<?php
declare(strict_types=1);

function fail_json(int $status, string $message): never {
    http_response_code($status);
    header('Content-Type: application/json; charset=utf-8');
    header('Cache-Control: no-store');
    echo json_encode(['error' => $message, 'serverTime' => (int) round(microtime(true) * 1000)], JSON_UNESCAPED_UNICODE | JSON_UNESCAPED_SLASHES);
    exit;
}

$portFile = __DIR__ . DIRECTORY_SEPARATOR . '.linkfield-port';
if (!is_file($portFile)) {
    fail_json(503, 'LinkField server is not running. Run npm start in this directory.');
}
$portText = trim((string) @file_get_contents($portFile));
$port = filter_var($portText, FILTER_VALIDATE_INT, ['options' => ['min_range' => 1, 'max_range' => 65535]]);
if ($port === false) {
    fail_json(503, 'LinkField server port information is invalid. Restart npm start.');
}

$targetPath = isset($_GET['path']) ? (string) $_GET['path'] : '';
if (!preg_match('#^/api/(?:cloud|player|realtime)(?:/|$)#', $targetPath)) {
    fail_json(400, 'Invalid LinkField API path.');
}
$query = $_GET;
unset($query['path']);
if ($query) {
    $targetPath .= '?' . http_build_query($query, '', '&', PHP_QUERY_RFC3986);
}

$method = strtoupper((string) ($_SERVER['REQUEST_METHOD'] ?? 'GET'));
if (!in_array($method, ['GET', 'POST', 'HEAD'], true)) {
    fail_json(405, 'Method not allowed.');
}
$body = file_get_contents('php://input');
if ($body === false) $body = '';
if (strlen($body) > 64 * 1024 * 1024) {
    fail_json(413, 'Request body is too large.');
}

$authorization = '';
if (function_exists('getallheaders')) {
    $headers = getallheaders();
    if (is_array($headers)) {
        foreach ($headers as $name => $value) {
            if (strcasecmp((string) $name, 'Authorization') === 0) $authorization = (string) $value;
            if (strcasecmp((string) $name, 'X-LinkField-Authorization') === 0 && $authorization === '') $authorization = (string) $value;
        }
    }
}
if ($authorization === '') {
    $authorization = (string) ($_SERVER['HTTP_AUTHORIZATION'] ?? $_SERVER['REDIRECT_HTTP_AUTHORIZATION'] ?? $_SERVER['HTTP_X_LINKFIELD_AUTHORIZATION'] ?? '');
}

$socket = @stream_socket_client(
    'tcp://127.0.0.1:' . $port,
    $errorNumber,
    $errorMessage,
    3,
    STREAM_CLIENT_CONNECT
);
if (!is_resource($socket)) {
    fail_json(502, 'LinkField server is not reachable on its local port. Restart npm start.');
}
stream_set_timeout($socket, 15);

$requestHeaders = [
    $method . ' ' . $targetPath . " HTTP/1.1",
    'Host: 127.0.0.1:' . $port,
    'Connection: close',
    'Accept: application/json',
    'Content-Type: application/json',
    'Content-Length: ' . strlen($body),
];
if ($authorization !== '') $requestHeaders[] = 'Authorization: ' . str_replace(["\r", "\n"], '', $authorization);
$request = implode("\r\n", $requestHeaders) . "\r\n\r\n" . $body;
$written = 0;
$length = strlen($request);
while ($written < $length) {
    $result = fwrite($socket, substr($request, $written));
    if ($result === false || $result === 0) {
        fclose($socket);
        fail_json(502, 'Failed to send the request to the LinkField server.');
    }
    $written += $result;
}
$response = stream_get_contents($socket);
$meta = stream_get_meta_data($socket);
fclose($socket);
if ($response === false || $response === '' || !empty($meta['timed_out'])) {
    fail_json(504, 'LinkField server did not respond in time.');
}

$separator = strpos($response, "\r\n\r\n");
if ($separator === false) fail_json(502, 'Invalid response from the LinkField server.');
$headerText = substr($response, 0, $separator);
$responseBody = substr($response, $separator + 4);
$headerLines = explode("\r\n", $headerText);
$statusLine = array_shift($headerLines);
if (!preg_match('#^HTTP/\d(?:\.\d)?\s+(\d{3})#', (string) $statusLine, $statusMatch)) {
    fail_json(502, 'Invalid status from the LinkField server.');
}
http_response_code((int) $statusMatch[1]);
foreach ($headerLines as $line) {
    $colon = strpos($line, ':');
    if ($colon === false) continue;
    $name = trim(substr($line, 0, $colon));
    $value = trim(substr($line, $colon + 1));
    if (in_array(strtolower($name), ['content-type', 'cache-control', 'x-content-type-options'], true)) {
        header($name . ': ' . $value, true);
    }
}
header('X-LinkField-Bridge: php', true);
if ($method !== 'HEAD') echo $responseBody;