The existing module-level Map<songId, CachedLyrics> only survived
within a session. After every app restart the lyrics fetch chain
(server → lrclib → netease) ran from scratch for every track the user
played, even ones whose lyrics were already resolved 5 minutes ago
before the previous session ended.
Add an IndexedDB layer that's only consulted on RAM miss:
- L1 (RAM): unchanged, sync, hit on tab switch / track repeat
- L2 (IndexedDB, async): hit after restart, hydrates RAM
- Network: unchanged fallback chain
Key format `${serverId}:${songId}` so the same songId on two different
Subsonic servers cannot collide.
TTLs: 90 days for resolved lyrics (they rarely change once shipped),
7 days for `notFound` entries (gives the user / admin a chance to add
lyrics later without an indefinite negative cache).
YouLyPlus mode skips L2 — a persisted entry from the standard pipeline
wouldn't have word-level sync, which is the whole point of lyricsplus.
Co-authored-by: Psychotoxical <dev@psysonic.app>
Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Frank Stellmacher