-- 0059_duplicate_groups.up.sql — proposed duplicates and the sweeps that find
-- them (Scribe milestone #400: #3910).
--
-- The sweep compares fingerprints (track_fingerprints, 0058) and proposes groups
-- of tracks that hold one recording. Nothing here merges anything: a group is a
-- proposal the operator reviews, and the merge (#3911) is a separate act.

-- One row per sweep. Lets the report tell "the sweep has never run" apart from
-- "it ran and found nothing", and gives the in-flight guard something to check,
-- the same way scan_runs does for the library scan.
CREATE TABLE duplicate_sweeps (
    id                uuid        PRIMARY KEY DEFAULT gen_random_uuid(),
    started_at        timestamptz NOT NULL DEFAULT now(),
    finished_at       timestamptz,
    candidates        integer,
    groups_found      integer,
    oversize_clusters integer,
    error_message     text
);
CREATE INDEX duplicate_sweeps_started_at_idx ON duplicate_sweeps (started_at DESC);

CREATE TABLE duplicate_groups (
    id                   uuid        PRIMARY KEY DEFAULT gen_random_uuid(),
    -- The group's identity: its member track ids, sorted and joined. A sweep
    -- that finds the same tracks again updates this row rather than proposing
    -- them twice, and a dismissal stays attached to the set it was made about.
    member_key           text        NOT NULL UNIQUE,
    -- Rule 36: a new value for either CHECK swaps the constraint in the same
    -- migration.
    tier                 text        NOT NULL CHECK (tier IN ('exact', 'acoustic')),
    -- Largest disagreement between any two members; NULL for exact groups,
    -- which have no score.
    worst_bit_error_rate real,
    status               text        NOT NULL DEFAULT 'pending'
        CHECK (status IN ('pending', 'dismissed', 'merged')),
    detected_at          timestamptz NOT NULL DEFAULT now(),
    last_seen_sweep_id   uuid        REFERENCES duplicate_sweeps (id) ON DELETE SET NULL,
    resolved_at          timestamptz
);
CREATE INDEX duplicate_groups_status_idx ON duplicate_groups (status);

CREATE TABLE duplicate_group_members (
    group_id uuid NOT NULL REFERENCES duplicate_groups (id) ON DELETE CASCADE,
    -- CASCADE is right here: a track that genuinely leaves the library has no
    -- place in a proposal about its duplicates.
    track_id uuid NOT NULL REFERENCES tracks (id) ON DELETE CASCADE,
    PRIMARY KEY (group_id, track_id)
);
CREATE INDEX duplicate_group_members_track_idx ON duplicate_group_members (track_id);

-- The sweep streams candidates in (duration_ms, id) order, keyset-paged, so it
-- only ever holds a few seconds' worth of durations in memory. Without this each
-- page would sort the whole library again.
CREATE INDEX tracks_duration_id_idx ON tracks (duration_ms, id);