inline.go (view raw)
1//
2// Blackfriday Markdown Processor
3// Available at http://github.com/russross/blackfriday
4//
5// Copyright © 2011 Russ Ross <russ@russross.com>.
6// Distributed under the Simplified BSD License.
7// See README.md for details.
8//
9
10//
11// Functions to parse inline elements.
12//
13
14package blackfriday
15
16import (
17 "bytes"
18 "regexp"
19 "strconv"
20)
21
22var (
23 urlRe = `((https?|ftp):\/\/|\/)[-A-Za-z0-9+&@#\/%?=~_|!:,.;\(\)]+`
24 anchorRe = regexp.MustCompile(`^(<a\shref="` + urlRe + `"(\stitle="[^"<>]+")?\s?>` + urlRe + `<\/a>)`)
25
26 // TODO: improve this regexp to catch all possible entities:
27 htmlEntityRe = regexp.MustCompile(`&[a-z]{2,5};`)
28)
29
30// Functions to parse text within a block
31// Each function returns the number of chars taken care of
32// data is the complete block being rendered
33// offset is the number of valid chars before the current cursor
34
35func (p *Parser) inline(currBlock *Node, data []byte) {
36 // handlers might call us recursively: enforce a maximum depth
37 if p.nesting >= p.maxNesting || len(data) == 0 {
38 return
39 }
40 p.nesting++
41 beg, end := 0, 0
42 for end < len(data) {
43 handler := p.inlineCallback[data[end]]
44 if handler != nil {
45 if consumed, node := handler(p, data, end); consumed == 0 {
46 // No action from the callback.
47 end++
48 } else {
49 // Copy inactive chars into the output.
50 currBlock.AppendChild(text(data[beg:end]))
51 if node != nil {
52 currBlock.AppendChild(node)
53 }
54 // Skip past whatever the callback used.
55 beg = end + consumed
56 end = beg
57 }
58 } else {
59 end++
60 }
61 }
62 if beg < len(data) {
63 if data[end-1] == '\n' {
64 end--
65 }
66 currBlock.AppendChild(text(data[beg:end]))
67 }
68 p.nesting--
69}
70
71// single and double emphasis parsing
72func emphasis(p *Parser, data []byte, offset int) (int, *Node) {
73 data = data[offset:]
74 c := data[0]
75
76 if len(data) > 2 && data[1] != c {
77 // whitespace cannot follow an opening emphasis;
78 // strikethrough only takes two characters '~~'
79 if c == '~' || isspace(data[1]) {
80 return 0, nil
81 }
82 ret, node := helperEmphasis(p, data[1:], c)
83 if ret == 0 {
84 return 0, nil
85 }
86
87 return ret + 1, node
88 }
89
90 if len(data) > 3 && data[1] == c && data[2] != c {
91 if isspace(data[2]) {
92 return 0, nil
93 }
94 ret, node := helperDoubleEmphasis(p, data[2:], c)
95 if ret == 0 {
96 return 0, nil
97 }
98
99 return ret + 2, node
100 }
101
102 if len(data) > 4 && data[1] == c && data[2] == c && data[3] != c {
103 if c == '~' || isspace(data[3]) {
104 return 0, nil
105 }
106 ret, node := helperTripleEmphasis(p, data, 3, c)
107 if ret == 0 {
108 return 0, nil
109 }
110
111 return ret + 3, node
112 }
113
114 return 0, nil
115}
116
117func codeSpan(p *Parser, data []byte, offset int) (int, *Node) {
118 data = data[offset:]
119
120 nb := 0
121
122 // count the number of backticks in the delimiter
123 for nb < len(data) && data[nb] == '`' {
124 nb++
125 }
126
127 // find the next delimiter
128 i, end := 0, 0
129 for end = nb; end < len(data) && i < nb; end++ {
130 if data[end] == '`' {
131 i++
132 } else {
133 i = 0
134 }
135 }
136
137 // no matching delimiter?
138 if i < nb && end >= len(data) {
139 return 0, nil
140 }
141
142 // trim outside whitespace
143 fBegin := nb
144 for fBegin < end && data[fBegin] == ' ' {
145 fBegin++
146 }
147
148 fEnd := end - nb
149 for fEnd > fBegin && data[fEnd-1] == ' ' {
150 fEnd--
151 }
152
153 // render the code span
154 if fBegin != fEnd {
155 code := NewNode(Code)
156 code.Literal = data[fBegin:fEnd]
157 return end, code
158 }
159
160 return end, nil
161}
162
163// newline preceded by two spaces becomes <br>
164func maybeLineBreak(p *Parser, data []byte, offset int) (int, *Node) {
165 origOffset := offset
166 for offset < len(data) && data[offset] == ' ' {
167 offset++
168 }
169
170 if offset < len(data) && data[offset] == '\n' {
171 if offset-origOffset >= 2 {
172 return offset - origOffset + 1, NewNode(Hardbreak)
173 }
174 return offset - origOffset, nil
175 }
176 return 0, nil
177}
178
179// newline without two spaces works when HardLineBreak is enabled
180func lineBreak(p *Parser, data []byte, offset int) (int, *Node) {
181 if p.flags&HardLineBreak != 0 {
182 return 1, NewNode(Hardbreak)
183 }
184 return 0, nil
185}
186
187type linkType int
188
189const (
190 linkNormal linkType = iota
191 linkImg
192 linkDeferredFootnote
193 linkInlineFootnote
194)
195
196func isReferenceStyleLink(data []byte, pos int, t linkType) bool {
197 if t == linkDeferredFootnote {
198 return false
199 }
200 return pos < len(data)-1 && data[pos] == '[' && data[pos+1] != '^'
201}
202
203func maybeImage(p *Parser, data []byte, offset int) (int, *Node) {
204 if offset < len(data)-1 && data[offset+1] == '[' {
205 return link(p, data, offset)
206 }
207 return 0, nil
208}
209
210func maybeInlineFootnote(p *Parser, data []byte, offset int) (int, *Node) {
211 if offset < len(data)-1 && data[offset+1] == '[' {
212 return link(p, data, offset)
213 }
214 return 0, nil
215}
216
217// '[': parse a link or an image or a footnote
218func link(p *Parser, data []byte, offset int) (int, *Node) {
219 // no links allowed inside regular links, footnote, and deferred footnotes
220 if p.insideLink && (offset > 0 && data[offset-1] == '[' || len(data)-1 > offset && data[offset+1] == '^') {
221 return 0, nil
222 }
223
224 var t linkType
225 switch {
226 // special case: ![^text] == deferred footnote (that follows something with
227 // an exclamation point)
228 case p.flags&Footnotes != 0 && len(data)-1 > offset && data[offset+1] == '^':
229 t = linkDeferredFootnote
230 // ![alt] == image
231 case offset >= 0 && data[offset] == '!':
232 t = linkImg
233 offset++
234 // ^[text] == inline footnote
235 // [^refId] == deferred footnote
236 case p.flags&Footnotes != 0:
237 if offset >= 0 && data[offset] == '^' {
238 t = linkInlineFootnote
239 offset++
240 } else if len(data)-1 > offset && data[offset+1] == '^' {
241 t = linkDeferredFootnote
242 }
243 // [text] == regular link
244 default:
245 t = linkNormal
246 }
247
248 data = data[offset:]
249
250 var (
251 i = 1
252 noteID int
253 title, link, altContent []byte
254 textHasNl = false
255 )
256
257 if t == linkDeferredFootnote {
258 i++
259 }
260
261 // look for the matching closing bracket
262 for level := 1; level > 0 && i < len(data); i++ {
263 switch {
264 case data[i] == '\n':
265 textHasNl = true
266
267 case data[i-1] == '\\':
268 continue
269
270 case data[i] == '[':
271 level++
272
273 case data[i] == ']':
274 level--
275 if level <= 0 {
276 i-- // compensate for extra i++ in for loop
277 }
278 }
279 }
280
281 if i >= len(data) {
282 return 0, nil
283 }
284
285 txtE := i
286 i++
287 var footnoteNode *Node
288
289 // skip any amount of whitespace or newline
290 // (this is much more lax than original markdown syntax)
291 for i < len(data) && isspace(data[i]) {
292 i++
293 }
294
295 // inline style link
296 switch {
297 case i < len(data) && data[i] == '(':
298 // skip initial whitespace
299 i++
300
301 for i < len(data) && isspace(data[i]) {
302 i++
303 }
304
305 linkB := i
306
307 // look for link end: ' " )
308 findlinkend:
309 for i < len(data) {
310 switch {
311 case data[i] == '\\':
312 i += 2
313
314 case data[i] == ')' || data[i] == '\'' || data[i] == '"':
315 break findlinkend
316
317 default:
318 i++
319 }
320 }
321
322 if i >= len(data) {
323 return 0, nil
324 }
325 linkE := i
326
327 // look for title end if present
328 titleB, titleE := 0, 0
329 if data[i] == '\'' || data[i] == '"' {
330 i++
331 titleB = i
332
333 findtitleend:
334 for i < len(data) {
335 switch {
336 case data[i] == '\\':
337 i += 2
338
339 case data[i] == ')':
340 break findtitleend
341
342 default:
343 i++
344 }
345 }
346
347 if i >= len(data) {
348 return 0, nil
349 }
350
351 // skip whitespace after title
352 titleE = i - 1
353 for titleE > titleB && isspace(data[titleE]) {
354 titleE--
355 }
356
357 // check for closing quote presence
358 if data[titleE] != '\'' && data[titleE] != '"' {
359 titleB, titleE = 0, 0
360 linkE = i
361 }
362 }
363
364 // remove whitespace at the end of the link
365 for linkE > linkB && isspace(data[linkE-1]) {
366 linkE--
367 }
368
369 // remove optional angle brackets around the link
370 if data[linkB] == '<' {
371 linkB++
372 }
373 if data[linkE-1] == '>' {
374 linkE--
375 }
376
377 // build escaped link and title
378 if linkE > linkB {
379 link = data[linkB:linkE]
380 }
381
382 if titleE > titleB {
383 title = data[titleB:titleE]
384 }
385
386 i++
387
388 // reference style link
389 case isReferenceStyleLink(data, i, t):
390 var id []byte
391 altContentConsidered := false
392
393 // look for the id
394 i++
395 linkB := i
396 for i < len(data) && data[i] != ']' {
397 i++
398 }
399 if i >= len(data) {
400 return 0, nil
401 }
402 linkE := i
403
404 // find the reference
405 if linkB == linkE {
406 if textHasNl {
407 var b bytes.Buffer
408
409 for j := 1; j < txtE; j++ {
410 switch {
411 case data[j] != '\n':
412 b.WriteByte(data[j])
413 case data[j-1] != ' ':
414 b.WriteByte(' ')
415 }
416 }
417
418 id = b.Bytes()
419 } else {
420 id = data[1:txtE]
421 altContentConsidered = true
422 }
423 } else {
424 id = data[linkB:linkE]
425 }
426
427 // find the reference with matching id
428 lr, ok := p.getRef(string(id))
429 if !ok {
430 return 0, nil
431 }
432
433 // keep link and title from reference
434 link = lr.link
435 title = lr.title
436 if altContentConsidered {
437 altContent = lr.text
438 }
439 i++
440
441 // shortcut reference style link or reference or inline footnote
442 default:
443 var id []byte
444
445 // craft the id
446 if textHasNl {
447 var b bytes.Buffer
448
449 for j := 1; j < txtE; j++ {
450 switch {
451 case data[j] != '\n':
452 b.WriteByte(data[j])
453 case data[j-1] != ' ':
454 b.WriteByte(' ')
455 }
456 }
457
458 id = b.Bytes()
459 } else {
460 if t == linkDeferredFootnote {
461 id = data[2:txtE] // get rid of the ^
462 } else {
463 id = data[1:txtE]
464 }
465 }
466
467 footnoteNode = NewNode(Item)
468 if t == linkInlineFootnote {
469 // create a new reference
470 noteID = len(p.notes) + 1
471
472 var fragment []byte
473 if len(id) > 0 {
474 if len(id) < 16 {
475 fragment = make([]byte, len(id))
476 } else {
477 fragment = make([]byte, 16)
478 }
479 copy(fragment, slugify(id))
480 } else {
481 fragment = append([]byte("footnote-"), []byte(strconv.Itoa(noteID))...)
482 }
483
484 ref := &reference{
485 noteID: noteID,
486 hasBlock: false,
487 link: fragment,
488 title: id,
489 footnote: footnoteNode,
490 }
491
492 p.notes = append(p.notes, ref)
493
494 link = ref.link
495 title = ref.title
496 } else {
497 // find the reference with matching id
498 lr, ok := p.getRef(string(id))
499 if !ok {
500 return 0, nil
501 }
502
503 if t == linkDeferredFootnote {
504 lr.noteID = len(p.notes) + 1
505 lr.footnote = footnoteNode
506 p.notes = append(p.notes, lr)
507 }
508
509 // keep link and title from reference
510 link = lr.link
511 // if inline footnote, title == footnote contents
512 title = lr.title
513 noteID = lr.noteID
514 }
515
516 // rewind the whitespace
517 i = txtE + 1
518 }
519
520 var uLink []byte
521 if t == linkNormal || t == linkImg {
522 if len(link) > 0 {
523 var uLinkBuf bytes.Buffer
524 unescapeText(&uLinkBuf, link)
525 uLink = uLinkBuf.Bytes()
526 }
527
528 // links need something to click on and somewhere to go
529 if len(uLink) == 0 || (t == linkNormal && txtE <= 1) {
530 return 0, nil
531 }
532 }
533
534 // call the relevant rendering function
535 var linkNode *Node
536 switch t {
537 case linkNormal:
538 linkNode = NewNode(Link)
539 linkNode.Destination = normalizeURI(uLink)
540 linkNode.Title = title
541 if len(altContent) > 0 {
542 linkNode.AppendChild(text(altContent))
543 } else {
544 // links cannot contain other links, so turn off link parsing
545 // temporarily and recurse
546 insideLink := p.insideLink
547 p.insideLink = true
548 p.inline(linkNode, data[1:txtE])
549 p.insideLink = insideLink
550 }
551
552 case linkImg:
553 linkNode = NewNode(Image)
554 linkNode.Destination = uLink
555 linkNode.Title = title
556 linkNode.AppendChild(text(data[1:txtE]))
557 i++
558
559 case linkInlineFootnote, linkDeferredFootnote:
560 linkNode = NewNode(Link)
561 linkNode.Destination = link
562 linkNode.Title = title
563 linkNode.NoteID = noteID
564 linkNode.Footnote = footnoteNode
565 if t == linkInlineFootnote {
566 i++
567 }
568
569 default:
570 return 0, nil
571 }
572
573 return i, linkNode
574}
575
576func (p *Parser) inlineHTMLComment(data []byte) int {
577 if len(data) < 5 {
578 return 0
579 }
580 if data[0] != '<' || data[1] != '!' || data[2] != '-' || data[3] != '-' {
581 return 0
582 }
583 i := 5
584 // scan for an end-of-comment marker, across lines if necessary
585 for i < len(data) && !(data[i-2] == '-' && data[i-1] == '-' && data[i] == '>') {
586 i++
587 }
588 // no end-of-comment marker
589 if i >= len(data) {
590 return 0
591 }
592 return i + 1
593}
594
595func stripMailto(link []byte) []byte {
596 if bytes.HasPrefix(link, []byte("mailto://")) {
597 return link[9:]
598 } else if bytes.HasPrefix(link, []byte("mailto:")) {
599 return link[7:]
600 } else {
601 return link
602 }
603}
604
605// autolinkType specifies a kind of autolink that gets detected.
606type autolinkType int
607
608// These are the possible flag values for the autolink renderer.
609const (
610 notAutolink autolinkType = iota
611 normalAutolink
612 emailAutolink
613)
614
615// '<' when tags or autolinks are allowed
616func leftAngle(p *Parser, data []byte, offset int) (int, *Node) {
617 data = data[offset:]
618 altype, end := tagLength(data)
619 if size := p.inlineHTMLComment(data); size > 0 {
620 end = size
621 }
622 if end > 2 {
623 if altype != notAutolink {
624 var uLink bytes.Buffer
625 unescapeText(&uLink, data[1:end+1-2])
626 if uLink.Len() > 0 {
627 link := uLink.Bytes()
628 node := NewNode(Link)
629 node.Destination = link
630 if altype == emailAutolink {
631 node.Destination = append([]byte("mailto:"), link...)
632 }
633 node.AppendChild(text(stripMailto(link)))
634 return end, node
635 }
636 } else {
637 htmlTag := NewNode(HTMLSpan)
638 htmlTag.Literal = data[:end]
639 return end, htmlTag
640 }
641 }
642
643 return end, nil
644}
645
646// '\\' backslash escape
647var escapeChars = []byte("\\`*_{}[]()#+-.!:|&<>~")
648
649func escape(p *Parser, data []byte, offset int) (int, *Node) {
650 data = data[offset:]
651
652 if len(data) > 1 {
653 if p.flags&BackslashLineBreak != 0 && data[1] == '\n' {
654 return 2, NewNode(Hardbreak)
655 }
656 if bytes.IndexByte(escapeChars, data[1]) < 0 {
657 return 0, nil
658 }
659
660 return 2, text(data[1:2])
661 }
662
663 return 2, nil
664}
665
666func unescapeText(ob *bytes.Buffer, src []byte) {
667 i := 0
668 for i < len(src) {
669 org := i
670 for i < len(src) && src[i] != '\\' {
671 i++
672 }
673
674 if i > org {
675 ob.Write(src[org:i])
676 }
677
678 if i+1 >= len(src) {
679 break
680 }
681
682 ob.WriteByte(src[i+1])
683 i += 2
684 }
685}
686
687// '&' escaped when it doesn't belong to an entity
688// valid entities are assumed to be anything matching &#?[A-Za-z0-9]+;
689func entity(p *Parser, data []byte, offset int) (int, *Node) {
690 data = data[offset:]
691
692 end := 1
693
694 if end < len(data) && data[end] == '#' {
695 end++
696 }
697
698 for end < len(data) && isalnum(data[end]) {
699 end++
700 }
701
702 if end < len(data) && data[end] == ';' {
703 end++ // real entity
704 } else {
705 return 0, nil // lone '&'
706 }
707
708 ent := data[:end]
709 // undo & escaping or it will be converted to &amp; by another
710 // escaper in the renderer
711 if bytes.Equal(ent, []byte("&")) {
712 ent = []byte{'&'}
713 }
714
715 return end, text(ent)
716}
717
718func linkEndsWithEntity(data []byte, linkEnd int) bool {
719 entityRanges := htmlEntityRe.FindAllIndex(data[:linkEnd], -1)
720 return entityRanges != nil && entityRanges[len(entityRanges)-1][1] == linkEnd
721}
722
723// hasPrefixCaseInsensitive is a custom implementation of
724// strings.HasPrefix(strings.ToLower(s), prefix)
725// we rolled our own because ToLower pulls in a huge machinery of lowercasing
726// anything from Unicode and that's very slow. Since this func will only be
727// used on ASCII protocol prefixes, we can take shortcuts.
728func hasPrefixCaseInsensitive(s, prefix []byte) bool {
729 if len(s) < len(prefix) {
730 return false
731 }
732 delta := byte('a' - 'A')
733 for i, b := range prefix {
734 if b != s[i] && b != s[i]+delta {
735 return false
736 }
737 }
738 return true
739}
740
741var protocolPrefixes = [][]byte{
742 []byte("http://"),
743 []byte("https://"),
744 []byte("ftp://"),
745 []byte("file://"),
746 []byte("mailto:"),
747}
748
749const shortestPrefix = 6 // len("ftp://"), the shortest of the above
750
751func maybeAutoLink(p *Parser, data []byte, offset int) (int, *Node) {
752 // quick check to rule out most false hits
753 if p.insideLink || len(data) < offset+shortestPrefix {
754 return 0, nil
755 }
756 for _, prefix := range protocolPrefixes {
757 endOfHead := offset + 8 // 8 is the len() of the longest prefix
758 if endOfHead > len(data) {
759 endOfHead = len(data)
760 }
761 if hasPrefixCaseInsensitive(data[offset:endOfHead], prefix) {
762 return autoLink(p, data, offset)
763 }
764 }
765 return 0, nil
766}
767
768func autoLink(p *Parser, data []byte, offset int) (int, *Node) {
769 // Now a more expensive check to see if we're not inside an anchor element
770 anchorStart := offset
771 offsetFromAnchor := 0
772 for anchorStart > 0 && data[anchorStart] != '<' {
773 anchorStart--
774 offsetFromAnchor++
775 }
776
777 anchorStr := anchorRe.Find(data[anchorStart:])
778 if anchorStr != nil {
779 anchorClose := NewNode(HTMLSpan)
780 anchorClose.Literal = anchorStr[offsetFromAnchor:]
781 return len(anchorStr) - offsetFromAnchor, anchorClose
782 }
783
784 // scan backward for a word boundary
785 rewind := 0
786 for offset-rewind > 0 && rewind <= 7 && isletter(data[offset-rewind-1]) {
787 rewind++
788 }
789 if rewind > 6 { // longest supported protocol is "mailto" which has 6 letters
790 return 0, nil
791 }
792
793 origData := data
794 data = data[offset-rewind:]
795
796 if !isSafeLink(data) {
797 return 0, nil
798 }
799
800 linkEnd := 0
801 for linkEnd < len(data) && !isEndOfLink(data[linkEnd]) {
802 linkEnd++
803 }
804
805 // Skip punctuation at the end of the link
806 if (data[linkEnd-1] == '.' || data[linkEnd-1] == ',') && data[linkEnd-2] != '\\' {
807 linkEnd--
808 }
809
810 // But don't skip semicolon if it's a part of escaped entity:
811 if data[linkEnd-1] == ';' && data[linkEnd-2] != '\\' && !linkEndsWithEntity(data, linkEnd) {
812 linkEnd--
813 }
814
815 // See if the link finishes with a punctuation sign that can be closed.
816 var copen byte
817 switch data[linkEnd-1] {
818 case '"':
819 copen = '"'
820 case '\'':
821 copen = '\''
822 case ')':
823 copen = '('
824 case ']':
825 copen = '['
826 case '}':
827 copen = '{'
828 default:
829 copen = 0
830 }
831
832 if copen != 0 {
833 bufEnd := offset - rewind + linkEnd - 2
834
835 openDelim := 1
836
837 /* Try to close the final punctuation sign in this same line;
838 * if we managed to close it outside of the URL, that means that it's
839 * not part of the URL. If it closes inside the URL, that means it
840 * is part of the URL.
841 *
842 * Examples:
843 *
844 * foo http://www.pokemon.com/Pikachu_(Electric) bar
845 * => http://www.pokemon.com/Pikachu_(Electric)
846 *
847 * foo (http://www.pokemon.com/Pikachu_(Electric)) bar
848 * => http://www.pokemon.com/Pikachu_(Electric)
849 *
850 * foo http://www.pokemon.com/Pikachu_(Electric)) bar
851 * => http://www.pokemon.com/Pikachu_(Electric))
852 *
853 * (foo http://www.pokemon.com/Pikachu_(Electric)) bar
854 * => foo http://www.pokemon.com/Pikachu_(Electric)
855 */
856
857 for bufEnd >= 0 && origData[bufEnd] != '\n' && openDelim != 0 {
858 if origData[bufEnd] == data[linkEnd-1] {
859 openDelim++
860 }
861
862 if origData[bufEnd] == copen {
863 openDelim--
864 }
865
866 bufEnd--
867 }
868
869 if openDelim == 0 {
870 linkEnd--
871 }
872 }
873
874 var uLink bytes.Buffer
875 unescapeText(&uLink, data[:linkEnd])
876
877 if uLink.Len() > 0 {
878 node := NewNode(Link)
879 node.Destination = uLink.Bytes()
880 node.AppendChild(text(uLink.Bytes()))
881 return linkEnd, node
882 }
883
884 return linkEnd, nil
885}
886
887func isEndOfLink(char byte) bool {
888 return isspace(char) || char == '<'
889}
890
891var validUris = [][]byte{[]byte("http://"), []byte("https://"), []byte("ftp://"), []byte("mailto://")}
892var validPaths = [][]byte{[]byte("/"), []byte("./"), []byte("../")}
893
894func isSafeLink(link []byte) bool {
895 for _, path := range validPaths {
896 if len(link) >= len(path) && bytes.Equal(link[:len(path)], path) {
897 if len(link) == len(path) {
898 return true
899 } else if isalnum(link[len(path)]) {
900 return true
901 }
902 }
903 }
904
905 for _, prefix := range validUris {
906 // TODO: handle unicode here
907 // case-insensitive prefix test
908 if len(link) > len(prefix) && bytes.Equal(bytes.ToLower(link[:len(prefix)]), prefix) && isalnum(link[len(prefix)]) {
909 return true
910 }
911 }
912
913 return false
914}
915
916// return the length of the given tag, or 0 is it's not valid
917func tagLength(data []byte) (autolink autolinkType, end int) {
918 var i, j int
919
920 // a valid tag can't be shorter than 3 chars
921 if len(data) < 3 {
922 return notAutolink, 0
923 }
924
925 // begins with a '<' optionally followed by '/', followed by letter or number
926 if data[0] != '<' {
927 return notAutolink, 0
928 }
929 if data[1] == '/' {
930 i = 2
931 } else {
932 i = 1
933 }
934
935 if !isalnum(data[i]) {
936 return notAutolink, 0
937 }
938
939 // scheme test
940 autolink = notAutolink
941
942 // try to find the beginning of an URI
943 for i < len(data) && (isalnum(data[i]) || data[i] == '.' || data[i] == '+' || data[i] == '-') {
944 i++
945 }
946
947 if i > 1 && i < len(data) && data[i] == '@' {
948 if j = isMailtoAutoLink(data[i:]); j != 0 {
949 return emailAutolink, i + j
950 }
951 }
952
953 if i > 2 && i < len(data) && data[i] == ':' {
954 autolink = normalAutolink
955 i++
956 }
957
958 // complete autolink test: no whitespace or ' or "
959 switch {
960 case i >= len(data):
961 autolink = notAutolink
962 case autolink != notAutolink:
963 j = i
964
965 for i < len(data) {
966 if data[i] == '\\' {
967 i += 2
968 } else if data[i] == '>' || data[i] == '\'' || data[i] == '"' || isspace(data[i]) {
969 break
970 } else {
971 i++
972 }
973
974 }
975
976 if i >= len(data) {
977 return autolink, 0
978 }
979 if i > j && data[i] == '>' {
980 return autolink, i + 1
981 }
982
983 // one of the forbidden chars has been found
984 autolink = notAutolink
985 }
986 i += bytes.IndexByte(data[i:], '>')
987 if i < 0 {
988 return autolink, 0
989 }
990 return autolink, i + 1
991}
992
993// look for the address part of a mail autolink and '>'
994// this is less strict than the original markdown e-mail address matching
995func isMailtoAutoLink(data []byte) int {
996 nb := 0
997
998 // address is assumed to be: [-@._a-zA-Z0-9]+ with exactly one '@'
999 for i := 0; i < len(data); i++ {
1000 if isalnum(data[i]) {
1001 continue
1002 }
1003
1004 switch data[i] {
1005 case '@':
1006 nb++
1007
1008 case '-', '.', '_':
1009 break
1010
1011 case '>':
1012 if nb == 1 {
1013 return i + 1
1014 }
1015 return 0
1016 default:
1017 return 0
1018 }
1019 }
1020
1021 return 0
1022}
1023
1024// look for the next emph char, skipping other constructs
1025func helperFindEmphChar(data []byte, c byte) int {
1026 i := 0
1027
1028 for i < len(data) {
1029 for i < len(data) && data[i] != c && data[i] != '`' && data[i] != '[' {
1030 i++
1031 }
1032 if i >= len(data) {
1033 return 0
1034 }
1035 // do not count escaped chars
1036 if i != 0 && data[i-1] == '\\' {
1037 i++
1038 continue
1039 }
1040 if data[i] == c {
1041 return i
1042 }
1043
1044 if data[i] == '`' {
1045 // skip a code span
1046 tmpI := 0
1047 i++
1048 for i < len(data) && data[i] != '`' {
1049 if tmpI == 0 && data[i] == c {
1050 tmpI = i
1051 }
1052 i++
1053 }
1054 if i >= len(data) {
1055 return tmpI
1056 }
1057 i++
1058 } else if data[i] == '[' {
1059 // skip a link
1060 tmpI := 0
1061 i++
1062 for i < len(data) && data[i] != ']' {
1063 if tmpI == 0 && data[i] == c {
1064 tmpI = i
1065 }
1066 i++
1067 }
1068 i++
1069 for i < len(data) && (data[i] == ' ' || data[i] == '\n') {
1070 i++
1071 }
1072 if i >= len(data) {
1073 return tmpI
1074 }
1075 if data[i] != '[' && data[i] != '(' { // not a link
1076 if tmpI > 0 {
1077 return tmpI
1078 }
1079 continue
1080 }
1081 cc := data[i]
1082 i++
1083 for i < len(data) && data[i] != cc {
1084 if tmpI == 0 && data[i] == c {
1085 return i
1086 }
1087 i++
1088 }
1089 if i >= len(data) {
1090 return tmpI
1091 }
1092 i++
1093 }
1094 }
1095 return 0
1096}
1097
1098func helperEmphasis(p *Parser, data []byte, c byte) (int, *Node) {
1099 i := 0
1100
1101 // skip one symbol if coming from emph3
1102 if len(data) > 1 && data[0] == c && data[1] == c {
1103 i = 1
1104 }
1105
1106 for i < len(data) {
1107 length := helperFindEmphChar(data[i:], c)
1108 if length == 0 {
1109 return 0, nil
1110 }
1111 i += length
1112 if i >= len(data) {
1113 return 0, nil
1114 }
1115
1116 if i+1 < len(data) && data[i+1] == c {
1117 i++
1118 continue
1119 }
1120
1121 if data[i] == c && !isspace(data[i-1]) {
1122
1123 if p.flags&NoIntraEmphasis != 0 {
1124 if !(i+1 == len(data) || isspace(data[i+1]) || ispunct(data[i+1])) {
1125 continue
1126 }
1127 }
1128
1129 emph := NewNode(Emph)
1130 p.inline(emph, data[:i])
1131 return i + 1, emph
1132 }
1133 }
1134
1135 return 0, nil
1136}
1137
1138func helperDoubleEmphasis(p *Parser, data []byte, c byte) (int, *Node) {
1139 i := 0
1140
1141 for i < len(data) {
1142 length := helperFindEmphChar(data[i:], c)
1143 if length == 0 {
1144 return 0, nil
1145 }
1146 i += length
1147
1148 if i+1 < len(data) && data[i] == c && data[i+1] == c && i > 0 && !isspace(data[i-1]) {
1149 nodeType := Strong
1150 if c == '~' {
1151 nodeType = Del
1152 }
1153 node := NewNode(nodeType)
1154 p.inline(node, data[:i])
1155 return i + 2, node
1156 }
1157 i++
1158 }
1159 return 0, nil
1160}
1161
1162func helperTripleEmphasis(p *Parser, data []byte, offset int, c byte) (int, *Node) {
1163 i := 0
1164 origData := data
1165 data = data[offset:]
1166
1167 for i < len(data) {
1168 length := helperFindEmphChar(data[i:], c)
1169 if length == 0 {
1170 return 0, nil
1171 }
1172 i += length
1173
1174 // skip whitespace preceded symbols
1175 if data[i] != c || isspace(data[i-1]) {
1176 continue
1177 }
1178
1179 switch {
1180 case i+2 < len(data) && data[i+1] == c && data[i+2] == c:
1181 // triple symbol found
1182 strong := NewNode(Strong)
1183 em := NewNode(Emph)
1184 strong.AppendChild(em)
1185 p.inline(em, data[:i])
1186 return i + 3, strong
1187 case (i+1 < len(data) && data[i+1] == c):
1188 // double symbol found, hand over to emph1
1189 length, node := helperEmphasis(p, origData[offset-2:], c)
1190 if length == 0 {
1191 return 0, nil
1192 }
1193 return length - 2, node
1194 default:
1195 // single symbol found, hand over to emph2
1196 length, node := helperDoubleEmphasis(p, origData[offset-1:], c)
1197 if length == 0 {
1198 return 0, nil
1199 }
1200 return length - 1, node
1201 }
1202 }
1203 return 0, nil
1204}
1205
1206func text(s []byte) *Node {
1207 node := NewNode(Text)
1208 node.Literal = s
1209 return node
1210}
1211
1212func normalizeURI(s []byte) []byte {
1213 return s // TODO: implement
1214}