<?php
  /**
   * Copyright (c) 2012 Frank Karlitschek <frank@owncloud.org>
   *               2013 Bjoern Schiessle <schiessle@owncloud.com>
   * This file is licensed under the Affero General Public License version 3 or
   * later.
   * See the COPYING-README file.
   */
  
  /**
   * Versions
   *
   * A class to handle the versioning of files.
   */
  
  namespace OCA\Files_Versions;
  
  class Storage {
  
  	const DEFAULTENABLED=true;
  	const DEFAULTMAXSIZE=50; // unit: percentage; 50% of available disk space/quota

  	const VERSIONS_ROOT = 'files_versions/';
  
  	// files for which we can remove the versions after the delete operation was successful
  	private static $deletedFiles = array();

  
  	private static $max_versions_per_interval = array(
  		//first 10sec, one version every 2sec
  		1 => array('intervalEndsAfter' => 10,      'step' => 2),
  		//next minute, one version every 10sec
  		2 => array('intervalEndsAfter' => 60,      'step' => 10),
  		//next hour, one version every minute
  		3 => array('intervalEndsAfter' => 3600,    'step' => 60),
  		//next 24h, one version every hour
  		4 => array('intervalEndsAfter' => 86400,   'step' => 3600),
  		//next 30days, one version per day
  		5 => array('intervalEndsAfter' => 2592000, 'step' => 86400),
  		//until the end one version per week
  		6 => array('intervalEndsAfter' => -1,      'step' => 604800),
  	);
  
  	public static function getUidAndFilename($filename) {
  		$uid = \OC\Files\Filesystem::getOwner($filename);
  		\OC\Files\Filesystem::initMountPoints($uid);
  		if ( $uid != \OCP\User::getUser() ) {
  			$info = \OC\Files\Filesystem::getFileInfo($filename);
  			$ownerView = new \OC\Files\View('/'.$uid.'/files');
  			$filename = $ownerView->getPath($info['fileid']);
  		}
  		return array($uid, $filename);
  	}
  
  	/**
  	 * get current size of all versions from a given user
  	 *

  	 * @param string $user user who owns the versions
  	 * @return int versions size

  	 */
  	private static function getVersionsSize($user) {

  		$view = new \OC\Files\View('/' . $user);
  		$fileInfo = $view->getFileInfo('/files_versions');
  		return isset($fileInfo['size']) ? $fileInfo['size'] : 0;

  	}
  
  	/**
  	 * store a new version of a file.
  	 */
  	public static function store($filename) {
  		if(\OCP\Config::getSystemValue('files_versions', Storage::DEFAULTENABLED)=='true') {
  
  			// if the file gets streamed we need to remove the .part extension
  			// to get the right target
  			$ext = pathinfo($filename, PATHINFO_EXTENSION);
  			if ($ext === 'part') {
  				$filename = substr($filename, 0, strlen($filename)-5);
  			}
  
  			list($uid, $filename) = self::getUidAndFilename($filename);
  
  			$files_view = new \OC\Files\View('/'.$uid .'/files');
  			$users_view = new \OC\Files\View('/'.$uid);

  
  			// check if filename is a directory
  			if($files_view->is_dir($filename)) {
  				return false;
  			}
  
  			// we should have a source file to work with, and the file shouldn't
  			// be empty
  			$fileExists = $files_view->file_exists($filename);
  			if (!($fileExists && $files_view->filesize($filename) > 0)) {
  				return false;
  			}
  
  			// create all parent folders
  			self::createMissingDirectories($filename, $users_view);
  
  			$versionsSize = self::getVersionsSize($uid);

  
  			// assumption: we need filesize($filename) for the new version +
  			// some more free space for the modified file which might be
  			// 1.5 times as large as the current version -> 2.5
  			$neededSpace = $files_view->filesize($filename) * 2.5;

  			self::expire($filename, $versionsSize, $neededSpace);

  
  			// disable proxy to prevent multiple fopen calls
  			$proxyStatus = \OC_FileProxy::$enabled;
  			\OC_FileProxy::$enabled = false;
  
  			// store a new version of a file

  			$mtime = $users_view->filemtime('files'.$filename);
  			$users_view->copy('files'.$filename, 'files_versions'.$filename.'.v'. $mtime);
  			// call getFileInfo to enforce a file cache entry for the new version
  			$users_view->getFileInfo('files_versions'.$filename.'.v'.$mtime);

  
  			// reset proxy state
  			\OC_FileProxy::$enabled = $proxyStatus;

  		}
  	}
  
  
  	/**

  	 * mark file as deleted so that we can remove the versions if the file is gone

  	 * @param string $path
  	 */
  	public static function markDeletedFile($path) {
  		list($uid, $filename) = self::getUidAndFilename($path);
  		self::$deletedFiles[$path] = array(
  			'uid' => $uid,
  			'filename' => $filename);
  	}
  
  	/**

  	 * delete the version from the storage and cache
  	 *
  	 * @param \OC\Files\View $view
  	 * @param string $path
  	 */
  	protected static function deleteVersion($view, $path) {
  		$view->unlink($path);
  		/**
  		 * @var \OC\Files\Storage\Storage $storage
  		 * @var string $internalPath
  		 */
  		list($storage, $internalPath) = $view->resolvePath($path);
  		$cache = $storage->getCache($internalPath);
  		$cache->remove($internalPath);
  	}
  
  	/**

  	 * Delete versions of a file
  	 */

  	public static function delete($path) {

  		$deletedFile = self::$deletedFiles[$path];
  		$uid = $deletedFile['uid'];
  		$filename = $deletedFile['filename'];
  
  		if (!\OC\Files\Filesystem::file_exists($path)) {

  			$view = new \OC\Files\View('/' . $uid . '/files_versions');

  			$versions = self::getVersions($uid, $filename);
  			if (!empty($versions)) {

  				foreach ($versions as $v) {

  					\OC_Hook::emit('\OCP\Versions', 'preDelete', array('path' => $path . $v['version']));
  					self::deleteVersion($view, $filename . '.v' . $v['version']);
  					\OC_Hook::emit('\OCP\Versions', 'delete', array('path' => $path . $v['version']));

  				}

  			}

  		}

  		unset(self::$deletedFiles[$path]);

  	}
  
  	/**

  	 * rename or copy versions of a file
  	 * @param string $old_path
  	 * @param string $new_path
  	 * @param string $operation can be 'copy' or 'rename'

  	 */

  	public static function renameOrCopy($old_path, $new_path, $operation) {

  		list($uid, $oldpath) = self::getUidAndFilename($old_path);
  		list($uidn, $newpath) = self::getUidAndFilename($new_path);
  		$versions_view = new \OC\Files\View('/'.$uid .'/files_versions');
  		$files_view = new \OC\Files\View('/'.$uid .'/files');
  
  		// if the file already exists than it was a upload of a existing file
  		// over the web interface -> store() is the right function we need here
  		if ($files_view->file_exists($newpath)) {
  			return self::store($new_path);
  		}

  		if ( $files_view->is_dir($oldpath) && $versions_view->is_dir($oldpath) ) {

  			$versions_view->$operation($oldpath, $newpath);

  		} else  if ( ($versions = Storage::getVersions($uid, $oldpath)) ) {
  			// create missing dirs if necessary
  			self::createMissingDirectories($newpath, new \OC\Files\View('/'. $uidn));
  
  			foreach ($versions as $v) {

  				$versions_view->$operation($oldpath.'.v'.$v['version'], $newpath.'.v'.$v['version']);

  			}
  		}

  
  		if (!$files_view->is_dir($newpath)) {
  			self::expire($newpath);
  		}

  	}
  
  	/**
  	 * rollback to an old version of a file.
  	 */
  	public static function rollback($file, $revision) {
  
  		if(\OCP\Config::getSystemValue('files_versions', Storage::DEFAULTENABLED)=='true') {
  			list($uid, $filename) = self::getUidAndFilename($file);
  			$users_view = new \OC\Files\View('/'.$uid);
  			$files_view = new \OC\Files\View('/'.\OCP\User::getUser().'/files');
  			$versionCreated = false;
  
  			//first create a new version
  			$version = 'files_versions'.$filename.'.v'.$users_view->filemtime('files'.$filename);
  			if ( !$users_view->file_exists($version)) {
  
  				// disable proxy to prevent multiple fopen calls
  				$proxyStatus = \OC_FileProxy::$enabled;
  				\OC_FileProxy::$enabled = false;
  
  				$users_view->copy('files'.$filename, 'files_versions'.$filename.'.v'.$users_view->filemtime('files'.$filename));
  
  				// reset proxy state
  				\OC_FileProxy::$enabled = $proxyStatus;
  
  				$versionCreated = true;
  			}
  
  			// rollback
  			if( @$users_view->rename('files_versions'.$filename.'.v'.$revision, 'files'.$filename) ) {
  				$files_view->touch($file, $revision);
  				Storage::expire($file);
  				return true;
  
  			}else if ( $versionCreated ) {

  				self::deleteVersion($users_view, $version);

  			}
  		}
  		return false;
  
  	}
  
  
  	/**

  	 * get a list of all available versions of a file in descending chronological order

  	 * @param string $uid user id from the owner of the file
  	 * @param string $filename file to find versions of, relative to the user files dir
  	 * @param string $userFullPath

  	 * @return array versions newest version first

  	 */

  	public static function getVersions($uid, $filename, $userFullPath = '') {

  		$versions = array();
  		// fetch for old versions

  		$view = new \OC\Files\View('/' . $uid . '/');

  
  		$pathinfo = pathinfo($filename);

  		$versionedFile = $pathinfo['basename'];

  		$dir = self::VERSIONS_ROOT . '/' . $pathinfo['dirname'];

  		$dirContent = false;
  		if ($view->is_dir($dir)) {
  			$dirContent = $view->opendir($dir);
  		}

  		if ($dirContent === false) {
  			return $versions;
  		}
  
  		if (is_resource($dirContent)) {
  			while (($entryName = readdir($dirContent)) !== false) {
  				if (!\OC\Files\Filesystem::isIgnoredDir($entryName)) {
  					$pathparts = pathinfo($entryName);
  					$filename = $pathparts['filename'];
  					if ($filename === $versionedFile) {
  						$pathparts = pathinfo($entryName);
  						$timestamp = substr($pathparts['extension'], 1);
  						$filename = $pathparts['filename'];
  						$key = $timestamp . '#' . $filename;
  						$versions[$key]['version'] = $timestamp;
  						$versions[$key]['humanReadableTimestamp'] = self::getHumanReadableTimestamp($timestamp);
  						if (empty($userFullPath)) {
  							$versions[$key]['preview'] = '';
  						} else {
  							$versions[$key]['preview'] = \OCP\Util::linkToRoute('core_ajax_versions_preview', array('file' => $userFullPath, 'version' => $timestamp));
  						}
  						$versions[$key]['path'] = $filename;
  						$versions[$key]['name'] = $versionedFile;
  						$versions[$key]['size'] = $view->filesize($dir . '/' . $entryName);

  					}

  				}
  			}

  			closedir($dirContent);

  		}

  		// sort with newest version first
  		krsort($versions);

  		return $versions;
  	}

  	/**

  	 * translate a timestamp into a string like "5 days ago"

  	 * @param int $timestamp
  	 * @return string for example "5 days ago"
  	 */
  	private static function getHumanReadableTimestamp($timestamp) {
  
  		$diff = time() - $timestamp;
  
  		if ($diff < 60) { // first minute
  			return  $diff . " seconds ago";
  		} elseif ($diff < 3600) { //first hour
  			return round($diff / 60) . " minutes ago";
  		} elseif ($diff < 86400) { // first day
  			return round($diff / 3600) . " hours ago";
  		} elseif ($diff < 604800) { //first week
  			return round($diff / 86400) . " days ago";
  		} elseif ($diff < 2419200) { //first month
  			return round($diff / 604800) . " weeks ago";
  		} elseif ($diff < 29030400) { // first year
  			return round($diff / 2419200) . " months ago";

  		} else {

  			return round($diff / 29030400) . " years ago";

  		}
  
  	}

  	/**

  	 * returns all stored file versions from a given user
  	 * @param string $uid id of the user

  	 * @return array with contains two arrays 'all' which contains all versions sorted by age and 'by_file' which contains all versions sorted by filename
  	 */
  	private static function getAllVersions($uid) {

  		$view = new \OC\Files\View('/' . $uid . '/');
  		$dirs = array(self::VERSIONS_ROOT);

  		$versions = array();

  		while (!empty($dirs)) {
  			$dir = array_pop($dirs);
  			$files = $view->getDirectoryContent($dir);

  			foreach ($files as $file) {
  				if ($file['type'] === 'dir') {
  					array_push($dirs, $file['path']);
  				} else {
  					$versionsBegin = strrpos($file['path'], '.v');
  					$relPathStart = strlen(self::VERSIONS_ROOT);
  					$version = substr($file['path'], $versionsBegin + 2);
  					$relpath = substr($file['path'], $relPathStart, $versionsBegin - $relPathStart);
  					$key = $version . '#' . $relpath;
  					$versions[$key] = array('path' => $relpath, 'timestamp' => $version);

  				}
  			}

  		}

  		// newest version first

  		krsort($versions);

  		$result = array();

  		foreach ($versions as $key => $value) {

  			$size = $view->filesize(self::VERSIONS_ROOT.'/'.$value['path'].'.v'.$value['timestamp']);

  			$filename = $value['path'];

  			$result['all'][$key]['version'] = $value['timestamp'];
  			$result['all'][$key]['path'] = $filename;
  			$result['all'][$key]['size'] = $size;

  			$result['by_file'][$filename][$key]['version'] = $value['timestamp'];
  			$result['by_file'][$filename][$key]['path'] = $filename;
  			$result['by_file'][$filename][$key]['size'] = $size;

  		}

  
  		return $result;

  	}
  
  	/**

  	 * get list of files we want to expire
  	 * @param array $versions list of versions
  	 * @param integer $time
  	 * @return array containing the list of to deleted versions and the size of them
  	 */
  	protected static function getExpireList($time, $versions) {
  
  		$size = 0;
  		$toDelete = array();  // versions we want to delete
  
  		$interval = 1;
  		$step = Storage::$max_versions_per_interval[$interval]['step'];
  		if (Storage::$max_versions_per_interval[$interval]['intervalEndsAfter'] == -1) {
  			$nextInterval = -1;
  		} else {
  			$nextInterval = $time - Storage::$max_versions_per_interval[$interval]['intervalEndsAfter'];
  		}
  
  		$firstVersion = reset($versions);
  		$firstKey = key($versions);
  		$prevTimestamp = $firstVersion['version'];
  		$nextVersion = $firstVersion['version'] - $step;
  		unset($versions[$firstKey]);
  
  		foreach ($versions as $key => $version) {
  			$newInterval = true;
  			while ($newInterval) {
  				if ($nextInterval == -1 || $prevTimestamp > $nextInterval) {
  					if ($version['version'] > $nextVersion) {
  						//distance between two version too small, mark to delete
  						$toDelete[$key] = $version['path'] . '.v' . $version['version'];
  						$size += $version['size'];
  						\OCP\Util::writeLog('files_versions', 'Mark to expire '. $version['path'] .' next version should be ' . $nextVersion . " or smaller. (prevTimestamp: " . $prevTimestamp . "; step: " . $step, \OCP\Util::DEBUG);
  					} else {
  						$nextVersion = $version['version'] - $step;
  						$prevTimestamp = $version['version'];
  					}
  					$newInterval = false; // version checked so we can move to the next one
  				} else { // time to move on to the next interval
  					$interval++;
  					$step = Storage::$max_versions_per_interval[$interval]['step'];
  					$nextVersion = $prevTimestamp - $step;
  					if (Storage::$max_versions_per_interval[$interval]['intervalEndsAfter'] == -1) {
  						$nextInterval = -1;
  					} else {
  						$nextInterval = $time - Storage::$max_versions_per_interval[$interval]['intervalEndsAfter'];
  					}
  					$newInterval = true; // we changed the interval -> check same version with new interval
  				}
  			}
  		}
  
  		return array($toDelete, $size);
  
  	}
  
  	/**
  	 * Erase a file's versions which exceed the set quota

  	 */
  	private static function expire($filename, $versionsSize = null, $offset = 0) {
  		if(\OCP\Config::getSystemValue('files_versions', Storage::DEFAULTENABLED)=='true') {
  			list($uid, $filename) = self::getUidAndFilename($filename);
  			$versionsFileview = new \OC\Files\View('/'.$uid.'/files_versions');
  
  			// get available disk space for user
  			$softQuota = true;
  			$quota = \OC_Preferences::getValue($uid, 'files', 'quota');
  			if ( $quota === null || $quota === 'default') {

  				$quota = \OC::$server->getAppConfig()->getValue('files', 'default_quota');

  			}
  			if ( $quota === null || $quota === 'none' ) {
  				$quota = \OC\Files\Filesystem::free_space('/');
  				$softQuota = false;
  			} else {
  				$quota = \OCP\Util::computerFileSize($quota);
  			}
  
  			// make sure that we have the current size of the version history
  			if ( $versionsSize === null ) {
  				$versionsSize = self::getVersionsSize($uid);

  			}
  
  			// calculate available space for version history
  			// subtract size of files and current versions size from quota
  			if ($softQuota) {
  				$files_view = new \OC\Files\View('/'.$uid.'/files');

  				$rootInfo = $files_view->getFileInfo('/', false);

  				$free = $quota-$rootInfo['size']; // remaining free space for user
  				if ( $free > 0 ) {
  					$availableSpace = ($free * self::DEFAULTMAXSIZE / 100) - ($versionsSize + $offset); // how much space can be used for versions
  				} else {
  					$availableSpace = $free - $versionsSize - $offset;
  				}
  			} else {
  				$availableSpace = $quota - $offset;
  			}

  			$allVersions = Storage::getVersions($uid, $filename);

  			$time = time();
  			list($toDelete, $sizeOfDeletedVersions) = self::getExpireList($time, $allVersions);

  			$availableSpace = $availableSpace + $sizeOfDeletedVersions;
  			$versionsSize = $versionsSize - $sizeOfDeletedVersions;
  
  			// if still not enough free space we rearrange the versions from all files

  			if ($availableSpace <= 0) {

  				$result = Storage::getAllVersions($uid);

  				$allVersions = $result['all'];

  				foreach ($result['by_file'] as $versions) {
  					list($toDeleteNew, $size) = self::getExpireList($time, $versions);
  					$toDelete = array_merge($toDelete, $toDeleteNew);
  					$sizeOfDeletedVersions += $size;
  				}

  				$availableSpace = $availableSpace + $sizeOfDeletedVersions;
  				$versionsSize = $versionsSize - $sizeOfDeletedVersions;
  			}

  			foreach($toDelete as $key => $path) {
  				\OC_Hook::emit('\OCP\Versions', 'preDelete', array('path' => $path));
  				self::deleteVersion($versionsFileview, $path);
  				\OC_Hook::emit('\OCP\Versions', 'delete', array('path' => $path));
  				unset($allVersions[$key]); // update array with the versions we keep
  				\OCP\Util::writeLog('files_versions', "Expire: " . $path, \OCP\Util::DEBUG);
  			}

  			// Check if enough space is available after versions are rearranged.
  			// If not we delete the oldest versions until we meet the size limit for versions,
  			// but always keep the two latest versions
  			$numOfVersions = count($allVersions) -2 ;
  			$i = 0;
  			while ($availableSpace < 0 && $i < $numOfVersions) {
  				$version = current($allVersions);

  				\OC_Hook::emit('\OCP\Versions', 'preDelete', array('path' => $version['path'].'.v'.$version['version']));
  				self::deleteVersion($versionsFileview, $version['path'] . '.v' . $version['version']);

  				\OC_Hook::emit('\OCP\Versions', 'delete', array('path' => $version['path'].'.v'.$version['version']));

  				\OCP\Util::writeLog('files_versions', 'running out of space! Delete oldest version: ' . $version['path'].'.v'.$version['version'] , \OCP\Util::DEBUG);

  				$versionsSize -= $version['size'];
  				$availableSpace += $version['size'];
  				next($allVersions);
  				$i++;
  			}
  
  			return $versionsSize; // finally return the new size of the version history
  		}
  
  		return false;
  	}
  
  	/**

  	 * create recursively missing directories

  	 * @param string $filename $path to a file
  	 * @param \OC\Files\View $view view on data/user/
  	 */
  	private static function createMissingDirectories($filename, $view) {

  		$dirname = \OC\Files\Filesystem::normalizePath(dirname($filename));

  		$dirParts = explode('/', $dirname);
  		$dir = "/files_versions";
  		foreach ($dirParts as $part) {
  			$dir = $dir . '/' . $part;
  			if (!$view->file_exists($dir)) {
  				$view->mkdir($dir);
  			}
  		}
  	}
  
  }