<?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 $user user who owns the versions
  	 * @return mixed versions size or false if no versions size is stored
  	 */
  	private static function getVersionsSize($user) {
  		$query = \OC_DB::prepare('SELECT `size` FROM `*PREFIX*files_versions` WHERE `user`=?');
  		$result = $query->execute(array($user))->fetchAll();
  
  		if ($result) {
  			return $result[0]['size'];
  		}
  		return false;
  	}
  
  	/**
  	 * write to the database how much space is in use for versions
  	 *
  	 * @param $user owner of the versions
  	 * @param $size size of the versions
  	 */
  	private static function setVersionsSize($user, $size) {
  		if ( self::getVersionsSize($user) === false) {
  			$query = \OC_DB::prepare('INSERT INTO `*PREFIX*files_versions` (`size`, `user`) VALUES (?, ?)');
  		}else {
  			$query = \OC_DB::prepare('UPDATE `*PREFIX*files_versions` SET `size`=? WHERE `user`=?');
  		}
  		$query->execute(array($size, $user));
  	}
  
  	/**
  	 * 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);
  			$versions_view = new \OC\Files\View('/'.$uid.'/files_versions');
  
  			// 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);
  			if (  $versionsSize === false || $versionsSize < 0 ) {
  				$versionsSize = self::calculateSize($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;
  
  			$versionsSize = self::expire($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
  			$users_view->copy('files'.$filename, 'files_versions'.$filename.'.v'.$users_view->filemtime('files'.$filename));
  
  			// reset proxy state
  			\OC_FileProxy::$enabled = $proxyStatus;
  
  			$versionsSize += $users_view->filesize('files'.$filename);
  
  			self::setVersionsSize($uid, $versionsSize);
  		}
  	}
  
  
  	/**

  	 * @brief 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 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)) {
  
  			$versions_fileview = new \OC\Files\View('/' . $uid . '/files_versions');
  
  			$abs_path = $versions_fileview->getLocalFile($filename . '.v');
  			$versions = self::getVersions($uid, $filename);
  			if (!empty($versions)) {
  				$versionsSize = self::getVersionsSize($uid);
  				if ($versionsSize === false || $versionsSize < 0) {
  					$versionsSize = self::calculateSize($uid);
  				}
  				foreach ($versions as $v) {
  					unlink($abs_path . $v['version']);
  					\OC_Hook::emit('\OCP\Versions', 'delete', array('path' => $abs_path . $v['version']));
  					$versionsSize -= $v['size'];
  				}
  				self::setVersionsSize($uid, $versionsSize);

  			}

  		}

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

  	}
  
  	/**
  	 * rename versions of a file
  	 */
  	public static function rename($old_path, $new_path) {
  		list($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);
  		}
  
  		self::expire($newpath);
  
  		if ( $files_view->is_dir($oldpath) && $versions_view->is_dir($oldpath) ) {
  			$versions_view->rename($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) {
  				$versions_view->rename($oldpath.'.v'.$v['version'], $newpath.'.v'.$v['version']);
  			}
  		}
  	}
  
  	/**
  	 * 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 ) {
  				$users_view->unlink($version);
  			}
  		}
  		return false;
  
  	}
  
  
  	/**
  	 * @brief get a list of all available versions of a file in descending chronological order
  	 * @param $uid user id from the owner of the file
  	 * @param $filename file to find versions of, relative to the user files dir

  	 * @returns array
  	 */

  	public static function getVersions($uid, $filename) {
  		$versions = array();
  		// fetch for old versions
  		$view = new \OC\Files\View('/' . $uid . '/' . self::VERSIONS_ROOT);
  
  		$pathinfo = pathinfo($filename);
  
  		$files = $view->getDirectoryContent($pathinfo['dirname']);
  
  		$versionedFile = $pathinfo['basename'];
  
  		foreach ($files as $file) {
  			if ($file['type'] === 'file') {
  				$pos = strrpos($file['path'], '.v');
  				$currentFile = substr($file['name'], 0, strrpos($file['name'], '.v'));
  				if ($currentFile === $versionedFile) {
  					$version = substr($file['path'], $pos + 2);
  					$key = $version . '#' . $filename;
  					$versions[$key]['cur'] = 0;
  					$versions[$key]['version'] = $version;
  					$versions[$key]['humanReadableTimestamp'] = self::getHumanReadableTimestamp($version);
  					$versions[$key]['preview'] = \OCP\Util::linkToRoute('core_ajax_versions_preview', array('file' => $filename, 'version' => $version, 'user' => $uid));
  					$versions[$key]['path'] = $filename;
  					$versions[$key]['name'] = $versionedFile;
  					$versions[$key]['size'] = $file['size'];

  				}
  			}

  		}

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

  		return $versions;
  	}

  	/**
  	 * @brief 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";

  		}
  
  	}

  	/**
  	 * @brief deletes used space for files versions in db if user was deleted
  	 *
  	 * @param type $uid id of deleted user
  	 * @return result of db delete operation
  	 */
  	public static function deleteUser($uid) {
  		$query = \OC_DB::prepare('DELETE FROM `*PREFIX*files_versions` WHERE `user`=?');
  		return $query->execute(array($uid));
  	}
  
  	/**
  	 * @brief get the size of all stored versions from a given user
  	 * @param $uid id from the user
  	 * @return size of vesions
  	 */
  	private static function calculateSize($uid) {

  		if (\OCP\Config::getSystemValue('files_versions', Storage::DEFAULTENABLED) == 'true') {
  			$view = new \OC\Files\View('/' . $uid . '/files_versions');

  
  			$size = 0;

  			$dirContent = $view->getDirectoryContent('/');
  
  			while (!empty($dirContent)) {
  				$path = reset($dirContent);
  				if ($path['type'] === 'dir') {
  					$dirContent = array_merge($dirContent, $view->getDirectoryContent(substr($path['path'], strlen('files_versions'))));
  				} else {
  					$size += $view->filesize(substr($path['path'], strlen('files_versions')));

  				}

  				unset($dirContent[key($dirContent)]);

  			}
  
  			return $size;
  		}
  	}
  
  	/**
  	 * @brief returns all stored file versions from a given user
  	 * @param $uid id to the user
  	 * @return array with contains two arrays 'all' which contains all versions sorted by age and 'by_file' which contains all versions sorted by filename
  	 */
  	private static function getAllVersions($uid) {

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

  		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);

  				}
  			}

  		}

  		ksort($versions);

  		$result = array();

  		foreach ($versions as $key => $value) {
  			$size = $view->filesize($value['path']);
  			$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;

  	}
  
  	/**
  	 * @brief 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_Appconfig::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);
  				if (  $versionsSize === false || $versionsSize < 0 ) {
  					$versionsSize = self::calculateSize($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('/');
  				$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;
  			}
  
  
  			// with the  probability of 0.1% we reduce the number of all versions not only for the current file
  			$random = rand(0, 1000);
  			if ($random == 0) {
  				$allFiles = true;
  			} else {
  				$allFiles = false;
  			}
  
  			$allVersions = Storage::getVersions($uid, $filename);
  			$versionsByFile[$filename] = $allVersions;
  
  			$sizeOfDeletedVersions = self::delOldVersions($versionsByFile, $allVersions, $versionsFileview);
  			$availableSpace = $availableSpace + $sizeOfDeletedVersions;
  			$versionsSize = $versionsSize - $sizeOfDeletedVersions;
  
  			// if still not enough free space we rearrange the versions from all files
  			if ($availableSpace <= 0 || $allFiles) {
  				$result = Storage::getAllVersions($uid);
  				$versionsByFile = $result['by_file'];
  				$allVersions = $result['all'];
  
  				$sizeOfDeletedVersions = self::delOldVersions($versionsByFile, $allVersions, $versionsFileview);
  				$availableSpace = $availableSpace + $sizeOfDeletedVersions;
  				$versionsSize = $versionsSize - $sizeOfDeletedVersions;
  			}
  
  			// 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);
  				$versionsFileview->unlink($version['path'].'.v'.$version['version']);

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

  				$versionsSize -= $version['size'];
  				$availableSpace += $version['size'];
  				next($allVersions);
  				$i++;
  			}
  
  			return $versionsSize; // finally return the new size of the version history
  		}
  
  		return false;
  	}
  
  	/**
  	 * @brief delete old version from a given list of versions
  	 *
  	 * @param array $versionsByFile list of versions ordered by files
  	 * @param array $allVversions all versions accross multiple files
  	 * @param $versionsFileview OC\Files\View on data/user/files_versions
  	 * @return size of releted versions
  	 */
  	private static function delOldVersions($versionsByFile, &$allVersions, $versionsFileview) {
  
  		$time = time();
  		$size = 0;
  
  		// delete old versions for every given file
  		foreach ($versionsByFile as $versions) {
  			$versions = array_reverse($versions); // newest version first
  
  			$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 || $version['version'] >= $nextInterval) {
  						if ($version['version'] > $nextVersion) {
  							//distance between two version too small, delete version
  							$versionsFileview->unlink($version['path'] . '.v' . $version['version']);

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

  							$size += $version['size'];
  							unset($allVersions[$key]); // update array with all versions
  						} else {
  							$nextVersion = $version['version'] - $step;
  						}
  						$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
  					}
  				}
  				$prevTimestamp = $version['version'];
  			}
  		}
  		return $size;
  	}
  
  	/**
  	 * @brief 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) {
  		$dirname = \OC_Filesystem::normalizePath(dirname($filename));
  		$dirParts = explode('/', $dirname);
  		$dir = "/files_versions";
  		foreach ($dirParts as $part) {
  			$dir = $dir . '/' . $part;
  			if (!$view->file_exists($dir)) {
  				$view->mkdir($dir);
  			}
  		}
  	}
  
  }