Add wikilink support as a markdown-it plugin with unit tests

src/renderer/wikilinks.ts

@@ -0,0 +1,82 @@
+import type { MarkdownIt, StateInline } from "markdown-it";
+
+export interface WikilinkTarget {
+  id: string;
+  title: string;
+}
+
+export interface WikilinkOpts {
+  chapters: WikilinkTarget[];
+}
+
+export function wikilinkPlugin(md: MarkdownIt, opts: WikilinkOpts): void {
+  const chapters = opts?.chapters ?? [];
+  const byTitle = new Map(
+    chapters.map((c) => [String(c.title).toLowerCase(), c.id])
+  );
+  const byId = new Set(chapters.map((c) => String(c.id)));
+
+  const resolveId = (target: string): string | null => {
+    const key = target.toLowerCase();
+    if (byTitle.has(key)) return byTitle.get(key)!;
+    if (byId.has(target)) return target;
+    return null;
+  };
+
+  const parse = (state: StateInline, silent: boolean): boolean => {
+    const src = state.src;
+    const max = state.posMax;
+    const start = state.pos;
+    if (start + 2 > max) return false;
+    if (src.charCodeAt(start) !== 0x5b /* [ */ || src.charCodeAt(start + 1) !== 0x5b /* [ */)
+      return false;
+
+    let end = -1;
+    for (let i = start + 2; i < max - 1; i++) {
+      const ch = src.charCodeAt(i);
+      if (ch === 0x5b /* [ */) return false;
+      if (ch === 0x0a /* newline */) return false;
+      if (ch === 0x5d /* ] */ && src.charCodeAt(i + 1) === 0x5d) {
+        end = i;
+        break;
+      }
+    }
+    if (end === -1) return false;
+
+    const raw = src.slice(start + 2, end).trim();
+    if (!raw) return false;
+
+    let target = raw;
+    let label = raw;
+    const pipe = raw.indexOf("|");
+    if (pipe >= 0) {
+      target = raw.slice(0, pipe).trim();
+      const alias = raw.slice(pipe + 1).trim();
+      label = alias.length ? alias : target;
+    }
+    if (!target) return false;
+
+    if (silent) {
+      state.pos = end + 2;
+      return true;
+    }
+
+    const id = resolveId(target);
+    const open = state.push("link_open", "a", 1);
+    if (id !== null) {
+      open.attrs = [
+        ["href", `folio:chapter/${encodeURIComponent(id)}`],
+        ["class", "wikilink internal"],
+      ];
+    } else {
+      open.attrs = [["href", "#"], ["class", "wikilink missing"]];
+    }
+    const text = state.push("text", "", 0);
+    text.content = label;
+    state.push("link_close", "a", -1);
+    state.pos = end + 2;
+    return true;
+  };
+
+  md.inline.ruler.before("link", "wikilink", parse);
+}