network.swift

//
//  HTTPNetworking.swift
//  urlSessionDemo
//
//  Created by Nick on 12/2/18.
//  Copyright © 2018 NickOwn. All rights reserved.
//

import Foundation
import UIKit

protocol Networking {
    
    typealias CompletionHandler = (Data?, URLResponse?, Error?) -> Void
    
    func request(from currentVC:UIViewController, url:URL, completion:@escaping(_ data:Data?) ->() )
    
}

struct HTTPNetworking: Networking {
    
    func request(from currentVC:UIViewController,url: URL, completion:@escaping (_ data:Data?) -> ()) {
        let task = createDataTask(from: currentVC, url: url, completion: { data,response, error in
            //if error, call handleError method
            guard let httpResponse = response as? HTTPURLResponse, (200...299).contains(httpResponse.statusCode) else {
                self.handleError(currentVC, response)
                return
            }
            
            completion(data)
            
            
        })
        task.resume()
    }
    
    //handle server side error with alert view controller
    func handleError(_ vc:UIViewController,_ response: URLResponse?) {
        let alertVC = UIAlertController(title: "Error", message: "Something wrong", preferredStyle: .alert)
        let action_OK = UIAlertAction(title: "Got it", style: .cancel, handler: nil)
        alertVC.addAction(action_OK)
        vc.present(alertVC, animated: true, completion: nil)
        
    }
    
    private func createDataTask(from currentVC:UIViewController, url:URL, completion:@escaping CompletionHandler) -> URLSessionTask{
        return URLSession.shared.dataTask(with: url){ data, response, error in
            completion(data, response, error)
        }
    }
    
}