music: index artist discographies (album → release type) for the app

Each Albums/<Artist>/_discography.md (author-maintained source of truth, never
modified) is compiled into a per-artist discography.json in the cache = album
folder → normalized release type (Studio/Live/Compilation/Single/EP/…), so the
player can split an artist's album list into sections.

- indexer.ts: parse the md table, normalize the Type (EP?→EP, Compilation (VA)→
  Compilation, …), write discography.json. The artist folder's `v` now includes
  _discography.md so regenerating it re-syncs just that small JSON (isolated from
  the albums' meta/cover). Manifest gains `disco: true` on such entries. Also
  fixed the skip check to require all expected outputs to exist, so artist/
  cover-only folders no longer rebuild every run. New `discographies` counter.
- sidecar: GET /discography?path=<artist rel> (ETag/304), documented in the
  contract header.
- MUSIC_API.md: §2.4 + manifest disco flag + resync algorithm updated.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

MUSIC_API.md

@@ -64,12 +64,15 @@ GET /api/music/manifest
   "generatedAt": 1785034701973,          // ms; when the index was last built
   "albums": {
     "Albums/AC-DC/[1980] Back in Black": { "v": "50856380f1ca8f9", "cover": true, "tracks": 10 },
-    "DJ Sets/Dave Clarke":              { "v": "a1b2c3d4e5f6a7b", "cover": false, "tracks": 3 }
+    "DJ Sets/Dave Clarke":              { "v": "a1b2c3d4e5f6a7b", "cover": false, "tracks": 3 },
+    "Albums/AC-DC":                     { "v": "c0ffee1234567890", "cover": true, "tracks": 0, "disco": true }
     // …
   }
 }
 ```
-`404` if the index has never been built (see §3).
+`404` if the index has never been built (see §3). Entries with **`tracks: 0`** are container folders (e.g. an
+**artist** folder). An entry with **`disco: true`** is an artist folder that has a discography — fetch its
+grouping via `/discography` (§2.4).
 
 ### 2.2 Album metadata
 
@@ -107,6 +110,36 @@ GET /api/music/cover?path=<rel>
 Compressed JPEG (≤600px on the long edge, ~30–80 KB). Sends `ETag: <v>`; `If-None-Match: <v>` → `304`.
 Only meaningful when the manifest entry has `"cover": true`.
 
+### 2.4 Discography (artist album grouping)
+
+For artist folders (manifest entry with `"disco": true`), this returns a map of **album folder → release
+type**, so the player can split an artist's album list into sections (Studio, Live, Compilation, Single, EP…).
+
+```
+GET /api/music/discography?path=<artist rel>      e.g. path=Albums/AC-DC
+```
+Sends `ETag: <v>`; `If-None-Match: <v>` → `304`.
+```jsonc
+{
+  "artist": "Anthrax",
+  "albums": {
+    "[1984] Fistful Of Metal": "Studio",
+    "[1985] Armed And Dangerous": "EP",
+    "[1994] The Island Years": "Live",
+    "[1991] Attack Of The Killer B's": "Compilation"
+    // …
+  }
+}
+```
+- Keys are **album folder names** (`[year] title`) — they map 1:1 to the artist's album folders, i.e. the
+  last path segment of that album's manifest `<rel>`. Group the artist's albums by looking each up here.
+- **Types** are a normalized set: `Studio`, `Live`, `Compilation`, `Single`, `EP`, `Soundtrack`, `Remix`,
+  `DJ-Mix`, `Demo`, `Mixtape`, `Bootleg`, `Other` (unknown values pass through as-is). The player defines
+  section order.
+- An album folder **not present** here has no classification → put it in an "Other"/uncategorized section.
+- Source of truth is each artist's `_discography.md` (author-maintained); this JSON is derived from it and
+  re-generated whenever that file changes (its `v` bumps independently of the albums' `meta`/`cover`).
+
 ---
 
 ## 3. Building / refreshing the index
@@ -127,7 +160,7 @@ GET  /api/music/reindex/status   → IndexStatus snapshot
   "running": true,
   "startedAt": 1785034701973, "finishedAt": null,
   "foldersScanned": 45, "albumsBuilt": 12, "albumsSkipped": 3,
-  "tracksIndexed": 320, "coversSaved": 12,
+  "tracksIndexed": 320, "coversSaved": 12, "discographies": 3,
   "currentPath": "Albums/AC-DC/[1980] Back in Black",
   "error": null
 }
@@ -153,7 +186,7 @@ data: {"albums":15,"built":12,"skipped":3,"foldersScanned":45,"tracksIndexed":32
 `IndexReport` (the `done` payload):
 ```jsonc
 { "albums": 15, "built": 12, "skipped": 3, "foldersScanned": 45,
-  "tracksIndexed": 320, "coversSaved": 12, "elapsedSec": 37.2, "error": null }
+  "tracksIndexed": 320, "coversSaved": 12, "discographies": 3, "elapsedSec": 37.2, "error": null }
 ```
 
 > First build of a large library takes a few minutes; re-runs are near-instant (unchanged albums skip via `v`).
@@ -167,7 +200,7 @@ Keep the last `manifest.albums` you synced. On resync:
 1. `GET /api/music/manifest`.
 2. For each `<rel>` in the new manifest:
    - **new**, or **`v` differs** from your stored copy → fetch `GET /meta?path=<rel>` (+ `GET /cover?path=<rel>`
-     if `cover:true`); store them under your local `<rel>/`.
+     if `cover:true`, + `GET /discography?path=<rel>` if `disco:true`); store them under your local `<rel>/`.
    - **`v` unchanged** → **skip** (no download).
 3. For each `<rel>` you have locally that's **absent** from the new manifest → delete it.
 4. Save the new manifest as your baseline.

src/servers/sidecar/music/index.ts

@@ -10,6 +10,7 @@ import {
   albumVersion,
   metaFilePath,
   coverFilePath,
+  discographyFilePath,
   onIndexProgress,
   buildReport,
 } from './indexer';
@@ -30,9 +31,14 @@ const DATA_PATH = process.env.DATA_PATH ?? join(process.cwd(), 'data');
 //
 //   GET  /stream?path=<home-relative>      audio with Range→206 (Content-Range/Length/Accept-Ranges)
 //                                          + `X-Audio-Duration` (seconds, ffprobe). 400/404/416.
-//   GET  /manifest                         { version, generatedAt, albums: { "<rel>": { v, cover, tracks } } }
+//   GET  /manifest                         { version, generatedAt, albums: { "<rel>": { v, cover, tracks, disco? } } }
 //   GET  /meta?path=<rel>                  album meta.json (IndexMeta). ETag: <v>; If-None-Match → 304.
 //   GET  /cover?path=<rel>                 compressed cover.jpg.       ETag: <v>; If-None-Match → 304.
+//   GET  /discography?path=<artist rel>    artist discography.json (only where manifest entry has
+//                                          disco:true) = { artist, albums: { "<[year] album folder>":
+//                                          "<Type>" } }, Type ∈ Studio/Live/Compilation/Single/EP/…
+//                                          ETag: <v>; If-None-Match → 304. Source: each artist folder's
+//                                          _discography.md (normalized; the md itself is never modified).
 //   POST /reindex                          start an async build; returns IndexStatus (running: true).
 //   GET  /reindex/status                   IndexStatus snapshot.
 //   GET  /reindex/stream                   SSE. Triggers a build if idle (`?trigger=0` = watch-only).
@@ -135,21 +141,21 @@ const server = Bun.serve({
     // ── Sync surface ──
     if (url.pathname === '/manifest') return json(await getManifest());
 
-    if (url.pathname === '/meta' || url.pathname === '/cover') {
+    if (url.pathname === '/meta' || url.pathname === '/cover' || url.pathname === '/discography') {
       const rel = url.searchParams.get('path');
       if (rel === null) return new Response('path is required', { status: 400 });
-      const isMeta = url.pathname === '/meta';
+      const spec = {
-      const file = isMeta ? metaFilePath(rel) : coverFilePath(rel);
+        '/meta': { file: metaFilePath(rel), type: 'application/json' },
-      if (!file) return new Response('Invalid path', { status: 400 });
+        '/cover': { file: coverFilePath(rel), type: 'image/jpeg' },
-      if (!(await Bun.file(file).exists())) return new Response('Not found', { status: 404 });
+        '/discography': { file: discographyFilePath(rel), type: 'application/json' },
+      }[url.pathname]!;
+      if (!spec.file) return new Response('Invalid path', { status: 400 });
+      if (!(await Bun.file(spec.file).exists())) return new Response('Not found', { status: 404 });
 
       const v = await albumVersion(rel);
       if (v && req.headers.get('if-none-match') === v) return new Response(null, { status: 304 });
-      return new Response(Bun.file(file), {
+      return new Response(Bun.file(spec.file), {
-        headers: {
+        headers: { 'Content-Type': spec.type, ...(v ? { ETag: v } : {}) },
-          'Content-Type': isMeta ? 'application/json' : 'image/jpeg',
-          ...(v ? { ETag: v } : {}),
-        },
       });
     }
 

src/servers/sidecar/music/indexer.ts

@@ -1,6 +1,6 @@
 import { readdir, stat, mkdir, writeFile, readFile, rm } from 'node:fs/promises';
 import { existsSync } from 'node:fs';
-import { join, relative } from 'node:path';
+import { join, relative, basename } from 'node:path';
 import { homedir } from 'node:os';
 
 // Server-side music library indexer — the platform counterpart of the app's music-index.ts. Walks the
@@ -23,6 +23,7 @@ const MANIFEST_PATH = join(CACHE_ROOT, 'manifest.json');
 
 const AUDIO_EXT = new Set(['mp3', 'flac', 'm4a', 'aac', 'ogg', 'opus', 'wav', 'wma', 'mp4']);
 const COVER_FILES = ['folder.jpg', 'cover.jpg', 'folder.png', 'cover.png'];
+const DISCO_FILE = '_discography.md';
 const TRACK_CONCURRENCY = 6;
 const COVER_MAX_PX = 600;
 
@@ -40,9 +41,45 @@ export type IndexTrack = {
 };
 export type IndexMeta = { path: string; cover?: string; tracks: IndexTrack[] };
 
-type ManifestEntry = { v: string; cover: boolean; tracks: number };
+type ManifestEntry = { v: string; cover: boolean; tracks: number; disco?: boolean };
 type Manifest = { version: number; generatedAt: number; albums: Record<string, ManifestEntry> };
 
+// ── Discography (artist-level _discography.md → album folder → normalized type) ──
+
+/** Canonical section for a Type cell. The source _discography.md is NEVER modified — this only cleans
+ *  the derived JSON so the phone groups into tidy sections. Unknown types pass through trimmed. */
+function normalizeType(raw: string): string {
+  const t = raw.trim().replace(/\?+$/, '').trim(); // "EP?" → "EP", "Single?" → "Single"
+  const lower = t.toLowerCase();
+  if (lower.startsWith('compilation')) return 'Compilation'; // "Compilation (VA)" → "Compilation"
+  const map: Record<string, string> = {
+    studio: 'Studio',
+    live: 'Live',
+    single: 'Single',
+    ep: 'EP',
+    soundtrack: 'Soundtrack',
+    remix: 'Remix',
+    'dj-mix': 'DJ-Mix',
+    djmix: 'DJ-Mix',
+    demo: 'Demo',
+    mixtape: 'Mixtape',
+    bootleg: 'Bootleg',
+    other: 'Other',
+  };
+  return map[lower] ?? t;
+}
+
+/** Parse the md table into { "[year] album" (folder name) → normalized type }. */
+function parseDiscography(mdText: string): Record<string, string> {
+  const albums: Record<string, string> = {};
+  for (const line of mdText.split('\n')) {
+    const m = line.match(/^\|\s*(\d{4})\s*\|\s*(.+?)\s*\|\s*([^|]+?)\s*\|/);
+    if (!m) continue; // header/separator/non-rows don't match (Year isn't 4 digits)
+    albums[`[${m[1]}] ${m[2]}`] = normalizeType(m[3]!);
+  }
+  return albums;
+}
+
 export type IndexStatus = {
   running: boolean;
   startedAt: number | null;
@@ -52,6 +89,7 @@ export type IndexStatus = {
   albumsSkipped: number; // unchanged (v matched)
   tracksIndexed: number;
   coversSaved: number;
+  discographies: number; // artist discography.json files written
   currentPath: string;
   error: string | null;
 };
@@ -93,6 +131,7 @@ const status: IndexStatus = {
   albumsSkipped: 0,
   tracksIndexed: 0,
   coversSaved: 0,
+  discographies: 0,
   currentPath: '',
   error: null,
 };
@@ -108,6 +147,7 @@ export type IndexReport = {
   foldersScanned: number;
   tracksIndexed: number;
   coversSaved: number;
+  discographies: number;
   elapsedSec: number;
   error: string | null;
 };
@@ -121,6 +161,7 @@ export function buildReport(s: IndexStatus = status): IndexReport {
     foldersScanned: s.foldersScanned,
     tracksIndexed: s.tracksIndexed,
     coversSaved: s.coversSaved,
+    discographies: s.discographies,
     elapsedSec: Math.round(elapsed * 10) / 10,
     error: s.error,
   };
@@ -250,6 +291,7 @@ export async function buildMusicIndex(): Promise<IndexStatus> {
     albumsSkipped: 0,
     tracksIndexed: 0,
     coversSaved: 0,
+    discographies: 0,
     currentPath: '',
     error: null,
   });
@@ -300,8 +342,11 @@ async function walk(dirAbs: string, prev: Manifest, next: Manifest): Promise<voi
   const coverName = COVER_FILES.find((c) => files.some((e) => e.name === c));
   const rel = relative(MUSIC_ROOT, dirAbs); // '' at root
 
-  if (audio.length || coverName) {
+  const hasDisco = files.some((e) => e.name === DISCO_FILE);
-    // Source signature → version.
+
+  if (audio.length || coverName || hasDisco) {
+    // Source signature → version (includes _discography.md so regenerating it bumps v — isolated from
+    // the album meta/cover of the tracks underneath).
     const sigParts: string[] = [];
     for (const name of [...audio].sort()) {
       const st = await stat(join(dirAbs, name)).catch(() => null);
@@ -311,11 +356,23 @@ async function walk(dirAbs: string, prev: Manifest, next: Manifest): Promise<voi
       const st = await stat(join(dirAbs, coverName)).catch(() => null);
       if (st) sigParts.push(`cover:${coverName}:${st.size}:${Math.round(st.mtimeMs)}`);
     }
+    if (hasDisco) {
+      const st = await stat(join(dirAbs, DISCO_FILE)).catch(() => null);
+      if (st) sigParts.push(`disco:${st.size}:${Math.round(st.mtimeMs)}`);
+    }
     const v = Bun.hash(sigParts.join('|')).toString(16);
     const cacheDir = join(CACHE_ROOT, rel);
-    const metaExists = existsSync(join(cacheDir, 'meta.json'));
 
-    if (prev.albums[rel]?.v === v && metaExists) {
+    // Skip only if v matches AND every expected output already exists (fixes cover-only/artist folders
+    // that have no meta.json from rebuilding every run).
+    const expected = [
+      audio.length ? 'meta.json' : null,
+      coverName ? 'cover.jpg' : null,
+      hasDisco ? 'discography.json' : null,
+    ].filter((f): f is string => f !== null);
+    const outputsExist = expected.every((f) => existsSync(join(cacheDir, f)));
+
+    if (prev.albums[rel]?.v === v && outputsExist) {
       status.albumsSkipped += 1;
     } else {
       await mkdir(cacheDir, { recursive: true });
@@ -335,10 +392,22 @@ async function walk(dirAbs: string, prev: Manifest, next: Manifest): Promise<voi
         const meta: IndexMeta = { path: rel, cover: coverName ? 'cover.jpg' : undefined, tracks };
         await writeFile(join(cacheDir, 'meta.json'), JSON.stringify(meta));
       }
+
+      if (hasDisco) {
+        try {
+          const md = await readFile(join(dirAbs, DISCO_FILE), 'utf8');
+          const disco = { artist: basename(dirAbs), albums: parseDiscography(md) };
+          await writeFile(join(cacheDir, 'discography.json'), JSON.stringify(disco));
+          status.discographies += 1;
+        } catch {
+          /* skip discography on failure */
+        }
+      }
+
       status.albumsBuilt += 1;
     }
 
-    next.albums[rel] = { v, cover: !!coverName, tracks: audio.length };
+    next.albums[rel] = { v, cover: !!coverName, tracks: audio.length, ...(hasDisco ? { disco: true } : {}) };
   }
 
   for (const d of subdirs) await walk(join(dirAbs, d.name), prev, next);
@@ -359,3 +428,6 @@ export function metaFilePath(rel: string): string | null {
 export function coverFilePath(rel: string): string | null {
   return resolveCachePath(rel, 'cover.jpg');
 }
+export function discographyFilePath(rel: string): string | null {
+  return resolveCachePath(rel, 'discography.json');
+}