DO $$
BEGIN
  IF EXISTS (
    SELECT 1
    FROM users
    WHERE billing_customer_id IS NOT NULL AND billing_customer_id <> ''
    GROUP BY billing_customer_id
    HAVING COUNT(*) > 1
  ) THEN
    RAISE EXCEPTION 'duplicate users.billing_customer_id values require Stripe reconciliation before migration 017';
  END IF;

  IF EXISTS (
    SELECT 1
    FROM subscriptions
    WHERE provider = 'stripe' AND status <> 'canceled'
    GROUP BY user_id
    HAVING COUNT(*) > 1
  ) THEN
    RAISE EXCEPTION 'multiple open Stripe subscriptions per user require reconciliation before migration 017';
  END IF;
END $$;

CREATE UNIQUE INDEX IF NOT EXISTS idx_users_billing_customer_unique
  ON users(billing_customer_id)
  WHERE billing_customer_id IS NOT NULL AND billing_customer_id <> '';

CREATE UNIQUE INDEX IF NOT EXISTS idx_subscriptions_user_open_stripe_unique
  ON subscriptions(user_id)
  WHERE provider = 'stripe' AND status <> 'canceled';

CREATE TABLE IF NOT EXISTS billing_checkout_sessions (
  id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
  user_id UUID NOT NULL REFERENCES users(id) ON DELETE CASCADE,
  plan_id UUID NOT NULL REFERENCES plans(id),
  stripe_customer_id VARCHAR(200),
  stripe_session_id VARCHAR(200),
  checkout_url TEXT,
  status VARCHAR(20) NOT NULL DEFAULT 'pending',
  expires_at TIMESTAMPTZ NOT NULL,
  lease_owner UUID,
  lease_until TIMESTAMPTZ,
  error_message TEXT,
  created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
  updated_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
  completed_at TIMESTAMPTZ,
  CONSTRAINT billing_checkout_sessions_status_check
    CHECK (status IN ('pending', 'completed', 'expired', 'failed', 'canceled')),
  CONSTRAINT billing_checkout_sessions_stripe_session_unique
    UNIQUE (stripe_session_id)
);

CREATE UNIQUE INDEX IF NOT EXISTS idx_billing_checkout_sessions_user_pending
  ON billing_checkout_sessions(user_id)
  WHERE status = 'pending';

CREATE INDEX IF NOT EXISTS idx_billing_checkout_sessions_expiry
  ON billing_checkout_sessions(expires_at)
  WHERE status = 'pending';