First piece of "export a mirrored playlist to Spotify/Deezer" (diegocade1). Reuses the exact
machinery the ListenBrainz/JSPF export already proves out, additively:
- resolve_playlist_tracks gains an `id_key` param (default "recording_mbid" → LB/JSPF callers
byte-for-byte unchanged). The dedup/stats/order logic is ID-agnostic; only the output field
name differs, so service export plugs in with id_key="service_track_id".
- export_sources gains db_service_track_id(artist, title, service) + build_service_resolve_fn —
text-matches a library track (same pattern as the MBID resolver) and returns its stored
spotify_track_id / deezer_id. Enrichment already pinned those IDs, so export is a lookup, not a
re-search — which is what makes the reverse direction reliable (no fuzzy guessing).
No schema change needed: get/set_playlist_export_target already key by service name, so Spotify/
Deezer targets store for free (idempotent re-export, like the LB #903 fix).
7 tests: LB default id_key unchanged, service id_key carries the id + unmatched handling, service→
column mapping, unknown-service/no-title guards, resolve_fn id+source. 38 export tests green,
ruff clean.
Remaining increments: Spotify write client (+ playlist-modify scope / re-auth), Deezer write via
the ARL gw-light gateway, the export-job branch + endpoint, the modal options.
Phase 3. Additive backbone for the export job:
- mb_recording_cache table (IF NOT EXISTS) + core/exports/recording_mbid_cache.py: persistent
(artist,title)->recording_mbid cache, mirrors album_mbid_cache (lazy DB, error-degrades to
miss). The MusicBrainz tail is ~1 req/s, so a resolved MBID is remembered once and reused
across every export/playlist.
- core/exports/playlist_export.py: resolve_playlist_tracks(tracks, resolve_fn) — walks tracks,
dedups repeated songs within a run (resolve once), builds the ordered pseudo-playlist, tallies
live stats (resolved/unmatched/deduped/by_source). Pure (I/O injected via resolve_fn + progress
callback), so dedup + accounting are unit-tested with no DB/network. 5 tests.
No wiring into runtime yet; nothing existing touched except the additive table.
