-- 0027_system_playlist_rotation.up.sql — sample-history dedup for
-- system playlists (Fable #415). Two parts:
--
-- 1. play_events.source: which system playlist a play originated
--    from ('for_you' | 'discover' | future kinds), or NULL for any
--    play not launched from a system-playlist surface (library,
--    user playlist, radio, Subsonic). Lets the ingest path know a
--    play should count against that playlist's rotation.
--
-- 2. system_playlist_rotation_state: per (user, playlist_kind) set
--    of track ids already played in the current rotation window.
--    Shuffle-on-play prefers the unplayed tail; when the snapshot
--    is exhausted the set resets and rotation_started_at advances.
--    Centralized server-side so phone / web / watch share one
--    rotation, mirroring how radio dedup already lives server-side.
ALTER TABLE play_events
    ADD COLUMN source text;

CREATE TABLE system_playlist_rotation_state (
    user_id             uuid        NOT NULL REFERENCES users(id) ON DELETE CASCADE,
    playlist_kind       text        NOT NULL,
    played_track_ids    uuid[]      NOT NULL DEFAULT '{}',
    rotation_started_at timestamptz NOT NULL DEFAULT now(),
    updated_at          timestamptz NOT NULL DEFAULT now(),
    PRIMARY KEY (user_id, playlist_kind)
);