<?php
/**
 * Copyright 2011 Facebook, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may
 * not use this file except in compliance with the License. You may obtain
 * a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations
 * under the License.
 */

if ( ! function_exists( 'curl_init' ) ) {
	throw new Exception( 'Facebook needs the CURL PHP extension.' );
}
if ( ! function_exists( 'json_decode' ) ) {
	throw new Exception( 'Facebook needs the JSON PHP extension.' );
}

/**
 * Thrown when an API call returns an exception.
 *
 * @author Naitik Shah <naitik@facebook.com>
 */
class FacebookApiException extends Exception {
	/**
	 * The result from the API server that represents the exception information.
	 */
	protected $result;

	/**
	 * Make a new API Exception with the given result.
	 *
	 * @param array $result The result from the API server
	 */
	public function __construct( $result ) {
		$this->result = $result;

		$code = isset( $result[ 'error_code' ] ) ? $result[ 'error_code' ] : 0;

		if ( isset( $result[ 'error_description' ] ) ) {
			// OAuth 2.0 Draft 10 style
			$msg = $result[ 'error_description' ];
		} else if ( isset( $result[ 'error' ] ) && is_array( $result[ 'error' ] ) ) {
			// OAuth 2.0 Draft 00 style
			$msg = $result[ 'error' ][ 'message' ];
		} else if ( isset( $result[ 'error_msg' ] ) ) {
			// Rest server style
			$msg = $result[ 'error_msg' ];
		} else {
			$msg = 'Unknown Error. Check getResult()';
		}

		parent::__construct( $msg, $code );
	}

	/**
	 * Return the associated result object returned by the API server.
	 *
	 * @return array The result from the API server
	 */
	public function getResult() {
		return $this->result;
	}

	/**
	 * Returns the associated type for the error. This will default to
	 * 'Exception' when a type is not available.
	 *
	 * @return string
	 */
	public function getType() {
		if ( isset( $this->result[ 'error' ] ) ) {
			$error = $this->result[ 'error' ];
			if ( is_string( $error ) ) {
				// OAuth 2.0 Draft 10 style
				return $error;
			} else if ( is_array( $error ) ) {
				// OAuth 2.0 Draft 00 style
				if ( isset( $error[ 'type' ] ) ) {
					return $error[ 'type' ];
				}
			}
		}

		return 'Exception';
	}

	/**
	 * To make debugging easier.
	 *
	 * @return string The string representation of the error
	 */
	public function __toString() {
		$str = $this->getType() . ': ';
		if ( $this->code != 0 ) {
			$str .= $this->code . ': ';
		}

		return $str . $this->message;
	}
}

/**
 * Provides access to the Facebook Platform.  This class provides
 * a majority of the functionality needed, but the class is abstract
 * because it is designed to be sub-classed.  The subclass must
 * implement the four abstract methods listed at the bottom of
 * the file.
 *
 * @author Naitik Shah <naitik@facebook.com>
 */
abstract class BaseFacebook {
	/**
	 * Version.
	 */
	const VERSION = '3.2.2';

	/**
	 * Signed Request Algorithm.
	 */
	const SIGNED_REQUEST_ALGORITHM = 'HMAC-SHA256';

	/**
	 * Default options for curl.
	 */
	public static $CURL_OPTS = array(
		CURLOPT_CONNECTTIMEOUT => 10,
		CURLOPT_RETURNTRANSFER => true,
		CURLOPT_TIMEOUT        => 60,
		CURLOPT_USERAGENT      => 'facebook-php-3.2',
	);

	/**
	 * List of query parameters that get automatically dropped when rebuilding
	 * the current URL.
	 */
	protected static $DROP_QUERY_PARAMS = array(
		'code',
		'state',
		'signed_request',
	);

	/**
	 * Maps aliases to Facebook domains.
	 */
	public static $DOMAIN_MAP = array(
		'api'         => 'https://api.facebook.com/',
		'api_video'   => 'https://api-video.facebook.com/',
		'api_read'    => 'https://api-read.facebook.com/',
		'graph'       => 'https://graph.facebook.com/',
		'graph_video' => 'https://graph-video.facebook.com/',
		'www'         => 'https://www.facebook.com/',
	);

	/**
	 * The Application ID.
	 *
	 * @var string
	 */
	protected $appId;

	/**
	 * The Application App Secret.
	 *
	 * @var string
	 */
	protected $appSecret;

	/**
	 * The ID of the Facebook user, or 0 if the user is logged out.
	 *
	 * @var integer
	 */
	protected $user;

	/**
	 * The data from the signed_request token.
	 */
	protected $signedRequest;

	/**
	 * A CSRF state variable to assist in the defense against CSRF attacks.
	 */
	protected $state;

	/**
	 * The OAuth access token received in exchange for a valid authorization
	 * code.  null means the access token has yet to be determined.
	 *
	 * @var string
	 */
	protected $accessToken = null;

	/**
	 * Indicates if the CURL based @ syntax for file uploads is enabled.
	 *
	 * @var boolean
	 */
	protected $fileUploadSupport = false;

	/**
	 * Indicates if we trust HTTP_X_FORWARDED_* headers.
	 *
	 * @var boolean
	 */
	protected $trustForwarded = false;

	/**
	 * Initialize a Facebook Application.
	 *
	 * The configuration:
	 * - appId: the application ID
	 * - secret: the application secret
	 * - fileUpload: (optional) boolean indicating if file uploads are enabled
	 *
	 * @param array $config The application configuration
	 */
	public function __construct( $config ) {
		$this->setAppId( $config[ 'appId' ] );
		$this->setAppSecret( $config[ 'secret' ] );
		if ( isset( $config[ 'fileUpload' ] ) ) {
			$this->setFileUploadSupport( $config[ 'fileUpload' ] );
		}
		if ( isset( $config[ 'trustForwarded' ] ) && $config[ 'trustForwarded' ] ) {
			$this->trustForwarded = true;
		}
		$state = $this->getPersistentData( 'state' );
		if ( ! empty( $state ) ) {
			$this->state = $state;
		}
	}

	/**
	 * Set the Application ID.
	 *
	 * @param string $appId The Application ID
	 *
	 * @return BaseFacebook
	 */
	public function setAppId( $appId ) {
		$this->appId = $appId;

		return $this;
	}

	/**
	 * Get the Application ID.
	 *
	 * @return string the Application ID
	 */
	public function getAppId() {
		return $this->appId;
	}

	/**
	 * Set the App Secret.
	 *
	 * @param string $apiSecret The App Secret
	 *
	 * @return BaseFacebook
	 * @deprecated
	 */
	public function setApiSecret( $apiSecret ) {
		$this->setAppSecret( $apiSecret );

		return $this;
	}

	/**
	 * Set the App Secret.
	 *
	 * @param string $appSecret The App Secret
	 *
	 * @return BaseFacebook
	 */
	public function setAppSecret( $appSecret ) {
		$this->appSecret = $appSecret;

		return $this;
	}

	/**
	 * Get the App Secret.
	 *
	 * @return string the App Secret
	 * @deprecated
	 */
	public function getApiSecret() {
		return $this->getAppSecret();
	}

	/**
	 * Get the App Secret.
	 *
	 * @return string the App Secret
	 */
	public function getAppSecret() {
		return $this->appSecret;
	}

	/**
	 * Set the file upload support status.
	 *
	 * @param boolean $fileUploadSupport The file upload support status.
	 *
	 * @return BaseFacebook
	 */
	public function setFileUploadSupport( $fileUploadSupport ) {
		$this->fileUploadSupport = $fileUploadSupport;

		return $this;
	}

	/**
	 * Get the file upload support status.
	 *
	 * @return boolean true if and only if the server supports file upload.
	 */
	public function getFileUploadSupport() {
		return $this->fileUploadSupport;
	}

	/**
	 * DEPRECATED! Please use getFileUploadSupport instead.
	 *
	 * Get the file upload support status.
	 *
	 * @return boolean true if and only if the server supports file upload.
	 */
	public function useFileUploadSupport() {
		return $this->getFileUploadSupport();
	}

	/**
	 * Sets the access token for api calls.  Use this if you get
	 * your access token by other means and just want the SDK
	 * to use it.
	 *
	 * @param string $access_token an access token.
	 *
	 * @return BaseFacebook
	 */
	public function setAccessToken( $access_token ) {
		$this->accessToken = $access_token;

		return $this;
	}

	/**
	 * Extend an access token, while removing the short-lived token that might
	 * have been generated via client-side flow. Thanks to http://bit.ly/b0Pt0H
	 * for the workaround.
	 */
	public function setExtendedAccessToken() {
		try {
			// need to circumvent json_decode by calling _oauthRequest
			// directly, since response isn't JSON format.
			$access_token_response = $this->_oauthRequest( $this->getUrl( 'graph', '/oauth/access_token' ), $params = array(
				'client_id'         => $this->getAppId(),
				'client_secret'     => $this->getAppSecret(),
				'grant_type'        => 'fb_exchange_token',
				'fb_exchange_token' => $this->getAccessToken(),
			) );
		} catch ( FacebookApiException $e ) {
			// most likely that user very recently revoked authorization.
			// In any event, we don't have an access token, so say so.
			return false;
		}

		if ( empty( $access_token_response ) ) {
			return false;
		}

		//Version 2.2 and down (Deprecated).  For more info, see http://stackoverflow.com/a/43016312/114558
		// $response_params = array();
		// parse_str($access_token_response, $response_params);
		//
		// if (!isset($response_params['access_token'])) {
		//   return false;
		// }
		//
		// $this->destroySession();
		//
		// $this->setPersistentData(
		//   'access_token', $response_params['access_token']
		// );

		//Version 2.3 and up.
		$response = json_decode( $access_token_response );
		if ( ! isset( $response->access_token ) ) {
			return false;
		}

		$this->destroySession();

		$this->setPersistentData( 'access_token', $response->access_token );
	}

	/**
	 * Determines the access token that should be used for API calls.
	 * The first time this is called, $this->accessToken is set equal
	 * to either a valid user access token, or it's set to the application
	 * access token if a valid user access token wasn't available.  Subsequent
	 * calls return whatever the first call returned.
	 *
	 * @return string The access token
	 */
	public function getAccessToken() {
		if ( $this->accessToken !== null ) {
			// we've done this already and cached it.  Just return.
			return $this->accessToken;
		}

		// first establish access token to be the application
		// access token, in case we navigate to the /oauth/access_token
		// endpoint, where SOME access token is required.
		$this->setAccessToken( $this->getApplicationAccessToken() );
		$user_access_token = $this->getUserAccessToken();
		if ( $user_access_token ) {
			$this->setAccessToken( $user_access_token );
		}

		return $this->accessToken;
	}

	/**
	 * Determines and returns the user access token, first using
	 * the signed request if present, and then falling back on
	 * the authorization code if present.  The intent is to
	 * return a valid user access token, or false if one is determined
	 * to not be available.
	 *
	 * @return string A valid user access token, or false if one
	 *                could not be determined.
	 */
	protected function getUserAccessToken() {
		// first, consider a signed request if it's supplied.
		// if there is a signed request, then it alone determines
		// the access token.
		$signed_request = $this->getSignedRequest();
		if ( $signed_request ) {
			// apps.facebook.com hands the access_token in the signed_request
			if ( array_key_exists( 'oauth_token', $signed_request ) ) {
				$access_token = $signed_request[ 'oauth_token' ];
				$this->setPersistentData( 'access_token', $access_token );

				return $access_token;
			}

			// the JS SDK puts a code in with the redirect_uri of ''
			if ( array_key_exists( 'code', $signed_request ) ) {
				$code = $signed_request[ 'code' ];
				if ( $code && $code == $this->getPersistentData( 'code' ) ) {
					// short-circuit if the code we have is the same as the one presented
					return $this->getPersistentData( 'access_token' );
				}

				$access_token = $this->getAccessTokenFromCode( $code, '' );
				if ( $access_token ) {
					$this->setPersistentData( 'code', $code );
					$this->setPersistentData( 'access_token', $access_token );

					return $access_token;
				}
			}

			// signed request states there's no access token, so anything
			// stored should be cleared.
			$this->clearAllPersistentData();

			return false; // respect the signed request's data, even
			// if there's an authorization code or something else
		}

		$code = $this->getCode();
		if ( $code && $code != $this->getPersistentData( 'code' ) ) {
			$access_token = $this->getAccessTokenFromCode( $code );
			if ( $access_token ) {
				$this->setPersistentData( 'code', $code );
				$this->setPersistentData( 'access_token', $access_token );

				return $access_token;
			}

			// code was bogus, so everything based on it should be invalidated.
			$this->clearAllPersistentData();

			return false;
		}

		// as a fallback, just return whatever is in the persistent
		// store, knowing nothing explicit (signed request, authorization
		// code, etc.) was present to shadow it (or we saw a code in $_REQUEST,
		// but it's the same as what's in the persistent store)
		return $this->getPersistentData( 'access_token' );
	}

	/**
	 * Retrieve the signed request, either from a request parameter or,
	 * if not present, from a cookie.
	 *
	 * @return string the signed request, if available, or null otherwise.
	 */
	public function getSignedRequest() {
		if ( ! $this->signedRequest ) {
			if ( ! empty( $_REQUEST[ 'signed_request' ] ) ) {
				$this->signedRequest = $this->parseSignedRequest( $_REQUEST[ 'signed_request' ] );
			} else if ( ! empty( $_COOKIE[ $this->getSignedRequestCookieName() ] ) ) {
				$this->signedRequest = $this->parseSignedRequest( $_COOKIE[ $this->getSignedRequestCookieName() ] );
			}
		}

		return $this->signedRequest;
	}

	/**
	 * Get the UID of the connected user, or 0
	 * if the Facebook user is not connected.
	 *
	 * @return string the UID if available.
	 */
	public function getUser() {
		if ( $this->user !== null ) {
			// we've already determined this and cached the value.
			return $this->user;
		}

		return $this->user = $this->getUserFromAvailableData();
	}

	/**
	 * Determines the connected user by first examining any signed
	 * requests, then considering an authorization code, and then
	 * falling back to any persistent store storing the user.
	 *
	 * @return integer The id of the connected Facebook user,
	 *                 or 0 if no such user exists.
	 */
	protected function getUserFromAvailableData() {
		// if a signed request is supplied, then it solely determines
		// who the user is.
		$signed_request = $this->getSignedRequest();
		if ( $signed_request ) {
			if ( array_key_exists( 'user_id', $signed_request ) ) {
				$user = $signed_request[ 'user_id' ];

				if ( $user != $this->getPersistentData( 'user_id' ) ) {
					$this->clearAllPersistentData();
				}

				$this->setPersistentData( 'user_id', $signed_request[ 'user_id' ] );

				return $user;
			}

			// if the signed request didn't present a user id, then invalidate
			// all entries in any persistent store.
			$this->clearAllPersistentData();

			return 0;
		}

		$user                   = $this->getPersistentData( 'user_id', $default = 0 );
		$persisted_access_token = $this->getPersistentData( 'access_token' );

		// use access_token to fetch user id if we have a user access_token, or if
		// the cached access token has changed.
		$access_token = $this->getAccessToken();
		if ( $access_token && $access_token != $this->getApplicationAccessToken() && ! ( $user && $persisted_access_token == $access_token ) ) {
			$user = $this->getUserFromAccessToken();
			if ( $user ) {
				$this->setPersistentData( 'user_id', $user );
			} else {
				$this->clearAllPersistentData();
			}
		}

		return $user;
	}

	/**
	 * Get a Login URL for use with redirects. By default, full page redirect is
	 * assumed. If you are using the generated URL with a window.open() call in
	 * JavaScript, you can pass in display=popup as part of the $params.
	 *
	 * The parameters:
	 * - redirect_uri: the url to go to after a successful login
	 * - scope: comma separated list of requested extended perms
	 *
	 * @param array $params Provide custom parameters
	 *
	 * @return string The URL for the login flow
	 */
	public function getLoginUrl( $params = array() ) {
		$this->establishCSRFTokenState();
		$currentUrl = $this->getCurrentUrl();

		// if 'scope' is passed as an array, convert to comma separated list
		$scopeParams = isset( $params[ 'scope' ] ) ? $params[ 'scope' ] : null;
		if ( $scopeParams && is_array( $scopeParams ) ) {
			$params[ 'scope' ] = implode( ',', $scopeParams );
		}

		return $this->getUrl( 'www', 'dialog/oauth', array_merge( array(
			'client_id'    => $this->getAppId(),
			'redirect_uri' => $currentUrl, // possibly overwritten
			'state'        => $this->state,
		), $params ) );
	}

	/**
	 * Get a Logout URL suitable for use with redirects.
	 *
	 * The parameters:
	 * - next: the url to go to after a successful logout
	 *
	 * @param array $params Provide custom parameters
	 *
	 * @return string The URL for the logout flow
	 */
	public function getLogoutUrl( $params = array() ) {
		return $this->getUrl( 'www', 'logout.php', array_merge( array(
			'next'         => $this->getCurrentUrl(),
			'access_token' => $this->getUserAccessToken(),
		), $params ) );
	}

	/**
	 * Get a login status URL to fetch the status from Facebook.
	 *
	 * The parameters:
	 * - ok_session: the URL to go to if a session is found
	 * - no_session: the URL to go to if the user is not connected
	 * - no_user: the URL to go to if the user is not signed into facebook
	 *
	 * @param array $params Provide custom parameters
	 *
	 * @return string The URL for the logout flow
	 */
	public function getLoginStatusUrl( $params = array() ) {
		return $this->getUrl( 'www', 'extern/login_status.php', array_merge( array(
			'api_key'         => $this->getAppId(),
			'no_session'      => $this->getCurrentUrl(),
			'no_user'         => $this->getCurrentUrl(),
			'ok_session'      => $this->getCurrentUrl(),
			'session_version' => 3,
		), $params ) );
	}

	/**
	 * Make an API call.
	 *
	 * @return mixed The decoded response
	 */
	public function api(/* polymorphic */ ) {
		$args = func_get_args();
		if ( is_array( $args[ 0 ] ) ) {
			return $this->_restserver( $args[ 0 ] );
		} else {
			return call_user_func_array( array( $this, '_graph' ), $args );
		}
	}

	/**
	 * Constructs and returns the name of the cookie that
	 * potentially houses the signed request for the app user.
	 * The cookie is not set by the BaseFacebook class, but
	 * it may be set by the JavaScript SDK.
	 *
	 * @return string the name of the cookie that would house
	 *         the signed request value.
	 */
	protected function getSignedRequestCookieName() {
		return 'fbsr_' . $this->getAppId();
	}

	/**
	 * Constructs and returns the name of the coookie that potentially contain
	 * metadata. The cookie is not set by the BaseFacebook class, but it may be
	 * set by the JavaScript SDK.
	 *
	 * @return string the name of the cookie that would house metadata.
	 */
	protected function getMetadataCookieName() {
		return 'fbm_' . $this->getAppId();
	}

	/**
	 * Get the authorization code from the query parameters, if it exists,
	 * and otherwise return false to signal no authorization code was
	 * discoverable.
	 *
	 * @return mixed The authorization code, or false if the authorization
	 *               code could not be determined.
	 */
	protected function getCode() {
		if ( isset( $_REQUEST[ 'code' ] ) ) {
			if ( $this->state !== null && isset( $_REQUEST[ 'state' ] ) && $this->state === $_REQUEST[ 'state' ] ) {

				// CSRF state has done its job, so clear it
				$this->state = null;
				$this->clearPersistentData( 'state' );

				return $_REQUEST[ 'code' ];
			} else {
				self::errorLog( 'CSRF state token does not match one provided.' );

				return false;
			}
		}

		return false;
	}

	/**
	 * Retrieves the UID with the understanding that
	 * $this->accessToken has already been set and is
	 * seemingly legitimate.  It relies on Facebook's Graph API
	 * to retrieve user information and then extract
	 * the user ID.
	 *
	 * @return integer Returns the UID of the Facebook user, or 0
	 *                 if the Facebook user could not be determined.
	 */
	protected function getUserFromAccessToken() {
		try {
			$user_info = $this->api( '/me' );

			return $user_info[ 'id' ];
		} catch ( FacebookApiException $e ) {
			return 0;
		}
	}

	/**
	 * Returns the access token that should be used for logged out
	 * users when no authorization code is available.
	 *
	 * @return string The application access token, useful for gathering
	 *                public information about users and applications.
	 */
	protected function getApplicationAccessToken() {
		return $this->appId . '|' . $this->appSecret;
	}

	/**
	 * Lays down a CSRF state token for this process.
	 *
	 * @return void
	 */
	protected function establishCSRFTokenState() {
		if ( $this->state === null ) {
			$this->state = md5( uniqid( mt_rand(), true ) );
			$this->setPersistentData( 'state', $this->state );
		}
	}

	/**
	 * Retrieves an access token for the given authorization code
	 * (previously generated from www.facebook.com on behalf of
	 * a specific user).  The authorization code is sent to graph.facebook.com
	 * and a legitimate access token is generated provided the access token
	 * and the user for which it was generated all match, and the user is
	 * either logged in to Facebook or has granted an offline access permission.
	 *
	 * @param string $code An authorization code.
	 *
	 * @return mixed An access token exchanged for the authorization code, or
	 *               false if an access token could not be generated.
	 */
	protected function getAccessTokenFromCode( $code, $redirect_uri = null ) {
		if ( empty( $code ) ) {
			return false;
		}

		if ( $redirect_uri === null ) {
			$redirect_uri = $this->getCurrentUrl();
		}

		try {
			// need to circumvent json_decode by calling _oauthRequest
			// directly, since response isn't JSON format.
			$access_token_response = $this->_oauthRequest( $this->getUrl( 'graph', '/oauth/access_token' ), $params = array(
				'client_id'     => $this->getAppId(),
				'client_secret' => $this->getAppSecret(),
				'redirect_uri'  => $redirect_uri,
				'code'          => $code,
			) );
		} catch ( FacebookApiException $e ) {
			// most likely that user very recently revoked authorization.
			// In any event, we don't have an access token, so say so.
			return false;
		}

		if ( empty( $access_token_response ) ) {
			return false;
		}

		//		v2.2
		//		$response_params = array();
		//		parse_str($access_token_response, $response_params);
		//		if (!isset($response_params['access_token'])) {
		//			return false;
		//		}
		//		return $response_params['access_token'];

		//		v2.3 and up
		$response = json_decode( $access_token_response );
		if ( ! isset( $response->access_token ) ) {
			return false;
		}

		return $response->access_token;
	}

	/**
	 * Invoke the old restserver.php endpoint.
	 *
	 * @param array $params Method call object
	 *
	 * @return mixed The decoded response object
	 * @throws FacebookApiException
	 */
	protected function _restserver( $params ) {
		// generic application level parameters
		$params[ 'api_key' ] = $this->getAppId();
		$params[ 'format' ]  = 'json-strings';

		$result = json_decode( $this->_oauthRequest( $this->getApiUrl( $params[ 'method' ] ), $params ), true );

		// results are returned, errors are thrown
		if ( is_array( $result ) && isset( $result[ 'error_code' ] ) ) {
			$this->throwAPIException( $result );
			// @codeCoverageIgnoreStart
		}
		// @codeCoverageIgnoreEnd

		$method = strtolower( $params[ 'method' ] );
		if ( $method === 'auth.expiresession' || $method === 'auth.revokeauthorization' ) {
			$this->destroySession();
		}

		return $result;
	}

	/**
	 * Return true if this is video post.
	 *
	 * @param string $path   The path
	 * @param string $method The http method (default 'GET')
	 *
	 * @return boolean true if this is video post
	 */
	protected function isVideoPost( $path, $method = 'GET' ) {
		if ( $method == 'POST' && preg_match( "/^(\/)(.+)(\/)(videos)$/", $path ) ) {
			return true;
		}

		return false;
	}

	/**
	 * Invoke the Graph API.
	 *
	 * @param string $path   The path (required)
	 * @param string $method The http method (default 'GET')
	 * @param array  $params The query/post data
	 *
	 * @return mixed The decoded response object
	 * @throws FacebookApiException
	 */
	protected function _graph( $path, $method = 'GET', $params = array() ) {
		if ( is_array( $method ) && empty( $params ) ) {
			$params = $method;
			$method = 'GET';
		}
		$params[ 'method' ] = $method; // method override as we always do a POST

		if ( $this->isVideoPost( $path, $method ) ) {
			$domainKey = 'graph_video';
		} else {
			$domainKey = 'graph';
		}

		$result = json_decode( $this->_oauthRequest( $this->getUrl( $domainKey, $path ), $params ), true );

		// results are returned, errors are thrown
		if ( is_array( $result ) && isset( $result[ 'error' ] ) ) {
			$this->throwAPIException( $result );
			// @codeCoverageIgnoreStart
		}

		// @codeCoverageIgnoreEnd

		return $result;
	}

	/**
	 * Make a OAuth Request.
	 *
	 * @param string $url    The path (required)
	 * @param array  $params The query/post data
	 *
	 * @return string The decoded response object
	 * @throws FacebookApiException
	 */
	protected function _oauthRequest( $url, $params ) {
		if ( ! isset( $params[ 'access_token' ] ) ) {
			$params[ 'access_token' ] = $this->getAccessToken();
		}

		if ( isset( $params[ 'access_token' ] ) ) {
			$params[ 'appsecret_proof' ] = $this->getAppSecretProof( $params[ 'access_token' ] );
		}

		// json_encode all params values that are not strings
		foreach ( $params as $key => $value ) {
			if ( ! is_string( $value ) ) {
				$params[ $key ] = json_encode( $value );
			}
		}

		return $this->makeRequest( $url, $params );
	}

	/**
	 * Generate a proof of App Secret
	 * This is required for all API calls originating from a server
	 * It is a sha256 hash of the access_token made using the app secret
	 *
	 * @param string $access_token The access_token to be hashed (required)
	 *
	 * @return string The sha256 hash of the access_token
	 */
	protected function getAppSecretProof( $access_token ) {
		return hash_hmac( 'sha256', $access_token, $this->getAppSecret() );
	}

	/**
	 * Makes an HTTP request. This method can be overridden by subclasses if
	 * developers want to do fancier things or use something other than curl to
	 * make the request.
	 *
	 * @param string      $url    The URL to make the request to
	 * @param array       $params The parameters to use for the POST body
	 * @param CurlHandler $ch     Initialized curl handle
	 *
	 * @return string The response text
	 */
	protected function makeRequest( $url, $params, $ch = null ) {
		if ( ! $ch ) {
			$ch = curl_init();
		}

		$opts = self::$CURL_OPTS;
		if ( $this->getFileUploadSupport() ) {
			$opts[ CURLOPT_POSTFIELDS ] = $params;
		} else {
			$opts[ CURLOPT_POSTFIELDS ] = http_build_query( $params, null, '&' );
		}
		$opts[ CURLOPT_URL ] = $url;

		// disable the 'Expect: 100-continue' behaviour. This causes CURL to wait
		// for 2 seconds if the server does not support this header.
		if ( isset( $opts[ CURLOPT_HTTPHEADER ] ) ) {
			$existing_headers           = $opts[ CURLOPT_HTTPHEADER ];
			$existing_headers[]         = 'Expect:';
			$opts[ CURLOPT_HTTPHEADER ] = $existing_headers;
		} else {
			$opts[ CURLOPT_HTTPHEADER ] = array( 'Expect:' );
		}

		curl_setopt_array( $ch, $opts );
		$result = curl_exec( $ch );

		if ( curl_errno( $ch ) == 60 ) { // CURLE_SSL_CACERT
			self::errorLog( 'Invalid or no certificate authority found, ' . 'using bundled information' );
			curl_setopt( $ch, CURLOPT_CAINFO, dirname( __FILE__ ) . '/fb_ca_chain_bundle.crt' );
			$result = curl_exec( $ch );
		}

		// With dual stacked DNS responses, it's possible for a server to
		// have IPv6 enabled but not have IPv6 connectivity.  If this is
		// the case, curl will try IPv4 first and if that fails, then it will
		// fall back to IPv6 and the error EHOSTUNREACH is returned by the
		// operating system.
		if ( $result === false && empty( $opts[ CURLOPT_IPRESOLVE ] ) ) {
			$matches = array();
			$regex   = '/Failed to connect to ([^:].*): Network is unreachable/';
			if ( preg_match( $regex, curl_error( $ch ), $matches ) ) {
				if ( strlen( @inet_pton( $matches[ 1 ] ) ) === 16 ) {
					self::errorLog( 'Invalid IPv6 configuration on server, ' . 'Please disable or get native IPv6 on your server.' );
					self::$CURL_OPTS[ CURLOPT_IPRESOLVE ] = CURL_IPRESOLVE_V4;
					curl_setopt( $ch, CURLOPT_IPRESOLVE, CURL_IPRESOLVE_V4 );
					$result = curl_exec( $ch );
				}
			}
		}

		if ( $result === false ) {
			$e = new FacebookApiException( array(
				'error_code' => curl_errno( $ch ),
				'error'      => array(
					'message' => curl_error( $ch ),
					'type'    => 'CurlException',
				),
			) );
			curl_close( $ch );
			throw $e;
		}
		curl_close( $ch );

		return $result;
	}

	/**
	 * Parses a signed_request and validates the signature.
	 *
	 * @param string $signed_request A signed token
	 *
	 * @return array The payload inside it or null if the sig is wrong
	 */
	protected function parseSignedRequest( $signed_request ) {
		list( $encoded_sig, $payload ) = explode( '.', $signed_request, 2 );

		// decode the data
		$sig  = self::base64UrlDecode( $encoded_sig );
		$data = json_decode( self::base64UrlDecode( $payload ), true );

		if ( strtoupper( $data[ 'algorithm' ] ) !== self::SIGNED_REQUEST_ALGORITHM ) {
			self::errorLog( 'Unknown algorithm. Expected ' . self::SIGNED_REQUEST_ALGORITHM );

			return null;
		}

		// check sig
		$expected_sig = hash_hmac( 'sha256', $payload, $this->getAppSecret(), $raw = true );
		if ( $sig !== $expected_sig ) {
			self::errorLog( 'Bad Signed JSON signature!' );

			return null;
		}

		return $data;
	}

	/**
	 * Makes a signed_request blob using the given data.
	 *
	 * @param array The data array.
	 *
	 * @return string The signed request.
	 */
	protected function makeSignedRequest( $data ) {
		if ( ! is_array( $data ) ) {
			throw new InvalidArgumentException( 'makeSignedRequest expects an array. Got: ' . print_r( $data, true ) );
		}
		$data[ 'algorithm' ] = self::SIGNED_REQUEST_ALGORITHM;
		$data[ 'issued_at' ] = time();
		$json                = json_encode( $data );
		$b64                 = self::base64UrlEncode( $json );
		$raw_sig             = hash_hmac( 'sha256', $b64, $this->getAppSecret(), $raw = true );
		$sig                 = self::base64UrlEncode( $raw_sig );

		return $sig . '.' . $b64;
	}

	/**
	 * Build the URL for api given parameters.
	 *
	 * @param $method String the method name.
	 *
	 * @return string The URL for the given parameters
	 */
	protected function getApiUrl( $method ) {
		static $READ_ONLY_CALLS = array(
			'admin.getallocation'                  => 1,
			'admin.getappproperties'               => 1,
			'admin.getbannedusers'                 => 1,
			'admin.getlivestreamvialink'           => 1,
			'admin.getmetrics'                     => 1,
			'admin.getrestrictioninfo'             => 1,
			'application.getpublicinfo'            => 1,
			'auth.getapppublickey'                 => 1,
			'auth.getsession'                      => 1,
			'auth.getsignedpublicsessiondata'      => 1,
			'comments.get'                         => 1,
			'connect.getunconnectedfriendscount'   => 1,
			'dashboard.getactivity'                => 1,
			'dashboard.getcount'                   => 1,
			'dashboard.getglobalnews'              => 1,
			'dashboard.getnews'                    => 1,
			'dashboard.multigetcount'              => 1,
			'dashboard.multigetnews'               => 1,
			'data.getcookies'                      => 1,
			'events.get'                           => 1,
			'events.getmembers'                    => 1,
			'fbml.getcustomtags'                   => 1,
			'feed.getappfriendstories'             => 1,
			'feed.getregisteredtemplatebundlebyid' => 1,
			'feed.getregisteredtemplatebundles'    => 1,
			'fql.multiquery'                       => 1,
			'fql.query'                            => 1,
			'friends.arefriends'                   => 1,
			'friends.get'                          => 1,
			'friends.getappusers'                  => 1,
			'friends.getlists'                     => 1,
			'friends.getmutualfriends'             => 1,
			'gifts.get'                            => 1,
			'groups.get'                           => 1,
			'groups.getmembers'                    => 1,
			'intl.gettranslations'                 => 1,
			'links.get'                            => 1,
			'notes.get'                            => 1,
			'notifications.get'                    => 1,
			'pages.getinfo'                        => 1,
			'pages.isadmin'                        => 1,
			'pages.isappadded'                     => 1,
			'pages.isfan'                          => 1,
			'permissions.checkavailableapiaccess'  => 1,
			'permissions.checkgrantedapiaccess'    => 1,
			'photos.get'                           => 1,
			'photos.getalbums'                     => 1,
			'photos.gettags'                       => 1,
			'profile.getinfo'                      => 1,
			'profile.getinfooptions'               => 1,
			'stream.get'                           => 1,
			'stream.getcomments'                   => 1,
			'stream.getfilters'                    => 1,
			'users.getinfo'                        => 1,
			'users.getloggedinuser'                => 1,
			'users.getstandardinfo'                => 1,
			'users.hasapppermission'               => 1,
			'users.isappuser'                      => 1,
			'users.isverified'                     => 1,
			'video.getuploadlimits'                => 1,
		);
		$name = 'api';
		if ( isset( $READ_ONLY_CALLS[ strtolower( $method ) ] ) ) {
			$name = 'api_read';
		} else if ( strtolower( $method ) == 'video.upload' ) {
			$name = 'api_video';
		}

		return self::getUrl( $name, 'restserver.php' );
	}

	/**
	 * Build the URL for given domain alias, path and parameters.
	 *
	 * @param $name   string The name of the domain
	 * @param $path   string Optional path (without a leading slash)
	 * @param $params array Optional query parameters
	 *
	 * @return string The URL for the given parameters
	 */
	protected function getUrl( $name, $path = '', $params = array() ) {
		$url = self::$DOMAIN_MAP[ $name ];
		if ( $path ) {
			if ( $path[ 0 ] === '/' ) {
				$path = substr( $path, 1 );
			}
			$url .= $path;
		}
		if ( $params ) {
			$url .= '?' . http_build_query( $params, null, '&' );
		}

		return $url;
	}

	protected function getHttpHost() {
		if ( $this->trustForwarded && isset( $_SERVER[ 'HTTP_X_FORWARDED_HOST' ] ) ) {
			return $_SERVER[ 'HTTP_X_FORWARDED_HOST' ];
		}

		return $_SERVER[ 'HTTP_HOST' ];
	}

	protected function getHttpProtocol() {
		if ( $this->trustForwarded && isset( $_SERVER[ 'HTTP_X_FORWARDED_PROTO' ] ) ) {
			if ( $_SERVER[ 'HTTP_X_FORWARDED_PROTO' ] === 'https' ) {
				return 'https';
			}

			return 'http';
		}
		/*apache + variants specific way of checking for https*/
		if ( isset( $_SERVER[ 'HTTPS' ] ) && ( $_SERVER[ 'HTTPS' ] === 'on' || $_SERVER[ 'HTTPS' ] == 1 ) ) {
			return 'https';
		}
		/*nginx way of checking for https*/
		if ( isset( $_SERVER[ 'SERVER_PORT' ] ) && ( $_SERVER[ 'SERVER_PORT' ] === '443' ) ) {
			return 'https';
		}

		return 'http';
	}

	/**
	 * Get the base domain used for the cookie.
	 */
	protected function getBaseDomain() {
		// The base domain is stored in the metadata cookie if not we fallback
		// to the current hostname
		$metadata = $this->getMetadataCookie();
		if ( array_key_exists( 'base_domain', $metadata ) && ! empty( $metadata[ 'base_domain' ] ) ) {
			return trim( $metadata[ 'base_domain' ], '.' );
		}

		return $this->getHttpHost();
	}

	/**
	 *
	 * /**
	 * Returns the Current URL, stripping it of known FB parameters that should
	 * not persist.
	 *
	 * @return string The current URL
	 */
	protected function getCurrentUrl() {
		$protocol   = $this->getHttpProtocol() . '://';
		$host       = $this->getHttpHost();
		$currentUrl = $protocol . $host . $_SERVER[ 'REQUEST_URI' ];
		$parts      = parse_url( $currentUrl );

		$query = '';
		if ( ! empty( $parts[ 'query' ] ) ) {
			// drop known fb params
			$params          = explode( '&', $parts[ 'query' ] );
			$retained_params = array();
			foreach ( $params as $param ) {
				if ( $this->shouldRetainParam( $param ) ) {
					$retained_params[] = $param;
				}
			}

			if ( ! empty( $retained_params ) ) {
				$query = '?' . implode( $retained_params, '&' );
			}
		}

		// use port if non default
		$port = isset( $parts[ 'port' ] ) && ( ( $protocol === 'http://' && $parts[ 'port' ] !== 80 ) || ( $protocol === 'https://' && $parts[ 'port' ] !== 443 ) ) ? ':' . $parts[ 'port' ] : '';

		// rebuild
		return $protocol . $parts[ 'host' ] . $port . $parts[ 'path' ] . $query;
	}

	/**
	 * Returns true if and only if the key or key/value pair should
	 * be retained as part of the query string.  This amounts to
	 * a brute-force search of the very small list of Facebook-specific
	 * params that should be stripped out.
	 *
	 * @param string $param A key or key/value pair within a URL's query (e.g.
	 *                      'foo=a', 'foo=', or 'foo'.
	 *
	 * @return boolean
	 */
	protected function shouldRetainParam( $param ) {
		foreach ( self::$DROP_QUERY_PARAMS as $drop_query_param ) {
			if ( strpos( $param, $drop_query_param . '=' ) === 0 ) {
				return false;
			}
		}

		return true;
	}

	/**
	 * Analyzes the supplied result to see if it was thrown
	 * because the access token is no longer valid.  If that is
	 * the case, then we destroy the session.
	 *
	 * @param $result       array A record storing the error message returned
	 *                      by a failed API call.
	 */
	protected function throwAPIException( $result ) {
		$e = new FacebookApiException( $result );
		switch ( $e->getType() ) {
			// OAuth 2.0 Draft 00 style
			case 'OAuthException':
				// OAuth 2.0 Draft 10 style
			case 'invalid_token':
				// REST server errors are just Exceptions
			case 'Exception':
				$message = $e->getMessage();
				if ( ( strpos( $message, 'Error validating access token' ) !== false ) || ( strpos( $message, 'Invalid OAuth access token' ) !== false ) || ( strpos( $message, 'An active access token must be used' ) !== false ) ) {
					$this->destroySession();
				}
				break;
		}

		throw $e;
	}

	/**
	 * Prints to the error log if you aren't in command line mode.
	 *
	 * @param string $msg Log message
	 */
	protected static function errorLog( $msg ) {
		// disable error log if we are running in a CLI environment
		// @codeCoverageIgnoreStart
		if ( php_sapi_name() != 'cli' ) {
			error_log( $msg );
		}
		// uncomment this if you want to see the errors on the page
		// print 'error_log: '.$msg."\n";
		// @codeCoverageIgnoreEnd
	}

	/**
	 * Base64 encoding that doesn't need to be urlencode()ed.
	 * Exactly the same as base64_encode except it uses
	 *   - instead of +
	 *   _ instead of /
	 *   No padded =
	 *
	 * @param string $input base64UrlEncoded string
	 *
	 * @return string
	 */
	protected static function base64UrlDecode( $input ) {
		return base64_decode( strtr( $input, '-_', '+/' ) );
	}

	/**
	 * Base64 encoding that doesn't need to be urlencode()ed.
	 * Exactly the same as base64_encode except it uses
	 *   - instead of +
	 *   _ instead of /
	 *
	 * @param string $input string
	 *
	 * @return string base64Url encoded string
	 */
	protected static function base64UrlEncode( $input ) {
		$str = strtr( base64_encode( $input ), '+/', '-_' );
		$str = str_replace( '=', '', $str );

		return $str;
	}

	/**
	 * Destroy the current session
	 */
	public function destroySession() {
		$this->accessToken   = null;
		$this->signedRequest = null;
		$this->user          = null;
		$this->clearAllPersistentData();

		// Javascript sets a cookie that will be used in getSignedRequest that we
		// need to clear if we can
		$cookie_name = $this->getSignedRequestCookieName();
		if ( array_key_exists( $cookie_name, $_COOKIE ) ) {
			unset( $_COOKIE[ $cookie_name ] );
			if ( ! headers_sent() ) {
				$base_domain = $this->getBaseDomain();
				setcookie( $cookie_name, '', 1, '/', '.' . $base_domain );
			} else {
				// @codeCoverageIgnoreStart
				self::errorLog( 'There exists a cookie that we wanted to clear that we couldn\'t ' . 'clear because headers was already sent. Make sure to do the first ' . 'API call before outputing anything.' );
				// @codeCoverageIgnoreEnd
			}
		}
	}

	/**
	 * Parses the metadata cookie that our Javascript API set
	 *
	 * @return  an array mapping key to value
	 */
	protected function getMetadataCookie() {
		$cookie_name = $this->getMetadataCookieName();
		if ( ! array_key_exists( $cookie_name, $_COOKIE ) ) {
			return array();
		}

		// The cookie value can be wrapped in "-characters so remove them
		$cookie_value = trim( $_COOKIE[ $cookie_name ], '"' );

		if ( empty( $cookie_value ) ) {
			return array();
		}

		$parts    = explode( '&', $cookie_value );
		$metadata = array();
		foreach ( $parts as $part ) {
			$pair = explode( '=', $part, 2 );
			if ( ! empty( $pair[ 0 ] ) ) {
				$metadata[ urldecode( $pair[ 0 ] ) ] = ( count( $pair ) > 1 ) ? urldecode( $pair[ 1 ] ) : '';
			}
		}

		return $metadata;
	}

	protected static function isAllowedDomain( $big, $small ) {
		if ( $big === $small ) {
			return true;
		}

		return self::endsWith( $big, '.' . $small );
	}

	protected static function endsWith( $big, $small ) {
		$len = strlen( $small );
		if ( $len === 0 ) {
			return true;
		}

		return substr( $big, - $len ) === $small;
	}

	/**
	 * Each of the following four methods should be overridden in
	 * a concrete subclass, as they are in the provided Facebook class.
	 * The Facebook class uses PHP sessions to provide a primitive
	 * persistent store, but another subclass--one that you implement--
	 * might use a database, memcache, or an in-memory cache.
	 *
	 * @see Facebook
	 */

	/**
	 * Stores the given ($key, $value) pair, so that future calls to
	 * getPersistentData($key) return $value. This call may be in another request.
	 *
	 * @param string $key
	 * @param array  $value
	 *
	 * @return void
	 */
	abstract protected function setPersistentData( $key, $value );

	/**
	 * Get the data for $key, persisted by BaseFacebook::setPersistentData()
	 *
	 * @param string  $key     The key of the data to retrieve
	 * @param boolean $default The default value to return if $key is not found
	 *
	 * @return mixed
	 */
	abstract protected function getPersistentData( $key, $default = false );

	/**
	 * Clear the data with $key from the persistent storage
	 *
	 * @param string $key
	 *
	 * @return void
	 */
	abstract protected function clearPersistentData( $key );

	/**
	 * Clear all data from the persistent storage
	 *
	 * @return void
	 */
	abstract protected function clearAllPersistentData();
}
