<?php
  /**
   * Copyright (c) 2012 Robin Appelman <icewind@owncloud.com>
   * This file is licensed under the Affero General Public License version 3 or
   * later.
   * See the COPYING-README file.
   */
  
  namespace OC\Files\Cache;
  
  /**
   * check the storage backends for updates and change the cache accordingly
   */
  class Watcher {

  	const CHECK_NEVER = 0; // never check the underlying filesystem for updates
  	const CHECK_ONCE = 1; // check the underlying filesystem for updates once every request for each file
  	const CHECK_ALWAYS = 2; // always check the underlying filesystem for updates
  
  	protected $watchPolicy = self::CHECK_ONCE;
  
  	protected $checkedPaths = array();

  	/**
  	 * @var \OC\Files\Storage\Storage $storage
  	 */

  	protected $storage;

  
  	/**
  	 * @var Cache $cache
  	 */

  	protected $cache;

  
  	/**

  	 * @var Scanner $scanner ;

  	 */

  	protected $scanner;

  
  	/**
  	 * @param \OC\Files\Storage\Storage $storage
  	 */
  	public function __construct(\OC\Files\Storage\Storage $storage) {
  		$this->storage = $storage;
  		$this->cache = $storage->getCache();
  		$this->scanner = $storage->getScanner();
  	}
  
  	/**

  	 * @param int $policy either \OC\Files\Cache\Watcher::CHECK_NEVER, \OC\Files\Cache\Watcher::CHECK_ONCE, \OC\Files\Cache\Watcher::CHECK_ALWAYS
  	 */
  	public function setPolicy($policy) {
  		$this->watchPolicy = $policy;
  	}
  
  	/**

  	 * check $path for updates
  	 *
  	 * @param string $path

  	 * @return boolean|array true if path was updated, otherwise the cached data is returned

  	 */
  	public function checkUpdate($path) {

  		if ($this->watchPolicy === self::CHECK_ALWAYS or ($this->watchPolicy === self::CHECK_ONCE and array_search($path, $this->checkedPaths) === false)) {
  			$cachedEntry = $this->cache->get($path);
  			$this->checkedPaths[] = $path;
  			if ($this->storage->hasUpdated($path, $cachedEntry['storage_mtime'])) {
  				if ($this->storage->is_dir($path)) {
  					$this->scanner->scan($path, Scanner::SCAN_SHALLOW);
  				} else {
  					$this->scanner->scanFile($path);
  				}
  				if ($cachedEntry['mimetype'] === 'httpd/unix-directory') {
  					$this->cleanFolder($path);
  				}
  				$this->cache->correctFolderSize($path);
  				return true;

  			}

  			return $cachedEntry;
  		} else {
  			return false;

  		}
  	}
  
  	/**
  	 * remove deleted files in $path from the cache
  	 *
  	 * @param string $path
  	 */
  	public function cleanFolder($path) {
  		$cachedContent = $this->cache->getFolderContents($path);
  		foreach ($cachedContent as $entry) {
  			if (!$this->storage->file_exists($entry['path'])) {
  				$this->cache->remove($entry['path']);
  			}
  		}
  	}
  }