Minimal Network Layer

Network.swift

//
//  Network.swift
//  Kirina
//
//  Created by Arash Kashi on 2017-12-11.
//  Copyright © 2017 Arash Kashi. All rights reserved.
//
import Foundation
import UIKit



/// Responsible for network communication with server. Network class uses routing information to compose the service request.
class Network {
   
   enum NetworkError: Error {
      case parsing(String)
      case network
   }
   
   enum Reponse<T> {
      
      case success(T)
      case fail(NetworkError)
   }
   
   private static var timeout: TimeInterval = 5000
   
   /// url session used for communication. it has a timeout interval of 10 seconds, and allows for the cookies to be set.
   /// For security reasons session is configured with ephemeral as it persists NO information of the session including cookies etc.
   static var session: URLSession = {
      
      let config = URLSessionConfiguration.ephemeral
      config.timeoutIntervalForRequest = Network.timeout
      config.httpShouldSetCookies = true
      
      return URLSession(configuration: config)
   }()
   
   
   /// Sends the request to the server. In debug mode it logs the status of communication data
   /// into the console. Logs are disabled in production due to security purposes.
   ///
   /// - Parameters:
   ///   - route: enum type variable which includes information of request such as http type, body of request, and headers.
   ///   - completion: call back in the case of finishing the network communication. The return value of completion is optional.
   ///                 the details of the failed operation is not included in the completion parameter.
   static func sendRequest(route: Routing,
                           completion: @escaping (Network.Reponse<Data>) -> Void) {
      let url = URLComponents(string: route.baseURL.absoluteString)!
      
      var req = URLRequest(url: url.url!,
                           cachePolicy: .reloadIgnoringLocalCacheData,
                           timeoutInterval: Network.timeout)
      
      req.allHTTPHeaderFields   = route.headers
      req.httpMethod            = route.httpMethod
      req.httpBody = route.bodyData
      
      #if DEBUG
         print("Network Request-----------------------------------------------------------------")
         print(req.url?.absoluteString ?? "unknown url")
         if let validBody =  route.bodyData {
            print((String(data: validBody, encoding: .utf8) ?? "unknown body"))
         }
         print("--------------------------------------------------------------------------------")
      #endif
      
      Network.session.dataTask(with: req, completionHandler: { (data, urlRes, error) in
         
         guard error == nil else {
            NSLog(error!.localizedDescription)
            DispatchQueue.main.async { completion(.fail(.network)) }; return
         }
         
         guard let valid = urlRes as? HTTPURLResponse else { completion(.fail(.network)); return }
         
         #if DEBUG
            print("Status Code-----------------------------------------------------------------")
            print(valid.statusCode)
            print("--------------------------------------------------------------------------------")
         #endif
         guard valid.statusCode == 200 else { completion(.fail(.network)); return }
         
         guard let validData = data else {
            DispatchQueue.main.async { completion(.fail(.network)) }; return
         }
         
         do {
            #if DEBUG
               let jsonObject = try JSONSerialization.jsonObject(with: validData)
               let prettyData = try JSONSerialization.data(withJSONObject: jsonObject,
                                                           options: .prettyPrinted)
               print(String(data: prettyData, encoding: .utf8) ?? "unknown")
               print(String(data: validData, encoding: .utf8) ?? "unknown")
               
            #endif
            completion(.success(validData))
         } catch {
            completion(.fail(.parsing(error.localizedDescription)))
         }
      }).resume()
   }
}