import Foundation

class MockURLProtocol: URLProtocol {
  
  override class func canInit(with request: URLRequest) -> Bool {
      // To check if this protocol can handle the given request.
      return true
  }

  override class func canonicalRequest(for request: URLRequest) -> URLRequest {
      // Here you return the canonical version of the request but most of the time you pass the orignal one.
      return request
  }

  override func startLoading() {
      guard let handler = MockURLProtocol.requestHandler else {
        fatalError("Handler is unavailable.")
      }
        
      do {
        // 2. Call handler with received request and capture the tuple of response and data.
        let (response, data) = try handler(request)
        
        // 3. Send received response to the client.
        client?.urlProtocol(self, didReceive: response, cacheStoragePolicy: .notAllowed)
        
        if let data = data {
          // 4. Send received data to the client.
          client?.urlProtocol(self, didLoad: data)
        }
        
        // 5. Notify request has been finished.
        client?.urlProtocolDidFinishLoading(self)
      } catch {
        // 6. Notify received error.
        client?.urlProtocol(self, didFailWithError: error)
      }
  }

  override func stopLoading() {
      // This is called if the request gets canceled or completed.
      print("")
  }
}