/**
 * @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 {ɵgetDOM as getDOM} from '@angular/platform-browser';
import {Observable} from 'rxjs/Observable';
import {Observer} from 'rxjs/Observer';
import {ResponseOptions} from '../base_response_options';
import {ContentType, ReadyState, RequestMethod, ResponseContentType, ResponseType} from '../enums';
import {Headers} from '../headers';
import {getResponseURL, isSuccess} from '../http_utils';
import {Connection, ConnectionBackend, XSRFStrategy} from '../interfaces';
import {Request} from '../static_request';
import {Response} from '../static_response';
import {BrowserXhr} from './browser_xhr';

const XSSI_PREFIX = /^\)\]\}',?\n/;

/**
 * Creates connections using `XMLHttpRequest`. Given a fully-qualified
 * request, an `XHRConnection` will immediately create an `XMLHttpRequest` object and send the
 * request.
 *
 * This class would typically not be created or interacted with directly inside applications, though
 * the {@link MockConnection} may be interacted with in tests.
 *
 * @experimental
 */
export class XHRConnection implements Connection {
  request: Request;
  /**
   * Response {@link EventEmitter} which emits a single {@link Response} value on load event of
   * `XMLHttpRequest`.
   */
  response: Observable<Response>;
  readyState: ReadyState;
  constructor(req: Request, browserXHR: BrowserXhr, baseResponseOptions?: ResponseOptions) {
    this.request = req;
    this.response = new Observable<Response>((responseObserver: Observer<Response>) => {
      const _xhr: XMLHttpRequest = browserXHR.build();
      _xhr.open(RequestMethod[req.method].toUpperCase(), req.url);
      if (req.withCredentials != null) {
        _xhr.withCredentials = req.withCredentials;
      }
      // load event handler
      const onLoad = () => {
        // normalize IE9 bug (http://bugs.jquery.com/ticket/1450)
        let status: number = _xhr.status === 1223 ? 204 : _xhr.status;

        let body: any = null;

        // HTTP 204 means no content
        if (status !== 204) {
          // responseText is the old-school way of retrieving response (supported by IE8 & 9)
          // response/responseType properties were introduced in ResourceLoader Level2 spec
          // (supported by IE10)
          body = (typeof _xhr.response === 'undefined') ? _xhr.responseText : _xhr.response;

          // Implicitly strip a potential XSSI prefix.
          if (typeof body === 'string') {
            body = body.replace(XSSI_PREFIX, '');
          }
        }

        // fix status code when it is 0 (0 status is undocumented).
        // Occurs when accessing file resources or on Android 4.1 stock browser
        // while retrieving files from application cache.
        if (status === 0) {
          status = body ? 200 : 0;
        }

        const headers: Headers = Headers.fromResponseHeaderString(_xhr.getAllResponseHeaders());
        // IE 9 does not provide the way to get URL of response
        const url = getResponseURL(_xhr) || req.url;
        const statusText: string = _xhr.statusText || 'OK';

        let responseOptions = new ResponseOptions({body, status, headers, statusText, url});
        if (baseResponseOptions != null) {
          responseOptions = baseResponseOptions.merge(responseOptions);
        }
        const response = new Response(responseOptions);
        response.ok = isSuccess(status);
        if (response.ok) {
          responseObserver.next(response);
          // TODO(gdi2290): defer complete if array buffer until done
          responseObserver.complete();
          return;
        }
        responseObserver.error(response);
      };
      // error event handler
      const onError = (err: ErrorEvent) => {
        let responseOptions = new ResponseOptions({
          body: err,
          type: ResponseType.Error,
          status: _xhr.status,
          statusText: _xhr.statusText,
        });
        if (baseResponseOptions != null) {
          responseOptions = baseResponseOptions.merge(responseOptions);
        }
        responseObserver.error(new Response(responseOptions));
      };

      this.setDetectedContentType(req, _xhr);

      if (req.headers == null) {
        req.headers = new Headers();
      }
      if (!req.headers.has('Accept')) {
        req.headers.append('Accept', 'application/json, text/plain, */*');
      }
      req.headers.forEach((values, name) => _xhr.setRequestHeader(name, values.join(',')));

      // Select the correct buffer type to store the response
      if (req.responseType != null && _xhr.responseType != null) {
        switch (req.responseType) {
          case ResponseContentType.ArrayBuffer:
            _xhr.responseType = 'arraybuffer';
            break;
          case ResponseContentType.Json:
            _xhr.responseType = 'json';
            break;
          case ResponseContentType.Text:
            _xhr.responseType = 'text';
            break;
          case ResponseContentType.Blob:
            _xhr.responseType = 'blob';
            break;
          default:
            throw new Error('The selected responseType is not supported');
        }
      }

      _xhr.addEventListener('load', onLoad);
      _xhr.addEventListener('error', onError);

      _xhr.send(this.request.getBody());

      return () => {
        _xhr.removeEventListener('load', onLoad);
        _xhr.removeEventListener('error', onError);
        _xhr.abort();
      };
    });
  }

  setDetectedContentType(req: any /** TODO Request */, _xhr: any /** XMLHttpRequest */) {
    // Skip if a custom Content-Type header is provided
    if (req.headers != null && req.headers.get('Content-Type') != null) {
      return;
    }

    // Set the detected content type
    switch (req.contentType) {
      case ContentType.NONE:
        break;
      case ContentType.JSON:
        _xhr.setRequestHeader('content-type', 'application/json');
        break;
      case ContentType.FORM:
        _xhr.setRequestHeader('content-type', 'application/x-www-form-urlencoded;charset=UTF-8');
        break;
      case ContentType.TEXT:
        _xhr.setRequestHeader('content-type', 'text/plain');
        break;
      case ContentType.BLOB:
        const blob = req.blob();
        if (blob.type) {
          _xhr.setRequestHeader('content-type', blob.type);
        }
        break;
    }
  }
}

/**
 * `XSRFConfiguration` sets up Cross Site Request Forgery (XSRF) protection for the application
 * using a cookie. See https://www.owasp.org/index.php/Cross-Site_Request_Forgery_(CSRF)
 * for more information on XSRF.
 *
 * Applications can configure custom cookie and header names by binding an instance of this class
 * with different `cookieName` and `headerName` values. See the main HTTP documentation for more
 * details.
 *
 * @experimental
 */
export class CookieXSRFStrategy implements XSRFStrategy {
  constructor(
      private _cookieName: string = 'XSRF-TOKEN', private _headerName: string = 'X-XSRF-TOKEN') {}

  configureRequest(req: Request): void {
    const xsrfToken = getDOM().getCookie(this._cookieName);
    if (xsrfToken) {
      req.headers.set(this._headerName, xsrfToken);
    }
  }
}

/**
 * Creates {@link XHRConnection} instances.
 *
 * This class would typically not be used by end users, but could be
 * overridden if a different backend implementation should be used,
 * such as in a node backend.
 *
 * ### Example
 *
 * ```
 * import {Http, MyNodeBackend, HTTP_PROVIDERS, BaseRequestOptions} from '@angular/http';
 * @Component({
 *   viewProviders: [
 *     HTTP_PROVIDERS,
 *     {provide: Http, useFactory: (backend, options) => {
 *       return new Http(backend, options);
 *     }, deps: [MyNodeBackend, BaseRequestOptions]}]
 * })
 * class MyComponent {
 *   constructor(http:Http) {
 *     http.request('people.json').subscribe(res => this.people = res.json());
 *   }
 * }
 * ```
 * @experimental
 */
@Injectable()
export class XHRBackend implements ConnectionBackend {
  constructor(
      private _browserXHR: BrowserXhr, private _baseResponseOptions: ResponseOptions,
      private _xsrfStrategy: XSRFStrategy) {}

  createConnection(request: Request): XHRConnection {
    this._xsrfStrategy.configureRequest(request);
    return new XHRConnection(request, this._browserXHR, this._baseResponseOptions);
  }
}