// Step 1: Compute Request Body Hash
String bodyChecksum = SHA256_Hex(requestBodyBytes);

// Step 2: Assemble Canonical Message String
String canonicalPayload = String.format("%s|%s|%s|%s|%s",
    httpMethod.toUpperCase(),  // e.g. "POST"
    requestURI.getPath(),      // e.g. "/v1/orders/checkout"
    timestampMs,               // e.g. "1723205160000"
    nonceHex,                  // e.g. "nonce_8f92a10b4c"
    bodyChecksum               // SHA-256 string
);

// Step 3: RSA 2048-bit Signature Verification
boolean isValid = Signature.getInstance("SHA256withRSA")
    .initVerify(userPublicKeyFromRedis)
    .update(canonicalPayload.getBytes(StandardCharsets.UTF_8))
    .verify(Base64.getDecoder().decode(xAuthSignature));

-- Redis Lua Script: cart_mutate.lua
-- KEYS[1]: Cart Redis Hash Key (e.g., "cart:user:usr_99812")
-- ARGV[1]: Product Variant ID (e.g., "prd_milktea_large")
-- ARGV[2]: Delta Quantity (+1 or -1)
-- ARGV[3]: Selected Options JSON String

local cartKey = KEYS[1]
local productId = ARGV[1]
local delta = tonumber(ARGV[2])

local currentQty = redis.call('HGET', cartKey, productId)
local newQty = 0

if currentQty then
    newQty = tonumber(currentQty) + delta
else
    newQty = delta
end

if newQty <= 0 then
    -- Remove product item from cart Hash
    redis.call('HDEL', cartKey, productId)
else
    -- Update item quantity atomically
    redis.call('HSET', cartKey, productId, newQty)
end

-- Refresh 24-hour expiration TTL
redis.call('EXPIRE', cartKey, 86400)

-- Return complete updated cart payload
return redis.call('HGETALL', cartKey)

-- Redis Lua Script: rate_limiter.lua
-- KEYS[1]: Rate limit ZSET key (e.g., "otp:rate:+84901234567")
-- ARGV[1]: Current Unix Timestamp (milliseconds)
-- ARGV[2]: Window Size (milliseconds, e.g., 60000 for 1 minute)
-- ARGV[3]: Max Requests Allowed (e.g., 1 request per min)

local rateKey = KEYS[1]
local now = tonumber(ARGV[1])
local window = tonumber(ARGV[2])
local maxLimit = tonumber(ARGV[3])
local clearBefore = now - window

-- 1. Remove expired timestamps outside the current window
redis.call('ZREMRANGEBYSCORE', rateKey, 0, clearBefore)

-- 2. Count remaining requests inside the sliding window
local currentRequests = redis.call('ZCARD', rateKey)

if currentRequests < maxLimit then
    -- 3. Add current timestamp to ZSET
    redis.call('ZADD', rateKey, now, now)
    redis.call('EXPIRE', rateKey, math.ceil(window / 1000))
    return 1 -- ALLOWED
else
    return 0 -- REJECTED (HTTP 429 Rate Limit Exceeded)
end

-- Redis Lua Script: release_lock.lua
-- KEYS[1]: Lock key (e.g., "payment:lock:txn_778129")
-- ARGV[1]: Unique Lock UUID generated by acquiring thread

if redis.call('GET', KEYS[1]) == ARGV[1] then
    -- Only delete if lock value matches worker thread UUID
    return redis.call('DEL', KEYS[1])
else
    -- Lock has expired or been acquired by another thread
    return 0
end

{
  "info": {
    "name": "ZAP Ecosystem Microservices API Catalog",
    "schema": "https://schema.getpostman.com/json/collection/v2.1.0/collection.json"
  },
  "item": [
    { "name": "commerce-service (215 APIs)" },
    { "name": "identity-service (83 APIs)" },
    { "name": "payment-service (44 APIs)" },
    { "name": "notification-service (7 APIs)" },
    { "name": "api-gateway (1 API)" }
  ]
}

@PostMapping("/v1/payments/payoo/ipn")
public ResponseEntity<?> handlePayooIpn(
        @RequestBody PayooIpnRequest req,
        @RequestHeader("X-Payoo-Checksum") String headerChecksum,
        HttpServletRequest http) {

    // 1. IP Whitelist Check
    String clientIp = http.getHeader("X-Forwarded-For");
    if (!PAYOO_ALLOWED_IPS.contains(clientIp))
        return ResponseEntity.status(403).build();

    // 2. Reconstruct canonical string & compute HMAC-SHA256
    String canonical = req.getAmount() + "|" + req.getOrderId()
                     + "|" + req.getResponseCode() + "|" + payooSecret;
    String computed   = HmacUtils.hmacSha256Hex(payooSecret, canonical);

    if (!computed.equalsIgnoreCase(headerChecksum))
        return ResponseEntity.status(400).body("INVALID_CHECKSUM");

    // 3. Redis Idempotency Lock — prevent double-processing
    String lockKey = "payment:ipn:lock:" + req.getOrderId();
    Boolean acquired = redisTemplate.opsForValue()
        .setIfAbsent(lockKey, "processing", Duration.ofMinutes(10));
    if (Boolean.FALSE.equals(acquired))
        return ResponseEntity.ok("ALREADY_PROCESSED");

    // 4. Process — update order status & publish payment.success.event
    paymentService.handlePayooSuccess(req);
    return ResponseEntity.ok("00"); // Payoo expects "00" = success
}

@PostMapping("/v1/payments/vietqr/ipn")
public ResponseEntity<?> handleVietQrIpn(@RequestBody VietQrIpnRequest req) {

    // 1. Reconstruct canonical string
    String canonical = vietQrClientId + "|" + vietQrApiKey
                     + "|" + req.getAmount() + "|" + req.getOrderId();
    String computed  = HmacUtils.hmacSha256Hex(vietQrApiKey, canonical);

    // 2. Compare with checksum in body
    if (!computed.equals(req.getChecksum()))
        return ResponseEntity.badRequest().body(Map.of("code", "01", "desc", "Checksum invalid"));

    // 3. Idempotency lock + event dispatch
    String lockKey = "payment:ipn:lock:" + req.getOrderId();
    if (Boolean.FALSE.equals(
            redisTemplate.opsForValue().setIfAbsent(lockKey, "1", Duration.ofMinutes(10))))
        return ResponseEntity.ok(Map.of("code", "00", "desc", "Already processed"));

    paymentService.handleVietQrSuccess(req);
    return ResponseEntity.ok(Map.of("code", "00", "desc", "Success"));
}

@PostMapping("/v1/payments/momo/ipn")
public ResponseEntity<?> handleMomoIpn(@RequestBody MomoIpnRequest req) {

    // 1. Reconstruct raw signature string (MoMo-sorted fields)
    String raw = "accessKey=" + momoAccessKey
        + "&amount=" + req.getAmount()
        + "&extraData=" + req.getExtraData()
        + "&message=" + req.getMessage()
        + "&orderId=" + req.getOrderId()
        + "&orderInfo=" + req.getOrderInfo()
        + "&orderType=" + req.getOrderType()
        + "&partnerCode=" + req.getPartnerCode()
        + "&payType=" + req.getPayType()
        + "&requestId=" + req.getRequestId()
        + "&responseTime=" + req.getResponseTime()
        + "&resultCode=" + req.getResultCode()
        + "&transId=" + req.getTransId();

    // 2. Compute HMAC-SHA256 with secretKey
    String computed = HmacUtils.hmacSha256Hex(momoSecretKey, raw);
    if (!computed.equals(req.getSignature()))
        return ResponseEntity.badRequest().body("Signature mismatch");

    // 3. Only process successful transactions (resultCode == 0)
    if (req.getResultCode() != 0)
        return ResponseEntity.ok("Noted — non-success callback");

    // 4. Idempotency + event
    paymentService.handleMomoSuccess(req);
    return ResponseEntity.ok("OK");
}

@PostMapping("/v1/payments/stripe/webhook")
public ResponseEntity<?> handleStripeWebhook(
        @RequestBody String payload,
        @RequestHeader("Stripe-Signature") String sigHeader) {

    // Stripe SDK validates HMAC-SHA256 + timestamp tolerance (300s)
    Event event;
    try {
        event = Webhook.constructEvent(payload, sigHeader, stripeWebhookSecret);
    } catch (SignatureVerificationException e) {
        return ResponseEntity.status(400).body("Invalid Stripe signature");
    }

    // Handle specific event types
    switch (event.getType()) {
        case "payment_intent.succeeded":
            PaymentIntent intent = (PaymentIntent) event.getData().getObject();
            paymentService.handleStripeSuccess(intent.getId(), intent.getAmount());
            break;
        case "payment_intent.payment_failed":
            paymentService.handleStripeFailure(intent.getId());
            break;
    }
    return ResponseEntity.ok("received");
}

-- Redis Lua Idempotency Guard: ipn_lock.lua
-- KEYS[1]: "payment:ipn:lock:{orderId}"
-- ARGV[1]: Current processor ID
-- ARGV[2]: TTL in seconds (600 = 10 minutes)

if redis.call('SET', KEYS[1], ARGV[1], 'NX', 'EX', ARGV[2]) then
    return 1  -- Lock acquired: safe to process IPN
else
    return 0  -- Lock already held: IPN already processed, skip
end

resilience4j:
  circuitbreaker:
    configs:
      default:
        slidingWindowSize: 10               # Evaluate last 10 requests
        failureRateThreshold: 50            # Trip if 50%+ requests fail
        waitDurationInOpenState: 30s        # Stay OPEN for 30 seconds
        permittedNumberOfCallsInHalfOpenState: 3
        registerHealthIndicator: true

  timelimiter:
    configs:
      default:
        timeoutDuration: 5s                 # Abort upstream call after 5s

spring:
  cloud:
    gateway:
      routes:
        - id: identity-service-route
          predicates:
            - Path=/api/v1/auth/**
          filters:
            - name: CircuitBreaker
              args:
                name: identity-service-cb
                fallbackUri: forward:/fallback/identity

// Circuit Breaker Fallback Controller
@RestController
public class FallbackController {

    @GetMapping("/fallback/identity")
    public Mono<ApiResponse<?>> identityFallback() {
        return Mono.just(ApiResponse.error(5000,
            "identity-service is temporarily unavailable. Please retry in 30 seconds."));
    }

    @GetMapping("/fallback/commerce")
    public Mono<ApiResponse<?>> commerceFallback() {
        return Mono.just(ApiResponse.error(5000,
            "commerce-service is temporarily unavailable."));
    }
}

// Generate 15-minute GCS Signed URL for direct client upload
public String generateSignedUploadUrl(String fileName, String contentType) {
    BlobInfo blobInfo = BlobInfo.newBuilder(
        BlobId.of("zap-media-assets", "products/" + UUID.randomUUID() + "_" + fileName)
    ).setContentType(contentType).build();

    return storage.signUrl(
        blobInfo,
        15, TimeUnit.MINUTES,
        Storage.SignUrlOption.withV4Signature(),
        Storage.SignUrlOption.httpMethod(HttpMethod.PUT)
    ).toString();
}

{
  "code": 1000,
  "message": "Operation completed successfully",
  "data": { ... },
  "timestamp": "2026-08-09T18:49:00Z"
}