alka-facebook.php

<?php
/**
 * Plugin Name:       Alka Facebook
 * Description:       Login and Register your users using Facebook's API
 * Version:           1.0.0
 * Author:            Alkaweb
 * Author URI:        http://alka-web.com
 * Text Domain:       alkaweb
 * License:           GPL-2.0+
 * License URI:       http://www.gnu.org/licenses/gpl-2.0.txt
 * GitHub Plugin URI: https://github.com/2Fwebd/alka-facebook
 */

/*
 * Import the Facebook SDK and load all the classes
 */
include( plugin_dir_path( __FILE__ ) . 'facebook-sdk/autoload.php' );

/*
 * Classes required to call the Facebook API
 * They will be used by our class
 */
use Facebook\Facebook;
use Facebook\Exceptions\FacebookSDKException;
use Facebook\Exceptions\FacebookResponseException;

/**
 * Class AlkaFacebook
 */
class AlkaFacebook {

	/**
	 * Facebook APP ID
	 *
	 * @var string
	 */
	private $app_id = 'xxxxxxxxxxxxxx';

	/**
	 * Facebook APP Secret
	 *
	 * @var string
	 */
	private $app_secret = 'xxxxxxxxxxxxxx';

	/**
	 * Callback URL used by the API
	 *
	 * @var string
	 */
	private $callback_url = 'http://your-site.com/wp-admin/admin-ajax.php?action=alka_facebook';

	/**
	 * Access token from Facebook
	 *
	 * @var string
	 */
	private $access_token;

	/**
	 * Where we redirect our user after the process
	 *
	 * @var string
	 */
	private $redirect_url;

	/**
	 * User details from the API
	 */
	private $facebook_details;

	/**
	 * AlkaFacebook constructor.
	 */
	public function __construct() {
		$facebook_creeds = get_option( 'alka_facebook', array() );
		if ( ! empty( $facebook_creeds['app_id'] ) ) {
			$this->app_id = $facebook_creeds['app_id'];
		}
		if ( ! empty( $facebook_creeds['app_secret'] ) ) {
			$this->app_secret = $facebook_creeds['app_secret'];
		}


		// We register our shortcode
		add_shortcode( 'alka_facebook', array( $this, 'renderShortcode' ) );

		// Callback URL
		add_action( 'wp_ajax_alka_facebook', array( $this, 'apiCallback' ) );
		add_action( 'wp_ajax_nopriv_alka_facebook', array( $this, 'apiCallback' ) );

		if ( is_admin() ) {
			require_once 'admin/alka-facebook-admin.php';
		}
	}

	/**
	 * Render the shortcode [alka_facebook/]
	 *
	 * It displays our Login / Register button
	 */
	public function renderShortcode() {

		// No need for the button is the user is already logged
		if ( is_user_logged_in() ) {
			return;
		}

		// Start the session
		if ( ! session_id() ) {
			@session_start();
		}

		// We save the URL for the redirection:
		if ( ! isset( $_SESSION['alka_facebook_url'] ) ) {
			$_SESSION['alka_facebook_url'] = 'http://' . $_SERVER['HTTP_HOST'] . $_SERVER['REQUEST_URI'];
		}

		// Different labels according to whether the user is allowed to register or not
		if ( get_option( 'users_can_register' ) ) {
			$button_label = __( 'Login or Register with Facebook', 'alkaweb' );
		} else {
			$button_label = __( 'Login with Facebook', 'alkaweb' );
		}

		// HTML markup
		$html = '<div id="alka-facebook-wrapper">';

		// Messages
		if ( isset( $_SESSION['alka_facebook_message'] ) ) {
			$message = $_SESSION['alka_facebook_message'];
			$html    .= '<div id="alka-facebook-message" class="alert alert-danger">' . $message . '</div>';
			// We remove them from the session
			unset( $_SESSION['alka_facebook_message'] );
		}

		// Button
		$html .= '<a href="' . $this->getLoginUrl() . '" class="btn" id="alka-facebook-button">' . $button_label . '</a>';

		$html .= '</div>';

		// Write it down
		return $html;

	}

	/**
	 * Init the API Connection
	 *
	 * @return Facebook
	 */
	private function initApi() {

		$facebook = new Facebook( [
			'app_id'                  => $this->app_id,
			'app_secret'              => $this->app_secret,
			'default_graph_version'   => 'v2.2',
			'persistent_data_handler' => 'session'
		] );

		return $facebook;

	}

	/**
	 * Login URL to Facebook API
	 *
	 * @return string
	 */
	private function getLoginUrl() {

		if ( ! session_id() ) {
			session_start();
		}

		$fb = $this->initApi();

		$helper = $fb->getRedirectLoginHelper();

		// Optional permissions
		$permissions = [ 'email' ];

		$url = $helper->getLoginUrl( $this->callback_url, $permissions );

		return esc_url( $url );

	}

	/**
	 * API call back running whenever we hit /wp-admin/admin-ajax.php?action=alka_facebook
	 * This code handles the Login / Regsitration part
	 */
	public function apiCallback() {

		if ( ! session_id() ) {
			session_start();
		}

		// Set the Redirect URL:
		$this->redirect_url = ( isset( $_SESSION['alka_facebook_url'] ) ) ? $_SESSION['alka_facebook_url'] : home_url();

		// We start the connection
		$fb = $this->initApi();

		// We save the token in our instance
		$this->access_token = $this->getToken( $fb );

		// We get the user details
		$this->facebook_details = $this->getUserDetails( $fb );

		// We first try to login the user
		$this->loginUser();

		// Otherwise, we create a new account
		$this->createUser();

		// Redirect the user
		header( "Location: " . $this->redirect_url, true );
		die();

	}

	/**
	 * Get a TOKEN from the Facebook API
	 * Or redirect back if there is an error
	 *
	 * @param $fb Facebook
	 *
	 * @return string - The Token
	 */
	private function getToken( $fb ) {

		// Assign the Session variable for Facebook
		$_SESSION['FBRLH_state'] = $_GET['state'];

		// Load the Facebook SDK helper
		$helper = $fb->getRedirectLoginHelper();

		// Try to get an access token
		try {
			$accessToken = $helper->getAccessToken();
		} // When Graph returns an error
		catch ( FacebookResponseException $e ) {
			$error   = __( 'Graph returned an error: ', 'alkaweb' ) . $e->getMessage();
			$message = array(
				'type'    => 'error',
				'content' => $error
			);
		} // When validation fails or other local issues
		catch ( FacebookSDKException $e ) {
			$error   = __( 'Facebook SDK returned an error: ', 'alkaweb' ) . $e->getMessage();
			$message = array(
				'type'    => 'error',
				'content' => $error,
			);
		}

		// If we don't got a token, it means we had an error
		if ( ! isset( $accessToken ) ) {
			// Report our errors
			$_SESSION['alka_facebook_message'] = $message;
			// Redirect
			header( "Location: " . $this->redirect_url, true );
			die();
		}

		return $accessToken->getValue();

	}

	/**
	 * Get user details through the Facebook API
	 *
	 * @link https://developers.facebook.com/docs/facebook-login/permissions#reference-public_profile
	 *
	 * @param $fb Facebook
	 *
	 * @return \Facebook\GraphNodes\GraphUser
	 */
	private function getUserDetails( $fb ) {

		try {
			$response = $fb->get( '/me?fields=id,name,first_name,last_name,email,link', $this->access_token );
		} catch ( FacebookResponseException $e ) {
			$error   = __( 'Graph returned an error: ', 'alkaweb' ) . $e->getMessage();
			$message = array(
				'type'    => 'error',
				'content' => $error,
			);
		} catch ( FacebookSDKException $e ) {
			$error   = __( 'Facebook SDK returned an error: ', 'alkaweb' ) . $e->getMessage();
			$message = array(
				'type'    => 'error',
				'content' => $error,
			);
		}

		// If we caught an error
		if ( isset( $message ) ) {
			// Report our errors
			$_SESSION['alka_facebook_message'] = $message;
			// Redirect
			header( "Location: " . $this->redirect_url, true );
			die();
		}

		return $response->getGraphUser();

	}

	/**
	 * Login an user to WordPress
	 *
	 * @link https://codex.wordpress.org/Function_Reference/get_users
	 * @return bool|void
	 */
	private function loginUser() {

		// We look for the `eo_facebook_id` to see if there is any match
		$wp_users = get_users( array(
			'meta_key'    => 'alka_facebook_id',
			'meta_value'  => $this->facebook_details['id'],
			'number'      => 1,
			'count_total' => false,
			'fields'      => 'id',
		) );

		if ( empty( $wp_users[0] ) ) {
			return false;
		}

		// Log the user ?
		wp_set_auth_cookie( $wp_users[0] );

	}

	/**
	 * Create a new WordPress account using Facebook Details
	 */
	private function createUser() {


		$fb_user = $this->facebook_details;

		// Create an username
		$username = sanitize_user( str_replace( ' ', '_', strtolower( $this->facebook_details['name'] ) ) );

		// Creating our user
		$new_user = wp_create_user( $username, wp_generate_password(), $fb_user['email'] );

		if ( is_wp_error( $new_user ) ) {
			// Report our errors
			$_SESSION['alka_facebook_message'] = $new_user->get_error_message();
			// Redirect
			header( "Location: " . $this->redirect_url, true );
			die();
		}

		// Setting the meta
		update_user_meta( $new_user, 'first_name', $fb_user['first_name'] );
		update_user_meta( $new_user, 'last_name', $fb_user['last_name'] );
		update_user_meta( $new_user, 'user_url', $fb_user['link'] );
		update_user_meta( $new_user, 'alka_facebook_id', $fb_user['id'] );

		// Log the user ?
		wp_set_auth_cookie( $new_user );

	}


}

/*
 * Starts our plugins, easy!
 */
new AlkaFacebook();