i]) {
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
}
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
}
// 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 i < len(data) && data[i] == '[':
var id []byte
// look for the id
i++
linkB := i
for i < len(data) && data[i] != ']' {
i++
}
if i >= len(data) {
return 0
}
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]
}
} else {
id = data[linkB:linkE]
}
// find the reference with matching id (ids are case-insensitive)
key := string(bytes.ToLower(id))
lr, ok := p.refs[key]
if !ok {
return 0
}
// keep link and title from reference
link = lr.link
title = lr.title
i++
// shortcut reference style link
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 {
id = data[1:txtE]
}
// find the reference with matching id
key := string(bytes.ToLower(id))
lr, ok := p.refs[key]
if !ok {
return 0
}
// keep link and title from reference
link = lr.link
title = lr.title
// rewind the whitespace
i = txtE + 1
}
// build content: img alt is escaped, link content is parsed
var content bytes.Buffer
if txtE > 1 {
if isImg {
content.Write(data[1:txtE])
} else {
// links cannot contain other links, so turn off link parsing temporarily
insideLink := p.insideLink
p.insideLink = true
p.inline(&content, data[1:txtE])
p.insideLink = insideLink
}
}
var uLink []byte
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 || (!isImg && content.Len() == 0) {
return 0
}
// call the relevant rendering function
if isImg {
outSize := out.Len()
outBytes := out.Bytes()
if outSize > 0 && outBytes[outSize-1] == '!' {
out.Truncate(outSize - 1)
}
p.r.Image(out, uLink, title, content.Bytes())
} else {
// no links allowed inside other links
if p.insideLink {
return 0
}
p.r.Link(out, uLink, title, content.Bytes())
}
return i
}
// '<' when tags or autolinks are allowed
func leftAngle(p *parser, out *bytes.Buffer, data []byte, offset int) int {
data = data[offset:]
altype := LINK_TYPE_NOT_AUTOLINK
end := tagLength(data, &altype)
if end > 2 {
if altype != LINK_TYPE_NOT_AUTOLINK {
var uLink bytes.Buffer
unescapeText(&uLink, data[1:end+1-2])
if uLink.Len() > 0 {
p.r.AutoLink(out, uLink.Bytes(), altype)
}
} else {
p.r.RawHtmlTag(out, data[:end])
}
}
return end
}
// '\\' backslash escape
var escapeChars = []byte("\\`*_{}[]()#+-.!:|&<>")
func escape(p *parser, out *bytes.Buffer, data []byte, offset int) int {
data = data[offset:]
if len(data) > 1 {
if bytes.IndexByte(escapeChars, data[1]) < 0 {
return 0
}
p.r.NormalText(out, data[1:2])
}
return 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, out *bytes.Buffer, data []byte, offset int) int {
data = data[offset:]
end := 1
if end < len(data) && data[end] == '#' {
end++
}
for end < len(data) && isalnum(data[end]) {
end++
}
if end < len(data) && data[end] == ';' {
end++ // real entity
} else {
return 0 // lone '&'
}
p.r.Entity(out, data[:end])
return end
}
func autoLink(p *parser, out *bytes.Buffer, data []byte, offset int) int {
// quick check to rule out most false hits on ':'
if p.insideLink || len(data) < offset+3 || data[offset+1] != '/' || data[offset+2] != '/' {
return 0
}
// scan backward for a word boundary
rewind := 0
for offset-rewind > 0 && rewind <= 7 && !isspace(data[offset-rewind-1]) && !isspace(data[offset-rewind-1]) {
rewind++
}
if rewind > 6 { // longest supported protocol is "mailto" which has 6 letters
return 0
}
origData := data
data = data[offset-rewind:]
if !isSafeLink(data) {
return 0
}
linkEnd := 0
for linkEnd < len(data) && !isspace(data[linkEnd]) {
linkEnd++
}
// Skip punctuation at the end of the link
if (data[linkEnd-1] == '.' || data[linkEnd-1] == ',' || data[linkEnd-1] == ';') && data[linkEnd-2] != '\\' {
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--
}
}
// we were triggered on the ':', so we need to rewind the output a bit
if out.Len() >= rewind {
out.Truncate(len(out.Bytes()) - rewind)
}
var uLink bytes.Buffer
unescapeText(&uLink, data[:linkEnd])
if uLink.Len() > 0 {
p.r.AutoLink(out, uLink.Bytes(), LINK_TYPE_NORMAL)
}
return linkEnd - rewind
}
var validUris = [][]byte{[]byte("http://"), []byte("https://"), []byte("ftp://"), []byte("mailto://")}
func isSafeLink(link []byte) bool {
for _, prefix := range validUris {
// TODO: handle unicode here
// case-insensitive prefix test
if len(link) > len(prefix) && bytes.Equal(bytes.ToLower(link[:len(prefix)]), prefix) && isalnum(link[len(prefix)]) {
return true
}
}
return false
}
// return the length of the given tag, or 0 is it's not valid
func tagLength(data []byte, autolink *int) int {
var i, j int
// a valid tag can't be shorter than 3 chars
if len(data) < 3 {
return 0
}
// begins with a '<' optionally followed by '/', followed by letter or number
if data[0] != '<' {
return 0
}
if data[1] == '/' {
i = 2
} else {
i = 1
}
if !isalnum(data[i]) {
return 0
}
// scheme test
*autolink = LINK_TYPE_NOT_AUTOLINK
// 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 {
*autolink = LINK_TYPE_EMAIL
return i + j
}
}
if i > 2 && i < len(data) && data[i] == ':' {
*autolink = LINK_TYPE_NORMAL
i++
}
// complete autolink test: no whitespace or ' or "
switch {
case i >= len(data):
*autolink = LINK_TYPE_NOT_AUTOLINK
case *autolink != 0:
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 0
}
if i > j && data[i] == '>' {
return i + 1
}
// one of the forbidden chars has been found
*autolink = LINK_TYPE_NOT_AUTOLINK
}
// look for something looking like a tag end
for i < len(data) && data[i] != '>' {
i++
}
if i >= len(data) {
return 0
}
return 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 := 0; i < len(data); i++ {
if isalnum(data[i]) {
continue
}
switch data[i] {
case '@':
nb++
case '-', '.', '_':
break
case '>':
if nb == 1 {
return i + 1
} else {
return 0
}
default:
return 0
}
}
return 0
}
// look for the next emph char, skipping other constructs
func helperFindEmphChar(data []byte, c byte) int {
i := 1
for i < len(data) {
for i < len(data) && data[i] != c && data[i] != '`' && data[i] != '[' {
i++
}
if i >= len(data) {
return 0
}
if data[i] == c {
return i
}
// do not count escaped chars
if i != 0 && data[i-1] == '\\' {
i++
continue
}
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
} else {
continue
}
}
cc := data[i]
i++
for i < len(data) && data[i] != cc {
if tmpI == 0 && data[i] == c {
tmpI = i
}
i++
}
if i >= len(data) {
return tmpI
}
i++
}
}
return 0
}
func helperEmphasis(p *parser, out *bytes.Buffer, data []byte, c byte) int {
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
}
i += length
if i >= len(data) {
return 0
}
if i+1 < len(data) && data[i+1] == c {
i++
continue
}
if data[i] == c && !isspace(data[i-1]) {
if p.flags&EXTENSION_NO_INTRA_EMPHASIS != 0 {
if !(i+1 == len(data) || isspace(data[i+1]) || ispunct(data[i+1])) {
continue
}
}
var work bytes.Buffer
p.inline(&work, data[:i])
p.r.Emphasis(out, work.Bytes())
return i + 1
}
}
return 0
}
func helperDoubleEmphasis(p *parser, out *bytes.Buffer, data []byte, c byte) int {
i := 0
for i < len(data) {
length := helperFindEmphChar(data[i:], c)
if length == 0 {
return 0
}
i += length
if i+1 < len(data) && data[i] == c && data[i+1] == c && i > 0 && !isspace(data[i-1]) {
var work bytes.Buffer
p.inline(&work, data[:i])
if work.Len() > 0 {
// pick the right renderer
if c == '~' {
p.r.StrikeThrough(out, work.Bytes())
} else {
p.r.DoubleEmphasis(out, work.Bytes())
}
}
return i + 2
}
i++
}
return 0
}
func helperTripleEmphasis(p *parser, out *bytes.Buffer, data []byte, offset int, c byte) int {
i := 0
origData := data
data = data[offset:]
for i < len(data) {
length := helperFindEmphChar(data[i:], c)
if length == 0 {
return 0
}
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
var work bytes.Buffer
p.inline(&work, data[:i])
if work.Len() > 0 {
p.r.TripleEmphasis(out, work.Bytes())
}
return i + 3
case (i+1 < len(data) && data[i+1] == c):
// double symbol found, hand over to emph1
length = helperEmphasis(p, out, origData[offset-2:], c)
if length == 0 {
return 0
} else {
return length - 2
}
default:
// single symbol found, hand over to emph2
length = helperDoubleEmphasis(p, out, origData[offset-1:], c)
if length == 0 {
return 0
} else {
return length - 1
}
}
}
return 0
}
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