masalah keamanan tidak bisa login stelah masukkan user & pas

// controller Login.php
<?php
defined('BASEPATH') OR exit ('No direct access allowed');

class Login extends CI_Controller {
	public function __construct()
	{
		parent::__construct();
		$this->load->model('kuale');

		$this->load->helper('form');

		$this->load->library('form_validation');

		$this->load->library('session');


	}
	public function ceklogin()
	{

		if(isset($_POST['login'])){
		$username = $this->input->post('username',true);
		$password = $this->input->post('password',true);
		$cek = $this->kuale->proseslogin($username,$password);
		$hasil = count($cek);
		echo $hasil;
		if($hasil > 0){
			$pelogin = $this->db->get_where('user',array('username' => $username, 'password' => $password))->row();
			$this->session->set_userdata($data);
			if($pelogin->level == 'admin'){
				redirect('admin/index');
			}elseif($pelogin->level == 'pesan'){
				redirect('admin/pelayan');
			}elseif($pelogin->level == 'kasir'){
				redirect('admin/kasir');
			}
		}

		else{
			echo"<script> alert('Username atau Password anda salah');
				window.history.back();</script>";
			}

		}
	}
}

// Model
<?php
defined('BASEPATH') OR exit('No direct script access allowed');

class Kuale extends CI_Model {
public function keamanan()
	{
		$username = $this->session->userdata('username');
		if(empty($username)){
			$this->session->sess_destroy();
			redirect('user/login');
		}
	}
}

//controller Admin.php
<?php
defined('BASEPATH') OR exit ('No direct script access allowed');

/**
*
*/
class Admin extends CI_Controller {

	public function __construct()
	{
		parent::__construct();
		$this->load->model('kuale');
		$this->kuale->keamanan();
	}


	public function index()
	{
		$data['data'] = $this->kuale->selectAll('tb_menu')->
		result_object();


		//$this->load->view('admin/header');
		$this->load->view('admin/data', $data);
		//$this->load->view('admin/footer');

	}
}