<?php
/**
 * CakePHP(tm) : Rapid Development Framework (http://cakephp.org)
 * Copyright (c) Cake Software Foundation, Inc. (http://cakefoundation.org)
 *
 * Licensed under The MIT License
 * For full copyright and license information, please see the LICENSE.txt
 * Redistributions of files must retain the above copyright notice.
 *
 * @copyright     Copyright (c) Cake Software Foundation, Inc. (http://cakefoundation.org)
 * @link          http://cakephp.org CakePHP(tm) Project
 * @since         3.0.0
 * @license       http://www.opensource.org/licenses/mit-license.php MIT License
 */
namespace Cake\View\Helper;

use Cake\View\Helper;
use UnexpectedValueException;

/**
 * FlashHelper class to render flash messages.
 *
 * After setting messages in your controllers with FlashComponent, you can use
 * this class to output your flash messages in your views.
 */
class FlashHelper extends Helper
{

    /**
     * Used to render the message set in FlashComponent::set()
     *
     * In your view: $this->Flash->render('somekey');
     * Will default to flash if no param is passed
     *
     * You can pass additional information into the flash message generation. This allows you
     * to consolidate all the parameters for a given type of flash message into the view.
     *
     * ```
     * echo $this->Flash->render('flash', ['params' => ['name' => $user['User']['name']]]);
     * ```
     *
     * This would pass the current user's name into the flash message, so you could create personalized
     * messages without the controller needing access to that data.
     *
     * Lastly you can choose the element that is used for rendering the flash message. Using
     * custom elements allows you to fully customize how flash messages are generated.
     *
     * ```
     * echo $this->Flash->render('flash', ['element' => 'my_custom_element']);
     * ```
     *
     * If you want to use an element from a plugin for rendering your flash message
     * you can use the dot notation for the plugin's element name:
     *
     * ```
     * echo $this->Flash->render('flash', [
     *   'element' => 'MyPlugin.my_custom_element',
     * ]);
     * ```
     *
     * If you have several messages stored in the Session, each message will be rendered in its own
     * element.
     *
     * @param string $key The [Flash.]key you are rendering in the view.
     * @param array $options Additional options to use for the creation of this flash message.
     *    Supports the 'params', and 'element' keys that are used in the helper.
     * @return string|null Rendered flash message or null if flash key does not exist
     *   in session.
     * @throws \UnexpectedValueException If value for flash settings key is not an array.
     */
    public function render($key = 'flash', array $options = [])
    {
        if (!$this->request->session()->check("Flash.$key")) {
            return null;
        }

        $flash = $this->request->session()->read("Flash.$key");
        if (!is_array($flash)) {
            throw new UnexpectedValueException(sprintf(
                'Value for flash setting key "%s" must be an array.',
                $key
            ));
        }
        $this->request->session()->delete("Flash.$key");

        $out = '';
        foreach ($flash as $message) {
            $message = $options + $message;
            $out .= $this->_View->element($message['element'], $message);
        }

        return $out;
    }

    /**
     * Event listeners.
     *
     * @return array
     */
    public function implementedEvents()
    {
        return [];
    }
}
