<?php
/**
 * @link http://www.yiiframework.com/
 * @copyright Copyright (c) 2008 Yii Software LLC
 * @license http://www.yiiframework.com/license/
 */

namespace yii\web;

use Yii;
use yii\base\ActionFilter;
use yii\base\Action;
use yii\caching\Dependency;

/**
 * The PageCache provides functionality for whole page caching
 *
 * It is an action filter that can be added to a controller and handles the `beforeAction` event.
 *
 * To use PageCache, declare it in the `behaviors()` method of your controller class.
 * In the following example the filter will be applied to the `list`-action and
 * cache the whole page for maximum 60 seconds or until the count of entries in the post table changes.
 * It also stores different versions of the page depended on the route ([[varyByRoute]] is true by default),
 * the application language and user id.
 *
 * ~~~
 * public function behaviors()
 * {
 *     return [
 *         'pageCache' => [
 *             'class' => \yii\web\PageCache::className(),
 *             'only' => ['list'],
 *             'duration' => 60,
 *             'dependecy' => [
 *                 'class' => 'yii\caching\DbDependency',
 *                 'sql' => 'SELECT COUNT(*) FROM post',
 *             ],
 *             'variations' => [
 *                 Yii::$app->language,
 *                 Yii::$app->user->id
 *             ]
 *         ],
 *     ];
 * }
 * ~~~
 *
 * @author Qiang Xue <qiang.xue@gmail.com>
 * @since 2.0
 */
class PageCache extends ActionFilter
{
	/**
	 * @var boolean whether the content being cached should be differentiated according to the route.
	 * A route consists of the requested controller ID and action ID. Defaults to true.
	 */
	public $varyByRoute = true;
	/**
	 * @var string the application component ID of the [[\yii\caching\Cache|cache]] object.
	 */
	public $cache = 'cache';
	/**
	 * @var integer number of seconds that the data can remain valid in cache.
	 * Use 0 to indicate that the cached data will never expire.
	 */
	public $duration = 60;
	/**
	 * @var array|Dependency the dependency that the cached content depends on.
	 * This can be either a [[Dependency]] object or a configuration array for creating the dependency object.
	 * For example,
	 *
	 * ~~~
	 * [
	 *     'class' => 'yii\caching\DbDependency',
	 *     'sql' => 'SELECT MAX(lastModified) FROM Post',
	 * ]
	 * ~~~
	 *
	 * would make the output cache depends on the last modified time of all posts.
	 * If any post has its modification time changed, the cached content would be invalidated.
	 */
	public $dependency;
	/**
	 * @var array list of factors that would cause the variation of the content being cached.
	 * Each factor is a string representing a variation (e.g. the language, a GET parameter).
	 * The following variation setting will cause the content to be cached in different versions
	 * according to the current application language:
	 *
	 * ~~~
	 * [
	 *     Yii::$app->language,
	 * ]
	 * ~~~
	 */
	public $variations;
	/**
	 * @var boolean whether to enable the fragment cache. You may use this property to turn on and off
	 * the fragment cache according to specific setting (e.g. enable fragment cache only for GET requests).
	 */
	public $enabled = true;
	/**
	 * @var \yii\base\View the view component to use for caching. If not set, the default application view component
	 * [[Application::view]] will be used.
	 */
	public $view;


	public function init()
	{
		parent::init();
		if ($this->view === null) {
			$this->view = Yii::$app->getView();
		}
	}

	/**
	 * This method is invoked right before an action is to be executed (after all possible filters.)
	 * You may override this method to do last-minute preparation for the action.
	 * @param Action $action the action to be executed.
	 * @return boolean whether the action should continue to be executed.
	 */
	public function beforeAction($action)
	{
		$properties = [];
		foreach (['cache', 'duration', 'dependency', 'variations', 'enabled'] as $name) {
			$properties[$name] = $this->$name;
		}
		$id = $this->varyByRoute ? $action->getUniqueId() : __CLASS__;
		ob_start();
		ob_implicit_flush(false);
		if ($this->view->beginCache($id, $properties)) {
			return true;
		} else {
			Yii::$app->getResponse()->content = ob_get_clean();
			return false;
		}
	}

	/**
	 * @inheritdoc
	 */
	public function afterAction($action, $result)
	{
		echo $result;
		$this->view->endCache();
		return ob_get_clean();
	}
}
