import { createHmac, randomUUID, timingSafeEqual } from 'node:crypto';
import { z } from 'zod';
import type {
  GatewayPort,
  PaymentRequest,
  RefundRequest,
} from '../../src/payments/gateway.contract';
import { commandHash } from '../../src/inventory/inventory.policy';
const captureSchema = z
  .object({
    eventId: z.uuid(),
    paymentId: z.uuid(),
    orderId: z.uuid(),
    amountMinor: z.string().regex(/^[1-9]\d{0,15}$/),
    currency: z.enum(['INR', 'USD', 'EUR', 'GBP']),
  })
  .strict();
// Deliberately confined to tests: this signature format is not a real provider protocol.
export class FakeGateway implements GatewayPort {
  private readonly payments = new Map<
    string,
    { hash: string; paymentId: string }
  >();
  private readonly refunds = new Map<
    string,
    { hash: string; refundId: string }
  >();
  constructor(private readonly secret: string) {}
  async createPayment(input: PaymentRequest) {
    const hash = commandHash(input.orderId, input.amountMinor, input.currency);
    const prior = this.payments.get(input.idempotencyKey);
    if (prior && prior.hash !== hash)
      throw new Error('Gateway idempotency conflict');
    const result = prior ?? { hash, paymentId: randomUUID() };
    this.payments.set(input.idempotencyKey, result);
    return { paymentId: result.paymentId };
  }
  sign(raw: Buffer) {
    return createHmac('sha256', this.secret).update(raw).digest('hex');
  }
  verifyCapture(raw: Buffer, signature: string) {
    if (
      raw.length > 32768 ||
      !/^[a-f0-9]{64}$/.test(signature) ||
      !timingSafeEqual(
        Buffer.from(signature, 'hex'),
        Buffer.from(this.sign(raw), 'hex'),
      )
    )
      throw new Error('Invalid gateway signature');
    return captureSchema.parse(JSON.parse(raw.toString('utf8')));
  }
  async requestRefund(input: RefundRequest) {
    const hash = commandHash(input.paymentId, input.amountMinor);
    const prior = this.refunds.get(input.idempotencyKey);
    if (prior && prior.hash !== hash)
      throw new Error('Refund idempotency conflict');
    const result = prior ?? { hash, refundId: randomUUID() };
    this.refunds.set(input.idempotencyKey, result);
    return { refundId: result.refundId, status: 'PENDING' as const };
  }
}