Refactor OAuth2 functions: Migrate from callbacks to async/await (Swift concurrency)

- Rewrote OAuth2 functions to utilize async/await syntax for improved readability and maintainability.
- Leveraged Swift concurrency to streamline asynchronous operations and reduce callback complexity.

Author: DominikPalo

Sources/Base/OAuth2Base.swift

@@ -132,14 +132,8 @@ open class OAuth2Base: OAuth2Securable {
 		set { clientConfig.customUserAgent = newValue }
 	}
 
-	
-	/// This closure is internally used with `authorize(params:callback:)` and only exposed for subclassing reason, do not mess with it!
-	public final var didAuthorizeOrFail: ((_ parameters: OAuth2JSON?, _ error: OAuth2Error?) -> Void)?
-	
 	/// Returns true if the receiver is currently authorizing.
-	public final var isAuthorizing: Bool {
-		return nil != didAuthorizeOrFail
-	}
+	public final var isAuthorizing: Bool = false
 
 	/// Returns true if the receiver is currently exchanging the refresh token.
 	public final var isExchangingRefreshToken: Bool = false
@@ -277,8 +271,7 @@ open class OAuth2Base: OAuth2Securable {
 			storeTokensToKeychain()
 		}
 		callOnMainThread() {
-			self.didAuthorizeOrFail?(parameters, nil)
-			self.didAuthorizeOrFail = nil
+			self.isAuthorizing = false
 			self.internalAfterAuthorizeOrFail?(false, nil)
 			self.afterAuthorizeOrFail?(parameters, nil)
 		}
@@ -301,8 +294,7 @@ open class OAuth2Base: OAuth2Securable {
 			finalError = OAuth2Error.requestCancelled
 		}
 		callOnMainThread() {
-			self.didAuthorizeOrFail?(nil, finalError)
-			self.didAuthorizeOrFail = nil
+			self.isAuthorizing = false
 			self.internalAfterAuthorizeOrFail?(true, finalError)
 			self.afterAuthorizeOrFail?(nil, finalError)
 		}

Sources/Base/OAuth2RequestPerformer.swift

@@ -17,14 +17,12 @@ The class `OAuth2DataTaskRequestPerformer` implements this protocol and is by de
 public protocol OAuth2RequestPerformer {
 
 	/**
-	This method should start executing the given request, returning a URLSessionTask if it chooses to do so. **You do not neet to call
-	`resume()` on this task**, it's supposed to already have started. It is being returned so you may be able to do additional stuff.
+	This method should execute the given request asynchronously.
 
 	- parameter request: An URLRequest object that provides the URL, cache policy, request type, body data or body stream, and so on.
-	- parameter completionHandler: The completion handler to call when the load request is complete.
-	- returns: An already running session task
+	- returns: Data and response.
 	*/
-	func perform(request: URLRequest, completionHandler: @escaping (Data?, URLResponse?, Error?) -> Void) -> URLSessionTask?
+	func perform(request: URLRequest) async throws -> (Data, URLResponse)
 }
 
 
@@ -36,7 +34,6 @@ open class OAuth2DataTaskRequestPerformer: OAuth2RequestPerformer {
 	/// The URLSession that should be used.
 	public var session: URLSession
 
-	
 	/**
 	Designated initializer.
 	*/
@@ -45,18 +42,13 @@ open class OAuth2DataTaskRequestPerformer: OAuth2RequestPerformer {
 	}
 
 	/**
-	This method should start executing the given request, returning a URLSessionTask if it chooses to do so. **You do not neet to call
-	`resume()` on this task**, it's supposed to already have started. It is being returned so you may be able to do additional stuff.
+	This method should execute the given request asynchronously.
 
 	- parameter request: An URLRequest object that provides the URL, cache policy, request type, body data or body stream, and so on.
-	- parameter completionHandler: The completion handler to call when the load request is complete.
-	- returns: An already running session data task
+	- returns: Data and response.
 	*/
-	@discardableResult
-	open func perform(request: URLRequest, completionHandler: @escaping (Data?, URLResponse?, Error?) -> Void) -> URLSessionTask? {
-		let task = session.dataTask(with: request, completionHandler: completionHandler)
-		task.resume()
-		return task
+	open func perform(request: URLRequest) async throws -> (Data, URLResponse) {
+		try await session.data(for: request)
 	}
 }
 

Sources/Base/OAuth2Requestable.swift

@@ -105,41 +105,40 @@ open class OAuth2Requestable {
 	open var requestPerformer: OAuth2RequestPerformer?
 
 	/**
-	Perform the supplied request and call the callback with the response JSON dict or an error. This method is intended for authorization
+	Perform the supplied request and return the response JSON dict or throw an error. This method is intended for authorization
 	calls, not for data calls outside of the OAuth2 dance.
 
-	This implementation uses the shared `NSURLSession` and executes a data task. If the server responds with an error, this will be
-	converted into an error according to information supplied in the response JSON (if availale).
-	
-	The callback returns a response object that is easy to use, like so:
-	
-	    perform(request: req) { response in
-	        do {
-	            let data = try response.responseData()
-	            // do what you must with `data` as Data and `response.response` as HTTPURLResponse
-	        }
-	        catch let error {
-	            // the request failed because of `error`
-	        }
-	    }
-	
-	Easy, right?
+	This implementation uses the shared `NSURLSession`. If the server responds with an error, this will be
+	converted into an error according to information supplied in the response JSON (if available).
 
 	- parameter request:  The request to execute
-	- parameter callback: The callback to call when the request completes/fails. Looks terrifying, see above on how to use it
+	- returns : OAuth2 response
 	*/
-	open func perform(request: URLRequest, callback: @escaping ((OAuth2Response) -> Void)) {
+	open func perform(request: URLRequest) async -> OAuth2Response {
 		self.logger?.trace("OAuth2", msg: "REQUEST\n\(request.debugDescription)\n---")
 		let performer = requestPerformer ?? OAuth2DataTaskRequestPerformer(session: session)
 		requestPerformer = performer
-		let task = performer.perform(request: request) { sessData, sessResponse, error in
-			self.abortableTask = nil
-			self.logger?.trace("OAuth2", msg: "RESPONSE\n\(sessResponse?.debugDescription ?? "no response")\n\n\(String(data: sessData ?? Data(), encoding: String.Encoding.utf8) ?? "no data")\n---")
-			let http = (sessResponse as? HTTPURLResponse) ?? HTTPURLResponse(url: request.url!, statusCode: 499, httpVersion: nil, headerFields: nil)!
-			let response = OAuth2Response(data: sessData, request: request, response: http, error: error)
-			callback(response)
+		
+		do {
+			// TODO: add support for aborting the request, see https://www.hackingwithswift.com/quick-start/concurrency/how-to-cancel-a-task
+			let (sessData, sessResponse) = try await performer.perform(request: request)
+			self.logger?.trace("OAuth2", msg: "RESPONSE\n\(sessResponse.debugDescription)\n\n\(String(data: sessData, encoding: String.Encoding.utf8) ?? "no data")\n---")
+			
+			guard let response = sessResponse as? HTTPURLResponse else {
+				throw CommonError.castError(
+					from: String(describing: sessResponse.self),
+					to: String(describing: HTTPURLResponse.self)
+				)
+			}
+
+			return OAuth2Response(data: sessData, request: request, response: response, error: nil)
+			
+		} catch {
+			self.logger?.trace("OAuth2", msg: "RESPONSE\nno response\n\nno data\n---")
+			
+			let http = HTTPURLResponse(url: request.url!, statusCode: 499, httpVersion: nil, headerFields: nil)!
+			return OAuth2Response(data: nil, request: request, response: http, error: error)
 		}
-		abortableTask = task
 	}
 
 	/// Currently running abortable session task.
@@ -222,3 +221,16 @@ public func callOnMainThread(_ callback: (() -> Void)) {
 	}
 }
 
+// TODO: move to a separate file
+enum CommonError: Error {
+	case castError(from: String, to: String)
+}
+
+extension CommonError: CustomStringConvertible {
+	public var description: String {
+		switch self {
+		case .castError(from: let from, to: let to):
+			return "Could not cast \(from) to \(to)"
+		}
+	}
+}

Sources/Base/OAuth2Response.swift

@@ -26,15 +26,14 @@ Encapsulates a URLResponse to a URLRequest.
 
 Instances of this class are returned from `OAuth2Requestable` calls, they can be used like so:
 
-    perform(request: req) { response in
-        do {
-            let data = try response.responseData()
-            // do what you must with `data` as Data and `response.response` as HTTPURLResponse
-        }
-        catch let error {
-            // the request failed because of `error`
-        }
-    }
+	await perform(request: req)
+	do {
+		let data = try response.responseData()
+		// do what you must with `data` as Data and `response.response` as HTTPURLResponse
+	}
+	catch let error {
+		// the request failed because of `error`
+	}
 */
 open class OAuth2Response {
 

Sources/DataLoader/OAuth2DataLoader.swift

@@ -80,7 +80,7 @@ open class OAuth2DataLoader: OAuth2Requestable {
 	- parameter request:  The request to execute
 	- parameter callback: The callback to call when the request completes/fails. Looks terrifying, see above on how to use it
 	*/
-	override open func perform(request: URLRequest, callback: @escaping ((OAuth2Response) -> Void)) {
+	open func perform(request: URLRequest, callback: @escaping ((OAuth2Response) -> Void)) {
 		perform(request: request, retry: true, callback: callback)
 	}
 
@@ -112,7 +112,9 @@ open class OAuth2DataLoader: OAuth2Requestable {
 			return
 		}
 
-		super.perform(request: request) { response in
+		Task {
+			let response = await super.perform(request: request)
+			
 			do {
 				if self.alsoIntercept403, 403 == response.response.statusCode {
 					throw OAuth2Error.unauthorizedClient(nil)
@@ -126,16 +128,19 @@ open class OAuth2DataLoader: OAuth2Requestable {
 				if retry {
 					self.enqueue(request: request, callback: callback)
 					self.oauth2.clientConfig.accessToken = nil
-					self.attemptToAuthorize() { json, error in
-						
-						// dequeue all if we're authorized, throw all away if something went wrong
-						if nil != json {
-							self.retryAll()
-						}
-						else {
-							self.throwAllAway(with: error ?? OAuth2Error.requestCancelled)
+					
+					
+					do {
+						let json = try await self.attemptToAuthorize()
+						guard  json != nil else {
+							throw OAuth2Error.requestCancelled
 						}
+	
+						self.retryAll()
+					} catch {
+						self.throwAllAway(with: error.asOAuth2Error)
 					}
+	
 				}
 				else {
 					callback(response)
@@ -157,14 +162,15 @@ open class OAuth2DataLoader: OAuth2Requestable {
 	- parameter callback: The callback passed on from `authorize(callback:)`. Authorization finishes successfully (auth parameters will be
 	                      non-nil but may be an empty dict), fails (error will be non-nil) or is canceled (both params and error are nil)
 	*/
-	open func attemptToAuthorize(callback: @escaping ((OAuth2JSON?, OAuth2Error?) -> Void)) {
-		if !isAuthorizing {
-			isAuthorizing = true
-			oauth2.authorize() { authParams, error in
-				self.isAuthorizing = false
-				callback(authParams, error)
-			}
+	open func attemptToAuthorize() async throws -> OAuth2JSON? {
+		guard !self.isAuthorizing else {
+			return nil
 		}
+		
+		self.isAuthorizing = true
+		let authParams = try await oauth2.authorize()
+		self.isAuthorizing = false
+		return authParams
 	}