<?php
/**
 * Copyright (c) 2012 Frank Karlitschek <frank@owncloud.org>
 * 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_Versions;

class Storage {


	// config.php configuration:
	//   - files_versions
	//   - files_versionsfolder
	//   - files_versionsmaxfilesize
	//
	// todo:
	//   - finish porting to OC_FilesystemView to enable network transparency
	//   - add transparent compression. first test if it´s worth it.

	const DEFAULTENABLED=true;
	const DEFAULTMAXSIZE=50; // unit: percentage; 50% of available disk space/quota
	
	private static $max_versions_per_interval = array(1 => array('intervalEndsAfter' => 10,     //first 10sec, one version every 2sec
																	'step' => 2),
														2 => array('intervalEndsAfter' => 60,     //next minute, one version every 10sec
																	'step' => 10),
														3 => array('intervalEndsAfter' => 3600,     //next hour, one version every minute
																	'step' => 60),
														4 => array('intervalEndsAfter' => 86400,   //next 24h, one version every hour
																	'step' => 3600),
														5 => array('intervalEndsAfter' => 2592000,   //next 30days, one version per day
																	'step' => 86400),
														6 => array('intervalEndsAfter' => -1,      //until the end one version per week
																	'step' => 604800),
			);	

	private static function getUidAndFilename($filename)
	{
		if (\OCP\App::isEnabled('files_sharing')
		    && substr($filename, 0, 7) == '/Shared'
		    && $source = \OCP\Share::getItemSharedWith('file',
					substr($filename, 7),
					\OC_Share_Backend_File::FORMAT_SHARED_STORAGE)) {
			$filename = $source['path'];
			$pos = strpos($filename, '/files', 1);
			$uid = substr($filename, 1, $pos - 1);
			$filename = substr($filename, $pos + 6);
		} else {
			$uid = \OCP\User::getUser();
		}
		return array($uid, $filename);
	}

	/**
	 * store a new version of a file.
	 */
	public function store($filename) {
		if(\OCP\Config::getSystemValue('files_versions', Storage::DEFAULTENABLED)=='true') {
			list($uid, $filename) = self::getUidAndFilename($filename);
			$files_view = new \OC_FilesystemView('/'.$uid .'/files');
			$users_view = new \OC_FilesystemView('/'.$uid);

			//check if source file already exist as version to avoid recursions.
			// todo does this check work?
			if ($users_view->file_exists($filename)) {
				return false;
			}

			// check if filename is a directory
			if($files_view->is_dir($filename)) {
				return false;
			}

			// we should have a source file to work with
			if (!$files_view->file_exists($filename)) {
				return false;
			}

			// create all parent folders
			$info=pathinfo($filename);
			if(!file_exists($versionsFolderName.'/'.$info['dirname'])) {
				mkdir($versionsFolderName.'/'.$info['dirname'], 0750, true);
			}

			// store a new version of a file
			$users_view->copy('files'.$filename, 'files_versions'.$filename.'.v'.$users_view->filemtime('files'.$filename));

			// expire old revisions if necessary
			Storage::expire($filename);
		}
	}


	/**
	 * rollback to an old version of a file.
	 */
	public static function rollback($filename, $revision) {

		if(\OCP\Config::getSystemValue('files_versions', Storage::DEFAULTENABLED)=='true') {
			list($uid, $filename) = self::getUidAndFilename($filename);
			$users_view = new \OC_FilesystemView('/'.$uid);

			//first create a new version
			if ( !$users_view->file_exists('files_versions'.$filename.'.v'.$users_view->filemtime('files'.$filename))) {
				$version = 'files_versions'.$filename.'.v'.$users_view->filemtime('files'.$filename);
				$users_view->copy('files'.$filename, 'files_versions'.$filename.'.v'.$users_view->filemtime('files'.$filename));
			}
			
			// rollback
			if( @$users_view->copy('files_versions'.$filename.'.v'.$revision, 'files'.$filename) ) {
				Storage::expire($filename);
				return true;

			}else{
				if (isset($version) ) {
					$users_view->unlink($version);
				return false;

				}
			}
		}

	}

	/**
	 * check if old versions of a file exist.
	 */
	public static function isversioned($filename) {
		if(\OCP\Config::getSystemValue('files_versions', Storage::DEFAULTENABLED)=='true') {
			list($uid, $filename) = self::getUidAndFilename($filename);
			$versions_fileview = new \OC_FilesystemView('/'.$uid.'/files_versions');

			$versionsName=\OCP\Config::getSystemValue('datadirectory').$versions_fileview->getAbsolutePath($filename);

			// check for old versions
			$matches=glob($versionsName.'.v*');
			if(count($matches)>0) {
				return true;
			}else{
				return false;
			}
		}else{
			return(false);
		}
	}


	/**
	 * @brief get a list of all available versions of a file in descending chronological order
	 * @param $filename file to find versions of, relative to the user files dir
	 * @param $count number of versions to return
	 * @returns array
	 */
	public static function getVersions( $filename, $count = 0 ) {
		if( \OCP\Config::getSystemValue('files_versions', Storage::DEFAULTENABLED)=='true' ) {
			list($uid, $filename) = self::getUidAndFilename($filename);
			$versions_fileview = new \OC_FilesystemView('/'.$uid.'/files_versions');

			$versionsName = \OCP\Config::getSystemValue('datadirectory').$versions_fileview->getAbsolutePath($filename);
			$versions = array();
			// fetch for old versions
			$matches = glob( $versionsName.'.v*' );

			sort( $matches );

			$i = 0;

			$files_view = new \OC_FilesystemView('/'.$uid.'/files');
			$local_file = $files_view->getLocalFile($filename);
			$versions_fileview = \OCP\Files::getStorage('files_versions');

			foreach( $matches as $ma ) {

				$i++;
				$versions[$i]['cur'] = 0;
				$parts = explode( '.v', $ma );
				$versions[$i]['version'] = ( end( $parts ) );
				$versions[$i]['size'] = $versions_fileview->filesize($filename.'.v'.$versions[$i]['version']);

				// if file with modified date exists, flag it in array as currently enabled version
				( \md5_file( $ma ) == \md5_file( $local_file ) ? $versions[$i]['fileMatch'] = 1 : $versions[$i]['fileMatch'] = 0 );

			}

			$versions = array_reverse( $versions );

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

				// flag the first matched file in array (which will have latest modification date) as current version
				if ( $value['fileMatch'] ) {

					$value['cur'] = 1;
					break;

				}

			}

			$versions = array_reverse( $versions );

			// only show the newest commits
			if( $count != 0 and ( count( $versions )>$count ) ) {

				$versions = array_slice( $versions, count( $versions ) - $count );

			}

			return( $versions );


		} else {

			// if versioning isn't enabled then return an empty array
			return( array() );

		}

	}

	/**
	 * @brief Erase a file's versions which exceed the set quota
	 */
	public static function expire($filename) {
		if(\OCP\Config::getSystemValue('files_versions', Storage::DEFAULTENABLED)=='true') {
			list($uid, $filename) = self::getUidAndFilename($filename);			
			$versions_fileview = new \OC_FilesystemView('/'.$uid.'/files_versions');
			
			// get available disk space for user
			$quota = \OCP\Util::computerFileSize(\OC_Preferences::getValue($uid, 'files', 'quota'));
			if ( $quota == null ) {
				$quota = \OCP\Util::computerFileSize(\OC_Appconfig::getValue('files', 'default_quota'));
			}
			if ( $quota == null ) {
				$quota = \OC_Filesystem::free_space('/');
			}

			$rootInfo = \OC_FileCache::get('', '/'. $uid . '/files');
			$free = $quota-$rootInfo['size']; // remaining free space for user

			if ( $free > 0 ) {
				$availableSpace = 100* self::DEFAULTMAXSIZE / ($quota-$rootInfo['size']); // how much space can be used for versions
			} // otherwise available space negative and we need to reach at least 0 at the end of the expiration process;
			
			$versions = Storage::getVersions($filename);
			$versions = array_reverse($versions);	// newest version first
			
			$time = time();
			$numOfVersions = count($versions);
			
			$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'];
			}
						
			$nextVersion = $versions[0]['version'] - $step;
			
			for ($i=1; $i<$numOfVersions; $i++) {
				if ( $nextInterval == -1 || $versions[$i]['version'] >= $nextInterval ) {
					if ( $versions[$i]['version'] > $nextVersion ) {
						//distance between two version to small, delete version
						$versions_fileview->unlink($filename.'.v'.$versions[$i]['version']);
						$availableSpace += $versions[$i]['size'];
					} else {
						$nextVersion = $versions[$i]['version'] - $step;
					}
				} else { // time to move on to the next interval
					$interval++;
					$step = Storage::$max_versions_per_interval[$interval]['step'];
					$nextVersion = $versions[$i]['version'] - $step;
					if ( Storage::$max_versions_per_interval[$interval]['intervalEndsAfter'] == -1 ) {
						$nextInterval = -1;
					} else {
						$nextInterval = $time - Storage::$max_versions_per_interval[$interval]['intervalEndsAfter'];
					}
				}
			}
			
			// check if enough space is available after versions are rearranged
			$versions = array_reverse( $versions ); // oldest version first
			$numOfVersions = count($versions);
			$i = 0; 
			while ($availableSpace < 0) {
				$versions_fileview->unlink($filename.'.v'.$versions[$i]['version']);
				$availableSpace += $versions[$i]['size'];
				$i++;
				if ($i = $numOfVersions-2) break; // keep at least the last version
			}
		}
	}
}