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<?php 
defined('BASEPATH') OR exit('No direct script access allowed'); 
 
/** 
 * Facebook PHP SDK v5 for CodeIgniter 3.x 
 * 
 * Library for Facebook PHP SDK v5. It helps the user to login with their Facebook account 
 * in CodeIgniter application. 
 * 
 * This library requires the Facebook PHP SDK v5 and it should be placed in libraries folder. 
 * 
 * It also requires social configuration file and it should be placed in the config directory. 
 * 
 * @package     CodeIgniter 
 * @category    Libraries 
 * @author      CodexWorld 
 * @license     http://www.codexworld.com/license/ 
 * @link        http://www.codexworld.com 
 * @version     3.0 
 */ 
 
// Include the autoloader provided in the SDK 
require_once APPPATH .'third_party/facebook-php-graph-sdk/autoload.php';  
 
use Facebook\Facebook as FB; 
use Facebook\Authentication\AccessToken; 
use Facebook\Exceptions\FacebookResponseException; 
use Facebook\Exceptions\FacebookSDKException; 
use Facebook\Helpers\FacebookJavaScriptHelper; 
use Facebook\Helpers\FacebookRedirectLoginHelper; 
Class Facebook 
{ 
    /** 
     * @var FB 
     */ 
    private $fb; 
    /** 
     * @var FacebookRedirectLoginHelper|FacebookJavaScriptHelper 
     */ 
    private $helper; 
 
    /** 
     * Facebook constructor. 
     */ 
    public function __construct(){ 
        // Load fb config 
        $this->load->config('facebook'); 
        // Load required libraries and helpers 
        $this->load->library('session'); 
        $this->load->helper('url'); 
        if (!isset($this->fb)){ 
            $this->fb = new FB([ 
                'app_id'                => $this->config->item('facebook_app_id'), 
                'app_secret'            => $this->config->item('facebook_app_secret'), 
                'default_graph_version' => $this->config->item('facebook_graph_version') 
            ]); 
        } 
        // Load correct helper depending on login type 
        // set in the config file 
        switch ($this->config->item('facebook_login_type')){ 
            case 'js': 
                $this->helper = $this->fb->getJavaScriptHelper(); 
                break; 
            case 'canvas': 
                $this->helper = $this->fb->getCanvasHelper(); 
                break; 
            case 'page_tab': 
                $this->helper = $this->fb->getPageTabHelper(); 
                break; 
            case 'web': 
                $this->helper = $this->fb->getRedirectLoginHelper(); 
                break; 
        } 
        if ($this->config->item('facebook_auth_on_load') === TRUE){ 
            // Try and authenticate the user right away (get valid access token) 
            $this->authenticate(); 
        } 
    } 
     
    /** 
     * @return FB 
     */ 
    public function object(){ 
        return $this->fb; 
    } 
     
    /** 
     * Check whether the user is logged in. 
     * by access token 
     * 
     * @return mixed|boolean 
     */ 
    public function is_authenticated(){ 
        $access_token = $this->authenticate(); 
        if(isset($access_token)){ 
            return $access_token; 
        } 
        return false; 
    } 
     
    /** 
     * Do Graph request 
     * 
     * @param       $method 
     * @param       $endpoint 
     * @param array $params 
     * @param null  $access_token 
     * 
     * @return array 
     */ 
    public function request($method, $endpoint, $params = [], $access_token = null){ 
        try{ 
            $response = $this->fb->{strtolower($method)}($endpoint, $params, $access_token); 
            return $response->getDecodedBody(); 
        }catch(FacebookResponseException $e){ 
            return $this->logError($e->getCode(), $e->getMessage()); 
        }catch (FacebookSDKException $e){ 
            return $this->logError($e->getCode(), $e->getMessage()); 
        } 
    } 
     
    /** 
     * Generate Facebook login url for web 
     * 
     * @return  string 
     */ 
    public function login_url(){ 
        // Login type must be web, else return empty string 
        if($this->config->item('facebook_login_type') != 'web'){ 
            return ''; 
        } 
        // Get login url 
        return $this->helper->getLoginUrl( 
            base_url() . $this->config->item('facebook_login_redirect_url'), 
            $this->config->item('facebook_permissions') 
        ); 
    } 
     
    /** 
     * Generate Facebook logout url for web 
     * 
     * @return string 
     */ 
    public function logout_url(){ 
        // Login type must be web, else return empty string 
        if($this->config->item('facebook_login_type') != 'web'){ 
            return ''; 
        } 
        // Get logout url 
        return $this->helper->getLogoutUrl( 
            $this->get_access_token(), 
            base_url() . $this->config->item('facebook_logout_redirect_url') 
        ); 
    } 
     
    /** 
     * Destroy local Facebook session 
     */ 
    public function destroy_session(){ 
        $this->session->unset_userdata('fb_access_token'); 
    } 
     
    /** 
     * Get a new access token from Facebook 
     * 
     * @return array|AccessToken|null|object|void 
     */ 
    private function authenticate(){ 
        $access_token = $this->get_access_token(); 
        if($access_token && $this->get_expire_time() > (time() + 30) || $access_token && !$this->get_expire_time()){ 
            $this->fb->setDefaultAccessToken($access_token); 
            return $access_token; 
        } 
        // If we did not have a stored access token or if it has expired, try get a new access token 
        if(!$access_token){ 
            try{ 
                $access_token = $this->helper->getAccessToken(); 
            }catch (FacebookSDKException $e){ 
                $this->logError($e->getCode(), $e->getMessage()); 
                return null; 
            } 
            // If we got a session we need to exchange it for a long lived session. 
            if(isset($access_token)){ 
                $access_token = $this->long_lived_token($access_token); 
                $this->set_expire_time($access_token->getExpiresAt()); 
                $this->set_access_token($access_token); 
                $this->fb->setDefaultAccessToken($access_token); 
                return $access_token; 
            } 
        } 
        // Collect errors if any when using web redirect based login 
        if($this->config->item('facebook_login_type') === 'web'){ 
            if($this->helper->getError()){ 
                // Collect error data 
                $error = array( 
                    'error'             => $this->helper->getError(), 
                    'error_code'        => $this->helper->getErrorCode(), 
                    'error_reason'      => $this->helper->getErrorReason(), 
                    'error_description' => $this->helper->getErrorDescription() 
                ); 
                return $error; 
            } 
        } 
        return $access_token; 
    } 
     
    /** 
     * Exchange short lived token for a long lived token 
     * 
     * @param AccessToken $access_token 
     * 
     * @return AccessToken|null 
     */ 
    private function long_lived_token(AccessToken $access_token){ 
        if(!$access_token->isLongLived()){ 
            $oauth2_client = $this->fb->getOAuth2Client(); 
            try{ 
                return $oauth2_client->getLongLivedAccessToken($access_token); 
            }catch (FacebookSDKException $e){ 
                $this->logError($e->getCode(), $e->getMessage()); 
                return null; 
            } 
        } 
        return $access_token; 
    } 
     
    /** 
     * Get stored access token 
     * 
     * @return mixed 
     */ 
    private function get_access_token(){ 
        return $this->session->userdata('fb_access_token'); 
    } 
     
    /** 
     * Store access token 
     * 
     * @param AccessToken $access_token 
     */ 
    private function set_access_token(AccessToken $access_token){ 
        $this->session->set_userdata('fb_access_token', $access_token->getValue()); 
    } 
     
    /** 
     * @return mixed 
     */ 
    private function get_expire_time(){ 
        return $this->session->userdata('fb_expire'); 
    } 
     
    /** 
     * @param DateTime $time 
     */ 
    private function set_expire_time(DateTime $time = null){ 
        if ($time) { 
            $this->session->set_userdata('fb_expire', $time->getTimestamp()); 
        } 
    } 
     
    /** 
     * @param $code 
     * @param $message 
     * 
     * @return array 
     */ 
    private function logError($code, $message){ 
        log_message('error', '[FACEBOOK PHP SDK] code: ' . $code.' | message: '.$message); 
        return ['error' => $code, 'message' => $message]; 
    } 
     
    /** 
     * Enables the use of CI super-global without having to define an extra variable. 
     * 
     * @param $var 
     * 
     * @return mixed 
     */ 
    public function __get($var){ 
        return get_instance()->$var; 
    } 
}