<?php

/**
 * Bencode
 *
 * LICENSE
 *
 * This source file is subject to the GPL license that is bundled
 * with this package in the file LICENSE.txt.
 * It is also available through the world-wide-web at this URL:
 * http://www.gnu.org/licenses/gpl.html
 * If you did not receive a copy of the license and are unable to
 * obtain it through the world-wide-web, please send an email
 * to y@dron.by so we can send you a copy immediately.
 *
 * @category   Helper
 * @package    Bencode
 * @copyright  Copyright (c) 2010 FTDeBUGgeR
 * @license    http://www.gnu.org/licenses/gpl.html     GPL License
 * @version    $Id: 20106 2010-19-06 15:06:09$
 */


class Bencode_Exception extends Exception {}

class Bencode_Decode
{
    protected
        $_data = "",
        $_position = 0,
        $_length = 0;

    /**
     * @param string $data
     * @return array
     */

    public function decodeString($data)
    {
        $this -> _data = $data;
        $this -> _position = 0;
        $this -> _length = strlen($data);

        return $this -> detect();
    }

    /**
     * @param string $file
     * @return array
     */

    public function decodeFile($file)
    {
        if (!file_exists($file))
        {
            throw new Bencode_Exception('File not found');
        }

        return $this -> decodeString(file_get_contents($file));
    }

    /**
     * @return array
     */

    protected function detect()
    {
        $char = $this -> getChar();

        if ($char == "d")
        {
            return $this -> getDictionary();
        }
        else if ($char == 'i'){
            return $this -> getInt();
        }
        else if ( is_numeric($char))
        {
            return $this -> getString();
        }
        else if ($char == "l")
        {
            return $this -> getList();
        }

        throw new Bencode_Exception('File parsing error');
    }

    /**
     * @return array
     */

    protected function getDictionary()
    {
        $dict = array();

        $this -> next();

        while( ($char = $this -> getChar()) !== "e" )
        {
            $key = $this -> getString();
            $value = $this -> detect();

            $dict[$key] = $value;
        }

        $this -> next();

        return $dict;
    }

    /**
     * @return array
     */

    protected function getList()
    {
        $dict = array();

        $this -> next();

        while( ($char = $this -> getChar()) !== "e" )
        {
            $dict[] = $this -> detect();
        }

        $this -> next();

        return $dict;
    }

    /**
     * @return string
     */

    protected function getString()
    {
        $separator = strpos($this -> _data, ":", $this -> _position);

        if ($separator === false)
        {
            throw new Bencode_Exception('Bad format');
        }

        $length = substr($this -> _data, $this -> _position, $separator - $this -> _position);

        if (! is_numeric($length))
        {
            throw new Bencode_Exception('Bad format');
        }

        $this -> _position = $separator + $length + 1;

        return substr($this -> _data, $separator + 1, $length);
    }

    /**
     * @return string
     */

    protected function getInt()
    {
        $this -> next();

        $end = strpos($this -> _data, "e", $this -> _position);

        if ($end === false)
        {
            throw new Bencode_Exception('Bad format');
        }

        $int = substr($this -> _data, $this -> _position, $end - $this -> _position);

        if (! is_numeric($int))
        {
            throw new Bencode_Exception('Bad format');
        }

        $this -> _position = $end + 1;

        return $int;
    }

    /**
     * @return string
     */

    protected function getChar()
    {
        if ($this -> _position >= $this -> _length)
        {
            throw new Bencode_Exception('EOF');
        }

        return substr($this -> _data, $this -> _position, 1);
    }

    /**
     * @param int $count
     * @return Bencode_Decode
     */

    protected function next($count = 1)
    {
        $this -> _position += $count;
        return $this;
    }
}