<?php


function getApiClientIp(): string {
    if (!empty($_SERVER['HTTP_CF_CONNECTING_IP'])
        && filter_var($_SERVER['HTTP_CF_CONNECTING_IP'], FILTER_VALIDATE_IP)) {
        return $_SERVER['HTTP_CF_CONNECTING_IP'];
    }

    $remoteAddr = $_SERVER['REMOTE_ADDR'] ?? '0.0.0.0';
    $isTrustedProxy = filter_var(
        $remoteAddr,
        FILTER_VALIDATE_IP,
        FILTER_FLAG_NO_PRIV_RANGE | FILTER_FLAG_NO_RES_RANGE
    ) === false;

    if ($isTrustedProxy) {
        foreach (['HTTP_X_REAL_IP', 'HTTP_X_FORWARDED_FOR'] as $header) {
            if (empty($_SERVER[$header])) {
                continue;
            }
            $ip = trim(explode(',', $_SERVER[$header])[0]);
            if (filter_var($ip, FILTER_VALIDATE_IP)) {
                return $ip;
            }
        }
    }

    return $remoteAddr;
}


function checkApiRateLimit(string $endpoint, int $maxPerHour = 120): bool {
    $ip = getApiClientIp();
    $cacheFile = sys_get_temp_dir() . '/hexahost_api_' . md5($endpoint . '_' . $ip) . '.txt';
    $currentTime = time();
    $data = ['requests' => []];

    $handle = @fopen($cacheFile, 'c+');
    if ($handle === false) {
        return true;
    }

    try {
        if (!flock($handle, LOCK_EX)) {
            return true;
        }

        $contents = stream_get_contents($handle);
        if ($contents !== false && $contents !== '') {
            $decoded = json_decode($contents, true);
            if (is_array($decoded) && isset($decoded['requests'])) {
                $data = $decoded;
            }
        }

        $data['requests'] = array_values(array_filter(
            $data['requests'],
            static fn($timestamp) => ($currentTime - (int) $timestamp) < 3600
        ));

        if (count($data['requests']) >= $maxPerHour) {
            return false;
        }

        $data['requests'][] = $currentTime;
        ftruncate($handle, 0);
        rewind($handle);
        fwrite($handle, json_encode($data));
    } finally {
        flock($handle, LOCK_UN);
        fclose($handle);
    }

    return true;
}


function getValidatedDomainParam(string $param = 'domain'): ?string {
    if (empty($_GET[$param])) {
        return null;
    }

    $domain = trim((string) $_GET[$param]);
    $domain = preg_replace('/^(https?:\/\/)?/', '', $domain);
    $domain = explode('/', $domain)[0];
    $domain = explode(':', $domain)[0];

    if (!preg_match('/^[a-zA-Z0-9][a-zA-Z0-9\-\.]*\.[a-zA-Z]{2,}$/', $domain)) {
        return null;
    }

    return $domain;
}


function rejectApiRateLimit(): void {
    http_response_code(429);
    echo json_encode(['error' => 'Zu viele Anfragen. Bitte versuchen Sie es später erneut.']);
    exit;
}