/*!
 * Copyright 2016 Amazon.com,
 * Inc. or its affiliates. All Rights Reserved.
 *
 * Licensed under the Amazon Software License (the "License").
 * You may not use this file except in compliance with the
 * License. A copy of the License is located at
 *
 *     http://aws.amazon.com/asl/
 *
 * or in the "license" file accompanying this file. This file is
 * distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
 * CONDITIONS OF ANY KIND, express or implied. See the License
 * for the specific language governing permissions and
 * limitations under the License.
 */

/** @class */
export default class CognitoUserSession {
  /**
   * Constructs a new CognitoUserSession object
   * @param {CognitoIdToken} IdToken The session's Id token.
   * @param {CognitoRefreshToken=} RefreshToken The session's refresh token.
   * @param {CognitoAccessToken} AccessToken The session's access token.
   * @param {int} ClockDrift The saved computer's clock drift or undefined to force calculation.
   */
  constructor({ IdToken, RefreshToken, AccessToken, ClockDrift } = {}) {
    if (AccessToken == null || IdToken == null) {
      throw new Error('Id token and Access Token must be present.');
    }

    this.idToken = IdToken;
    this.refreshToken = RefreshToken;
    this.accessToken = AccessToken;
    this.clockDrift = ClockDrift === undefined ? this.calculateClockDrift() : ClockDrift;
  }

  /**
   * @returns {CognitoIdToken} the session's Id token
   */
  getIdToken() {
    return this.idToken;
  }

  /**
   * @returns {CognitoRefreshToken} the session's refresh token
   */
  getRefreshToken() {
    return this.refreshToken;
  }

  /**
   * @returns {CognitoAccessToken} the session's access token
   */
  getAccessToken() {
    return this.accessToken;
  }

  /**
   * @returns {int} the session's clock drift
   */
  getClockDrift() {
    return this.clockDrift;
  }

  /**
   * @returns {int} the computer's clock drift
   */
  calculateClockDrift() {
    const now = Math.floor(new Date() / 1000);
    const iat = Math.min(this.accessToken.getIssuedAt(), this.idToken.getIssuedAt());

    return now - iat;
  }

  /**
   * Checks to see if the session is still valid based on session expiry information found
   * in tokens and the current time (adjusted with clock drift)
   * @returns {boolean} if the session is still valid
   */
  isValid() {
    const now = Math.floor(new Date() / 1000);
    const adjusted = now - this.clockDrift;

    return adjusted < this.accessToken.getExpiration() && adjusted < this.idToken.getExpiration();
  }
}
