<?php
$cache = true;
$cachedir = dirname(__FILE__) . '/assets/cache';
$cssdir = dirname(__FILE__) . '/assets/css';
$jsdir = dirname(__FILE__) . '/assets/js';

// Determine the directory and type we should use
switch ($_GET['type']) {
    case 'css':
        $base = realpath($cssdir);
        break;
    case 'javascript':
        $base = realpath($jsdir);
        break;
    default:
        header("HTTP/1.0 503 Not Implemented");
        exit;
};

$type = $_GET['type'];
$elements = explode(',', $_GET['files']);

// Determine last modification date of the files
$lastmodified = 0;
while (list(, $element) = each($elements)) {
    $path = realpath($base . '/' . $element);

    if (($type == 'javascript' && substr($path, -3) != '.js') ||
        ($type == 'css' && substr($path, -4) != '.css')) {
        header("HTTP/1.0 403 Forbidden");
        exit;
    }

    if (substr($path, 0, strlen($base)) != $base || !file_exists($path)) {
        header("HTTP/1.0 404 Not Found");
        exit;
    }

    $lastmodified = max($lastmodified, filemtime($path));
}

// Send Etag hash
$hash = $lastmodified . '-' . md5($_GET['files']);
header("Etag: \"" . $hash . "\"");

if (isset($_SERVER['HTTP_IF_NONE_MATCH']) &&
    stripslashes($_SERVER['HTTP_IF_NONE_MATCH']) == '"' . $hash . '"') {
    // Return visit and no modifications, so do not send anything
    header("HTTP/1.0 304 Not Modified");
    header('Content-Length: 0');
} else {
    // First time visit or files were modified
    if ($cache) {
        // Determine supported compression method
        $gzip = strstr($_SERVER['HTTP_ACCEPT_ENCODING'], 'gzip');
        $deflate = strstr($_SERVER['HTTP_ACCEPT_ENCODING'], 'deflate');

        // Determine used compression method
        $encoding = $gzip ? 'gzip' : ($deflate ? 'deflate' : 'none');

        // Check for buggy versions of Internet Explorer
        if (!strstr($_SERVER['HTTP_USER_AGENT'], 'Opera') &&
            preg_match('/^Mozilla\/4\.0 \(compatible; MSIE ([0-9]\.[0-9])/i', $_SERVER['HTTP_USER_AGENT'], $matches)) {
            $version = floatval($matches[1]);

            if ($version < 6)
                $encoding = 'none';

            if ($version == 6 && !strstr($_SERVER['HTTP_USER_AGENT'], 'EV1'))
                $encoding = 'none';
        }

        // Try the cache first to see if the combined files were already generated
        $cachefile = 'cache-' . $hash . '.' . $type . ($encoding != 'none' ? '.' . $encoding : '');

        if (file_exists($cachedir . '/' . $cachefile)) {
            if ($fp = fopen($cachedir . '/' . $cachefile, 'rb')) {

                if ($encoding != 'none') {
                    header("Content-Encoding: " . $encoding);
                }

                header("Content-Type: text/" . $type);
                header("Content-Length: " . filesize($cachedir . '/' . $cachefile));

                fpassthru($fp);
                fclose($fp);
                exit;
            }
        }
    }

    // Get contents of the files
    $contents = '';
    reset($elements);
    while (list(, $element) = each($elements)) {
        $path = realpath($base . '/' . $element);
        $contents .= "\n\n" . file_get_contents($path);
//        $contents = fn_minify_css($contents);
    }

    // Send Content-Type
    header("Content-Type: text/" . $type);

    if (isset($encoding) && $encoding != 'none') {
        // Send compressed contents
        $contents = gzencode($contents, 9, $gzip ? FORCE_GZIP : FORCE_DEFLATE);
        header("Content-Encoding: " . $encoding);
        header('Content-Length: ' . strlen($contents));
        echo $contents;
    } else {
        // Send regular contents
        header('Content-Length: ' . strlen($contents));
        echo $contents;
    }
    echo strlen($contents);

    // Store cache
    if ($cache) {
        if ($fp = fopen($cachedir . '/' . $cachefile, 'wb')) {
            fwrite($fp, $contents);
            fclose($fp);
        }
    }
}

define('MINIFY_STRING', '"(?:[^"\\\]|\\\.)*"|\'(?:[^\'\\\]|\\\.)*\'');
define('MINIFY_COMMENT_CSS', '/\*[\s\S]*?\*/');
define('MINIFY_COMMENT_HTML', '<!\-{2}[\s\S]*?\-{2}>');
define('X', "\x1A");

function n($s)
{
    return str_replace(["\r\n", "\r"], "\n", $s);
}

function t($a, $b)
{
    if ($a && strpos($a, $b) === 0 && substr($a, -strlen($b)) === $b) {
        return substr(substr($a, strlen($b)), 0, -strlen($b));
    }
    return $a;
}

function fn_minify($pattern, $input)
{
    return preg_split('#(' . implode('|', $pattern) . ')#', $input, -1, PREG_SPLIT_NO_EMPTY | PREG_SPLIT_DELIM_CAPTURE);
}

function fn_minify_css($input, $comment = 2, $quote = 2)
{
    if (!is_string($input) || !$input = n(trim($input))) return $input;
    $output = $prev = "";
    foreach (fn_minify([MINIFY_COMMENT_CSS, MINIFY_STRING], $input) as $part) {
        if (trim($part) === "") continue;
        if ($comment !== 1 && strpos($part, '/*') === 0 && substr($part, -2) === '*/') {
            if (
                $comment === 2 && (
                    // Detect special comment(s) from the third character. It should be a `!` or `*` → `/*! keep */` or `/** keep */`
                    strpos('*!', $part[2]) !== false ||
                    // Detect license comment(s) from the content. It should contains character(s) like `@license`
                    stripos($part, '@licence') !== false || // noun
                    stripos($part, '@license') !== false || // verb
                    stripos($part, '@preserve') !== false
                )
            ) {
                $output .= $part;
            }
            continue;
        }
        if ($part[0] === '"' && substr($part, -1) === '"' || $part[0] === "'" && substr($part, -1) === "'") {
            // Remove quote(s) where possible …
            $q = $part[0];
            if (
                $quote !== 1 && (
                    // <https://www.w3.org/TR/CSS2/syndata.html#uri>
                    substr($prev, -4) === 'url(' && preg_match('#\burl\($#', $prev) ||
                    // <https://www.w3.org/TR/CSS2/syndata.html#characters>
                    substr($prev, -1) === '=' && preg_match('#^' . $q . '[a-zA-Z_][\w-]*?' . $q . '$#', $part)
                )
            ) {
                $part = t($part, $q); // trim quote(s)
            }
            $output .= $part;
        } else {
            $output .= fn_minify_css_union($part);
        }
        $prev = $part;
    }
    return trim($output);
}

function fn_minify_css_union($input)
{
    if (stripos($input, 'calc(') !== false) {
        // Keep important white–space(s) in `calc()`
        $input = preg_replace_callback('#\b(calc\()\s*(.*?)\s*\)#i', function ($m) {
            return $m[1] . preg_replace('#\s+#', X, $m[2]) . ')';
        }, $input);
    }
    $input = preg_replace([
        // Fix case for `#foo<space>[bar="baz"]`, `#foo<space>*` and `#foo<space>:first-child` [^1]
        '#(?<=[\w])\s+(\*|\[|:[\w-]+)#',
        // Fix case for `[bar="baz"]<space>.foo`, `*<space>.foo`, `:nth-child(2)<space>.foo` and `@media<space>(foo: bar)<space>and<space>(baz: qux)` [^2]
        '#([*\]\)])\s+(?=[\w\#.])#', '#\b\s+\(#', '#\)\s+\b#',
        // Minify HEX color code … [^3]
        '#\#([a-f\d])\1([a-f\d])\2([a-f\d])\3\b#i',
        // Remove white–space(s) around punctuation(s) [^4]
        '#\s*([~!@*\(\)+=\{\}\[\]:;,>\/])\s*#',
        // Replace zero unit(s) with `0` [^5]
        '#\b(?<!\d\.)(?:0+\.)?0+(?:[a-z]+\b)#i',
        // Replace `0.6` with `.6` [^6]
        '#\b0+\.(\d+)#',
        // Replace `:0 0`, `:0 0 0` and `:0 0 0 0` with `:0` [^7]
        '#:(0\s+){0,3}0(?=[!,;\)\}]|$)#',
        // Replace `background(?:-position)?:(0|none)` with `background$1:0 0` [^8]
        '#\b(background(?:-position)?):(?:0|none)([;,\}])#i',
        // Replace `(border(?:-radius)?|outline):none` with `$1:0` [^9]
        '#\b(border(?:-radius)?|outline):none\b#i',
        // Remove empty selector(s) [^10]
        '#(^|[\{\}])(?:[^\{\}]+)\{\}#',
        // Remove the last semi–colon and replace multiple semi–colon(s) with a semi–colon [^11]
        '#;+([;\}])#',
        // Replace multiple white–space(s) with a space [^12]
        '#\s+#'
    ], [
        // [^1]
        X . '$1',
        // [^2]
        '$1' . X, X . '(', ')' . X,
        // [^3]
        '#$1$2$3',
        // [^4]
        '$1',
        // [^5]
        '0',
        // [^6]
        '.$1',
        // [^7]
        ':0',
        // [^8]
        '$1:0 0$2',
        // [^9]
        '$1:0',
        // [^10]
        '$1',
        // [^11]
        '$1',
        // [^12]
        ' '
    ], $input);
    return trim(str_replace(X, ' ', $input));
}