<?php
/**
 * ownCloud
 *
 * @author Robin Appelman
 * @copyright 2011 Robin Appelman icewind1991@gmail.com
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU AFFERO GENERAL PUBLIC LICENSE
 * License as published by the Free Software Foundation; either
 * version 3 of the License, or any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU AFFERO GENERAL PUBLIC LICENSE for more details.
 *
 * You should have received a copy of the GNU Affero General Public
 * License along with this library.  If not, see <http://www.gnu.org/licenses/>.
 *
 */

/**
 * transparently encrypted filestream
 *
 * you can use it as wrapper around an existing stream by setting CryptStream::$sourceStreams['foo']=array('path'=>$path,'stream'=>$stream)
 *   and then fopen('crypt://streams/foo');
 */

namespace OCA_Encryption;

class Stream {

	public static $sourceStreams = array();
	private $source;
	private $path;
	private $readBuffer; // For streams that dont support seeking
	private $meta = array(); // Header / meta for source stream
	private $count;
	private $writeCache;
	private $size;
	private static $view;

	public function stream_open( $path, $mode, $options, &$opened_path ) {
	
		// Get access to filesystem via filesystemview object
		if ( !self::$view ) {

			self::$view = new \OC_FilesystemView( '' );

		}
		
		// Get the bare file path
		$path = str_replace( 'crypt://', '', $path );

		if ( 
		dirname( $path ) == 'streams' 
		and isset( self::$sourceStreams[basename( $path )] ) 
		) {

			$this->source = self::$sourceStreams[basename( $path )]['stream'];

			$this->path = self::$sourceStreams[basename( $path )]['path'];

			$this->size = self::$sourceStreams[basename( $path )]['size'];

		} else {

			if ( 
			$mode == 'w' 
			or $mode == 'w+' 
			or $mode == 'wb' 
			or $mode == 'wb+' 
			) {

				$this->size = 0;

			} else {

				$this->size = self::$view->filesize( $path, $mode );

			}

			// Disable fileproxies so we can open the source file without recursive encryption
			\OC_FileProxy::$enabled = false;

			$this->source = self::$view->fopen( $path, $mode );

			\OC_FileProxy::$enabled = true;

			if ( !is_resource( $this->source ) ) {

				\OCP\Util::writeLog( 'files_encryption','failed to open '.$path,OCP\Util::ERROR );

			}

		}

		if ( is_resource( $this->source ) ) {

			$this->meta = stream_get_meta_data( $this->source );

		}

		return is_resource( $this->source );

	}
	
	public function stream_seek($offset, $whence=SEEK_SET) {
		$this->flush();
		fseek($this->source,$offset,$whence);
	}
	
	public function stream_tell() {
		return ftell($this->source);
	}
	
	public function stream_read($count) {
		//$count will always be 8192 https://bugs.php.net/bug.php?id=21641
		//This makes this function a lot simpler but will breake everything the moment it's fixed
		$this->writeCache='';
		if ($count!=8192) {
			OCP\Util::writeLog('files_encryption','php bug 21641 no longer holds, decryption will not work',OCP\Util::FATAL);
			die();
		}
		$pos=ftell($this->source);
		$data=fread($this->source,8192);
		if (strlen($data)) {
			$result=Crypt::decrypt($data);
		}else{
			$result='';
		}
		$length=$this->size-$pos;
		if ($length<8192) {
			$result=substr($result,0,$length);
		}
		return $result;
	}
	
	/**
	 * @brief 
	 */
	public function stream_write( $data ) {

		$length = strlen( $data );

		$written = 0;

		$currentPos = ftell( $this->source );
		
		# TODO: Move this user call out of here - it belongs elsewhere
		$user = \OCP\User::getUser();
		
		if ( self::$view->file_exists( $this->path . $user ) ) {
		
			$key = Keymanager::getFileKey( $this->path . $user );
			
		} else {
		
			$key = Crypt::generateKey();
			
			Keymanager::setFileKey( $path, $key, new \OC_FilesystemView );
			
		}

		if ( $this->writeCache ) {

			$data = $this->writeCache . $data;

			$this->writeCache = '';

		}
		
		// Make sure we always start on a block start
		if ( $currentPos % 8192 != 0 ) {

			fseek( $this->source, - ( $currentPos % 8192 ), SEEK_CUR );

			$encryptedBlock = fread( $this->source, 8192 );

			fseek( $this->source, - ( $currentPos % 8192 ), SEEK_CUR );

			$block = Crypt::symmetricDecryptFileContent( $encryptedBlock, $key );

			$data = substr( $block, 0, $currentPos % 8192 ) . $data;

			fseek( $this->source, - ( $currentPos % 8192 ), SEEK_CUR );

		}

		$currentPos = ftell( $this->source );

		while( $remainingLength = strlen( $data )>0 ) {

			if ( $remainingLength<8192 ) {

				$this->writeCache = $data;

				$data = '';

			} else {

				$encrypted = Crypt::symmetricBlockEncryptFileContent( $data, $key );
				
				fwrite( $this->source . $user, $encrypted );

				$data = substr( $data,8192 );

			}

		}

		$this->size = max( $this->size, $currentPos + $length );

		return $length;

	}


	public function stream_set_option($option,$arg1,$arg2) {
		switch($option) {
			case STREAM_OPTION_BLOCKING:
				stream_set_blocking($this->source,$arg1);
				break;
			case STREAM_OPTION_READ_TIMEOUT:
				stream_set_timeout($this->source,$arg1,$arg2);
				break;
			case STREAM_OPTION_WRITE_BUFFER:
				stream_set_write_buffer($this->source,$arg1,$arg2);
		}
	}

	public function stream_stat() {
		return fstat($this->source);
	}
	
	public function stream_lock($mode) {
		flock($this->source,$mode);
	}
	
	public function stream_flush() {
		return fflush($this->source);
	}

	public function stream_eof() {
		return feof($this->source);
	}

	private function flush() {
		if ($this->writeCache) {
			$encrypted=Crypt::encrypt($this->writeCache);
			fwrite($this->source,$encrypted);
			$this->writeCache='';
		}
	}

	public function stream_close() {
		$this->flush();
		if ($this->meta['mode']!='r' and $this->meta['mode']!='rb') {
			OC_FileCache::put($this->path,array('encrypted'=>true,'size'=>$this->size),'');
		}
		return fclose($this->source);
	}
}