<?php
/**
 * Telegram Media Proxy with cache
 *
 * GET /media.php?url=https://tg.i-c-a.su/media/CHANNEL/POSTID/HASH.ext
 *
 * Returns cached image or proxies from tg.i-c-a.su.
 * Old cache files are cleaned up probabilistically (~2% of requests).
 */

define('IMG_DIR', __DIR__ . '/cache/img');
define('TG_BASE', 'https://tg.i-c-a.su');
define('UA', 'Mozilla/5.0 (compatible; ProxyBot/1.0)');
define('MEDIA_TTL', 86400);

$url = $_GET['url'] ?? '';
if (!$url || strpos($url, TG_BASE) !== 0) {
    header('HTTP/1.1 400 Bad Request');
    echo 'Invalid URL';
    exit;
}

if (!is_dir(IMG_DIR)) mkdir(IMG_DIR, 0755, true);

// Determine cache path from URL
$path = parse_url($url, PHP_URL_PATH);
$basename = basename($path);
if (!preg_match('/\.\w+$/', $basename)) {
    $basename .= '.jpg';
}
$cacheFile = IMG_DIR . '/' . $basename;

// Content type map
$extToType = [
    'jpg'  => 'image/jpeg',
    'jpeg' => 'image/jpeg',
    'png'  => 'image/png',
    'gif'  => 'image/gif',
    'webp' => 'image/webp',
];
$ext = strtolower(pathinfo($basename, PATHINFO_EXTENSION));
$contentType = $extToType[$ext] ?? 'image/jpeg';

// Periodic cleanup (~2% of requests)
maybeCleanOldCache();

// Serve from cache if fresh
if (file_exists($cacheFile) && filemtime($cacheFile) > time() - MEDIA_TTL) {
    header('Content-Type: ' . $contentType);
    header('Content-Length: ' . filesize($cacheFile));
    header('Cache-Control: public, max-age=' . MEDIA_TTL);
    header('X-Cache: HIT');
    readfile($cacheFile);
    exit;
}

// Fetch from tg.i-c-a.su
$ctx = stream_context_create(['http' => ['timeout' => 60, 'user_agent' => UA, 'follow_location' => true]]);
$data = @file_get_contents($url, false, $ctx);

if (!$data) {
    header('HTTP/1.1 502 Bad Gateway');
    echo 'Failed to fetch media';
    exit;
}

// Verify it's actually an image before caching
$imageSignatures = [
    "\xff\xd8\xff",     // JPEG
    "\x89\x50\x4e\x47", // PNG
    "GIF87a",           // GIF
    "GIF89a",           // GIF
    "RIFF",             // WebP
];
$isImage = false;
foreach ($imageSignatures as $sig) {
    if (strncmp($data, $sig, strlen($sig)) === 0) {
        $isImage = true;
        break;
    }
}

if (!$isImage) {
    header('HTTP/1.1 415 Unsupported Media Type');
    header('Content-Type: text/plain');
    echo 'Not an image';
    exit;
}

// Save to cache
file_put_contents($cacheFile, $data);

// Return
header('Content-Type: ' . $contentType);
header('Content-Length: ' . strlen($data));
header('Cache-Control: public, max-age=' . MEDIA_TTL);
header('X-Cache: MISS');
echo $data;

// Clean files older than TTL, runs ~2% of requests
function maybeCleanOldCache(): void {
    if (rand(1, 50) !== 1) return;
    $dir = IMG_DIR;
    if (!is_dir($dir)) return;
    $cutoff = time() - MEDIA_TTL;
    $imgExts = ['jpg', 'jpeg', 'png', 'gif', 'webp'];
    $dh = opendir($dir);
    if (!$dh) return;
    while (($f = readdir($dh)) !== false) {
        if ($f === '.' || $f === '..') continue;
        $fp = $dir . '/' . $f;
        if (!is_file($fp)) continue;
        $ext = strtolower(pathinfo($fp, PATHINFO_EXTENSION));
        // Remove non-image files and files older than TTL
        if (!in_array($ext, $imgExts) || filemtime($fp) < $cutoff) {
            unlink($fp);
        }
    }
    closedir($dh);
}