feat(course-format): markdown extraction, discovery, loading, repository

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

packages/course-format/src/repository.ts

@@ -0,0 +1,42 @@
+import { extname } from "node:path";
+import { loadAll, resolveInside, type LoadedCourse } from "./load";
+import { extractSection } from "./markdown";
+
+export interface CourseRepository {
+  list(): LoadedCourse[];
+  get(id: string): LoadedCourse | null;
+  /** Re-scans the course dirs. `id` is accepted for API symmetry; a rescan is cheap and keeps overlay shadowing correct. */
+  reload(id?: string): Promise<void>;
+  readLessonMarkdown(courseId: string, lessonId: string): Promise<string | null>;
+  /** Absolute real path if inside the course root (symlinks followed), else null. */
+  resolvePath(courseId: string, relPath: string): string | null;
+}
+
+const MD = new Set([".md", ".markdown"]);
+
+export async function createCourseRepository(courseDirs: string[]): Promise<CourseRepository> {
+  let courses = await loadAll(courseDirs);
+  const repo: CourseRepository = {
+    list: () => courses,
+    get: (id) => courses.find((c) => c.id === id) ?? null,
+    async reload() {
+      courses = await loadAll(courseDirs);
+    },
+    async readLessonMarkdown(courseId, lessonId) {
+      const entry = repo.get(courseId)?.lessonIndex.get(lessonId);
+      if (!entry) return null;
+      const { lesson } = entry;
+      const rel = lesson.type === "video" ? lesson.transcript : lesson.file;
+      if (!rel || !MD.has(extname(rel).toLowerCase())) return null;
+      const abs = repo.resolvePath(courseId, rel);
+      if (!abs) return null;
+      const text = await Bun.file(abs).text();
+      return lesson.anchor ? extractSection(text, lesson.anchor) : text;
+    },
+    resolvePath(courseId, relPath) {
+      const c = repo.get(courseId);
+      return c ? resolveInside(c.root, relPath) : null;
+    },
+  };
+  return repo;
+}