<?php

/**
 * Controller
 *
 * class handles POST requests and redirects
 * the client after processing
 * - demo of singleton pattern
 */
class Controller extends BaseObject {
  // static strings used in views

  const ACTION = 'action';
  const METHOD_POST = 'POST';
  const PAGE = 'page';
  const CC_NAME = 'nameOnCard';
  const CC_NUMBER = 'cardNumber';
  const ACTION_ADD = 'addToCart';
  const ACTION_REMOVE = 'removeFromCart';
  const ACTION_ORDER = 'placeOrder';
  const ACTION_LOGIN = 'login';
  const USR_NAME = 'userName';
  const USR_PASSWORD = 'password';
  const ACTION_LOGOUT = 'logout';

  private static $instance = false;

  /**
   *
   * @return Controller
   */
  public static function getInstance() {

    if (!self::$instance) {
      self::$instance = new Controller();
    }
    return self::$instance;
  }

  private function __construct() {

  }

  /**
   *
   * processes POST requests and redirects client depending on selected
   * action
   *
   * @return bool
   * @throws Exception
   */
  public function invokePostAction() {

    if ($_SERVER['REQUEST_METHOD'] != self::METHOD_POST) {
      throw new Exception('Controller can only handle POST requests.');
      return null;
    } elseif (!isset($_REQUEST[self::ACTION])) {
      throw new Exception('Action not specified.');
      return null;
    }


    // now process the assigned action
    $action = $_REQUEST[self::ACTION];

    switch ($action) {

      case self::ACTION_ADD :
        ShoppingCart::add((int) $_REQUEST['bookId']);
        Util::redirect();
        break;

      case self::ACTION_REMOVE :
        ShoppingCart::remove((int) $_REQUEST['bookId']);
        Util::redirect();
        break;

      case self::ACTION_ORDER :
        $user = AuthenticationManager::getAuthenticatedUser();
        // abort
        if ($user == null) {
          $this->forwardRequest(array('Not logged in.'));
          break;
        }
        // else
        if ($this->processCheckout($_POST[self::CC_NAME], $_POST[self::CC_NUMBER]))
          break;
        else
          return null;

      case self::ACTION_LOGIN :
        //try to authenticate the given user
        if (!AuthenticationManager::authenticate($_REQUEST[self::USR_NAME], $_REQUEST[self::USR_PASSWORD])) {
          $this->forwardRequest(array('Invalid user name or password.'));
        }
        Util::redirect();
        break;

      case self::ACTION_LOGOUT :
        //sign out current user
        AuthenticationManager::signOut();
        Util::redirect();
        break;

      default : throw new Exception('Unknown controller action: ' . $action);
    }
  }

  /**
   *
   * @param string $nameOnCard
   * @param integer $cardNumber
   * @return bool
   */
  protected function processCheckout($nameOnCard = null, $cardNumber = null) {

    $errors = array();
    $nameOnCard = trim($nameOnCard);
    if ($nameOnCard == null || strlen($nameOnCard) == 0) {
      $errors[] = 'Invalid name on card.';
    }
    if ($cardNumber == null || strlen($cardNumber) != 16 || !ctype_digit($cardNumber)) {
      $errors[] = 'Invalid card number. Card number must be sixteen digits.';
    }

    if (count($errors) > 0) {
      $this->forwardRequest($errors);
      return false;
    }

    //check cart
    if (ShoppingCart::size() == 0) {
      $this->forwardRequest(array('No items in cart.'));
      return false;
    }

    //try to place a new order
    $user = AuthenticationManager::getAuthenticatedUser();
    $orderId = DataManager::createOrder($user->getId(), ShoppingCart::getAll(), $nameOnCard, $cardNumber);
    if (!$orderId) {
      $this->forwardRequest(array('Could not create order.'));
      return false;
    }
    //clear shopping card and redirect to success page
    ShoppingCart::clear();
    Util::redirect('index.php?view=success&orderId=' . rawurlencode($orderId));

    return true;
  }

  /**
   *
   * @param array $errors : optional assign it to
   * @param string $target : url for redirect of the request
   */
  protected function forwardRequest(array $errors = null, $target = null) {
    //check for given target and try to fall back to previous page if needed
    if ($target == null) {
      if (!isset($_REQUEST[self::PAGE])) {
        throw new Exception('Missing target for forward.');
      }
      $target = $_REQUEST[self::PAGE];
    }
    //forward request to target
    // optional - add errors to redirect and process them in view
    if (count($errors) > 0)
      $target .= '&errors=' . urlencode(serialize($errors));
    header('location: ' . $target);
    exit();
  }

}