<?php
/**
 * CAPTCHA antispam plugin - sound generator
 *
 * @license    GPL 2 (http://www.gnu.org/licenses/gpl.html)
 * @author     Andreas Gohr <gohr@cosmocode.de>
 */

if (!defined('DOKU_INC')) define('DOKU_INC', dirname(__FILE__) . '/../../../');
define('NOSESSION', true);
define('DOKU_DISABLE_GZIP_OUTPUT', 1);
require_once(DOKU_INC . 'inc/init.php');
require_once(DOKU_INC . 'inc/auth.php');

$ID = $_REQUEST['id'];
/** @var $plugin helper_plugin_captcha */
$plugin = plugin_load('helper', 'captcha');

if ($plugin->getConf('mode') != 'audio' && $plugin->getConf('mode') != 'svgaudio') {
    http_status(404);
    exit;
}

$rand = $plugin->decrypt($_REQUEST['secret']);
$code = strtolower($plugin->_generateCAPTCHA($plugin->_fixedIdent(), $rand));

// prepare an array of wavfiles
$lc = dirname(__FILE__) . '/lang/' . $conf['lang'] . '/audio/';
$en = dirname(__FILE__) . '/lang/en/audio/';
$wavs = array();
$lettercount = $plugin->getConf('lettercount');
if ($lettercount > strlen($code)) $lettercount = strlen($code);
for ($i = 0; $i < $lettercount; $i++) {
    $file = $lc . $code[$i] . '.wav';
    if (!@file_exists($file)) $file = $en . $code[$i] . '.wav';
    $wavs[] = $file;
}

header('Content-type: audio/x-wav');
header('Content-Disposition: attachment;filename=captcha.wav');

echo joinwavs($wavs);

/**
 * Join multiple wav files
 *
 * All wave files need to have the same format and need to be uncompressed.
 * The headers of the last file will be used (with recalculated datasize
 * of course)
 *
 * @link http://ccrma.stanford.edu/CCRMA/Courses/422/projects/WaveFormat/
 * @link http://www.thescripts.com/forum/thread3770.html
 */
function joinwavs($wavs)
{
    $fields = join(
        '/', array(
            'H8ChunkID',
            'VChunkSize',
            'H8Format',
            'H8Subchunk1ID',
            'VSubchunk1Size',
            'vAudioFormat',
            'vNumChannels',
            'VSampleRate',
            'VByteRate',
            'vBlockAlign',
            'vBitsPerSample',
        )
    );

    $data = '';
    foreach ($wavs as $wav) {
        $fp = fopen($wav, 'rb');
        $header = fread($fp, 36);
        $info = unpack($fields, $header);

        // read optional extra stuff
        if ($info['Subchunk1Size'] > 16) {
            $header .= fread($fp, ($info['Subchunk1Size'] - 16));
        }

        // read SubChunk2ID
        $header .= fread($fp, 4);

        // read Subchunk2Size
        $size = unpack('vsize', fread($fp, 4));
        $size = $size['size'];

        // read data
        $data .= fread($fp, $size);
    }

    return $header . pack('V', strlen($data)) . $data;
}