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

package.json

@@ -13,7 +13,7 @@
     "dev": "concurrently -k \"npm run build:watch\" \"wait-on dist/main.js && npm run electron\"",
     "start": "npm run build && npm run electron",
     "lint": "tsc --noEmit",
-    "test": "node tests/run-project-test.mjs && node tests/run-chapters-test.mjs",
+    "test": "node tests/run-project-test.mjs && node tests/run-chapters-test.mjs && node tests/run-wikilinks-test.mjs",
     "package": "electron-builder",
     "test:e2e": "sh tests/run-e2e.sh"
   },

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);
+}

tests/run-wikilinks-test.mjs

@@ -0,0 +1,107 @@
+// Standalone test for the Obsidian-style wikilink plugin.
+// Run with: node tests/run-wikilinks-test.mjs
+import esbuild from "esbuild";
+import MarkdownIt from "markdown-it";
+import fs from "fs";
+import os from "os";
+import path from "path";
+import url from "url";
+
+const out = path.join(os.tmpdir(), `folio-wikilinks-${process.pid}.mjs`);
+await esbuild.build({
+  entryPoints: [path.resolve("src/renderer/wikilinks.ts")],
+  bundle: true,
+  platform: "node",
+  format: "esm",
+  outfile: out,
+  write: true,
+  logLevel: "silent",
+});
+
+const mod = await import(url.pathToFileURL(out).href);
+const { wikilinkPlugin } = mod;
+
+const chapters = [
+  { id: "introduction-1", title: "Introduction" },
+  { id: "money-2", title: "Money" },
+];
+
+function makeMd() {
+  const md = new MarkdownIt({ html: false, linkify: true, typographer: true });
+  md.use(wikilinkPlugin, { chapters });
+  return md;
+}
+
+let failures = 0;
+function ok(cond, msg) {
+  if (cond) console.log("  ok -", msg);
+  else {
+    failures++;
+    console.error("FAIL -", msg);
+  }
+}
+
+const md = makeMd();
+
+// basic wikilink resolves by title (case-insensitive)
+const html1 = md.render("See [[Introduction]] for details.");
+ok(
+  html1.includes('<a href="folio:chapter/introduction-1" class="wikilink internal">Introduction</a>'),
+  "wikilink resolves by title -> internal link with chapter id"
+);
+
+// wikilink resolves by id
+const html2 = md.render("Link to [[introduction-1]] too.");
+ok(
+  html2.includes('href="folio:chapter/introduction-1"') &&
+    html2.includes("class=\"wikilink internal\""),
+  "wikilink resolves by chapter id"
+);
+
+// label-only match: title takes priority over id
+const html2b = md.render("[[Money]]");
+ok(html2b.includes('href="folio:chapter/money-2"'), "title match wins over id when both plausible");
+
+// missing wikilink renders as missing
+const html3 = md.render("A [[Nonexistent]] thing.");
+ok(
+  html3.includes('href="#"') && html3.includes('class="wikilink missing"'),
+  "unresolved wikilink renders as missing"
+);
+
+// alias / label syntax [[target|label]]
+const html4 = md.render("[[Introduction|custom label]]");
+ok(
+  html4.includes('href="folio:chapter/introduction-1"') &&
+    html4.includes(">custom label<"),
+  "alias syntax renders custom label pointing at resolved target"
+);
+
+// alias of a missing target is still missing
+const html5 = md.render("[[Nope|shown]]");
+ok(
+  html5.includes('class="wikilink missing"') && html5.includes(">shown<"),
+  "alias of missing target renders missing with alias label"
+);
+
+// regression: standard markdown links still work alongside wikilinks
+const html6 = md.render("[external](https://example.com) and [[Introduction]]");
+ok(html6.includes('<a href="https://example.com">external</a>'), "standard link still renders");
+ok(html6.includes('href="folio:chapter/introduction-1"'), "wikilink renders next to standard link");
+
+// regression: bold/italic still parse
+const html7 = md.render("**bold** and [[Introduction]]");
+ok(html7.includes("<strong>bold</strong>"), "emphasis still parses with wikilinks present");
+
+// nested brackets are not treated as wikilinks
+const html8 = md.render("not a [[a [[b]] c]] wikilink");
+ok(!html8.includes('class="wikilink"'), "nested brackets not parsed as wikilink");
+
+// empty [[ ]] is not a wikilink
+const html9 = md.render("empty [[] here");
+ok(!html9.includes('class="wikilink"'), "empty wikilink target not parsed");
+
+fs.rmSync(out, { force: true });
+
+console.log("\nWikilink tests: " + (failures === 0 ? "ALL PASSED" : failures + " FAILED"));
+process.exit(failures === 0 ? 0 : 1);