<?
class BEncode {
    /**
    * Encode a var in BEncode format
    *
    * @param mixed    Variable to encode
    * @return string
    * @throws File_Bittorrent2_Exception if unsupported type should be encoded
    */
    function encode($mixed)
    {
        switch (gettype($mixed)) {
        case is_null($mixed):
            return $this->encode_string('');
        case 'string':
            return $this->encode_string($mixed);
        case 'integer':
        case 'double':
            return  $this->encode_int(round($mixed));
        case 'array':
            return $this->encode_array($mixed);
        default:
			print ('Unsupported type. Variable must be one of \'string\', \'integer\', \'double\' or \'array\''."\n");
        }
    }

    /**
    * BEncodes a string
    *
    * Strings are prefixed with their length followed by a colon.
    * For example, "Monduna" would bEncode to 7:Monduna and "BitTorrents"
    * would bEncode to 11:BitTorrents.
    *
    * @param string
    * @return string
    */
    function encode_string($str)
    {
        return strlen($str) . ':' . $str;
    }

    /**
    * BEncodes a integer
    *
    * Integers are prefixed with an i and terminated by an e. For
    * example, 123 would bEcode to i123e, -3272002 would bEncode to
    * i-3272002e.
    *
    * @param int
    * @return string
    */
    function encode_int($int)
    {
        return 'i' . $int . 'e';
    }

    /**
    * BEncodes an array
    * This code assumes arrays with purely integer indexes are lists,
    * arrays which use string indexes assumed to be dictionaries.
    *
    * Dictionaries are prefixed with a d and terminated by an e. They
    * are similar to list, except that items are in key value pairs. The
    * dictionary {"key":"value", "Monduna":"com", "bit":"Torrents", "number":7}
    * would bEncode to d3:key5:value7:Monduna3:com3:bit:8:Torrents6:numberi7ee
    *
    * Lists are prefixed with a l and terminated by an e. The list
    * should contain a series of bEncoded elements. For example, the
    * list of strings ["Monduna", "Bit", "Torrents"] would bEncode to
    * l7:Monduna3:Bit8:Torrentse. The list [1, "Monduna", 3, ["Sub", "List"]]
    * would bEncode to li1e7:Mondunai3el3:Sub4:Listee
    *
    * @param array
    * @return string
    */
    function encode_array(array $array)
    {
        // Check for strings in the keys
        $isList = true;
        foreach (array_keys($array) as $key) {
            if (!is_int($key)) {
                $isList = false;
                break;
            }
        }
        if ($isList) {
            // Wie build a list
            ksort($array, SORT_NUMERIC);
            $return = 'l';
            foreach ($array as $val) {
                $return .= $this->encode($val);
            }
            $return .= 'e';
        } else {
            // We build a Dictionary
            ksort($array, SORT_STRING);
            $return = 'd';
            foreach ($array as $key => $val) {
                $return .= $this->encode(strval($key));
                $return .= $this->encode($val);
            }
            $return .= 'e';
        }
        return $return;
    }
}
?>