import type { Coupon, Prisma } from '../generated/prisma/client';
import type { Principal } from '../identity/identity.types';
import { AppError } from '../common/errors/app-error';
import { minor, discountFor } from '../checkout/money';

export function assertCoupon(
  coupon: Coupon | null,
  currency: string,
  subtotal: bigint,
  now: Date,
  uses: number,
  userUses: number,
): asserts coupon is Coupon {
  if (!coupon) throw new AppError('COUPON_INELIGIBLE', 'COUPON_UNKNOWN');
  const failures: [boolean, string][] = [
    [!coupon.active, 'COUPON_DISABLED'],
    [coupon.currency !== currency, 'COUPON_CURRENCY'],
    [coupon.startsAt > now, 'COUPON_NOT_STARTED'],
    [coupon.endsAt <= now, 'COUPON_EXPIRED'],
    [minor(coupon.minimumSubtotal.toString()) > subtotal, 'COUPON_MINIMUM'],
    [uses >= coupon.maxUses, 'COUPON_TOTAL_LIMIT'],
    [userUses >= coupon.perUserLimit, 'COUPON_USER_LIMIT'],
  ];
  const failure = failures.find(([failed]) => failed);
  if (failure) throw new AppError('COUPON_INELIGIBLE', failure[1]);
}
export async function priceCoupon(
  tx: Prisma.TransactionClient,
  actor: Principal,
  code: string | undefined,
  currency: string,
  subtotal: bigint,
  now: Date,
) {
  if (!code) return { discount: 0n, coupon: null };
  const coupon = await tx.coupon.findUnique({
    where: {
      organizationId_code: { organizationId: actor.organizationId, code },
    },
  });
  const where = {
    couponId: coupon?.id ?? '00000000-0000-0000-0000-000000000000',
    status: 'PENDING_PAYMENT' as const,
    expiresAt: { gt: now },
  };
  const uses = await tx.order.count({ where });
  const userUses = await tx.order.count({
    where: { ...where, userId: actor.userId },
  });
  assertCoupon(coupon, currency, subtotal, now, uses, userUses);
  return {
    coupon,
    discount: discountFor(subtotal, {
      kind: coupon.kind,
      amount: coupon.amount?.toString() ?? null,
      percentBps: coupon.percentBps,
    }),
  };
}