-- Genre mixes: one daily system playlist per genre the user listens to
-- ("Post-Punk mix", "Jazz mix", ...). Several per user, like
-- songs_like_artist, but seedless: the genre lives in the playlist name and
-- seed_artist_id is NULL.
--
-- Postgres has no ALTER CONSTRAINT for CHECK, so both constraints are
-- dropped and re-added with 'genre_mix' in the accepted set.

ALTER TABLE playlists DROP CONSTRAINT IF EXISTS playlists_kind_variant_consistent;
ALTER TABLE playlists
    ADD CONSTRAINT playlists_kind_variant_consistent CHECK (
        (kind = 'user'   AND system_variant IS NULL)
        OR
        (kind = 'system' AND system_variant IN (
            'for_you', 'songs_like_artist', 'discover',
            'deep_cuts', 'rediscover', 'new_for_you',
            'on_this_day', 'first_listens', 'genre_mix'
        ))
    );

ALTER TABLE playlists DROP CONSTRAINT IF EXISTS playlists_seed_consistent;
ALTER TABLE playlists
    ADD CONSTRAINT playlists_seed_consistent CHECK (
        (system_variant IS NULL                 AND seed_artist_id IS NULL)
        OR
        (system_variant = 'for_you'             AND seed_artist_id IS NULL)
        OR
        (system_variant = 'discover'            AND seed_artist_id IS NULL)
        OR
        (system_variant = 'deep_cuts'           AND seed_artist_id IS NULL)
        OR
        (system_variant = 'rediscover'          AND seed_artist_id IS NULL)
        OR
        (system_variant = 'new_for_you'         AND seed_artist_id IS NULL)
        OR
        (system_variant = 'on_this_day'         AND seed_artist_id IS NULL)
        OR
        (system_variant = 'first_listens'       AND seed_artist_id IS NULL)
        OR
        (system_variant = 'genre_mix'           AND seed_artist_id IS NULL)
        OR
        (system_variant = 'songs_like_artist'   AND seed_artist_id IS NOT NULL)
    );