-- Song links (M498 #5438): copies of one song on different releases share a
-- song_key (migration 0076).

-- name: LinkTracksAsSong :one
-- Links the tracks into one song, joining any songs they already belong to.
-- The song keeps the lowest key among them, so linking the same set again
-- changes nothing. Returns that key and how many tracks moved to it.
WITH keys AS (
    SELECT DISTINCT song_key FROM tracks WHERE id = ANY(sqlc.arg(track_ids)::uuid[])
), target AS (
    SELECT song_key FROM keys ORDER BY song_key LIMIT 1
), moved AS (
    UPDATE tracks t
       SET song_id = (SELECT song_key FROM target)
     WHERE t.song_key IN (SELECT song_key FROM keys)
       AND t.song_key <> (SELECT song_key FROM target)
    RETURNING t.id
)
SELECT (SELECT song_key FROM target)::uuid AS song_key,
       (SELECT count(*) FROM moved)::bigint AS moved;

-- name: ShareSongLikes :many
-- A like on any copy of the song becomes a like on every copy, dated the
-- earliest. Returns the likes added, for the sync log.
INSERT INTO general_likes (user_id, track_id, liked_at)
SELECT l.user_id, t.id, min(l.liked_at)
  FROM general_likes l
  JOIN tracks lt ON lt.id = l.track_id
  JOIN tracks t  ON t.song_key = lt.song_key
 WHERE lt.song_key = sqlc.arg(song_key)::uuid
 GROUP BY l.user_id, t.id
ON CONFLICT (user_id, track_id) DO NOTHING
RETURNING user_id, track_id;

-- name: UnlinkDuplicateGroupSongs :exec
-- "Not the same song": the group's copies stop sharing a song. Likes already
-- shared stay where they are.
UPDATE tracks SET song_id = NULL
 WHERE song_id IS NOT NULL
   AND id IN (SELECT track_id FROM duplicate_group_members WHERE group_id = sqlc.arg(group_id));

-- name: ListTrackSongKeys :many
-- What the mix writer needs to place a track: its song, and whether it is a
-- video rip held back from the mixes (#5439).
SELECT id, song_key, (source_verdict IS NOT DISTINCT FROM 'suspect')::boolean AS held_back
  FROM tracks WHERE id = ANY(sqlc.arg(ids)::uuid[]);

-- name: MergeInheritSongLink :exec
-- A merge keeps the removed copy's song link: when the copy being removed was
-- linked to copies on other releases and the survivor was not, the survivor
-- joins that song. The copy whose id names the song has no song_id of its
-- own, so "linked" is another copy sharing its key, not a song_id.
UPDATE tracks s
   SET song_id = l.song_key
  FROM tracks l
 WHERE s.id = sqlc.arg(survivor_id)::uuid
   AND l.id = sqlc.arg(loser_id)::uuid
   AND s.song_id IS NULL
   AND EXISTS (SELECT 1 FROM tracks o
                WHERE o.song_key = l.song_key AND o.id <> l.id AND o.id <> s.id);