Implement a Simple In-Memory Cache for API Responses

class ApiCache {
  constructor(ttlMs = 5 * 60 * 1000) { // Default TTL: 5 minutes
    this.cache = new Map();
    this.ttlMs = ttlMs;
  }

  /**
   * Gets data from cache or fetches it if not present/expired.
   * @param {string} key - The cache key.
   * @param {Function} fetcher - Async function to fetch data if not in cache.
   * @returns {Promise<any>} The cached or fetched data.
   */
  async get(key, fetcher) {
    const cachedItem = this.cache.get(key);
    const now = Date.now();

    if (cachedItem && now < cachedItem.expiry) {
      console.log(`Cache hit for key: ${key}`);
      return cachedItem.data;
    }

    console.log(`Cache miss/expired for key: ${key}. Fetching...`);
    try {
      const data = await fetcher();
      this.set(key, data);
      return data;
    } catch (error) {
      console.error(`Failed to fetch data for key ${key}:`, error);
      throw error;
    }
  }

  /**
   * Sets data in the cache.
   * @param {string} key - The cache key.
   * @param {any} data - The data to cache.
   */
  set(key, data) {
    const expiry = Date.now() + this.ttlMs;
    this.cache.set(key, { data, expiry });
    console.log(`Cached data for key: ${key}, expires at ${new Date(expiry).toLocaleTimeString()}`);
  }

  /**
   * Clears a specific item from the cache.
   * @param {string} key - The cache key to clear.
   */
  clear(key) {
    this.cache.delete(key);
    console.log(`Cleared cache for key: ${key}`);
  }

  /**
   * Clears all items from the cache.
   */
  clearAll() {
    this.cache.clear();
    console.log('Cleared all cache items.');
  }
}

// Example Usage:
// const apiCache = new ApiCache(60 * 1000); // 1 minute TTL

// async function fetchProducts() {
//   return await apiCache.get('all-products', async () => {
//     const response = await fetch('https://api.example.com/products');
//     if (!response.ok) throw new Error('Failed to fetch products');
//     return response.json();
//   });
// }

// (async () => {
//   console.log('First call:');
//   const products1 = await fetchProducts();
//   console.log(products1.slice(0, 2)); // Show first two products

//   await new Promise(resolve => setTimeout(resolve, 500)); // Wait a bit

//   console.log('
Second call (should be from cache):');
//   const products2 = await fetchProducts();
//   console.log(products2.slice(0, 2));

//   await new Promise(resolve => setTimeout(resolve, 60 * 1000 + 500)); // Wait for cache to expire

//   console.log('
Third call (should re-fetch after TTL):');
//   const products3 = await fetchProducts();
//   console.log(products3.slice(0, 2));
// })();