<?php

    final class User
    {

        public $isLoggedIn = false, $sessionKeys = array( 'user-agent', 'username', 'password', 'id', 'data' ), $data = array();

        public function __construct()
        {

            $this->isLoggedIn = $this->_checkForSessions();

        }

        public function sessionDestroy()
        {

            foreach( $this->sessionKeys as $key )
            {

                unset( $_SESSION[$key] );

            }

        }

        private function _checkForSessions()
        {

            foreach( $this->sessionKeys as $key )
            {

                if( !$_SESSION[$key] )
                {

                    return false;

                }

            }

            $Query = MySQL::newQuery()
                     ->Query('SELECT null FROM users WHERE username = ? AND password = ? LIMIT 1;')
                     ->bind('ss', $_SESSION['username'], $_SESSION['password'] );

            if( $Query->count() == 0 ) { return false; } else {

                $this->data = $_SESSION['data'];

                return true;

            }

        }

        public function login( $userName, $passWord )
        {

            if( !$userName || !$passWord ) return 'Please enter valid login details';

            $Query = MySQL::newQuery()
                     ->Query('SELECT * FROM users WHERE username = ? AND password = ? LIMIT 1;')
                     ->bind('ss', $userName, $passWord);

            if( $Query->count() == 0 )

                return 'Please enter valid login details';

            else
            {

                $data = $Query->fetch();

                $_SESSION['id'] = $data['id'];
                $_SESSION['username'] = $data['username'];
                $_SESSION['password'] = $data['password'];
                $_SESSION['user-agent'] = md5( $_SERVER['HTTP_USER_AGENT'] . '10202' );

                $_SESSION['data'] = $data;

                header('Location: /');

            }

        }

    }