URLSessionDelegateExample.swift

import UIKit
import PlaygroundSupport
import Foundation

PlaygroundPage.current.needsIndefiniteExecution = true

//URLSessionTaskDelegate
//You use this protocol in one of two ways, depending on how you use a URLSession:
//If you create tasks with Swift’s async-await syntax, using methods like bytes(for:delegate:) and data(for:delegate:), you pass a delegate argument of this type. The delegate receives callbacks for things like task progress, while the call point awaits the completion of the task. A delegate that receives life cycle and authentication challenge callbacks as the transfer progresses.
//If you add tasks to the session with methods like dataTask(with:) and downloadTask(with:), then you implement this protocol’s methods in a delegate you set on the session. This session delegate may also implement other protocols as appropriate, like URLSessionDownloadDelegate and URLSessionDataDelegate. You can also assign a delegate of this type directly to the task to intercept callbacks before the task delivers them to the session’s delegate.

//TODO?: https://developer.apple.com/documentation/foundation/urlsessiondownloaddelegate
//would appear to work exclusively with downloadTask not .download


//https://github.com/apple/swift-corelibs-foundation/blob/main/Sources/FoundationNetworking/URLSession/URLSessionTask.swift

@available(iOS 15.0, *)
public class TestDelegate: NSObject, URLSessionDataDelegate, URLSessionTaskDelegate {
    private var session: URLSession! = nil
    
    private var dataTask: URLSessionDataTask?
    
    private var sessionTask: URLSessionTask?
    
    
    public init(urlSession:URLSession? = nil) {
        super.init()
        if urlSession != nil {
            self.session = urlSession!
        } else {
            let config = URLSessionConfiguration.default
            config.requestCachePolicy = .reloadIgnoringLocalCacheData
            self.session = URLSession(configuration: config, delegate: self, delegateQueue: .main)
        }
    }
    
    let urlString_redirect = "http:www.apple.com"
    let urlString_json = "https://jsonplaceholder.typicode.com/posts/1"
    let urlString_auth = "https://httpbin.org/basic-auth/hello/dolly"
    
    public func simpleGet() async throws {
        let url = URL(string:urlString_json)!
        let (data, response) = try await self.session.data(from:url, delegate: self)
        print(sessionTask?.state.rawValue)
        print(sessionTask?.progress)
        print(sessionTask?.progress.fileOperationKind)
        let httpResponse = response as? HTTPURLResponse
        print("Task \(sessionTask?.description ?? "") heard \(httpResponse?.statusCode ?? 0)")
        print(await session.tasks)
        print("I got data. \(data.count)")
    }
    
    public func simpleDataTask() {
        let url = URL(string:urlString_json)!
        self.dataTask = self.session.dataTask(with: URLRequest(url: url))
        dataTask?.resume()
    }
    
    
    //MARK: WORKS .data & .dataTask
    public func urlSession(_ session: URLSession, didCreateTask task: URLSessionTask) {
        print("I made a task:\(task)")
        self.sessionTask = task
    }
    
    //fires on finish
    public func urlSession(_ session: URLSession, task: URLSessionTask, didFinishCollecting metrics: URLSessionTaskMetrics) {
        print("metrics for \(task) recieved.")
        //print(metrics)
    }
    
    public func urlSession(_ session: URLSession, task: URLSessionTask, willPerformHTTPRedirection response: HTTPURLResponse, newRequest request: URLRequest) async -> URLRequest? {
        print("redirecting... \(String(describing: request.url))")
        return request
    }
    
    //MARK: Worked JUST for .data
    //presumably the one with a completion handler is for .dataTask
    //but was challenge even maybe when wasn't supposed to have been?
    public func urlSession(
        _ session: URLSession,
      task: URLSessionTask,
      didReceive challenge: URLAuthenticationChallenge
    ) async -> (URLSession.AuthChallengeDisposition, URLCredential?) {
        print("challenged \(task) with \(challenge)")
        
      if challenge.protectionSpace.authenticationMethod == NSURLAuthenticationMethodHTTPBasic {
        do {
          let (username, password) = ("hello", "dolly")
          return (.useCredential, URLCredential(user: username, password: password, persistence: .forSession))
        } catch {
          return (.cancelAuthenticationChallenge, nil)
        }
      } else {
        return (.performDefaultHandling, nil)
      }
    }
    
    //MARK: Works with dataTask only
    public func urlSession(_ session: URLSession, dataTask: URLSessionDataTask, didReceive response: URLResponse) async -> URLSession.ResponseDisposition {
        let httpResponse = response as? HTTPURLResponse
        print("Task \(dataTask) heard \(httpResponse?.statusCode ?? 0)")
        return URLSession.ResponseDisposition.allow
    }
    
    public func urlSession(_ session: URLSession, dataTask: URLSessionDataTask, didReceive data: Data) {
        print("I heard that...\(data.count)")
        //NSLog("task data: %@", data as NSData)
        //print("task data: %@", data as NSData)
    }
    
    public func urlSession(_ session: URLSession, task: URLSessionTask, didCompleteWithError error: Error?) {
        if let error = error as NSError? {
            //NSLog("task error: %@ / %d", error.domain, error.code)
            print("task error: %@ / %d", error.domain, error.code)
        } else {
            print("task complete")
            //NSLog("task complete")
        }
    }
    
    public func urlSession(_ session: URLSession, dataTask: URLSessionDataTask, didBecome downloadTask: URLSessionDownloadTask) {
        print("downLoadTask\(downloadTask) from dataTask \(dataTask)")
    }
    
    
    public func urlSession(_ session: URLSession, dataTask: URLSessionDataTask, didBecome streamTask: URLSessionStreamTask) {
        print("streamTask\(streamTask) from dataTask \(dataTask)")
    }
    
    //auth catch for data task.
//    public func urlSession(_ session: URLSession, didReceive challenge: URLAuthenticationChallenge, completionHandler: @escaping (URLSession.AuthChallengeDisposition, URLCredential?) -> Void) {
//        print("challenged with \(challenge)")
//        //No idea what else to do.
//    }
    
//    public func urlSession(_ session: URLSession, task: URLSessionTask, willBeginDelayedRequest request: URLRequest) async -> (URLSession.DelayedRequestDisposition, URLRequest?) {
//        <#code#>
//    }
    
}


let testDelegate = TestDelegate()

Task {
    do {
        try await testDelegate.simpleGet()
        testDelegate.simpleDataTask()
    } catch {
        print(error.self)
    }
}