Network layer refactoring (#262)

* Added APIEndpoint inheritance to all network classes

* working implementation

* working adapter

* Updated JSONSerializable & added generic update() method

* More update refactoring

* Added generic delete request

* Added create() method

* Create comment reworked

* Added views create() method

* minor

* refactored create() for attempts and submissions

* Added retrieve() for one object by id

* Added retrieve with parameters

* minor

* Added retrieve() with fetch to NotificationsAPI

* minor

* Refactored UnitsAPI

* multiple fixes

* Refactored UserActivitiesAPI

* Refactor DiscussionProxiesAPI

* Refactored getObjectsByIds

* Refactored CommentsAPI

* Added deprecations to CommentsAPI

* Added default implementation of async fetch using DatabaseFetchService

* fixed GET requests & added deprecations to CoursesAPI

* Refactored CertificatesAPI

* Refactored CourseListsAPI

* Refactored NotificationsStatusesAPI

* fixed formatting

* Removed some checkToken() calls

* Fixed JSONSerializables

* AsyncFetchService -> DatabaseFetchService

* Cleaned up UserActivitiesAPI

* minor format

* fixed force unwrap

* Removed forced unwraps

* Renamed IdType & some more

* Added CoreDataRepresentable protocol for IdType of IDFetchable

* fixed "Submit" localization

* Deleted not passing tests file

* minor

Stepic.xcodeproj/xcuserdata/Ostrenkiy.xcuserdatad/xcschemes/xcschememanagement.plist

@@ -118,6 +118,11 @@
 			<key>orderHint</key>
 			<integer>86</integer>
 		</dict>
+		<key>Adaptive GMAT.xcscheme</key>
+		<dict>
+			<key>orderHint</key>
+			<integer>95</integer>
+		</dict>
 		<key>SberbankUniversity.xcscheme</key>
 		<dict>
 			<key>isShown</key>
@@ -154,7 +159,7 @@
 		<key>StepikTV.xcscheme_^#shared#^_</key>
 		<dict>
 			<key>orderHint</key>
-			<integer>87</integer>
+			<integer>96</integer>
 		</dict>
 		<key>StickerPackExtension.xcscheme</key>
 		<dict>

Stepic/APIEndpoint.swift

@@ -36,10 +36,23 @@ class APIEndpoint {
 
     let manager: Alamofire.SessionManager
 
+    var update: UpdateRequestMaker
+    var delete: DeleteRequestMaker
+    var create: CreateRequestMaker
+    var retrieve: RetrieveRequestMaker
+
     init() {
         let configuration = URLSessionConfiguration.default
         configuration.timeoutIntervalForRequest = 15
         manager = Alamofire.SessionManager(configuration: configuration)
+        let retrier = ApiRequestRetrier()
+        manager.retrier = retrier
+        manager.adapter = retrier
+
+        update = UpdateRequestMaker()
+        delete = DeleteRequestMaker()
+        create = CreateRequestMaker()
+        retrieve = RetrieveRequestMaker()
     }
 
     func cancelAllTasks() {
@@ -60,123 +73,23 @@ class APIEndpoint {
         return result
     }
 
-    func getObjectsByIds<T: JSONInitializable>(ids: [T.idType], updating: [T], headers: [String: String] = AuthInfo.shared.initialHTTPHeaders, printOutput: Bool = false) -> Promise<([T])> {
-        let name = self.name
-        return Promise<([T])> {
-            fulfill, reject in
-            let params: Parameters = [
-                "ids": ids
-            ]
-
-            manager.request("\(StepicApplicationsInfo.apiURL)/\(name)", parameters: params, encoding: URLEncoding.default, headers: headers).validate().responseSwiftyJSON { response in
-                switch response.result {
-
-                case .failure(let error):
-                    reject(RetrieveError(error: error))
-
-                case .success(let json):
-                    let jsonArray: [JSON] = json[name].array ?? []
-                    let resultArray: [T] = jsonArray.map {
-                        objectJSON in
-                        if let recoveredIndex = updating.index(where: { $0.hasEqualId(json: objectJSON) }) {
-                            updating[recoveredIndex].update(json: objectJSON)
-                            return updating[recoveredIndex]
-                        } else {
-                            return T(json: objectJSON)
-                        }
-                    }
-
-                    CoreDataHelper.instance.save()
-                    fulfill((resultArray))
-                }
-
-            }
-        }
+    //TODO: Remove this in next refactoring iterations
+    func getObjectsByIds<T: JSONSerializable>(ids: [T.IdType], updating: [T], printOutput: Bool = false) -> Promise<([T])> {
+        return retrieve.request(requestEndpoint: name, paramName: name, ids: ids, updating: updating, withManager: manager)
     }
 
-    func getObjectsByIds<T: JSONInitializable>(requestString: String, headers: [String: String] = AuthInfo.shared.initialHTTPHeaders, printOutput: Bool = false, ids: [T.idType], deleteObjects: [T], refreshMode: RefreshMode, success: (([T]) -> Void)?, failure : @escaping (_ error: RetrieveError) -> Void) -> Request? {
-
-        let params: Parameters = [:]
-
-        let idString = constructIdsString(array: ids)
-        if idString == "" {
-            success?([])
-            return nil
-        }
-
-        return manager.request("\(StepicApplicationsInfo.apiURL)/\(requestString)?\(idString)", parameters: params, encoding: URLEncoding.default, headers: headers).responseSwiftyJSON({
-            response in
-
-            var error = response.result.error
-            var json: JSON = [:]
-            if response.result.value == nil {
-                if error == nil {
-                    error = NSError()
-                }
-            } else {
-                json = response.result.value!
-            }
-            let response = response.response
-
-            if printOutput {
-                print(json)
-            }
-
-            if let e = error as NSError? {
-                print("RETRIEVE \(requestString)?\(ids): error \(e.domain) \(e.code): \(e.localizedDescription)")
-                if e.code == -999 {
-                    failure(.cancelled)
-                    return
-                } else {
-                    failure(.connectionError)
-                    return
-                }
-            }
-
-            if response?.statusCode != 200 {
-                print("RETRIEVE \(requestString)?\(ids)): bad response status code \(String(describing: response?.statusCode))")
-                failure(.badStatus)
+    func getObjectsByIds<T: JSONSerializable>(requestString: String, printOutput: Bool = false, ids: [T.IdType], deleteObjects: [T], refreshMode: RefreshMode, success: (([T]) -> Void)?, failure : @escaping (_ error: RetrieveError) -> Void) -> Request? {
+        getObjectsByIds(ids: ids, updating: deleteObjects).then {
+            objects in
+            success?(objects)
+        }.catch {
+            error in
+            guard let e = error as? RetrieveError else {
+                failure(RetrieveError(error: error))
                 return
             }
-
-            var newObjects: [T] = []
-
-            switch refreshMode {
-
-            case .delete:
-
-                for object in deleteObjects {
-                    CoreDataHelper.instance.deleteFromStore(object as! NSManagedObject, save: false)
-                }
-
-                for objectJSON in json[requestString].arrayValue {
-                    newObjects += [T(json: objectJSON)]
-                }
-
-            case .update:
-
-                for objectJSON in json[requestString].arrayValue {
-                    let existing = deleteObjects.filter({obj in obj.hasEqualId(json: objectJSON)})
-
-                    switch existing.count {
-                    case 0:
-                        newObjects += [T(json: objectJSON)]
-                    case 1:
-                        let obj = existing[0]
-                        obj.update(json: objectJSON)
-                        newObjects += [obj]
-                    default:
-                        //TODO: Fix this in the next releases! We have some problems with deleting entities from CoreData
-                        let obj = existing[0]
-                        obj.update(json: objectJSON)
-                        newObjects += [obj]
-                        print("More than 1 object with the same id!")
-                    }
-                }
-            }
-
-            CoreDataHelper.instance.save()
-            success?(newObjects)
-        })
+            failure(e)
+        }
+        return nil
     }
 }

Stepic/AdaptiveRatingsAPI.swift

@@ -11,6 +11,7 @@ import Alamofire
 import SwiftyJSON
 import PromiseKit
 
+//TODO: Better refactor this to two classes
 class AdaptiveRatingsAPI: APIEndpoint {
     override var name: String { return "rating" }
     var restoreName: String { return "rating-restore" }

Stepic/ApiRequestRetrier.swift

@@ -0,0 +1,34 @@
+//
+//  ApiRequestRetrier.swift
+//  Stepic
+//
+//  Created by Ostrenkiy on 18.03.2018.
+//  Copyright © 2018 Alex Karpov. All rights reserved.
+//
+import Foundation
+import Alamofire
+import PromiseKit
+
+class ApiRequestRetrier: RequestRetrier, RequestAdapter {
+
+    func adapt(_ urlRequest: URLRequest) throws -> URLRequest {
+        var urlRequest = urlRequest
+        for (headerField, value) in AuthInfo.shared.initialHTTPHeaders {
+            urlRequest.setValue(value, forHTTPHeaderField: headerField)
+        }
+        return urlRequest
+    }
+
+    func should(_ manager: SessionManager, retry request: Request, with error: Error, completion: @escaping RequestRetryCompletion) {
+        if let response = request.task?.response as? HTTPURLResponse, response.statusCode == 401 && request.retryCount == 0 {
+            checkToken().then {
+                completion(true, 0.0)
+            }.catch {
+                _ in
+                completion(false, 0.0)
+            }
+        } else {
+            completion(false, 0.0)
+        }
+    }
+}

Stepic/AppDelegate.swift

@@ -97,9 +97,7 @@ class AppDelegate: UIResponder, UIApplicationDelegate {
             return
         }
 
-        checkToken().then {
-            ApiDataDownloader.notificationsStatusAPI.retrieve()
-        }.then { result -> Void in
+        ApiDataDownloader.notificationsStatusAPI.retrieve().then { result -> Void in
             NotificationsBadgesManager.shared.set(number: result.totalCount)
         }.catch { _ in
             print("notifications: unable to fetch badges count on launch")

Stepic/Assignment.swift

@@ -10,9 +10,10 @@ import Foundation
 import CoreData
 import SwiftyJSON
 
-class Assignment: NSManagedObject, JSONInitializable {
+@objc
+class Assignment: NSManagedObject, JSONSerializable {
 
-    typealias idType = Int
+    typealias IdType = Int
 
     convenience required init(json: JSON) {
         self.init()
@@ -28,8 +29,4 @@ class Assignment: NSManagedObject, JSONInitializable {
     func update(json: JSON) {
         initialize(json)
     }
-
-    func hasEqualId(json: JSON) -> Bool {
-        return id == json["id"].intValue
-    }
 }

Stepic/AssignmentsAPI.swift

@@ -14,6 +14,6 @@ class AssignmentsAPI: APIEndpoint {
     override var name: String { return "assignments" }
 
     @discardableResult func retrieve(ids: [Int], headers: [String: String] = AuthInfo.shared.initialHTTPHeaders, existing: [Assignment], refreshMode: RefreshMode, success: @escaping (([Assignment]) -> Void), error errorHandler: @escaping ((RetrieveError) -> Void)) -> Request? {
-        return getObjectsByIds(requestString: name, headers: headers, printOutput: false, ids: ids, deleteObjects: existing, refreshMode: refreshMode, success: success, failure: errorHandler)
+        return getObjectsByIds(requestString: name, printOutput: false, ids: ids, deleteObjects: existing, refreshMode: refreshMode, success: success, failure: errorHandler)
     }
 }

Stepic/Attempt.swift

@@ -9,17 +9,45 @@
 import UIKit
 import SwiftyJSON
 
-class Attempt: NSObject {
+class Attempt: JSONSerializable {
 
-    var id: Int?
+    typealias IdType = Int
+
+    var id: Int = 0
     var dataset: Dataset?
     var datasetUrl: String?
     var time: String?
     var status: String?
-    var step: Int
+    var step: Int = 0
     var timeLeft: String?
     var user: Int?
 
+    func update(json: JSON) {
+        id = json["id"].intValue
+        datasetUrl = json["dataset_url"].string
+        time = json["time"].string
+        status = json["status"].string
+        step = json["step"].intValue
+        timeLeft = json["time_left"].string
+        user = json["user"].int
+    }
+
+    func hasEqualId(json: JSON) -> Bool {
+        return id == json["id"].int
+    }
+
+    init(step: Int) {
+        self.step = step
+    }
+
+    required init(json: JSON) {
+        self.update(json: json)
+    }
+
+    func initDataset(json: JSON, stepName: String) {
+        dataset = getDatasetFromJSON(json, stepName: stepName)
+    }
+
     init(json: JSON, stepName: String) {
         id = json["id"].intValue
         dataset = nil
@@ -29,10 +57,15 @@ class Attempt: NSObject {
         step = json["step"].intValue
         timeLeft = json["time_left"].string
         user = json["user"].int
-        super.init()
         dataset = getDatasetFromJSON(json["dataset"], stepName: stepName)
     }
 
+    var json: JSON {
+        return [
+            "step": step
+        ]
+    }
+
     fileprivate func getDatasetFromJSON(_ json: JSON, stepName: String) -> Dataset? {
         switch stepName {
         case "choice" :