<?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;
  
  use OC\Files\Filesystem;
  use OC\Hooks\BasicEmitter;
  
  /**
   * Class Scanner
   *
   * Hooks available in scope \OC\Files\Cache\Scanner:
   *  - scanFile(string $path, string $storageId)
   *  - scanFolder(string $path, string $storageId)

   *  - postScanFile(string $path, string $storageId)
   *  - postScanFolder(string $path, string $storageId)

   *
   * @package OC\Files\Cache
   */
  class Scanner extends BasicEmitter {
  	/**
  	 * @var \OC\Files\Storage\Storage $storage
  	 */
  	private $storage;
  
  	/**
  	 * @var string $storageId
  	 */
  	private $storageId;
  
  	/**
  	 * @var \OC\Files\Cache\Cache $cache
  	 */
  	private $cache;

  	/**
  	 * @var \OC\Files\Cache\Permissions $permissionsCache
  	 */
  	private $permissionsCache;

  	const SCAN_RECURSIVE = true;
  	const SCAN_SHALLOW = false;
  
  	const REUSE_ETAG = 1;
  	const REUSE_SIZE = 2;
  
  	public function __construct(\OC\Files\Storage\Storage $storage) {
  		$this->storage = $storage;
  		$this->storageId = $this->storage->getId();
  		$this->cache = $storage->getCache();

  		$this->permissionsCache = $storage->getPermissionsCache();

  	}
  
  	/**
  	 * get all the metadata of a file or folder
  	 * *
  	 *
  	 * @param string $path
  	 * @return array with metadata of the file
  	 */
  	public function getData($path) {

  		if (!$this->storage->isReadable($path)) {
  			//cant read, nothing we can do
  			\OCP\Util::writeLog('OC\Files\Cache\Scanner', "!!! Path '$path' is not readable !!!", \OCP\Util::DEBUG);
  			return null;
  		}

  		$data = array();

  		$data['mimetype'] = $this->storage->getMimeType($path);
  		$data['mtime'] = $this->storage->filemtime($path);
  		if ($data['mimetype'] == 'httpd/unix-directory') {
  			$data['size'] = -1; //unknown
  		} else {
  			$data['size'] = $this->storage->filesize($path);
  		}
  		$data['etag'] = $this->storage->getETag($path);

  		$data['storage_mtime'] = $data['mtime'];

  		return $data;
  	}
  
  	/**
  	 * scan a single file and store it in the cache
  	 *
  	 * @param string $file
  	 * @param int $reuseExisting
  	 * @param bool $parentExistsInCache
  	 * @return array with metadata of the scanned file
  	 */
  	public function scanFile($file, $reuseExisting = 0, $parentExistsInCache = false) {
  		if (!self::isPartialFile($file)
  			and !Filesystem::isFileBlacklisted($file)
  		) {
  			$this->emit('\OC\Files\Cache\Scanner', 'scanFile', array($file, $this->storageId));
  			\OC_Hook::emit('\OC\Files\Cache\Scanner', 'scan_file', array('path' => $file, 'storage' => $this->storageId));
  			$data = $this->getData($file);
  			if ($data) {
  				if ($file and !$parentExistsInCache) {
  					$parent = dirname($file);
  					if ($parent === '.' or $parent === '/') {
  						$parent = '';
  					}
  					if (!$this->cache->inCache($parent)) {
  						$this->scanFile($parent);
  					}
  				}
  				$newData = $data;

  				$cacheData = $this->cache->get($file);
  				if ($cacheData) {
  					if (isset($cacheData['fileid'])) {
  						$this->permissionsCache->remove($cacheData['fileid']);
  					}
  					if ($reuseExisting) {
  						// prevent empty etag
  						$etag = $cacheData['etag'];
  						$propagateETagChange = false;
  						if (empty($etag)) {
  							$etag = $data['etag'];
  							$propagateETagChange = true;
  						}
  						// only reuse data if the file hasn't explicitly changed
  						if (isset($data['mtime']) && isset($cacheData['mtime']) && $data['mtime'] === $cacheData['mtime']) {
  							if (($reuseExisting & self::REUSE_SIZE) && ($data['size'] === -1)) {
  								$data['size'] = $cacheData['size'];
  							}
  							if ($reuseExisting & self::REUSE_ETAG) {
  								$data['etag'] = $etag;
  								if ($propagateETagChange) {
  									$parent = $file;
  									while ($parent !== '') {
  										$parent = dirname($parent);
  										if ($parent === '.') {
  											$parent = '';
  										}
  										$parentCacheData = $this->cache->get($parent);
  										$this->cache->update($parentCacheData['fileid'], array(
  											'etag' => $this->storage->getETag($parent),
  										));
  									}
  								}
  							}

  						}

  						// Only update metadata that has changed
  						$newData = array_diff_assoc($data, $cacheData);
  						if (isset($newData['etag'])) {
  							$cacheDataString = print_r($cacheData, true);
  							$dataString = print_r($data, true);
  							\OCP\Util::writeLog('OC\Files\Cache\Scanner',
  								"!!! No reuse of etag for '$file' !!! 
  cache: $cacheDataString 
  data: $dataString",
  								\OCP\Util::DEBUG);

  						}
  					}

  				}
  				if (!empty($newData)) {
  					$this->cache->put($file, $newData);

  					$this->emit('\OC\Files\Cache\Scanner', 'postScanFile', array($file, $this->storageId));
  					\OC_Hook::emit('\OC\Files\Cache\Scanner', 'post_scan_file', array('path' => $file, 'storage' => $this->storageId));

  				}
  			} else {
  				$this->cache->remove($file);
  			}
  			return $data;
  		}
  		return null;
  	}
  
  	/**
  	 * scan a folder and all it's children
  	 *
  	 * @param string $path
  	 * @param bool $recursive
  	 * @param int $reuse
  	 * @return int the size of the scanned folder or -1 if the size is unknown at this stage
  	 */
  	public function scan($path, $recursive = self::SCAN_RECURSIVE, $reuse = -1) {
  		if ($reuse === -1) {
  			$reuse = ($recursive === self::SCAN_SHALLOW) ? self::REUSE_ETAG | self::REUSE_SIZE : 0;
  		}
  		$this->scanFile($path, $reuse);
  		return $this->scanChildren($path, $recursive, $reuse);
  	}
  
  	/**
  	 * scan all the files and folders in a folder
  	 *
  	 * @param string $path
  	 * @param bool $recursive
  	 * @param int $reuse
  	 * @return int the size of the scanned folder or -1 if the size is unknown at this stage
  	 */
  	public function scanChildren($path, $recursive = self::SCAN_RECURSIVE, $reuse = -1) {
  		if ($reuse === -1) {
  			$reuse = ($recursive === self::SCAN_SHALLOW) ? self::REUSE_ETAG | self::REUSE_SIZE : 0;
  		}
  		$this->emit('\OC\Files\Cache\Scanner', 'scanFolder', array($path, $this->storageId));
  		$size = 0;
  		$childQueue = array();
  		$existingChildren = array();
  		if ($this->cache->inCache($path)) {
  			$children = $this->cache->getFolderContents($path);
  			foreach ($children as $child) {
  				$existingChildren[] = $child['name'];
  			}
  		}
  		$newChildren = array();
  		if ($this->storage->is_dir($path) && ($dh = $this->storage->opendir($path))) {

  			$exceptionOccurred = false;

  			\OC_DB::beginTransaction();

  			if (is_resource($dh)) {

  				while (($file = readdir($dh)) !== false) {
  					$child = ($path) ? $path . '/' . $file : $file;
  					if (!Filesystem::isIgnoredDir($file)) {
  						$newChildren[] = $file;

  						try {
  							$data = $this->scanFile($child, $reuse, true);
  							if ($data) {
  								if ($data['size'] === -1) {
  									if ($recursive === self::SCAN_RECURSIVE) {
  										$childQueue[] = $child;
  									} else {
  										$size = -1;
  									}
  								} else if ($size !== -1) {
  									$size += $data['size'];

  								}

  							}
  						}

  						catch (\Doctrine\DBAL\DBALException $ex){
  							// might happen if inserting duplicate while a scanning
  							// process is running in parallel
  							// log and ignore
  							\OC_Log::write('core', 'Exception while scanning file "' . $child . '": ' . $ex->getMessage(), \OC_Log::DEBUG);
  							$exceptionOccurred = true;
  						}

  					}
  				}
  			}
  			$removedChildren = \array_diff($existingChildren, $newChildren);
  			foreach ($removedChildren as $childName) {
  				$child = ($path) ? $path . '/' . $childName : $childName;
  				$this->cache->remove($child);
  			}
  			\OC_DB::commit();

  			if ($exceptionOccurred){
  				// It might happen that the parallel scan process has already
  				// inserted mimetypes but those weren't available yet inside the transaction
  				// To make sure to have the updated mime types in such cases,
  				// we reload them here
  				$this->cache->loadMimetypes();
  			}

  			foreach ($childQueue as $child) {
  				$childSize = $this->scanChildren($child, self::SCAN_RECURSIVE, $reuse);
  				if ($childSize === -1) {
  					$size = -1;
  				} else {
  					$size += $childSize;
  				}
  			}
  			$this->cache->put($path, array('size' => $size));
  		}

  		$this->emit('\OC\Files\Cache\Scanner', 'postScanFolder', array($path, $this->storageId));

  		return $size;
  	}
  
  	/**
  	 * @brief check if the file should be ignored when scanning
  	 * NOTE: files with a '.part' extension are ignored as well!
  	 *       prevents unfinished put requests to be scanned
  	 * @param String $file
  	 * @return boolean
  	 */
  	public static function isPartialFile($file) {
  		if (pathinfo($file, PATHINFO_EXTENSION) === 'part') {
  			return true;
  		}
  		return false;
  	}
  
  	/**
  	 * walk over any folders that are not fully scanned yet and scan them
  	 */
  	public function backgroundScan() {

  		$lastPath = null;
  		while (($path = $this->cache->getIncomplete()) !== false && $path !== $lastPath) {
  			$this->scan($path, self::SCAN_RECURSIVE, self::REUSE_ETAG);

  			$this->cache->correctFolderSize($path);

  			$lastPath = $path;

  		}
  	}
  }