Frontend (Browser)
    │
    ├── Direct to CDN (Intelligent Search)
    │   └── CDN Edge Cache (TTL: 2-5 min, SWR: 60s)
    │       └── VTEX Intelligent Search API
    │
    └── BFF Endpoints
        │
        ├── Cacheable routes (catalog, category tree)
        │   └── BFF Cache Layer (Redis/in-memory)
        │       └── VTEX Catalog API
        │
        └── Non-cacheable routes (checkout, profile, orders)
            └── Direct proxy to VTEX (NO CACHING)

// BFF route with in-memory cache for category tree
import { Router, Request, Response } from "express";

const router = Router();

interface CacheEntry<T> {
  data: T;
  expiresAt: number;
  staleAt: number;
}

const cache = new Map<string, CacheEntry<unknown>>();

function getCached<T>(key: string): { data: T; isStale: boolean } | null {
  const entry = cache.get(key) as CacheEntry<T> | undefined;
  if (!entry) return null;

  const now = Date.now();
  if (now > entry.expiresAt) {
    cache.delete(key);
    return null;
  }

  return {
    data: entry.data,
    isStale: now > entry.staleAt,
  };
}

function setCache<T>(key: string, data: T, maxAgeMs: number, swrMs: number): void {
  const now = Date.now();
  cache.set(key, {
    data,
    staleAt: now + maxAgeMs,
    expiresAt: now + maxAgeMs + swrMs,
  });
}

const VTEX_ACCOUNT = process.env.VTEX_ACCOUNT!;
const CATALOG_BASE = `https://${VTEX_ACCOUNT}.vtexcommercestable.com.br/api/catalog_system/pub`;

// Category tree — cache for 15 minutes, SWR for 5 minutes
router.get("/categories", async (_req: Request, res: Response) => {
  const cacheKey = "category-tree";
  const cached = getCached<unknown>(cacheKey);

  if (cached && !cached.isStale) {
    res.set("X-Cache", "HIT");
    return res.json(cached.data);
  }

  // If stale, serve stale data and refresh in background
  if (cached && cached.isStale) {
    res.set("X-Cache", "STALE");
    res.json(cached.data);

    // Background refresh
    fetch(`${CATALOG_BASE}/category/tree/3`)
      .then((r) => r.json())
      .then((data) => setCache(cacheKey, data, 15 * 60 * 1000, 5 * 60 * 1000))
      .catch((err) => console.error("Background cache refresh failed:", err));
    return;
  }

  // Cache miss — fetch and cache
  try {
    const response = await fetch(`${CATALOG_BASE}/category/tree/3`);
    const data = await response.json();
    setCache(cacheKey, data, 15 * 60 * 1000, 5 * 60 * 1000);
    res.set("X-Cache", "MISS");
    res.json(data);
  } catch (error) {
    console.error("Error fetching categories:", error);
    res.status(500).json({ error: "Failed to fetch categories" });
  }
});

// No caching — every request hits VTEX directly
router.get("/categories", async (_req: Request, res: Response) => {
  // This fires on EVERY request — 10,000 users = 10,000 API calls
  const response = await fetch(
    `https://mystore.vtexcommercestable.com.br/api/catalog_system/pub/category/tree/3`
  );
  const data = await response.json();
  res.json(data); // No cache headers, no BFF cache, no CDN cache
});

// BFF checkout route — explicitly no caching
import { Router, Request, Response } from "express";
import { vtexCheckout } from "../vtex-checkout-client";

export const checkoutRoutes = Router();

// Set no-cache headers for ALL checkout responses
checkoutRoutes.use((_req: Request, res: Response, next) => {
  res.set({
    "Cache-Control": "no-store, no-cache, must-revalidate, proxy-revalidate",
    Pragma: "no-cache",
    Expires: "0",
    "Surrogate-Control": "no-store",
  });
  next();
});

checkoutRoutes.get("/cart", async (req: Request, res: Response) => {
  const orderFormId = req.session.orderFormId;
  if (!orderFormId) {
    return res.status(400).json({ error: "No active cart" });
  }

  try {
    // Always fetch fresh — never cache
    const result = await vtexCheckout({
      path: `/api/checkout/pub/orderForm/${orderFormId}`,
      cookies: req.session.vtexCookies || {},
      userToken: req.session.vtexAuthToken,
    });

    req.session.vtexCookies = result.cookies;
    res.json(result.data);
  } catch (error) {
    console.error("Error fetching cart:", error);
    res.status(500).json({ error: "Failed to fetch cart" });
  }
});

// CATASTROPHIC: Caching checkout data in Redis
import Redis from "ioredis";
const redis = new Redis();

checkoutRoutes.get("/cart", async (req: Request, res: Response) => {
  const orderFormId = req.session.orderFormId;
  const cacheKey = `cart:${orderFormId}`;

  // WRONG: cached cart could have wrong items, old prices, or stale quantities
  const cached = await redis.get(cacheKey);
  if (cached) {
    return res.json(JSON.parse(cached)); // Serving stale transactional data!
  }

  const result = await vtexCheckout({
    path: `/api/checkout/pub/orderForm/${orderFormId}`,
    cookies: req.session.vtexCookies || {},
  });

  // WRONG: caching cart data that changes with every user action
  await redis.setex(cacheKey, 300, JSON.stringify(result.data));
  res.json(result.data);
});

// Cache with TTL + manual invalidation endpoint + event-driven invalidation
import { Router, Request, Response } from "express";

const router = Router();

// In-memory cache with TTL tracking
const productCache = new Map<string, { data: unknown; expiresAt: number }>();

function setProductCache(productId: string, data: unknown, ttlMs: number): void {
  productCache.set(productId, {
    data,
    expiresAt: Date.now() + ttlMs,
  });
}

function getProductCache(productId: string): unknown | null {
  const entry = productCache.get(productId);
  if (!entry || Date.now() > entry.expiresAt) {
    productCache.delete(productId);
    return null;
  }
  return entry.data;
}

// Regular product endpoint with cache
router.get("/products/:productId", async (req: Request, res: Response) => {
  const { productId } = req.params;
  const cached = getProductCache(productId);

  if (cached) {
    return res.json(cached);
  }

  const response = await fetch(
    `https://${process.env.VTEX_ACCOUNT}.vtexcommercestable.com.br/api/catalog_system/pub/products/search?fq=productId:${productId}`
  );
  const data = await response.json();

  setProductCache(productId, data, 5 * 60 * 1000); // 5-minute TTL
  res.json(data);
});

// Manual invalidation endpoint (secured with API key)
router.post("/cache/invalidate", (req: Request, res: Response) => {
  const adminKey = req.headers["x-admin-key"];
  if (adminKey !== process.env.ADMIN_API_KEY) {
    return res.status(403).json({ error: "Unauthorized" });
  }

  const { productId, pattern } = req.body as { productId?: string; pattern?: string };

  if (productId) {
    productCache.delete(productId);
    return res.json({ invalidated: [productId] });
  }

  if (pattern === "all") {
    const count = productCache.size;
    productCache.clear();
    return res.json({ invalidated: count });
  }

  res.status(400).json({ error: "Provide productId or pattern" });
});

// Webhook endpoint for VTEX catalog change events
router.post("/webhooks/catalog-change", (req: Request, res: Response) => {
  const { IdSku, productId } = req.body as { IdSku?: string; productId?: string };

  if (productId) {
    productCache.delete(productId);
    console.log(`Cache invalidated for product ${productId}`);
  }

  // Also invalidate related search cache entries
  // In production, use a more sophisticated invalidation strategy
  res.status(200).json({ received: true });
});

export default router;

// Cache with no TTL and no invalidation — data becomes permanently stale
const cache = new Map<string, unknown>();

router.get("/products/:productId", async (req: Request, res: Response) => {
  const { productId } = req.params;

  // Once cached, this data NEVER expires — price changes, stock updates are invisible
  if (cache.has(productId)) {
    return res.json(cache.get(productId));
  }

  const response = await fetch(`https://mystore.vtexcommercestable.com.br/api/catalog_system/pub/products/search?fq=productId:${productId}`);
  const data = await response.json();
  cache.set(productId, data); // No TTL! No invalidation! Stale forever!
  res.json(data);
});

// If you're using a CDN worker/edge function to add cache headers:
// cloudflare-worker.ts or similar edge function
async function handleSearchRequest(request: Request): Promise<Response> {
  const url = new URL(request.url);

  // Only cache GET requests to Intelligent Search
  if (request.method !== "GET") {
    return fetch(request);
  }

  // Check CDN cache first
  const cacheKey = new Request(url.toString(), request);
  const cachedResponse = await caches.default.match(cacheKey);
  if (cachedResponse) {
    return cachedResponse;
  }

  // Fetch from VTEX
  const response = await fetch(request);
  const responseClone = response.clone();

  // Add cache headers
  const cachedRes = new Response(responseClone.body, responseClone);
  cachedRes.headers.set(
    "Cache-Control",
    "public, max-age=120, stale-while-revalidate=60"
  );

  // Store in CDN cache
  await caches.default.put(cacheKey, cachedRes.clone());

  return cachedRes;
}

// server/cache/redis-cache.ts
import Redis from "ioredis";

const redis = new Redis(process.env.REDIS_URL!);

interface CacheOptions {
  ttlSeconds: number;
  swrSeconds?: number;
}

export async function getCachedOrFetch<T>(
  key: string,
  fetcher: () => Promise<T>,
  options: CacheOptions
): Promise<{ data: T; cacheStatus: "HIT" | "STALE" | "MISS" }> {
  const { ttlSeconds, swrSeconds = 0 } = options;

  // Try to get from cache
  const cached = await redis.get(key);
  if (cached) {
    const ttl = await redis.ttl(key);
    const isStale = ttl <= swrSeconds;

    if (isStale && swrSeconds > 0) {
      // Serve stale, refresh in background
      fetcher()
        .then((freshData) =>
          redis.setex(key, ttlSeconds + swrSeconds, JSON.stringify(freshData))
        )
        .catch((err) => console.error(`Background refresh failed for ${key}:`, err));

      return { data: JSON.parse(cached) as T, cacheStatus: "STALE" };
    }

    return { data: JSON.parse(cached) as T, cacheStatus: "HIT" };
  }

  // Cache miss — fetch and store
  const data = await fetcher();
  await redis.setex(key, ttlSeconds + swrSeconds, JSON.stringify(data));

  return { data, cacheStatus: "MISS" };
}

export async function invalidateCache(pattern: string): Promise<number> {
  const keys = await redis.keys(pattern);
  if (keys.length === 0) return 0;
  return redis.del(...keys);
}

// server/routes/catalog.ts
import { Router, Request, Response } from "express";
import { getCachedOrFetch, invalidateCache } from "../cache/redis-cache";

const router = Router();

const VTEX_ACCOUNT = process.env.VTEX_ACCOUNT!;
const VTEX_BASE = `https://${VTEX_ACCOUNT}.vtexcommercestable.com.br`;

// Category tree — long cache, changes rarely
router.get("/categories", async (_req: Request, res: Response) => {
  try {
    const result = await getCachedOrFetch(
      "catalog:categories",
      async () => {
        const response = await fetch(`${VTEX_BASE}/api/catalog_system/pub/category/tree/3`);
        return response.json();
      },
      { ttlSeconds: 900, swrSeconds: 300 } // 15 min cache, 5 min SWR
    );

    res.set("X-Cache", result.cacheStatus);
    res.json(result.data);
  } catch (error) {
    console.error("Error fetching categories:", error);
    res.status(500).json({ error: "Failed to fetch categories" });
  }
});

// Product details — moderate cache
router.get("/products/:productId", async (req: Request, res: Response) => {
  const { productId } = req.params;

  if (!/^\d+$/.test(productId)) {
    return res.status(400).json({ error: "Invalid product ID" });
  }

  try {
    const result = await getCachedOrFetch(
      `catalog:product:${productId}`,
      async () => {
        const response = await fetch(
          `${VTEX_BASE}/api/catalog_system/pub/products/search?fq=productId:${productId}`
        );
        return response.json();
      },
      { ttlSeconds: 300, swrSeconds: 60 } // 5 min cache, 1 min SWR
    );

    res.set("X-Cache", result.cacheStatus);
    res.json(result.data);
  } catch (error) {
    console.error("Error fetching product:", error);
    res.status(500).json({ error: "Failed to fetch product" });
  }
});

// Cart simulation — very short cache (same cart config may be checked by many users)
router.post("/simulation", async (req: Request, res: Response) => {
  const cacheKey = `catalog:simulation:${JSON.stringify(req.body)}`;

  try {
    const result = await getCachedOrFetch(
      cacheKey,
      async () => {
        const response = await fetch(
          `${VTEX_BASE}/api/checkout/pub/orderForms/simulation`,
          {
            method: "POST",
            headers: { "Content-Type": "application/json" },
            body: JSON.stringify(req.body),
          }
        );
        return response.json();
      },
      { ttlSeconds: 30, swrSeconds: 10 } // 30 sec cache, 10 sec SWR
    );

    res.set("X-Cache", result.cacheStatus);
    res.json(result.data);
  } catch (error) {
    console.error("Error simulating cart:", error);
    res.status(500).json({ error: "Failed to simulate cart" });
  }
});

// Webhook for catalog changes — invalidates affected cache
router.post("/webhooks/catalog", async (req: Request, res: Response) => {
  const { productId } = req.body as { productId?: string };

  if (productId) {
    await invalidateCache(`catalog:product:${productId}`);
  }

  // Invalidate category tree on any catalog change
  await invalidateCache("catalog:categories");

  res.status(200).json({ received: true });
});

export default router;