VK_helper.php

<?php

global $n, $i, $__USER_ID;

$n = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMN0PQRSTUVWXYZO123456789+/=';
$i = [
    'v' => function ($e) {
        return strrev($e);
    },
    'r' => function ($e, $t) {
        global $n;
        $e = str_split($e);
        for ($o = $n.$n, $s = count($e); $s--;) {
            $i = stripos($o, $e[$s]);
            if (~$i) {
                $e[$s] = substr($o, $i - $t, 1);
            }
        }

        return implode('', $e);
    },
    's' => function ($e, $t) {
        $n = strlen($e);
        if ($n) {
            $i = r($e, $t);
            $o = 0;
            $e = str_split($e);
            for (; ++$o < $n;) {
                $p = array_splice($e, $i[$n - 1 - $o], 1, $e[$o]);
                $e[$o] = $p[0];
            }
            $e = implode('', $e);
        }

        return $e;
    },
    'i' => function ($e, $t) {
        global $i, $__USER_ID;
        $k = $i['s'];

        return $k($e, $t ^ $__USER_ID);
    },
];

function a($e)
{
    global $n;
    if (!$e || strlen($e) % 4 == 1) {
        return !1;
    }
    $s = 0;
    for ($o = 0, $a = ''; $s < strlen($e);) {
        $i = $e[$s++];
        $i = strpos($n, $i);
        if ($i !== false) {
            $t = ($o % 4) ? 64 * $t + $i : $i;
            if ($o++ % 4) {
                $a .= chr(255 & $t >> (-2 * $o & 6));
            }
        }
    }

    return $a;
}

function r($e, $t)
{
    $n = strlen($e);
    $i = [];
    if ($n) {
        $o = $n;
        $t = abs($t);
        for (; $o--;) {
            $t = ($n * ($o + 1) ^ $t + $o) % $n;
            $i[$o] = $t;
        }
    }

    return $i;
}

function decode($e)
{
    global $i;
    if (strpos($e, 'audio_api_unavailable') !== false) {
        $t = explode('?extra=', $e);
        $t = $t[1];
        $t = explode('#', $t);
        $n = ('' === $t[1]) ? '' : a($t[1]);
        $t = a($t[0]);
        if (!is_string($n) || !$t) {
            return $e;
        }
        $n = $n ? explode(chr(9), $n) : [];
        for ($l = count($n); $l--;) {
            $r = explode(chr(11), $n[$l]);
            $s = array_splice($r, 0, 1, $t);
            $s = $s[0];
            if (!$i[$s]) {
                return $e;
            }
            $t = $i[$s](...$r);
        }
        if ($t && 'http' === substr($t, 0, 4)) {
            return $t;
        }
    }

    return $e;
}