/**
 * @license
 * Copyright Google Inc. All Rights Reserved.
 *
 * Use of this source code is governed by an MIT-style license that can be
 * found in the LICENSE file at https://angular.io/license
 */

import {Injectable} from '@angular/core';
import {Connection, ConnectionBackend, ReadyState, Request, Response} from '@angular/http';
import {ReplaySubject, Subject} from 'rxjs';
import {take} from 'rxjs/operators';


/**
 *
 * Mock Connection to represent a {@link Connection} for tests.
 *
 * @usageNotes
 * ### Example of `mockRespond()`
 *
 * ```
 * var connection;
 * backend.connections.subscribe(c => connection = c);
 * http.request('data.json').subscribe(res => console.log(res.text()));
 * connection.mockRespond(new Response(new ResponseOptions({ body: 'fake response' }))); //logs
 * 'fake response'
 * ```
 *
 * ### Example of `mockError()`
 *
 * ```
 * var connection;
 * backend.connections.subscribe(c => connection = c);
 * http.request('data.json').subscribe(res => res, err => console.log(err)));
 * connection.mockError(new Error('error'));
 * ```
 *
 * @deprecated see https://angular.io/guide/http
 * @publicApi
 */
export class MockConnection implements Connection {
  // TODO: Name `readyState` should change to be more generic, and states could be made to be more
  // descriptive than ResourceLoader states.
  /**
   * Describes the state of the connection, based on `XMLHttpRequest.readyState`, but with
   * additional states. For example, state 5 indicates an aborted connection.
   */
  readyState: ReadyState;

  /**
   * {@link Request} instance used to create the connection.
   */
  request: Request;

  /**
   * {@link EventEmitter} of {@link Response}. Can be subscribed to in order to be notified when a
   * response is available.
   */
  response: ReplaySubject<Response>;

  constructor(req: Request) {
    this.response = <any>new ReplaySubject(1).pipe(take(1));
    this.readyState = ReadyState.Open;
    this.request = req;
  }

  /**
   * Sends a mock response to the connection. This response is the value that is emitted to the
   * {@link EventEmitter} returned by {@link Http}.
   *
   */
  mockRespond(res: Response) {
    if (this.readyState === ReadyState.Done || this.readyState === ReadyState.Cancelled) {
      throw new Error('Connection has already been resolved');
    }
    this.readyState = ReadyState.Done;
    this.response.next(res);
    this.response.complete();
  }

  /**
   * Not yet implemented!
   *
   * Sends the provided {@link Response} to the `downloadObserver` of the `Request`
   * associated with this connection.
   */
  mockDownload(res: Response) {
    // this.request.downloadObserver.onNext(res);
    // if (res.bytesLoaded === res.totalBytes) {
    //   this.request.downloadObserver.onCompleted();
    // }
  }

  // TODO(jeffbcross): consider using Response type
  /**
   * Emits the provided error object as an error to the {@link Response} {@link EventEmitter}
   * returned
   * from {@link Http}.
   *
   */
  mockError(err?: Error) {
    // Matches ResourceLoader semantics
    this.readyState = ReadyState.Done;
    this.response.error(err);
  }
}

/**
 * A mock backend for testing the {@link Http} service.
 *
 * This class can be injected in tests, and should be used to override providers
 * to other backends, such as {@link XHRBackend}.
 *
 * @usageNotes
 * ### Example
 *
 * ```
 * import {Injectable, Injector} from '@angular/core';
 * import {async, fakeAsync, tick} from '@angular/core/testing';
 * import {BaseRequestOptions, ConnectionBackend, Http, RequestOptions} from '@angular/http';
 * import {Response, ResponseOptions} from '@angular/http';
 * import {MockBackend, MockConnection} from '@angular/http/testing';
 *
 * const HERO_ONE = 'HeroNrOne';
 * const HERO_TWO = 'WillBeAlwaysTheSecond';
 *
 * @Injectable()
 * class HeroService {
 *   constructor(private http: Http) {}
 *
 *   getHeroes(): Promise<String[]> {
 *     return this.http.get('myservices.de/api/heroes')
 *         .toPromise()
 *         .then(response => response.json().data)
 *         .catch(e => this.handleError(e));
 *   }
 *
 *   private handleError(error: any): Promise<any> {
 *     console.error('An error occurred', error);
 *     return Promise.reject(error.message || error);
 *   }
 * }
 *
 * describe('MockBackend HeroService Example', () => {
 *   beforeEach(() => {
 *     this.injector = Injector.create([
 *       {provide: ConnectionBackend, useClass: MockBackend},
 *       {provide: RequestOptions, useClass: BaseRequestOptions},
 *       Http,
 *       HeroService,
 *     ]);
 *     this.heroService = this.injector.get(HeroService);
 *     this.backend = this.injector.get(ConnectionBackend) as MockBackend;
 *     this.backend.connections.subscribe((connection: any) => this.lastConnection = connection);
 *   });
 *
 *   it('getHeroes() should query current service url', () => {
 *     this.heroService.getHeroes();
 *     expect(this.lastConnection).toBeDefined('no http service connection at all?');
 *     expect(this.lastConnection.request.url).toMatch(/api\/heroes$/, 'url invalid');
 *   });
 *
 *   it('getHeroes() should return some heroes', fakeAsync(() => {
 *        let result: String[];
 *        this.heroService.getHeroes().then((heroes: String[]) => result = heroes);
 *        this.lastConnection.mockRespond(new Response(new ResponseOptions({
 *          body: JSON.stringify({data: [HERO_ONE, HERO_TWO]}),
 *        })));
 *        tick();
 *        expect(result.length).toEqual(2, 'should contain given amount of heroes');
 *        expect(result[0]).toEqual(HERO_ONE, ' HERO_ONE should be the first hero');
 *        expect(result[1]).toEqual(HERO_TWO, ' HERO_TWO should be the second hero');
 *      }));
 *
 *   it('getHeroes() while server is down', fakeAsync(() => {
 *        let result: String[];
 *        let catchedError: any;
 *        this.heroService.getHeroes()
 *            .then((heroes: String[]) => result = heroes)
 *            .catch((error: any) => catchedError = error);
 *        this.lastConnection.mockError(new Response(new ResponseOptions({
 *          status: 404,
 *          statusText: 'URL not Found',
 *        })));
 *        tick();
 *        expect(result).toBeUndefined();
 *        expect(catchedError).toBeDefined();
 *      }));
 * });
 * ```
 *
 * @deprecated see https://angular.io/guide/http
 * @publicApi
 */
@Injectable()
export class MockBackend implements ConnectionBackend {
  /**
   * {@link EventEmitter}
   * of {@link MockConnection} instances that have been created by this backend. Can be subscribed
   * to in order to respond to connections.
   *
   * This property only exists in the mock implementation, not in real Backends.
   */
  connections: any;  //<MockConnection>

  /**
   * An array representation of `connections`. This array will be updated with each connection that
   * is created by this backend.
   *
   * This property only exists in the mock implementation, not in real Backends.
   */
  connectionsArray: MockConnection[];
  /**
   * {@link EventEmitter} of {@link MockConnection} instances that haven't yet been resolved (i.e.
   * with a `readyState`
   * less than 4). Used internally to verify that no connections are pending via the
   * `verifyNoPendingRequests` method.
   *
   * This property only exists in the mock implementation, not in real Backends.
   */
  pendingConnections: any;  // Subject<MockConnection>
  constructor() {
    this.connectionsArray = [];
    this.connections = new Subject();
    this.connections.subscribe(
        (connection: MockConnection) => this.connectionsArray.push(connection));
    this.pendingConnections = new Subject();
  }

  /**
   * Checks all connections, and raises an exception if any connection has not received a response.
   *
   * This method only exists in the mock implementation, not in real Backends.
   */
  verifyNoPendingRequests() {
    let pending = 0;
    this.pendingConnections.subscribe((c: MockConnection) => pending++);
    if (pending > 0) throw new Error(`${pending} pending connections to be resolved`);
  }

  /**
   * Can be used in conjunction with `verifyNoPendingRequests` to resolve any not-yet-resolve
   * connections, if it's expected that there are connections that have not yet received a response.
   *
   * This method only exists in the mock implementation, not in real Backends.
   */
  resolveAllConnections() { this.connections.subscribe((c: MockConnection) => c.readyState = 4); }

  /**
   * Creates a new {@link MockConnection}. This is equivalent to calling `new
   * MockConnection()`, except that it also will emit the new `Connection` to the `connections`
   * emitter of this `MockBackend` instance. This method will usually only be used by tests
   * against the framework itself, not by end-users.
   */
  createConnection(req: Request): MockConnection {
    if (!req || !(req instanceof Request)) {
      throw new Error(`createConnection requires an instance of Request, got ${req}`);
    }
    const connection = new MockConnection(req);
    this.connections.next(connection);
    return connection;
  }
}