<?php
/**
 * Copyright 2014 Facebook, Inc.
 *
 * You are hereby granted a non-exclusive, worldwide, royalty-free license to
 * use, copy, modify, and distribute this software in source code or binary
 * form for use in connection with the web services and APIs provided by
 * Facebook.
 *
 * As with any software that integrates with the Facebook platform, your use
 * of this software is subject to the Facebook Developer Principles and
 * Policies [http://developers.facebook.com/policy/]. This copyright notice
 * shall be included in all copies or substantial portions of the software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 * DEALINGS IN THE SOFTWARE.
 *
 */
namespace Facebook\Entities;

use Facebook\FacebookRequest;
use Facebook\FacebookRequestException;
use Facebook\FacebookSession;
use Facebook\GraphSessionInfo;

/**
 * Class AccessToken
 * @package Facebook
 */
class AccessToken
{

  /**
   * The access token.
   *
   * @var string
   */
  protected $accessToken;

  /**
   * A unique ID to identify a client.
   *
   * @var string
   */
  protected $machineId;

  /**
   * Date when token expires.
   *
   * @var \DateTime|null
   */
  protected $expiresAt;

  /**
   * Create a new access token entity.
   *
   * @param string $accessToken
   * @param int $expiresAt
   * @param string|null machineId
   */
  public function __construct($accessToken, $expiresAt = 0, $machineId = null)
  {
    $this->accessToken = $accessToken;
    if ($expiresAt) {
      $this->setExpiresAtFromTimeStamp($expiresAt);
    }
    $this->machineId = $machineId;
  }

  /**
   * Setter for expires_at.
   *
   * @param int $timeStamp
   */
  protected function setExpiresAtFromTimeStamp($timeStamp)
  {
    $dt = new \DateTime();
    $dt->setTimestamp($timeStamp);
    $this->expiresAt = $dt;
  }

  /**
   * Getter for expiresAt.
   *
   * @return \DateTime|null
   */
  public function getExpiresAt()
  {
    return $this->expiresAt;
  }

  /**
   * Getter for machineId.
   *
   * @return string|null
   */
  public function getMachineId()
  {
    return $this->machineId;
  }

  /**
   * Determines whether or not this is a long-lived token.
   *
   * @return bool
   */
  public function isLongLived()
  {
    if ($this->expiresAt) {
      return $this->expiresAt->getTimestamp() > time() + (60 * 60 * 2);
    }
    return false;
  }

  /**
   * Checks the validity of the access token.
   *
   * @param string|null $appId Application ID to use
   * @param string|null $appSecret App secret value to use
   * @param string|null $machineId
   *
   * @return boolean
   */
  public function isValid($appId = null, $appSecret = null, $machineId = null)
  {
    $accessTokenInfo = $this->getInfo($appId, $appSecret);
    $machineId = $machineId ?: $this->machineId;
    return static::validateAccessToken($accessTokenInfo, $appId, $machineId);
  }

  /**
   * Ensures the provided GraphSessionInfo object is valid,
   *   throwing an exception if not.  Ensures the appId matches,
   *   that the machineId matches if it's being used,
   *   that the token is valid and has not expired.
   *
   * @param GraphSessionInfo $tokenInfo
   * @param string|null $appId Application ID to use
   * @param string|null $machineId
   *
   * @return boolean
   */
  public static function validateAccessToken(GraphSessionInfo $tokenInfo,
                                             $appId = null, $machineId = null)
  {
    $targetAppId = FacebookSession::_getTargetAppId($appId);

    $appIdIsValid = $tokenInfo->getAppId() == $targetAppId;
    $machineIdIsValid = $tokenInfo->getProperty('machine_id') == $machineId;
    $accessTokenIsValid = $tokenInfo->isValid();

    $accessTokenIsStillAlive = true;
    // Not all access tokens return an expiration. E.g. an app access token.
    if ($tokenInfo->getExpiresAt() instanceof \DateTime) {
      $accessTokenIsStillAlive = $tokenInfo->getExpiresAt()->getTimestamp() >= time();
    }

    return $appIdIsValid && $machineIdIsValid && $accessTokenIsValid && $accessTokenIsStillAlive;
  }

  /**
   * Get a valid access token from a code.
   *
   * @param string $code
   * @param string|null $appId
   * @param string|null $appSecret
   * @param string|null $machineId
   *
   * @return AccessToken
   */
  public static function getAccessTokenFromCode($code, $appId = null, $appSecret = null, $machineId = null)
  {
    $params = array(
      'code' => $code,
      'redirect_uri' => '',
    );

    if ($machineId) {
      $params['machine_id'] = $machineId;
    }

    return static::requestAccessToken($params, $appId, $appSecret);
  }

  /**
   * Get a valid code from an access token.
   *
   * @param AccessToken|string $accessToken
   * @param string|null $appId
   * @param string|null $appSecret
   *
   * @return AccessToken
   */
  public static function getCodeFromAccessToken($accessToken, $appId = null, $appSecret = null)
  {
    $accessToken = (string) $accessToken;

    $params = array(
      'access_token' => $accessToken,
      'redirect_uri' => '',
    );

    return static::requestCode($params, $appId, $appSecret);
  }

  /**
   * Exchanges a short lived access token with a long lived access token.
   *
   * @param string|null $appId
   * @param string|null $appSecret
   *
   * @return AccessToken
   */
  public function extend($appId = null, $appSecret = null)
  {
    $params = array(
      'grant_type' => 'fb_exchange_token',
      'fb_exchange_token' => $this->accessToken,
    );

    return static::requestAccessToken($params, $appId, $appSecret);
  }

  /**
   * Request an access token based on a set of params.
   *
   * @param array $params
   * @param string|null $appId
   * @param string|null $appSecret
   *
   * @return AccessToken
   *
   * @throws FacebookRequestException
   */
  public static function requestAccessToken(array $params, $appId = null, $appSecret = null)
  {
    $response = static::request('/oauth/access_token', $params, $appId, $appSecret);
    $data = $response->getResponse();

    /**
     * @TODO fix this malarkey - getResponse() should always return an object
     * @see https://github.com/facebook/facebook-php-sdk-v4/issues/36
     */
    if (is_array($data)) {
      if (isset($data['access_token'])) {
        $expiresAt = isset($data['expires']) ? time() + $data['expires'] : 0;
        return new static($data['access_token'], $expiresAt);
      }
    } elseif($data instanceof \stdClass) {
      if (isset($data->access_token)) {
        $expiresAt = isset($data->expires_in) ? time() + $data->expires_in : 0;
        $machineId = isset($data->machine_id) ? (string) $data->machine_id : null;
        return new static((string) $data->access_token, $expiresAt, $machineId);
      }
    }

    throw FacebookRequestException::create(
      $response->getRawResponse(),
      $data,
      401
    );
  }

  /**
   * Request a code from a long lived access token.
   *
   * @param array $params
   * @param string|null $appId
   * @param string|null $appSecret
   *
   * @return string
   *
   * @throws FacebookRequestException
   */
  public static function requestCode(array $params, $appId = null, $appSecret = null)
  {
    $response = static::request('/oauth/client_code', $params, $appId, $appSecret);
    $data = $response->getResponse();

    if (isset($data->code)) {
      return (string) $data->code;
    }

    throw FacebookRequestException::create(
      $response->getRawResponse(),
      $data,
      401
    );
  }

  /**
   * Send a request to Graph with an app access token.
   *
   * @param string $endpoint
   * @param array $params
   * @param string|null $appId
   * @param string|null $appSecret
   *
   * @return \Facebook\FacebookResponse
   *
   * @throws FacebookRequestException
   */
  protected static function request($endpoint, array $params, $appId = null, $appSecret = null)
  {
    $targetAppId = FacebookSession::_getTargetAppId($appId);
    $targetAppSecret = FacebookSession::_getTargetAppSecret($appSecret);

    if (!isset($params['client_id'])) {
      $params['client_id'] = $targetAppId;
    }
    if (!isset($params['client_secret'])) {
      $params['client_secret'] = $targetAppSecret;
    }

    // The response for this endpoint is not JSON, so it must be handled
    //   differently, not as a GraphObject.
    $request = new FacebookRequest(
      FacebookSession::newAppSession($targetAppId, $targetAppSecret),
      'GET',
      $endpoint,
      $params
    );
    return $request->execute();
  }

  /**
   * Get more info about an access token.
   *
   * @param string|null $appId
   * @param string|null $appSecret
   *
   * @return GraphSessionInfo
   */
  public function getInfo($appId = null, $appSecret = null)
  {
    $params = array('input_token' => $this->accessToken);

    $request = new FacebookRequest(
      FacebookSession::newAppSession($appId, $appSecret),
      'GET',
      '/debug_token',
      $params
    );
    $response = $request->execute()->getGraphObject(GraphSessionInfo::className());

    // Update the data on this token
    if ($response->getExpiresAt()) {
      $this->expiresAt = $response->getExpiresAt();
    }

    return $response;
  }

  /**
   * Returns the access token as a string.
   *
   * @return string
   */
  public function __toString()
  {
    return $this->accessToken;
  }

  /**
   * Returns true if the access token is an app session token.
   *
   * @return bool
   */
  public function isAppSession()
  {
    return strpos($this->accessToken, '|') !== false;
  }

}