feat(session): Session object to perform requests (#3)

Author: pjechris

Sources/Pinata/Foundation/JSONDecoder+DataDecoder.swift

@@ -0,0 +1,5 @@
+import Foundation
+
+extension JSONDecoder: ContentDataDecoder {
+    public static let contentType = HTTPContentType.json
+}

Sources/Pinata/Foundation/URLRequest/URLRequest+HTTPHeader.swift

@@ -10,4 +10,12 @@ extension URLRequest {
             setValue(value, forHTTPHeaderField: header.key)
         }
     }
+    
+    public func settingHeaders(_ headers: HTTPHeaderFields) -> Self {
+        var urlRequest = self
+
+        urlRequest.setHeaders(headers)
+
+        return urlRequest
+    }
 }

Sources/Pinata/Foundation/URLRequest/URLRequest+URL.swift

@@ -0,0 +1,15 @@
+import Foundation
+
+extension URLRequest {
+    /// Return a new URLRequest whose endpoint is relative to `baseURL`
+    func relativeTo(_ baseURL: URL) -> URLRequest {
+        var urlRequest = self
+        var components = URLComponents(string: baseURL.appendingPathComponent(url?.path ?? "").absoluteString)
+        
+        components?.percentEncodedQuery = url?.query
+        
+        urlRequest.url = components?.url
+                
+        return urlRequest
+    }
+}

Sources/Pinata/Foundation/URLSession+Publisher.swift

@@ -0,0 +1,10 @@
+import Foundation
+
+extension URLSession {
+    /// Return a dataTaskPublisher as a `DataPublisher`
+    public func dataPublisher(for request: URLRequest) -> Session.RequestDataPublisher {
+        dataTaskPublisher(for: request)
+            .mapError { $0 as Error }
+            .eraseToAnyPublisher()
+    }
+}

Sources/Pinata/Interceptor/CompositeInterceptor.swift

@@ -0,0 +1,45 @@
+import Foundation
+import Combine
+
+/// Use an Array of `Interceptor` as a single `Interceptor`
+public struct CompositeInterceptor: ExpressibleByArrayLiteral, Sequence {
+    let interceptors: [Interceptor]
+    
+    public init(arrayLiteral interceptors: Interceptor...) {
+        self.interceptors = interceptors
+    }
+    
+    public func makeIterator() -> Array<Interceptor>.Iterator {
+        interceptors.makeIterator()
+    }
+}
+ 
+extension CompositeInterceptor: Interceptor {
+    public func adaptRequest<Output>(_ request: Request<Output>) -> Request<Output> {
+        reduce(request) { request, interceptor in
+            interceptor.adaptRequest(request)
+        }
+    }
+    
+    public func rescueRequest<Output>(_ request: Request<Output>, error: Error) -> AnyPublisher<Void, Error>? {
+        let publishers = compactMap { $0.rescueRequest(request, error: error) }
+        
+        guard !publishers.isEmpty else {
+            return nil
+        }
+        
+        return Publishers.MergeMany(publishers).eraseToAnyPublisher()
+    }
+    
+    public func adaptOutput<Output>(_ response: Output, for request: Request<Output>) throws -> Output {
+        try reduce(response) { response, interceptor in
+            try interceptor.adaptOutput(response, for: request)
+        }
+    }
+    
+    public func receivedResponse<Output>(_ result: Result<Output, Error>, for request: Request<Output>) {
+        forEach { interceptor in
+            interceptor.receivedResponse(result, for: request)
+        }
+    }
+}

Sources/Pinata/Interceptor/Interceptor.swift

@@ -0,0 +1,27 @@
+import Foundation
+import Combine
+
+public typealias Interceptor = RequestInterceptor & ResponseInterceptor
+
+/// a protocol intercepting a session request
+public protocol RequestInterceptor {
+  /// Should be called before making the request to provide modifications to `request`
+  func adaptRequest<Output>(_ request: Request<Output>) -> Request<Output>
+
+  /// catch and retry a failed request
+  /// - Returns: nil if the request should not be retried. Otherwise a publisher that will be executed before
+  /// retrying the request
+  func rescueRequest<Output>(_ request: Request<Output>, error: Error) -> AnyPublisher<Void, Error>?
+}
+
+/// a protocol intercepting a session response
+public protocol ResponseInterceptor {
+  /// Should be called once the request is done and output was received. Let one last chance to modify the output
+  /// optionally throwing an error instead if needed
+  /// - Parameter request: the request that was sent to the server
+  func adaptOutput<Output>(_ output: Output, for request: Request<Output>) throws -> Output
+
+  /// Notify of received response for `request`
+  /// - Parameter request: the request that was sent to the server
+  func receivedResponse<Output>(_ result: Result<Output, Error>, for request: Request<Output>)
+}

Sources/Pinata/Session/Session.swift

@@ -0,0 +1,124 @@
+import Foundation
+import Combine
+
+/// Primary class of the library used to perform http request using `Request` objects
+public class Session {
+    /// Data returned by a http request
+    public typealias RequestData = URLSession.DataTaskPublisher.Output
+    
+    /// a Publisher emitting `RequestData`
+    public typealias RequestDataPublisher = AnyPublisher<RequestData, Error>
+    
+    let baseURL: URL
+    let config: SessionConfiguration
+    /// a closure returning a publisher based for a given `URLRequest`
+    let urlRequestPublisher: (URLRequest) -> RequestDataPublisher
+    
+    /// init the class using a `URLSession` instance
+    /// - Parameter baseURL: common url for all the requests. Allow to switch environments easily
+    /// - Parameter configuration: session configuration to use
+    /// - Parameter urlSession: `URLSession` instance to use to make requests.
+    public convenience init(baseURL: URL, configuration: SessionConfiguration = .init(), urlSession: URLSession) {
+        self.init(
+            baseURL: baseURL,
+            configuration: configuration,
+            dataPublisher: urlSession.dataPublisher(for:)
+        )
+    }
+    
+    /// init the class with a base url for request
+    /// - Parameter baseURL: common url for all the requests. Allow to switch environments easily
+    /// - Parameter configuration: session configuration to use
+    /// - Parameter dataPublisher: publisher used by the class to make http requests. If none provided it default
+    /// to `URLSession.dataPublisher(for:)`
+    public init(
+        baseURL: URL,
+        configuration: SessionConfiguration = SessionConfiguration(),
+        dataPublisher: @escaping (URLRequest) -> RequestDataPublisher = { URLSession.shared.dataPublisher(for: $0) }
+    ) {
+        self.baseURL = baseURL
+        self.config = configuration
+        self.urlRequestPublisher = dataPublisher
+    }
+    
+    /// Return a publisher performing request and returning `Output` data
+    ///
+    /// The request is validated and decoded appropriately on success.
+    /// - Returns: a Publisher emitting Output on success, an error otherwise
+    public func publisher<Output: Decodable>(for request: Request<Output>) -> AnyPublisher<Output, Error> {
+        dataPublisher(for: request)
+            .receive(on: config.decodingQueue)
+            .map { response -> (output: Result<Output, Error>, request: Request<Output>) in
+                let output = Result {
+                    try self.config.interceptor.adaptOutput(
+                        try self.config.decoder.decode(Output.self, from: response.data),
+                        for: response.request
+                    )
+                }
+                
+                return (output: output, request: response.request)
+            }
+            .handleEvents(receiveOutput: { self.log($0.output, for: $0.request) })
+            .tryMap { try $0.output.get() }
+            .eraseToAnyPublisher()
+    }
+    
+    /// Return a publisher performing request which has no return value
+    public func publisher(for request: Request<Void>) -> AnyPublisher<Void, Error> {
+        dataPublisher(for: request)
+            .handleEvents(receiveOutput: { self.log(.success(()), for: $0.request) })
+            .map { _ in () }
+            .eraseToAnyPublisher()
+    }
+}
+
+extension Session {
+    private func dataPublisher<Output>(for request: Request<Output>) -> AnyPublisher<Response<Output>, Error> {
+        let adaptedRequest = config.interceptor.adaptRequest(request)
+        
+        do {
+            let urlRequest = try adaptedRequest
+                .toURLRequest(encoder: config.encoder)
+                .relativeTo(baseURL)
+                .settingHeaders([.accept: type(of: config.decoder).contentType.value])
+            
+            return urlRequestPublisher(urlRequest)
+                .validate(config.errorConverter)
+                .map { Response(data: $0.data, request: adaptedRequest) }
+                .handleEvents(receiveCompletion: { self.logIfFailure($0, for: adaptedRequest) })
+                .tryCatch { try self.rescue(error: $0, request: request) }
+                .eraseToAnyPublisher()
+        }
+        catch {
+            return Fail(error: error).eraseToAnyPublisher()
+        }
+    }
+    
+    /// log a request completion
+    private func logIfFailure<Output>(_ completion: Subscribers.Completion<Error>, for request: Request<Output>) {
+        if case .failure(let error) = completion {
+            config.interceptor.receivedResponse(.failure(error), for: request)
+        }
+    }
+    
+    private func log<Output>(_ response: Result<Output, Error>, for request: Request<Output>) {
+        config.interceptor.receivedResponse(response, for: request)
+    }
+    
+    /// try to rescue an error while making a request and retry it when rescue suceeded
+    private func rescue<Output>(error: Error, request: Request<Output>) throws -> AnyPublisher<Response<Output>, Error> {
+        guard let rescue = config.interceptor.rescueRequest(request, error: error) else {
+            throw error
+        }
+        
+        return rescue
+            .map { self.dataPublisher(for: request) }
+            .switchToLatest()
+            .eraseToAnyPublisher()
+    }
+}
+
+private struct Response<Output> {
+    let data: Data
+    let request: Request<Output>
+}

Sources/Pinata/Session/SessionConfiguration.swift

@@ -0,0 +1,45 @@
+import Foundation
+
+/// a type defining some parameters for a `Session`
+public struct SessionConfiguration {
+    /// encoder to use for request bodies
+    let encoder: ContentDataEncoder
+    /// decoder used to decode http responses
+    let decoder: ContentDataDecoder
+    /// queue on which to decode data
+    let decodingQueue: DispatchQueue
+    /// an interceptor to apply custom behavior on the session requests/responses.
+    /// To apply multiple interceptors use `ComposeInterceptor`
+    let interceptor: Interceptor
+    /// a function decoding data (using `decoder`) as a custom error
+    private(set) var errorConverter: DataErrorConverter?
+    
+    /// - Parameter encoder to use for request bodies
+    /// - Parameter decoder used to decode http responses
+    /// - Parameter decodeQueue: queue on which to decode data
+    /// - Parameter interceptors: interceptor list to apply on the session requests/responses
+    public init(
+        encoder: ContentDataEncoder = JSONEncoder(),
+        decoder: ContentDataDecoder = JSONDecoder(),
+        decodingQueue: DispatchQueue = .main,
+        interceptors: CompositeInterceptor = []) {
+            self.encoder = encoder
+            self.decoder = decoder
+            self.decodingQueue = decodingQueue
+            self.interceptor = interceptors
+        }
+    
+    /// - Parameter dataError: Error type to use when having error with data
+    public init<DataError: Error & Decodable>(
+        encoder: ContentDataEncoder = JSONEncoder(),
+        decoder: ContentDataDecoder = JSONDecoder(),
+        decodingQueue: DispatchQueue = .main,
+        interceptors: CompositeInterceptor = [],
+        dataError: DataError.Type
+    ) {
+        self.init(encoder: encoder, decoder: decoder,  decodingQueue: decodingQueue, interceptors: interceptors)
+        self.errorConverter = {
+            try decoder.decode(dataError, from: $0)
+        }
+    }
+}

Tests/PinataTests/Foundation/URLRequest/URLRequestTests+URL.swift

@@ -0,0 +1,40 @@
+import Foundation
+import XCTest
+@testable import Pinata
+
+class URLRequestURLTests: XCTestCase {
+    func test_relativeTo_requestURLHasBaseURL() {
+        let request = URLRequest(url: URL(string: "path")!)
+        let url = request.relativeTo(URL(string: "https://google.com")!).url
+        
+        XCTAssertEqual(url?.absoluteString, "https://google.com/path")
+    }
+    
+    func test_relativeTo_urlStartWithSlash_requestPathContainBothPaths() {
+        let request = URLRequest(url: URL(string: "/path")!)
+        let url = request.relativeTo(URL(string: "https://google.com/lostAndFound")!).url
+        
+        XCTAssertEqual(url?.absoluteString, "https://google.com/lostAndFound/path")
+    }
+    
+    func test_relativeTo_baseURLHasPath_requestContainBaseURLPath() {
+        let request = URLRequest(url: URL(string: "concatenated")!)
+        let url = request.relativeTo(URL(string: "https://google.com/firstPath")!).url
+        
+        XCTAssertEqual(url?.absoluteString, "https://google.com/firstPath/concatenated")
+    }
+    
+    func test_relativeTo_baseURLHasQuery_requestHasNoQuery() {
+        let request = URLRequest(url: URL(string: "concatenated")!)
+        let url = request.relativeTo(URL(string: "https://google.com?param=1")!).url
+        
+        XCTAssertEqual(url?.absoluteString, "https://google.com/concatenated")
+    }
+    
+    func test_relativeTo_urlHasQuery_requestHasQuery() {
+        let request = URLRequest(url: URL(string: "concatenated?toKeep=1")!)
+        let url = request.relativeTo(URL(string: "https://google.com?param=1")!).url
+        
+        XCTAssertEqual(url?.absoluteString, "https://google.com/concatenated?toKeep=1")
+    }
+}