<?php

class CartController extends AppController
{

  /**
   * Add a product to the shopping cart.
  */
 
  public function add_product($id)
  {
    $cart = new CartModel();
    $cart->addItem($id);              // Updates the PageModel stack (session)
    
    $page = new PageModel();
    $next = $page->popPage();
    
    switch($next->result) {
      case 'redirect':
        $this->redirect($next->url);
        break;
      case 'render':
        $this->render($next->view);
        break;
    }
  }
  
  public function details()
  {
    // ... display cart details ...
  }
  
} 

class CartModel extends AppModel
{

  public function addItem($id)
  {
    $user = new UserModel();
    $page = new PageModel();
    
    if (!$user->loggedIn()) {    
      $page->pushPage('redirect', "cart/add_product/$id");
      $page->pushPage('redirect', "user/login");    
      return;
    }
    
    // ... add item to the database ...
    
    $page->pushPage('render', 'cart_details.tpl');
    $page->message = 'Item has been successfully added to your cart.';
    
  }

}

class UserController extends AppController
{
	
  /**
   * User login form
  */
	
  public function login()
  {
    
    $page = new PageModel();
    $user = new UserModel();
    
    if ($_POST) {
	    
	  // ... code goes here to check password
	  
	  if ($login_ok) {
    
	    // ... if login is ok, continue
	      
      } else {
      
      	// ... if login failed, stack the form on the view again
      
      	$page->message = 'Invalid username or password. Try again.';
      	$page->pushPage('render', 'login_form.tpl');
      	
  	  }
      
    }
    
    $next = $page->popPage();
    
    switch($next->result) {
      case 'redirect':
        $this->redirect($next->url);
        break;
      case 'render':
        $this->render($next->view);
        break;
    }
    
  }
}
      
class PageModel extends AppModel
{
  public function pushPage($type, $target)
  {
    // ... add page to top of stack
  }
  
  public function popPage()
  {
    // ... get page (and remove) from top of stack
  }

}


/**
 * Summary: When the user attempts to add an item to the shopping cart and they are
 * not logged in, we push a login page onto the page stack. They go to the login
 * page and fill it out. If the login fails, the form is pushed onto the stack. If
 * the login succeeds, we automatically go back to attempting to add the item to the
 * shopping cart. This time, the user is logged-in so it will be successful.
*/