attachAssetsToMarkdown points every markdown reference to an attached file at that file's asset URL, and reports which arguments the markdown never referenced.  alone in a paragraph image: swap the path video: the bare URL, which plays  anywhere else image
(v attachableMarkdown)
| 91 | // |
| 92 | // A path inside a code fence or an inline code span is left alone. |
| 93 | func attachAssetsToMarkdown(v attachableMarkdown) (attachedMarkdown, error) { |
| 94 | md := v.markdown |
| 95 | if len(v.args) == 0 { |
| 96 | return attachedMarkdown{Rewritten: md}, nil |
| 97 | } |
| 98 | |
| 99 | src, refs, attachmentArgs := []byte(md), v.refs, v.args |
| 100 | |
| 101 | var edits []edit |
| 102 | |
| 103 | // Looping over the markdown references to produce a plan for edits. |
| 104 | for _, r := range refs { |
| 105 | arg := attachmentArgs[r.attachmentArg] |
| 106 | |
| 107 | // It's not been uploaded. |
| 108 | if arg.URL == "" { |
| 109 | continue |
| 110 | } |
| 111 | |
| 112 | // Reference style links get rewritten at their definitions, not inline. |
| 113 | if r.referenceStyle() { |
| 114 | for _, def := range r.defs { |
| 115 | dest, ok := linkReferenceDestination(src, def) |
| 116 | // TODO: We skip the edit because a definition split across a blockquote |
| 117 | // carries the ">" marker, and rewriting it would mangle the quote. The |
| 118 | // fallback that appends unrewritten files operates per file. A rewritable |
| 119 | // reference to the same file elsewhere suppresses the append fallback, |
| 120 | // leaving this definition pointing at its original local path. We accept |
| 121 | // this because the tool leaves the reference exactly as the author wrote |
| 122 | // it, rewriting only what can be safely rewritten. |
| 123 | if !ok { |
| 124 | continue |
| 125 | } |
| 126 | edits = append(edits, edit{r.attachmentArg, dest, arg.URL}) |
| 127 | } |
| 128 | continue |
| 129 | } |
| 130 | |
| 131 | at := r.ranges |
| 132 | playerEmbed := arg.RendersAsPlayer && r.isEmbed |
| 133 | |
| 134 | switch { |
| 135 | case !playerEmbed: |
| 136 | // Only the destination moves, so alt text, titles, and formatting |
| 137 | // inside the label survive. |
| 138 | edits = append(edits, edit{r.attachmentArg, at.dest, arg.URL}) |
| 139 | |
| 140 | case standsAlone(src, r.block, at.node): |
| 141 | // A player only renders from a bare URL alone in a paragraph, so |
| 142 | // the whole node goes and any alt text is dropped. |
| 143 | edits = append(edits, edit{r.attachmentArg, at.node, arg.URL}) |
| 144 | |
| 145 | default: |
| 146 | // Degrade to a link: only the "!" and the destination move, so a |
| 147 | // reference nested in the alt text is still rewritten in place. |
| 148 | // |
| 149 | // A literal "!" before the embed's own would pair with the "[" |
| 150 | // left behind and re-form an embed, so it is absorbed into the |