| 🛟 Updated. 28d5985 k33g 16h ago | 1 | package syntax |
| 2 | |
| 3 | // The inline half of the Markdown scanner: what can appear inside a line of |
| 4 | // prose, once the line's own shape has been decided by markdown.go. |
| 5 | |
| 6 | // scanMarkdownInline colours what can appear inside a line of prose. |
| 7 | func scanMarkdownInline(s *LineScanner) { |
| 8 | for !s.AtEnd() { |
| 9 | switch { |
| 10 | case s.Peek(0) == '`': |
| 11 | takeCodeSpan(s) |
| 12 | case s.Peek(0) == '!' && s.Peek(1) == '[': |
| 13 | takeLink(s, 1) |
| 14 | case s.Peek(0) == '[': |
| 15 | takeLink(s, 0) |
| 16 | case isEmphasisMarker(s.Peek(0)): |
| 17 | takeEmphasis(s) |
| 18 | default: |
| 19 | s.pos++ |
| 20 | } |
| 21 | } |
| 22 | } |
| 23 | |
| 24 | // isEmphasisMarker reports whether a rune can begin bold or italic text. |
| 25 | func isEmphasisMarker(r rune) bool { return r == '*' || r == '_' } |
| 26 | |
| 27 | // takeCodeSpan colours `code`, or the lone backtick when nothing closes it. |
| 28 | func takeCodeSpan(s *LineScanner) { |
| 29 | start := s.pos |
| 30 | for at := s.pos + 1; at < len(s.line); at++ { |
| 31 | if s.line[at] == '`' { |
| 32 | s.pos = at + 1 |
| 33 | s.Emit(start, s.pos, ClassString) |
| 34 | return |
| 35 | } |
| 36 | } |
| 37 | s.pos++ |
| 38 | } |
| 39 | |
| 40 | // takeEmphasis colours *italic*, **bold** and their underscore spellings. |
| 41 | // |
| 42 | // The run of markers at the start has to be matched by the same run at the |
| 43 | // end, so that **bold** is one span rather than an empty italic followed by |
| 44 | // stray text. |
| 45 | func takeEmphasis(s *LineScanner) { |
| 46 | marker := s.Peek(0) |
| 47 | run := 0 |
| 48 | for s.Peek(run) == marker { |
| 49 | run++ |
| 50 | } |
| 51 | |
| 52 | if end := findRun(s.line, s.pos+run, marker, run); end > 0 { |
| 53 | start := s.pos |
| 54 | s.pos = end + run |
| 55 | s.Emit(start, s.pos, ClassEmphasis) |
| 56 | return |
| 57 | } |
| 58 | s.pos += run |
| 59 | } |
| 60 | |
| 61 | // findRun returns where a run of exactly n markers starts at or after from, or |
| 62 | // -1 when the line holds none. |
| 63 | func findRun(line []rune, from int, marker rune, n int) int { |
| 64 | for at := from; at+n <= len(line); at++ { |
| 65 | if line[at] != marker { |
| 66 | continue |
| 67 | } |
| 68 | count := 0 |
| 69 | for at+count < len(line) && line[at+count] == marker { |
| 70 | count++ |
| 71 | } |
| 72 | if count == n { |
| 73 | return at |
| 74 | } |
| 75 | at += count - 1 |
| 76 | } |
| 77 | return -1 |
| 78 | } |
| 79 | |
| 80 | // takeLink colours [text](target) and its image form . |
| 81 | // |
| 82 | // Both halves are one span: a link is one thing to the eye, and splitting the |
| 83 | // text from the target would put two colours on something read as a unit. |
| 84 | func takeLink(s *LineScanner, offset int) { |
| 85 | closeBracket := indexFrom(s.line, s.pos+offset+1, ']') |
| 86 | if closeBracket < 0 || closeBracket+1 >= len(s.line) || s.line[closeBracket+1] != '(' { |
| 87 | s.pos += offset + 1 |
| 88 | return |
| 89 | } |
| 90 | |
| 91 | closeParen := indexFrom(s.line, closeBracket+2, ')') |
| 92 | if closeParen < 0 { |
| 93 | s.pos += offset + 1 |
| 94 | return |
| 95 | } |
| 96 | |
| 97 | start := s.pos |
| 98 | s.pos = closeParen + 1 |
| 99 | s.Emit(start, s.pos, ClassLink) |
| 100 | } |
| 101 | |
| 102 | // indexFrom returns where a rune first appears at or after an offset, or -1. |
| 103 | func indexFrom(line []rune, from int, want rune) int { |
| 104 | for at := max(from, 0); at < len(line); at++ { |
| 105 | if line[at] == want { |
| 106 | return at |
| 107 | } |
| 108 | } |
| 109 | return -1 |
| 110 | } |