-- Prevent task from being both cancelled and archived simultaneously
ALTER TABLE task_task ADD CONSTRAINT chk_task_not_cancelled_and_archived
    CHECK (NOT (is_cancelled = true AND is_archived = true));

-- Subscription tier must be a valid value
ALTER TABLE subscriptions_usersubscription ADD CONSTRAINT chk_subscription_tier
    CHECK (tier IN ('free', 'pro'));

-- Notification: sent_at must be set when sent is true
ALTER TABLE notifications_notification ADD CONSTRAINT chk_notification_sent_consistency
    CHECK ((sent = false) OR (sent = true AND sent_at IS NOT NULL));

-- One subscription per user
ALTER TABLE subscriptions_usersubscription ADD CONSTRAINT uq_subscription_user
    UNIQUE (user_id);

-- One notification preference per user
ALTER TABLE notifications_notificationpreference ADD CONSTRAINT uq_notif_pref_user
    UNIQUE (user_id);