platform/MUSIC_API.md

Music API (/api/music/*)

Platform API the mobile app uses to stream music and sync a server-built library index, so the app no longer pre-downloads whole tracks or walks/ID3-parses the library on-device.

• Source of truth for the code: src/servers/sidecar/music/index.ts (the officer-music sidecar owns all of this; the platform /api/music/* route is a transparent auth-ing proxy).
• Music root: ~/Music on the server. All path values are home-relative (e.g. Music/Albums/AC-DC/[1980] Back in Black/01 Hells Bells.mp3), identical to /api/file-browser/raw.
• <rel>: an album folder path relative to the Music root (e.g. Albums/AC-DC/[1980] Back in Black).

Auth

Every endpoint is behind the standard user auth. Two ways to pass the JWT:

• Header: Authorization: Bearer <jwt> (normal fetches).
• Query: ?token=<jwt> — for media elements / native players that can't set headers (audio, images).

401 = no token · 403 = invalid/expired token.

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1. Playback — stream a track

GET /api/music/stream?path=<home-relative>&token=<jwt>

Byte-range streaming so the player can seek without downloading the whole file.

Case	Status	Headers
No Range	200	Content-Type, Content-Length, Accept-Ranges: bytes, X-Audio-Duration
With Range: bytes=…	206	Content-Range, Content-Length, Accept-Ranges: bytes, Content-Type, X-Audio-Duration

• X-Audio-Duration: track duration in seconds (ffprobe-derived). Read this to set the player's duration up front — it's the fix for AVPlayer reporting an indefinite duration on progressively-streamed VBR MP3s. No need to scan the file.
• Errors: 400 invalid/missing path · 404 not found · 416 bad range.

curl -H "Authorization: Bearer $JWT" -H "Range: bytes=0-1023" \
  "$BASE/api/music/stream?path=Music/Albums/AC-DC/[1980]%20Back%20in%20Black/01%20Hells%20Bells.mp3" -D -

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2. Library index — the synced cache

The server maintains a cache tree that mirrors the library, one entry per album folder. The app syncs this instead of walking + ID3-parsing the library itself.

Each album has a version stamp v (hash of the album's source files' names/sizes/mtimes + its cover). v changes iff the album's content changed → it's the whole basis of the diff: unchanged v ⇒ skip.

2.1 Manifest — one call, whole library

GET /api/music/manifest

{
  "version": 1,
  "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 }
    // …
  }
}

404 if the index has never been built (see §3).

2.2 Album metadata

GET /api/music/meta?path=<rel>

Returns the album's meta.json. Sends ETag: <v>; a request with If-None-Match: <v> returns 304.

{
  "path": "Albums/AC-DC/[1980] Back in Black",
  "cover": "cover.jpg",                    // present only if a cover exists
  "tracks": [
    {
      "file": "01 Hells Bells.mp3",        // filename within the album folder
      "title": "Hells Bells",
      "artist": "AC/DC",
      "albumArtist": "AC/DC",
      "album": "Back in Black",
      "track": "1",
      "year": "1980",
      "durationSec": 312
    }
    // …
  ]
}

All track fields except file are optional (absent when the tag is missing). To stream a track: GET /api/music/stream?path=Music/<rel>/<file>.

2.3 Cover

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.

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3. Building / refreshing the index

The index is built on demand (nothing is pre-built or scheduled). A build is incremental — albums whose v is unchanged are skipped — and it prunes albums removed from the library.

3.1 Trigger

POST /api/music/reindex          → returns IndexStatus (running: true)
GET  /api/music/reindex/status   → IndexStatus snapshot

IndexStatus:

{
  "running": true,
  "startedAt": 1785034701973, "finishedAt": null,
  "foldersScanned": 45, "albumsBuilt": 12, "albumsSkipped": 3,
  "tracksIndexed": 320, "coversSaved": 12,
  "currentPath": "Albums/AC-DC/[1980] Back in Black",
  "error": null
}

3.2 Live progress — SSE

GET /api/music/reindex/stream

• Triggers a build if none is running. Pass ?trigger=0 to watch only (subscribe without starting one).
• Emits event: progress (an IndexStatus) throttled to ~200 ms, then a single event: done (an IndexReport) and closes the stream.

event: progress
data: {"running":true,"foldersScanned":45,"tracksIndexed":320,"albumsBuilt":12,"albumsSkipped":3,"coversSaved":12,"currentPath":"Albums/AC-DC/[1980] Back in Black", …}

event: done
data: {"albums":15,"built":12,"skipped":3,"foldersScanned":45,"tracksIndexed":320,"coversSaved":12,"elapsedSec":37.2,"error":null}

IndexReport (the done payload):

{ "albums": 15, "built": 12, "skipped": 3, "foldersScanned": 45,
  "tracksIndexed": 320, "coversSaved": 12, "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).

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4. Recommended resync algorithm (app side)

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>/.
   • 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.

Optionally trigger a fresh server build first via GET /reindex/stream (and show progress from its progress/done events) so the manifest reflects the latest library before you diff.

Result: a resync after adding one album = 1 manifest fetch + that one album's meta + cover. Nothing else moves.

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Notes

• Covers are server-compressed (≤600px / q5) — sync them as-is; no client-side resizing needed.
• Durations are exact (ffprobe) in both X-Audio-Duration and meta.json's durationSec (seconds).
• Playback still goes through /stream — the index is metadata + covers only. (Server-managed offline audio files is a separate, later feature.)
• Errors are plain HTTP: 503 if the music sidecar isn't connected, 502 if it's unreachable.