Refactor Kakapo to not be json centric

This is a draft PR to address #153, I want some feedback before proceeding with updating the documentation, README, tests
The idea is that Router now doesn’t work anymore w/ `Serializable` objects and `ResponseFieldsProvider` is not anymore a special `Serializable`.
Router now only accept `ResponseFieldsProvider`s an object that provides:
statusCode (Int)
headerfields (dict)
body (data)

`Serializable` became a `ResponseFieldsProvider` that by default has a status code == 200 and “Content-Type” == “application/json”.
It should have been like that since ever, so we can use Kakapo with images, xml or whatever we want by creating new `ResponseFieldsProvider `

The change is a breaking change but not a big one for users of Kakapo (only objects that were confirming to ResponseFieldsProvider will be broken)

Author: MP0w

Source/Router.swift

@@ -14,7 +14,7 @@ import Foundation
  By default, though, the Router will return a 200 status code and `["Content-Type": "application/json"]` header fields when only returning a Serializable object.
  In order to customize that behavior, check `ResponseFieldsProvider` to provide custom status code and header fields.
  */
-public typealias RouteHandler = (Request) -> Serializable?
+public typealias RouteHandler = (Request) -> ResponseFieldsProvider?
 
 /**
  A Request struct used in `RouteHandlers` to provide valid requests.
@@ -43,7 +43,7 @@ public struct Response: ResponseFieldsProvider {
     public let statusCode: Int
 
     /// The Serializable body object
-    public let body: Serializable
+    public let body: Data?
 
     /// An optional dictionary holding the response header fields
     public let headerFields: [String : String]?
@@ -57,7 +57,7 @@ public struct Response: ResponseFieldsProvider {
 
      - returns: A wrapper `Serializable` object that affect http requests.
      */
-    public init(statusCode: Int, body: Serializable, headerFields: [String : String]? = nil) {
+    public init(statusCode: Int, body: Data?, headerFields: [String : String]? = nil) {
         self.statusCode = statusCode
         self.body = body
         self.headerFields = headerFields
@@ -170,10 +170,8 @@ public final class Router {
     func startLoading(_ server: Server) {
         guard let requestURL = server.request.url,
                   let client = server.client else { return }
-        
-        var statusCode = 200
-        var headerFields: [String : String]? = ["Content-Type": "application/json"]
-        var serializableObject: Serializable?
+
+        var responseFieldsProvider: ResponseFieldsProvider?
 
         for (key, handler) in routes where key.method.rawValue == server.request.httpMethod {
             if let info = matchRoute(baseURL, path: key.path, requestURL: requestURL) {
@@ -182,24 +180,28 @@ public final class Router {
                 let dataBody = server.request.httpBody ?? URLProtocol.property(forKey: "kkp_requestHTTPBody", in: server.request) as? Data
 
                 let request = Request(components: info.components, queryParameters: info.queryParameters, httpBody: dataBody, httpHeaders: server.request.allHTTPHeaderFields)
-                serializableObject = handler(request)
+                responseFieldsProvider = handler(request)
                 break
             }
         }
-        
-        if let serializableObject = serializableObject as? ResponseFieldsProvider {
-            statusCode = serializableObject.statusCode
-            headerFields = serializableObject.headerFields
-        }
-        
-        if let response = HTTPURLResponse(url: requestURL, statusCode: statusCode, httpVersion: "HTTP/1.1", headerFields: headerFields) {
+
+        // In case we don't have a statusCode and headerFields
+        // we fallback on // https://tools.ietf.org/html/rfc2324
+        let response = HTTPURLResponse(
+            url: requestURL,
+            statusCode: responseFieldsProvider?.statusCode ?? 418,
+            httpVersion: "HTTP/1.1",
+            headerFields: responseFieldsProvider?.headerFields ?? ["Content-Type": "application/coffee-pot-command"]
+        )
+
+        if let response = response {
             client.urlProtocol(server, didReceive: response, cacheStoragePolicy: .allowedInMemoryOnly)
         }
-        
-        if let data = serializableObject?.toData() {
+
+        if let data = responseFieldsProvider?.body {
             client.urlProtocol(server, didLoad: data)
         }
-        
+
         let didFinishLoading: (URLProtocol) -> Void = { (server) in
             client.urlProtocolDidFinishLoading(server)
         }

Source/Serialization/JSONAPIError.swift

@@ -9,7 +9,7 @@
 import Foundation
 
 /// A convenience error object that conform to JSON API
-public struct JSONAPIError: ResponseFieldsProvider {
+public struct JSONAPIError: CustomSerializable {
 
     /// An object containing references to the source of the error, optionally including any of the following members
     public struct Source: Serializable {
@@ -78,29 +78,22 @@ public struct JSONAPIError: ResponseFieldsProvider {
     public var statusCode: Int {
         return builder.status
     }
-    
-    /// A `JSONAPIError.Builder` instance contains all the fields.
-    public var body: Serializable {
-        return builder
-    }
-    
-    /// The headerFields that will be returned by the HTTP response.
-    public let headerFields: [String : String]?
 
     /**
      Initialize a `JSONAPIError` and build it with `JSONAPIError.Builder`
 
      - parameter statusCode:   The status code of the response, will be used also to provide a statusCode for your request
-     - parameter headerFields: The headerFields that will be returned by the HTTP response.
      - parameter errorBuilder: A builder that can be used to fill the error objects, it contains all you need to provide an error object confiorming to JSON API (**see `JSONAPIError.Builder`**)
 
      - returns: An error that conforms to JSON API specifications and it's ready to be serialized
      */
-    public init(statusCode: Int, headerFields: [String: String]? = nil, errorBuilder: (_ error: Builder) -> Void) {
+    public init(statusCode: Int, errorBuilder: (_ error: Builder) -> Void) {
         let builder = Builder(statusCode: statusCode)
         errorBuilder(builder)
         self.builder = builder
-        self.headerFields = headerFields
     }
-    
+
+    public func customSerialized(transformingKeys keyTransformer: KeyTransformer?) -> Any? {
+        return builder.serialized()
+    }
 }

Source/Serialization/ResponseFieldsProvider.swift

@@ -13,21 +13,13 @@ import Foundation
  For example you may use `Response` to wrap your `Serializable` object to just achieve the result or directly implement the protocol.
  For example `JSONAPIError` implement the protocol in order to be able to provide custom status code in the response.
  */
-public protocol ResponseFieldsProvider: CustomSerializable {
+public protocol ResponseFieldsProvider {
     /// The response status code
     var statusCode: Int { get }
 
     /// The Serializable body object
-    var body: Serializable { get }
+    var body: Data? { get }
 
     /// An optional dictionary holding the response header fields
     var headerFields: [String : String]? { get }
 }
-
-extension ResponseFieldsProvider {
-
-    /// The default implementation just return the serialized body.
-    public func customSerialized(transformingKeys keyTransformer: KeyTransformer?) -> Any? {
-        return body.serialized(transformingKeys: keyTransformer)
-    }
-}

Source/Serialization/Serializer.swift

@@ -11,10 +11,32 @@ import Foundation
 /**
  *  A protocol to serialize types into JSON representations, the object will be Mirrored to be serialized. Use `CustomReflectable` if you need different behaviors or use `CustomSerializable`if it's not a valid option.
  */
-public protocol Serializable {
+public protocol Serializable: ResponseFieldsProvider {
     // empty protocol, marks that the object should be Mirrored to be serialized.
 }
 
+extension Serializable {
+    public var statusCode: Int {
+        return 200
+    }
+
+    public var headerFields: [String : String]? {
+        return ["Content-Type": "application/json"]
+    }
+
+    /**
+     Serialize a `Serializable` object and convert the serialized object to `Data`. Unless it is nil the return value is representing a JSON. Usually you don't need to use this method directly since `Router` will automatically serialize objects when needed.
+     */
+    public var body: Data? {
+        guard let object = serialized() else { return nil }
+
+        if !JSONSerialization.isValidJSONObject(object) {
+            return nil
+        }
+        return try? JSONSerialization.data(withJSONObject: object, options: .prettyPrinted)
+    }
+}
+
 /**
  *  Conforming to `CustomSerializable` the object won't be Mirrored to be serialized, use it in case `CustomReflectable` is not a viable option. Array for example use this to return an Array with its serialized objects inside.
  */
@@ -44,20 +66,6 @@ public extension Serializable {
         return serialize(self, keyTransformer: keyTransformer)
     }
 
-    /**
-     Serialize a `Serializable` object and convert the serialized object to `Data`. Unless it is nil the return value is representing a JSON. Usually you don't need to use this method directly since `Router` will automatically serialize objects when needed.
-     
-     - returns: The serialized object as `Data`
-     */
-    func toData() -> Data? {
-        guard let object = serialized() else { return nil }
-        
-        if !JSONSerialization.isValidJSONObject(object) {
-            return nil
-        }
-        return try? JSONSerialization.data(withJSONObject: object, options: .prettyPrinted)
-    }
-    
     fileprivate func serializeObject(_ value: Any, keyTransformer: KeyTransformer?) -> Any? {
         if let value = value as? Serializable {
             return value.serialized(transformingKeys: keyTransformer)

Tests/JSONAPIErrorTests.swift

@@ -80,31 +80,9 @@ class JSONAPIErrorsSpec: QuickSpec {
                         let response = response as! HTTPURLResponse
                         statusCode = response.statusCode
                         }.resume()
-                    // still the only test randomly failing for no reasons...
-                    // 99,9 % is not a router problem (otherwise wouldn't be the only one)
-                    // https://pbs.twimg.com/media/CfSQdwUW8AErog1.jpg
+
                     expect(statusCode).toEventually(equal(403), timeout: 2)
                 }
-                
-                it("should affect the header fields of the response") {
-                    let router = Router.register("http://www.test1234.com")
-                    
-                    router.get("/users") { _ in
-                        return JSONAPIError(statusCode: 404, headerFields: ["foo": "bar"]) { (error) in
-                            error.title = "test"
-                        }
-                    }
-                    
-                    var foo: String?
-                    let url = URL(string: "http://www.test1234.com/users")!
-                    URLSession.shared.dataTask(with: url) { (_, response, _) in
-                        let response = response as! HTTPURLResponse
-                        let headers = response.allHeaderFields as? [String: String]
-                        foo = headers?["foo"]
-                        }.resume()
-                    
-                    expect(foo).toEventually(equal("bar"))
-                }
             }
         }
     }

Tests/RouterTests.swift

@@ -15,12 +15,16 @@ import Nimble
 
 struct CustomResponse: ResponseFieldsProvider {
     let statusCode: Int
-    let body: Serializable
+    let wrapped: Serializable
     let headerFields: [String : String]?
+
+    var body: Data? {
+        return wrapped.body
+    }
 
-    init(statusCode: Int, body: Serializable, headerFields: [String : String]? = nil) {
+    init(statusCode: Int, wrapped: Serializable, headerFields: [String : String]? = nil) {
         self.statusCode = statusCode
-        self.body = body
+        self.wrapped = wrapped
         self.headerFields = headerFields
     }
 }
@@ -548,7 +552,8 @@ class RouterTests: QuickSpec {
                 var responseDictionary: [String: AnyObject]?
 
                 router.get("/users/:id") { request in
-                    return Response(statusCode: 200, body: store.find(User.self, id: request.components["id"]!)!)
+                    let user = store.find(User.self, id: request.components["id"]!)
+                    return Response(statusCode: 200, body: user.body)
                 }
 
                 URLSession.shared.dataTask(with: URL(string: "http://www.test.com/users/2")!) { (data, response, _) in
@@ -568,7 +573,7 @@ class RouterTests: QuickSpec {
 
                 router.get("/users/:id") { _ in
                     // Optional.some("none") -> not valid JSON object
-                    return Response(statusCode: 400, body: Optional.some("none"))
+                    return Response(statusCode: 400, body: Optional.some("none").body)
                 }
 
                 URLSession.shared.dataTask(with: URL(string: "http://www.test.com/users/2")!) { (data, response, _) in
@@ -585,7 +590,7 @@ class RouterTests: QuickSpec {
                 var allHeaders: [String : String]? = nil
 
                 router.get("/users/:id") { _ in
-                    let body = ["id": "foo", "type": "User"]
+                    let body = ["id": "foo", "type": "User"].body
                     let headerFields = ["access_token": "094850348502", "user_id": "124"]
                     return Response(statusCode: 400, body: body, headerFields: headerFields)
                 }
@@ -606,7 +611,7 @@ class RouterTests: QuickSpec {
                 var statusCode: Int? = nil
 
                 router.get("/users/:id") { _ in
-                    return CustomResponse(statusCode: 400, body: ["id": 2], headerFields: ["access_token": "094850348502"])
+                    return CustomResponse(statusCode: 400, wrapped: ["id": 2], headerFields: ["access_token": "094850348502"])
                 }
 
                 URLSession.shared.dataTask(with: URL(string: "http://www.test.com/users/2")!) { (data, response, _) in

Tests/SerializationTransformerTests.swift

@@ -145,14 +145,6 @@ class SerializationTransformerSpec: QuickSpec {
                 }
             }
 
-            context("ResponseFieldsProvider") {
-                it("should transform the keys") {
-                    let object = Response(statusCode: 200, body: friend)
-                    let serialized = UppercaseTransformer(wrapped: object).serialized() as! [String: AnyObject]
-                    expect(serialized["FRIENDS"]).toNot(beNil())
-                }
-            }
-            
             context("Array") {
                 it("should transform the keys") {
                     let object = [friend]

Tests/SerializerTests.swift

@@ -156,7 +156,7 @@ class SerializeSpec: QuickSpec {
             it("produces nil data and serialized object when nil") {
                 let nilInt: Int? = nil
                 expect(nilInt.serialized()).to(beNil())
-                expect(nilInt.toData()).to(beNil())
+                expect(nilInt.body).to(beNil())
             }
 
             it("serialize an optional") {