import { AppError } from '../common/errors/app-error';

export function minor(value: string): bigint {
  if (!/^\d+(\.\d{1,2})?$/.test(value)) throw new AppError('MONEY_RANGE');
  const [whole, fraction = ''] = value.split('.');
  return BigInt(whole) * 100n + BigInt(fraction.padEnd(2, '0'));
}
export function decimal(value: bigint): string {
  if (value < 0n || value > 9999999999999999n)
    throw new AppError('MONEY_RANGE');
  return `${value / 100n}.${(value % 100n).toString().padStart(2, '0')}`;
}
export function discountFor(
  subtotal: bigint,
  coupon: {
    kind: 'FIXED' | 'PERCENT';
    amount: string | null;
    percentBps: number | null;
  },
): bigint {
  const amount =
    coupon.kind === 'FIXED'
      ? minor(coupon.amount!)
      : (subtotal * BigInt(coupon.percentBps!) + 5000n) / 10000n;
  return amount > subtotal ? subtotal : amount;
}