gistfile1.txt

login(credentials): Observable<AuthenticationToken> {
    const data = 'username=' + encodeURIComponent(credentials.username) + '&password=' +
      encodeURIComponent(credentials.password) + '&grant_type=password&scope=read%20write&' +
      'client_secret=' + this.clientSecret + '&client_id=' + this.clientId;

    const headers = new HttpHeaders()
      .set('Content-Type', 'application/x-www-form-urlencoded')
      .set('Accept', 'application/json')
      .set('Authorization', 'Basic ' + this.base64('myapp' + ':' + 'mySecretOAuthSecret'));

    return this.http.post(this.urlLogin, data, {
      headers
    })
      .pipe(
      map(this.authSuccess.bind(this)),
      catchError((error: HttpErrorResponse) => {
        const errorMessage = `Server returned code: ${error.status}, error message is: ${error.message}`;
        return ErrorObservable.create(errorMessage);
      })
      );
  }
  
  private authSuccess(data): AuthenticationToken {
    const expiredAt = new Date();
    expiredAt.setSeconds(expiredAt.getSeconds() + data.expires_in);
    const authenticationToken: AuthenticationToken = {
      token: data.access_token,
      expiresIn: data.expires_in,
      expiresAt: expiredAt.getTime()
    };
    return authenticationToken
  }

  private base64(str): string {
    return btoa(str);
  }