Abstract NetworkService functionality

Sources/Hyperspace/HTTP/HTTP.swift

@@ -167,6 +167,16 @@ public struct HTTP {
         public var dataString: String? {
             return data.flatMap { String(data: $0, encoding: .utf8) }
         }
+
+        /// Initialize a new HTTP.Response with any given HTTP status code and Data.
+        ///
+        /// - Parameters:
+        ///   - code: The raw HTTP status code for this response.
+        ///   - data: The raw Data associated with the HTTP response, if any data was provided.
+        public init(code: Int, data: Data?) {
+            self.code = code
+            self.data = data
+        }
     }
 }
 // swiftlint:enable nesting

Sources/Hyperspace/Service/Backend/BackendService.swift

@@ -29,7 +29,7 @@ public class BackendService {
 // MARK: - BackendService Conformance to BackendServiceProtocol
 
 extension BackendService: BackendServiceProtocol {
-    public func execute<T: NetworkRequest, U>(request: T, completion: @escaping BackendServiceCompletion<U>) where T.ResponseType == U {
+    public func execute<T: NetworkRequest>(request: T, completion: @escaping BackendServiceCompletion<T.ResponseType>) {
         networkService.execute(request: request.urlRequest) { [weak self] (result) in
             switch result {
             case .success(let result):
@@ -46,7 +46,7 @@ extension BackendService: BackendServiceProtocol {
         networkService.cancelTask(for: request)
     }
 
-    private func handleResponseData<T: NetworkRequest, U>(_ data: Data, for request: T, completion: @escaping BackendServiceCompletion<U>) where T.ResponseType == U {
+    private func handleResponseData<T: NetworkRequest>(_ data: Data, for request: T, completion: @escaping BackendServiceCompletion<T.ResponseType>) {
         let transformResult = request.transformData(data)
 
         DispatchQueue.main.async {

Sources/Hyperspace/Service/Backend/BackendServiceProtocol.swift

@@ -41,14 +41,14 @@ public protocol BackendServiceProtocol {
     /// - Parameters:
     ///   - request: The NetworkRequest to be executed.
     ///   - completion: The completion block to invoke when execution has finished.
-    func execute<T: NetworkRequest, U>(request: T, completion: @escaping BackendServiceCompletion<U>) where T.ResponseType == U
+    func execute<T: NetworkRequest>(request: T, completion: @escaping BackendServiceCompletion<T.ResponseType>)
 
     /// Executes the NetworkRequest, calling the provided typed error completion block when finished.
     ///
     /// - Parameters:
     ///   - request: The NetworkRequest to be executed.
     ///   - completion: The completion block (with a specifcally typed error) to invoke when execution has finished.
-    func execute<T: NetworkRequest, U, E: BackendServiceErrorInitializable>(request: T, completion: @escaping TypedBackendServiceCompletion<U, E>) where T.ResponseType == U, T.ErrorType == E
+    func execute<T: NetworkRequest, E: BackendServiceErrorInitializable>(request: T, completion: @escaping TypedBackendServiceCompletion<T.ResponseType, E>) where T.ErrorType == E
 
     /// Cancels the task for the given request (if it is currently running).
     func cancelTask(for request: URLRequest)
@@ -57,8 +57,8 @@ public protocol BackendServiceProtocol {
 // MARK: - Default Typed Implementation
 
 extension BackendServiceProtocol {
-    public func execute<T: NetworkRequest, U, E: BackendServiceErrorInitializable>(request: T, completion: @escaping TypedBackendServiceCompletion<U, E>) where T.ResponseType == U, T.ErrorType == E {
-        execute(request: request) { (result: Result<U, BackendServiceError>) in
+    public func execute<T: NetworkRequest, E: BackendServiceErrorInitializable>(request: T, completion: @escaping TypedBackendServiceCompletion<T.ResponseType, E>) where T.ErrorType == E {
+        execute(request: request) { (result: Result<T.ResponseType, BackendServiceError>) in
             completion(result.flatMapError { .failure(E($0)) })
         }
     }

Sources/Hyperspace/Service/Network/NetworkService.swift

@@ -19,6 +19,7 @@
 //
 
 import Foundation
+import Result
 
 /// Adopts the NetworkServiceProtocol to perform HTTP communication via the execution of URLRequests.
 public class NetworkService {
@@ -43,41 +44,17 @@ public class NetworkService {
 
 extension NetworkService: NetworkServiceProtocol {
     public func execute(request: URLRequest, completion: @escaping NetworkServiceCompletion) {
-        let task = session.dataTask(with: request, completionHandler: { [weak self] (data, response, error) in
+        let task = session.dataTask(with: request) { (data, response, error) in
             guard let statusCode = (response as? HTTPURLResponse)?.statusCode else {
-                let responseError = self?.invalidHTTPResponseError(for: error) ?? .unknownError
-                let result = NetworkServiceFailure(error: responseError, response: nil)
-
-                completion(.failure(result))
+                let networkFailure = NetworkServiceHelper.networkServiceFailure(for: error)
+                completion(.failure(networkFailure))
                 return
             }
 
             let httpResponse = HTTP.Response(code: statusCode, data: data)
-
-            switch httpResponse.status {
-            case .unknown:
-                let result = NetworkServiceFailure(error: .unknownStatusCode, response: httpResponse)
-                completion(.failure(result))
-            case .success:
-                guard let data = data else {
-                    let result = NetworkServiceFailure(error: .noData, response: httpResponse)
-                    completion(.failure(result))
-                    return
-                }
-
-                let result = NetworkServiceSuccess(data: data, response: httpResponse)
-                completion(.success(result))
-            case .redirection:
-                let result = NetworkServiceFailure(error: .redirection, response: httpResponse)
-                completion(.failure(result))
-            case .clientError(let clientError):
-                let result = NetworkServiceFailure(error: .clientError(clientError), response: httpResponse)
-                completion(.failure(result))
-            case .serverError(let serverError):
-                let result = NetworkServiceFailure(error: .serverError(serverError), response: httpResponse)
-                completion(.failure(result))
-            }
-        })
+            let networkResult = NetworkServiceHelper.networkServiceResult(for: httpResponse)
+            completion(networkResult)
+        }
 
         tasks[request] = task
         task.resume()
@@ -91,3 +68,59 @@ extension NetworkService: NetworkServiceProtocol {
         tasks.forEach { cancelTask(for: $0.key) }
     }
 }
+
+/// A small helper struct which deals with the conversion of Data, URLResponse and Error objects to NetworkService successes and failures.
+public struct NetworkServiceHelper {
+
+    /// Used to convert a client error, such as those returned by a NetworkSessionDataTask, into a NetworkServiceResult.
+    ///
+    /// - Parameter clientError: The error returned by the NetworkSessionDataTask.
+    /// - Returns: The outcome NetworkServiceResult dictated by the error.
+    public static func networkServiceFailure(for clientError: Error?) -> NetworkServiceFailure {
+        let responseError = invalidHTTPResponseError(for: clientError)
+        return NetworkServiceFailure(error: responseError, response: nil)
+    }
+
+    /// Used to convert a valid HTTP.Response object, such as those returned by a NetworkSessionDataTask, into a NetworkServiceResult.
+    ///
+    /// - Parameter response: The HTTP.Response object returned by the NetworkSessionDataTask.
+    /// - Returns: The outcome NetworkServiceResult dictated by the HTTP.Response.
+    public static func networkServiceResult(for response: HTTP.Response) -> NetworkServiceResult {
+        switch response.status {
+        case .unknown:
+            return .failure(NetworkServiceFailure(error: .unknownStatusCode, response: response))
+        case .success:
+            guard let data = response.data else {
+                return .failure(NetworkServiceFailure(error: .noData, response: response))
+            }
+
+            return .success(NetworkServiceSuccess(data: data, response: response))
+        case .redirection:
+            return .failure(NetworkServiceFailure(error: .redirection, response: response))
+        case .clientError(let clientError):
+            return .failure(NetworkServiceFailure(error: .clientError(clientError), response: response))
+        case .serverError(let serverError):
+            return .failure(NetworkServiceFailure(error: .serverError(serverError), response: response))
+        }
+    }
+}
+
+private extension NetworkServiceHelper {
+
+    private static func invalidHTTPResponseError(for error: Error?) -> NetworkServiceError {
+        let networkError: NetworkServiceError = (error as NSError?).flatMap {
+            switch ($0.domain, $0.code) {
+            case (NSURLErrorDomain, NSURLErrorNotConnectedToInternet):
+                return .noInternetConnection
+            case (NSURLErrorDomain, NSURLErrorTimedOut):
+                return .timedOut
+            case (NSURLErrorDomain, NSURLErrorCancelled):
+                return .cancelled
+            default:
+                return .unknownError
+            }
+            } ?? .unknownError
+
+        return networkError
+    }
+}

Sources/Hyperspace/Service/Network/NetworkServiceProtocol.swift

@@ -31,18 +31,21 @@ public enum NetworkServiceError: Error {
 
 /// Represents the successful result of executing a NetworkRequest using a NetworkService.
 public struct NetworkServiceSuccess {
-    let data: Data
-    let response: HTTP.Response
+    public let data: Data
+    public let response: HTTP.Response
 }
 
 /// Represents the failed result of executing a NetworkRequest using a NetworkService.
 public struct NetworkServiceFailure: Error {
-    let error: NetworkServiceError
-    let response: HTTP.Response?
+    public let error: NetworkServiceError
+    public let response: HTTP.Response?
 }
 
+/// Represents the possible resulting values of a NetworkRequest using a NetworkService.
+public typealias NetworkServiceResult = Result<NetworkServiceSuccess, NetworkServiceFailure>
+
 /// Upon completion of executing a NetworkRequest using a NetworkService, the NetworkServiceResult is returned.
-public typealias NetworkServiceCompletion = (Result<NetworkServiceSuccess, NetworkServiceFailure>) -> Void
+public typealias NetworkServiceCompletion = (NetworkServiceResult) -> Void
 
 /// Represents something that can execute a URLRequest.
 public protocol NetworkServiceProtocol {