<?php
  /**
   * Copyright (c) 2013 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\Stream;
  
  /**
   * stream wrapper limits the amount of data that can be written to a stream
   *
   * usage: void \OC\Files\Stream\Quota::register($id, $stream, $limit)
   * or:    resource \OC\Files\Stream\Quota::wrap($stream, $limit)
   */
  class Quota {
  	private static $streams = array();
  
  	/**
  	 * @var resource $source
  	 */
  	private $source;
  
  	/**
  	 * @var int $limit
  	 */
  	private $limit;
  
  	/**
  	 * @param string $id
  	 * @param resource $stream
  	 * @param int $limit
  	 */
  	public static function register($id, $stream, $limit) {
  		self::$streams[$id] = array($stream, $limit);
  	}
  
  	/**
  	 * remove all registered streams
  	 */
  	public static function clear() {
  		self::$streams = array();
  	}
  
  	/**
  	 * @param resource $stream
  	 * @param int $limit
  	 * @return resource
  	 */
  	static public function wrap($stream, $limit) {
  		$id = uniqid();
  		self::register($id, $stream, $limit);
  		$meta = stream_get_meta_data($stream);
  		return fopen('quota://' . $id, $meta['mode']);
  	}
  
  	public function stream_open($path, $mode, $options, &$opened_path) {
  		$id = substr($path, strlen('quota://'));
  		if (isset(self::$streams[$id])) {
  			list($this->source, $this->limit) = self::$streams[$id];
  			return true;
  		} else {
  			return false;
  		}
  	}
  
  	public function stream_seek($offset, $whence = SEEK_SET) {
  		if ($whence === SEEK_END){
  			// go to the end to find out last position's offset
  			$oldOffset = $this->stream_tell();
  			if (fseek($this->source, 0, $whence) !== 0){
  				return false;
  			}
  			$whence = SEEK_SET;
  			$offset = $this->stream_tell() + $offset;
  			$this->limit += $oldOffset - $offset;
  		}
  		else if ($whence === SEEK_SET) {
  			$this->limit += $this->stream_tell() - $offset;
  		} else {
  			$this->limit -= $offset;
  		}
  		// this wrapper needs to return "true" for success.
  		// the fseek call itself returns 0 on succeess
  		return !fseek($this->source, $offset, $whence);
  	}
  
  	public function stream_tell() {
  		return ftell($this->source);
  	}
  
  	public function stream_read($count) {
  		$this->limit -= $count;
  		return fread($this->source, $count);
  	}
  
  	public function stream_write($data) {
  		$size = strlen($data);
  		if ($size > $this->limit) {
  			$data = substr($data, 0, $this->limit);
  			$size = $this->limit;
  		}
  		$this->limit -= $size;
  		return fwrite($this->source, $data);
  	}
  
  	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);
  	}
  
  	public function stream_close() {
  		fclose($this->source);
  	}
  }