Centralized API Client with Request Interceptors

class ApiClient {
  constructor(baseURL) {
    this.baseURL = baseURL;
    this.requestInterceptors = [];
    this.responseInterceptors = [];
  }

  addRequestInterceptor(interceptor) {
    this.requestInterceptors.push(interceptor);
  }

  addResponseInterceptor(interceptor) {
    this.responseInterceptors.push(interceptor);
  }

  async request(endpoint, options = {}) {
    let url = `${this.baseURL}${endpoint}`;
    let config = { ...options };

    // Apply request interceptors
    for (const interceptor of this.requestInterceptors) {
      config = await interceptor(url, config);
      if (config === null) { // Allow interceptor to block request
          throw new Error('Request blocked by interceptor');
      }
    }

    try {
      const response = await fetch(url, config);
      let processedResponse = response;

      // Apply response interceptors
      for (const interceptor of this.responseInterceptors) {
        processedResponse = await interceptor(processedResponse);
      }
      
      if (!processedResponse.ok) {
          throw new Error(`HTTP error! Status: ${processedResponse.status}`);
      }

      return processedResponse.json();
    } catch (error) {
      // Global error handling or re-throwing after response interceptors
      console.error('API client request failed:', error);
      throw error;
    }
  }
}

// Usage example:
// const apiClient = new ApiClient('https://jsonplaceholder.typicode.com');
//
// // Add a request interceptor for logging and adding headers
// apiClient.addRequestInterceptor(async (url, config) => {
//   console.log(`Sending request to: ${url}`);
//   config.headers = {
//     ...config.headers,
//     'X-Custom-Header': 'Intercepted-Value'
//   };
//   return config;
// });
//
// // Add a request interceptor for potential authentication token refresh (pseudo-code)
// apiClient.addRequestInterceptor(async (url, config) => {
//   // In a real app, check if token is expired and refresh if necessary
//   // const token = localStorage.getItem('authToken');
//   // if (token) {
//   //   config.headers = { ...config.headers, 'Authorization': `Bearer ${token}` };
//   // }
//   return config;
// });
//
// // Add a response interceptor for error logging or specific status code handling
// apiClient.addResponseInterceptor(async (response) => {
//   if (response.status === 401) {
//     console.warn('Unauthorized access - redirecting to login?');
//     // Potentially trigger a redirect or token refresh logic
//   }
//   return response;
// });
//
// apiClient.request('/posts/1')
//   .then(data => console.log('Fetched post:', data))
//   .catch(error => console.error('Failed to fetch post:', error));