| 1 | package codeview |
| 2 | |
| 3 | import ( |
| 4 | "html/template" |
| 5 | "strings" |
| 6 | ) |
| 7 | |
| 8 | // Highlight escapes source for an HTML text context and wraps five |
| 9 | // kinds of token in two-letter custom elements that the gallery's |
| 10 | // stylesheet colours: <ds-t> a tag's name with its opening bracket, |
| 11 | // <ds-a> an attribute name, <ds-v> an attribute value with its quotes, |
| 12 | // <ds-x> a template action's delimiters, keywords and fields, and <ds-s> |
| 13 | // a string literal inside an action. |
| 14 | // |
| 15 | // Custom elements rather than <span class>: a token costs 13 bytes this |
| 16 | // way and 29 the other, and on the heaviest page that difference was |
| 17 | // the page budget. An undefined element is inline with no role, so it |
| 18 | // changes nothing for assistive technology or for textContent. |
| 19 | // |
| 20 | // Only &, < and > are escaped. Quotes stay literal, which is valid in |
| 21 | // text and spares four bytes on every attribute a sample writes. |
| 22 | func Highlight(src string) template.HTML { |
| 23 | var b strings.Builder |
| 24 | for i := 0; i < len(src); { |
| 25 | switch { |
| 26 | case strings.HasPrefix(src[i:], "{{"): |
| 27 | end := actionEnd(src, i) |
| 28 | action(&b, src[i:end]) |
| 29 | i = end |
| 30 | case src[i] == '<' && tagEnd(src, i) > 0: |
| 31 | end := tagEnd(src, i) |
| 32 | tag(&b, src[i:end]) |
| 33 | i = end |
| 34 | default: |
| 35 | j := i + 1 |
| 36 | for j < len(src) && !strings.HasPrefix(src[j:], "{{") && !(src[j] == '<' && tagEnd(src, j) > 0) { |
| 37 | j++ |
| 38 | } |
| 39 | escape(&b, src[i:j]) |
| 40 | i = j |
| 41 | } |
| 42 | } |
| 43 | return template.HTML(b.String()) |
| 44 | } |
| 45 | |
| 46 | func escape(b *strings.Builder, s string) { |
| 47 | for i := 0; i < len(s); i++ { |
| 48 | switch s[i] { |
| 49 | case '&': |
| 50 | b.WriteString("&") |
| 51 | case '<': |
| 52 | b.WriteString("<") |
| 53 | case '>': |
| 54 | b.WriteString(">") |
| 55 | default: |
| 56 | b.WriteByte(s[i]) |
| 57 | } |
| 58 | } |
| 59 | } |
| 60 | |
| 61 | func wrapped(b *strings.Builder, kind, s string) { |
| 62 | b.WriteString("<ds-" + kind + ">") |
| 63 | escape(b, s) |
| 64 | b.WriteString("</ds-" + kind + ">") |
| 65 | } |
| 66 | |
| 67 | // tag writes one tag: its name, each attribute's name and value, and |
| 68 | // the whitespace and closing bracket between them as plain text. |
| 69 | func tag(b *strings.Builder, t string) { |
| 70 | n := 1 |
| 71 | if strings.HasPrefix(t, "</") { |
| 72 | n = 2 |
| 73 | } |
| 74 | for n < len(t) && !isSpace(t[n]) && t[n] != '>' && t[n] != '/' { |
| 75 | n++ |
| 76 | } |
| 77 | wrapped(b, "t", t[:n]) |
| 78 | for i := n; i < len(t); { |
| 79 | c := t[i] |
| 80 | switch { |
| 81 | case isSpace(c) || c == '/' || c == '>': |
| 82 | escape(b, t[i:i+1]) |
| 83 | i++ |
| 84 | case c == '=': |
| 85 | b.WriteByte('=') |
| 86 | i++ |
| 87 | j := i |
| 88 | if j < len(t) && (t[j] == '"' || t[j] == '\'') { |
| 89 | q := t[j] |
| 90 | j++ |
| 91 | for j < len(t) && t[j] != q { |
| 92 | j++ |
| 93 | } |
| 94 | if j < len(t) { |
| 95 | j++ |
| 96 | } |
| 97 | } else { |
| 98 | for j < len(t) && !isSpace(t[j]) && t[j] != '>' { |
| 99 | j++ |
| 100 | } |
| 101 | } |
| 102 | wrapped(b, "v", t[i:j]) |
| 103 | i = j |
| 104 | default: |
| 105 | j := i |
| 106 | for j < len(t) && !isSpace(t[j]) && t[j] != '=' && t[j] != '>' && !(t[j] == '/' && j+1 < len(t) && t[j+1] == '>') { |
| 107 | j++ |
| 108 | } |
| 109 | wrapped(b, "a", t[i:j]) |
| 110 | i = j |
| 111 | } |
| 112 | } |
| 113 | } |
| 114 | |
| 115 | // actionEnd returns the index just past the action starting at s[i], |
| 116 | // treating "}}" inside a string literal as part of the string. |
| 117 | func actionEnd(s string, i int) int { |
| 118 | for j := i + 2; j < len(s); j++ { |
| 119 | switch s[j] { |
| 120 | case '"': |
| 121 | for j++; j < len(s) && s[j] != '"'; j++ { |
| 122 | if s[j] == '\\' { |
| 123 | j++ |
| 124 | } |
| 125 | } |
| 126 | case '`': |
| 127 | for j++; j < len(s) && s[j] != '`'; j++ { |
| 128 | } |
| 129 | case '}': |
| 130 | if j+1 < len(s) && s[j+1] == '}' { |
| 131 | return j + 2 |
| 132 | } |
| 133 | } |
| 134 | } |
| 135 | return len(s) |
| 136 | } |
| 137 | |
| 138 | // action writes one {{…}}: the delimiters, identifiers and .Fields as |
| 139 | // <ds-x>, string literals as <ds-s>, and everything else as text. |
| 140 | func action(b *strings.Builder, a string) { |
| 141 | body, closed := strings.CutSuffix(a[2:], "}}") |
| 142 | wrapped(b, "x", "{{") |
| 143 | for i := 0; i < len(body); { |
| 144 | c := body[i] |
| 145 | switch { |
| 146 | case c == '"' || c == '`': |
| 147 | j := i + 1 |
| 148 | for j < len(body) && body[j] != c { |
| 149 | if c == '"' && body[j] == '\\' { |
| 150 | j++ |
| 151 | } |
| 152 | j++ |
| 153 | } |
| 154 | j = min(j+1, len(body)) |
| 155 | wrapped(b, "s", body[i:j]) |
| 156 | i = j |
| 157 | case isLetter(c) || c == '_' || c == '.': |
| 158 | j := i + 1 |
| 159 | for j < len(body) && (isLetter(body[j]) || body[j] == '_' || body[j] == '.' || body[j] >= '0' && body[j] <= '9') { |
| 160 | j++ |
| 161 | } |
| 162 | wrapped(b, "x", body[i:j]) |
| 163 | i = j |
| 164 | default: |
| 165 | escape(b, body[i:i+1]) |
| 166 | i++ |
| 167 | } |
| 168 | } |
| 169 | if closed { |
| 170 | wrapped(b, "x", "}}") |
| 171 | } |
| 172 | } |
| 173 | |
amadan