function facebook() {
    if($this->fbapp) {
        $getToken = $this->getFbToken($this->fbappid, $this->fbappsecret, $this->url.'/requests/connect.php?facebook=true', $this->fbcode);
        $user = $this->parseFbInfo($getToken['access_token']);

        if($getToken == null || $_SESSION['state'] == null || ($_SESSION['state'] != $this->fbstate) || empty($user->email)) {
            header("Location: ".$this->url);
        }
        if(!empty($user->email)) {
            $this->email = $user->email;

            $this->first_name = $user->first_name;
            $this->last_name = $user->last_name;
            $checkEmail = $this->verify_if_email_exists(1);

            // If user already exist
            if($checkEmail) {
                // Set sessions and log-in
                $_SESSION['username'] = $checkEmail['username'];
                $_SESSION['password'] = $checkEmail['password'];

                // Redirect user
                header("Location: ".$this->url);
            } else {
                $this->profile_image = $this->parseFbPicture($getToken['access_token']);
                $this->generateUsername();
                $this->password = $this->generatePassword(8);
                $this->query();

                $_SESSION['username'] = $this->username;
                $_SESSION['password'] = md5($this->password);

                return 1;
            }
        }
    }
}

function generateUsername($type = null) {
    // If type is set, generate a random username
    if($type) {
        $this->username = $this->parseUsername().rand(0, 999);
    } else {
        $this->username = $this->parseUsername();
    }

    // Replace the '.' sign with '_' (allows @user_mention)
    $this->username = str_replace('.', '_', $this->username);

    // Check if the username exists
    $checkUser = $this->verify_if_user_exist();

    if($checkUser) {
        $this->generateUsername(1);
    }
}

function parseUsername() {
    if(ctype_alnum($this->first_name) && ctype_alnum($this->last_name)) {
        return $this->username = $this->first_name.'.'.$this->last_name;
    } elseif(ctype_alnum($this->first_name)) {
        return $this->first_name;
    } elseif(ctype_alnum($this->last_name)) {
        return $this->last_name;
    } else {
        // Parse email address
        $email = explode('@', $this->email);
        $email = preg_replace("/[^a-z0-9]+/i", "", $email[0]);
        if(ctype_alnum($email)) {
            return $email;
        } else {
            return rand(0, 9999);
        }
    }
}

function generatePassword($length) {
    // Allowed characters
    $chars = str_split("abcdefghijklmnopqrstuvwxyz0123456789");

    // Generate password
    for($i = 1; $i <= $length; $i++) {
        // Get a random character
        $n = array_rand($chars, 1);

        // Store random char
        $password .= $chars[$n];
    }
    return $password;
}

function getFbToken($app_id, $app_secret, $redirect_url, $code) {
    // Build the token URL
    $url = 'https://graph.facebook.com/oauth/access_token?client_id='.$app_id.'&redirect_uri='.urlencode($redirect_url).'&client_secret='.$app_secret.'&code='.$code;

    // Get the file
    $response = json_decode(fetch($url), true);

    // Return parameters
    return $response;
}

function parseFbInfo($access_token) {
    // Build the Graph URL
    $url = "https://graph.facebook.com/me?fields=id,email,first_name,gender,last_name,link,locale,name,timezone,updated_time,verified&access_token=".$access_token;

    // Get the file
    $user = json_decode(fetch($url));

    // Return user
    if($user != null && isset($user->name)) {
        return $user;
    }
    return null;
}

function parseFbPicture($access_token) {
    // Build the Graph URL
    $url = "https://graph.facebook.com/me/picture?width=500&height=500&access_token=".$access_token;

    // Get the image
    $image = fetch($url);

    // Generate the file name
    $file_name = mt_rand().'_'.mt_rand().'_'.mt_rand().'.jpg';
    $file_path = __DIR__ .'/../uploads/avatars/';

    // Create the file
    $fp = fopen($file_path.$file_name, 'wb');

    // If the file can't be written
    if(!file_exists($file_path.$file_name)) {
        // Return the file name
        return false;
    }

    // Write the image
    fwrite($fp, $image);

    // Close
    fclose($fp);

    // Return the filename
    return $file_name;
}

function process() {
    global $LNG;

    // Prevents bypassing the FILTER_VALIDATE_EMAIL
    $this->email = htmlspecialchars($this->email, ENT_QUOTES, 'UTF-8');

    $arr = $this->validate_values(); // Must be stored in a variable before executing an empty condition
    if(empty($arr)) { // If there is no error message then execute the query;
        $this->query();

        // Set a session and log-in the user
        $_SESSION['username'] = $this->username;
        $_SESSION['password'] = md5($this->password);

        // Return (int) 1 if everything was validated
        return 1;

        // return $LNG['user_success'];
    } else { // If there is an error message
        foreach($arr as $err) {
            return notificationBox('error', $LNG["$err"], 1); // Return the error value for translation file
        }
    }
}

function verify_if_user_exist() {
    $query = sprintf("SELECT `username` FROM `users` WHERE `username` = '%s'", $this->db->real_escape_string(mb_strtolower($this->username)));
    $result = $this->db->query($query);

    return ($result->num_rows == 0 && !in_array(mb_strtolower($this->username), array('playlists', 'subscribers', 'subscriptions', 'about', 'messages'))) ? 0 : 1;
}

function verify_accounts_per_ip() {
    if($this->accounts_per_ip) {
        $query = $this->db->query(sprintf("SELECT COUNT(`ip`) FROM `users` WHERE `ip` = '%s'", $this->db->real_escape_string(getUserIP())));

        $result = $query->fetch_row();
        if($result[0] < $this->accounts_per_ip) {
            return true;
        } else {
            return false;
        }
    } else {
        return true;
    }
}

function verify_if_email_exists($type = null) {
    // Type 0: Normal check
    // Type 1: Facebook check & return type
    if($type) {
        $query = sprintf("SELECT `username`, `password` FROM `users` WHERE `email` = '%s'", $this->db->real_escape_string(mb_strtolower($this->email)));
    } else {
        $query = sprintf("SELECT `email` FROM `users` WHERE `email` = '%s'", $this->db->real_escape_string(mb_strtolower($this->email)));
    }
    $result = $this->db->query($query);

    if($type) {
        return ($result->num_rows == 0) ? 0 : $result->fetch_assoc();
    } else {
        return ($result->num_rows == 0) ? 0 : 1;
    }
}

function verify_captcha() {
    if($this->captcha_on) {
        if($this->captcha == "{$_SESSION['captcha']}" && !empty($this->captcha)) {
            return true;
        } else {
            return false;
        }
    } else {
        return true;
    }
}

function validate_values() {
    // Create the array which contains the Language variable
    $error = array();

    // Define the Language variable for each type of error
    if($this->verify_accounts_per_ip() == false) {
        $error[] = 'user_limit';
    }
    if($this->verify_if_user_exist() !== 0) {
        $error[] = 'user_exists';
    }
    if($this->verify_if_email_exists() !== 0) {
        $error[] = 'email_exists';
    }
    if(empty($this->username) && empty($this->password) && empty($email)) {
        $error[] = 'all_fields';
    }
    if(strlen($this->password) < 6) {
        $error[] = 'password_too_short';
    }
    if(!ctype_alnum($this->username)) {
        $error[] = 'user_alnum';
    }
    if(strlen($this->username) <= 2 || strlen($this->username) >= 33) {
        $error[] = 'user_too_short';
    }
    if(!filter_var($this->email, FILTER_VALIDATE_EMAIL)) {
        $error[] = 'invalid_email';
    }
    if($this->verify_captcha() == false) {
        $error[] = 'invalid_captcha';
    }

    return $error;
}

function query() {
    $query = sprintf("INSERT into `users` (`username`, `password`, `first_name`, `last_name`, `email`, `date`, `image`, `cover`, `online`, `ip`, `notificationl`, `notificationc`, `notificationd`, `notificationf`, `email_comment`, `email_like`, `email_new_friend`) VALUES ('%s', '%s', '%s', '%s', '%s', '%s', '%s', 'default.png', '%s', '%s', '%s', '%s', '%s', '%s', '%s', '%s', '%s');", $this->db->real_escape_string(mb_strtolower($this->username)), md5($this->db->real_escape_string($this->password)), $this->db->real_escape_string($this->first_name), $this->db->real_escape_string($this->last_name), $this->db->real_escape_string($this->email), date("Y-m-d H:i:s"), ($this->profile_image ? $this->profile_image : 'default.png'), time(), $this->db->real_escape_string(getUserIp()), 1, 1, 1, 1, $this->email_comment, $this->email_like, $this->email_new_friend);
    $this->db->query($query);
}