<?php

namespace SilverStripe\VersionFeed\Filters;

use SilverStripe\VersionFeed\VersionFeedController;
use SilverStripe\Core\Config\Configurable;
use Psr\SimpleCache\CacheInterface;
use SilverStripe\Core\Injector\Injector;


/**
 * Conditionally executes a given callback, attempting to return the desired results
 * of its execution.
 */
abstract class ContentFilter {

	use configurable;
	
	/**
	 * Nested content filter
	 *
	 * @var ContentFilter
	 */
	protected $nestedContentFilter;

	/**
	 * Cache lifetime
	 *
	 * @config
	 * @var int
	 */
	private static $cache_lifetime = 300;
	
	public function __construct($nestedContentFilter = null) {
		$this->nestedContentFilter = $nestedContentFilter;
	}
	
	/**
	 * Gets the cache to use
	 * 
	 * @return Zend_Cache_Frontend
	 */
	protected function getCache() {
		return Injector::inst()->get(
			CacheInterface::class . '.VersionFeedController'
		);
	}
	
	/**
	 * Evaluates the result of the given callback
	 * 
	 * @param string $key Unique key for this
	 * @param callable $callback Callback for evaluating the content
	 * @return mixed Result of $callback()
	 */
	public function getContent($key, $callback) {
		if($this->nestedContentFilter) {
			return $this->nestedContentFilter->getContent($key, $callback);
		} else {
			return call_user_func($callback);
		}
	}
}