-- M489: a persistent, per-user notifications inbox (#726).
--
-- The event bus is fire-and-forget: a client that is not connected when a
-- request completes, or when the scanner marks tracks missing, never hears of
-- it. A row here is the durable record; the bus only nudges open clients to
-- come and read it.
--
-- `kind` is CHECK-gated (rule 36). A new kind adds its value here, in the
-- same migration as the code that produces it. The list is mirrored in
-- internal/notifications/kinds.go, and both CHECKs below must agree with it.

CREATE TABLE user_notifications (
    id            uuid        PRIMARY KEY DEFAULT gen_random_uuid(),
    user_id       uuid        NOT NULL REFERENCES users(id) ON DELETE CASCADE,
    kind          text        NOT NULL CHECK (kind IN (
                      'request_approved',
                      'request_rejected',
                      'request_completed',
                      'request_pending',
                      'quarantine_flagged',
                      'scan_failed',
                      'tracks_missing',
                      'duplicates_found',
                      'playback_errors'
                  )),
    payload       jsonb       NOT NULL DEFAULT '{}'::jsonb,
    created_at    timestamptz NOT NULL DEFAULT now(),
    read_at       timestamptz,
    -- Burst-prone kinds share one key per user. While a row with that key is
    -- unread, a new event updates it in place rather than adding another, so
    -- fourteen missing tracks are one notification with a count.
    coalesce_key  text,
    -- Stamped once the row has gone out in an email (or been judged not to
    -- need one), so the digest never sends the same item twice.
    emailed_at    timestamptz
);

-- The inbox list, newest first.
CREATE INDEX user_notifications_user_created_idx
    ON user_notifications (user_id, created_at DESC);

-- The unread badge, and the digest's selection of unread rows.
CREATE INDEX user_notifications_unread_idx
    ON user_notifications (user_id, created_at DESC)
    WHERE read_at IS NULL;

-- At most one unread row per coalesce key per user. The upsert in
-- notifications.sql targets this index.
CREATE UNIQUE INDEX user_notifications_coalesce_idx
    ON user_notifications (user_id, coalesce_key)
    WHERE read_at IS NULL AND coalesce_key IS NOT NULL;

-- Per user, per kind: which channels a kind reaches. A missing row means the
-- kind's defaults (internal/notifications/kinds.go), so nothing is seeded and
-- a new kind needs no backfill.
CREATE TABLE user_notification_prefs (
    user_id     uuid        NOT NULL REFERENCES users(id) ON DELETE CASCADE,
    kind        text        NOT NULL CHECK (kind IN (
                    'request_approved',
                    'request_rejected',
                    'request_completed',
                    'request_pending',
                    'quarantine_flagged',
                    'scan_failed',
                    'tracks_missing',
                    'duplicates_found',
                    'playback_errors'
                )),
    inbox       boolean     NOT NULL,
    phone       boolean     NOT NULL,
    email       boolean     NOT NULL,
    updated_at  timestamptz NOT NULL DEFAULT now(),
    PRIMARY KEY (user_id, kind)
);