-- Duplicate merge (Scribe #3911). Every statement here runs inside the one
-- transaction library.MergeDuplicateGroup opens, after the removed copy's file
-- is already gone. The loser's own track row is deleted last with DeleteTrack;
-- what these do is move everything it carries onto the survivor first, so that
-- delete's CASCADE finds nothing left to destroy.

-- name: LockDuplicateGroupForMerge :one
-- Locks the group for the rest of the transaction, so two merges of one group
-- cannot run at once.
SELECT id, tier, status
  FROM duplicate_groups
 WHERE id = sqlc.arg(id)
   FOR UPDATE;

-- name: ListDuplicateGroupMergeMembers :many
SELECT t.id, t.file_path, t.file_format, t.file_size, t.added_at, t.album_id,
       t.mbid, albums.mbid AS album_mbid
  FROM duplicate_group_members m
  JOIN tracks t  ON t.id = m.track_id
  JOIN albums    ON albums.id = t.album_id
 WHERE m.group_id = sqlc.arg(group_id)
 ORDER BY t.id;

-- Plain repoints: no unique key involves track_id, so moving rows cannot collide.

-- name: MergeRepointPlayEvents :execrows
UPDATE play_events SET track_id = sqlc.arg(survivor_id)::uuid WHERE track_id = sqlc.arg(loser_id)::uuid;

-- name: MergeRepointSkipEvents :execrows
UPDATE skip_events SET track_id = sqlc.arg(survivor_id)::uuid WHERE track_id = sqlc.arg(loser_id)::uuid;

-- name: MergeRepointContextualLikes :execrows
UPDATE contextual_likes SET track_id = sqlc.arg(survivor_id)::uuid WHERE track_id = sqlc.arg(loser_id)::uuid;

-- name: MergeRepointPlaybackErrors :execrows
UPDATE playback_errors SET track_id = sqlc.arg(survivor_id)::uuid WHERE track_id = sqlc.arg(loser_id)::uuid;

-- name: MergeRepointLidarrRequests :execrows
UPDATE lidarr_requests SET matched_track_id = sqlc.arg(survivor_id)::uuid
 WHERE matched_track_id = sqlc.arg(loser_id)::uuid;

-- name: MergeRepointPlaylistTracks :many
-- playlist_tracks is keyed by (playlist_id, position), so repointing keeps every
-- entry exactly where it was. A playlist that held both copies simply holds the
-- survivor twice — the user put two entries there, and both stay.
UPDATE playlist_tracks SET track_id = sqlc.arg(survivor_id)::uuid
 WHERE track_id = sqlc.arg(loser_id)::uuid
RETURNING playlist_id;

-- Collision-safe merges: a unique key includes track_id, so the survivor may
-- already hold a matching row. Copy what it lacks; DeleteTrack's CASCADE then
-- removes the loser's originals.

-- name: MergeCopyGeneralLikes :many
-- One like per user. A user who liked both copies keeps a single like, dated to
-- the earlier of the two.
INSERT INTO general_likes (user_id, track_id, liked_at)
SELECT user_id, sqlc.arg(survivor_id)::uuid, liked_at
  FROM general_likes
 WHERE track_id = sqlc.arg(loser_id)::uuid
ON CONFLICT (user_id, track_id) DO UPDATE
   SET liked_at = LEAST(general_likes.liked_at, EXCLUDED.liked_at)
RETURNING user_id;

-- name: MergeCopyTrackTags :execrows
INSERT INTO track_tags (track_id, tag, weight)
SELECT sqlc.arg(survivor_id)::uuid, tag, weight
  FROM track_tags
 WHERE track_id = sqlc.arg(loser_id)::uuid
ON CONFLICT (track_id, tag) DO NOTHING;

-- name: MergeCopyTrackSimilarity :execrows
-- Rewrites the loser to the survivor on either side of an edge. An edge between
-- the two copies would become a track similar to itself — the table forbids
-- that, and it means nothing — so it is dropped. An edge the survivor already
-- has from the same source is kept as it is.
INSERT INTO track_similarity (track_a_id, track_b_id, score, source, fetched_at)
SELECT CASE WHEN track_a_id = sqlc.arg(loser_id)::uuid THEN sqlc.arg(survivor_id)::uuid ELSE track_a_id END,
       CASE WHEN track_b_id = sqlc.arg(loser_id)::uuid THEN sqlc.arg(survivor_id)::uuid ELSE track_b_id END,
       score, source, fetched_at
  FROM track_similarity
 WHERE (track_a_id = sqlc.arg(loser_id)::uuid OR track_b_id = sqlc.arg(loser_id)::uuid)
   AND (CASE WHEN track_a_id = sqlc.arg(loser_id)::uuid THEN sqlc.arg(survivor_id)::uuid ELSE track_a_id END)
    <> (CASE WHEN track_b_id = sqlc.arg(loser_id)::uuid THEN sqlc.arg(survivor_id)::uuid ELSE track_b_id END)
ON CONFLICT (track_a_id, track_b_id, source) DO NOTHING;

-- name: MergeInheritTrackMbid :exec
-- A recording MBID is what the similarity pipeline keys on. If only the removed
-- copy carried one, the survivor takes it rather than going dark to similarity.
UPDATE tracks AS survivor
   SET mbid = loser.mbid
  FROM tracks AS loser
 WHERE survivor.id = sqlc.arg(survivor_id)::uuid
   AND loser.id = sqlc.arg(loser_id)::uuid
   AND survivor.mbid IS NULL
   AND loser.mbid IS NOT NULL;

-- name: MarkDuplicateGroupMerged :execrows
UPDATE duplicate_groups
   SET status = 'merged', resolved_at = now()
 WHERE id = sqlc.arg(id) AND status = 'pending';