<?php
/**
 * HexaDNS - Ping/Verfügbarkeitstest API
 * 
 * Prüft die Erreichbarkeit einer Domain
 * 
 * Verwendung: GET /api/ping-check.php?domain=example.com
 */

require_once __DIR__ . '/../includes/api-helpers.php';

header('Content-Type: application/json; charset=utf-8');
header('Access-Control-Allow-Origin: *');
header('Access-Control-Allow-Methods: GET, OPTIONS');
header('Access-Control-Allow-Headers: Content-Type');

if ($_SERVER['REQUEST_METHOD'] === 'OPTIONS') {
    http_response_code(200);
    exit;
}

if (!checkApiRateLimit('ping-check')) {
    rejectApiRateLimit();
}

$domain = getValidatedDomainParam();

if ($domain === null) {
    http_response_code(400);
    echo json_encode(['error' => empty($_GET['domain']) ? 'Domain-Parameter fehlt' : 'Ungültiges Domain-Format']);
    exit;
}

$startTime = microtime(true);
$results = performConnectivityCheck($domain);
$totalTime = round((microtime(true) - $startTime) * 1000, 2);

echo json_encode([
    'success' => true,
    'domain' => $domain,
    'total_time_ms' => $totalTime,
    'timestamp' => date('Y-m-d H:i:s'),
    'results' => $results
], JSON_PRETTY_PRINT | JSON_UNESCAPED_UNICODE);

/**
 * Führt verschiedene Erreichbarkeitstests durch
 */
function performConnectivityCheck(string $domain): array {
    $results = [
        'dns_resolution' => checkDnsResolution($domain),
        'icmp_ping' => checkIcmpPing($domain),
        'http' => checkHttpConnection($domain, false),
        'https' => checkHttpConnection($domain, true),
        'overall_status' => 'offline'
    ];
    
    // Overall-Status bestimmen
    if ($results['https']['reachable'] || $results['http']['reachable']) {
        $results['overall_status'] = 'online';
    } elseif ($results['icmp_ping']['reachable']) {
        $results['overall_status'] = 'partial';
    } elseif ($results['dns_resolution']['resolved']) {
        $results['overall_status'] = 'dns_only';
    }
    
    return $results;
}

/**
 * DNS-Auflösung prüfen
 */
function checkDnsResolution(string $domain): array {
    $start = microtime(true);
    $ip = gethostbyname($domain);
    $time = round((microtime(true) - $start) * 1000, 2);
    
    $resolved = $ip !== $domain;
    
    return [
        'resolved' => $resolved,
        'ip' => $resolved ? $ip : null,
        'response_time_ms' => $time
    ];
}

/**
 * ICMP Ping (falls verfügbar)
 */
function checkIcmpPing(string $domain): array {
    $result = [
        'reachable' => false,
        'response_time_ms' => null,
        'packet_loss' => null
    ];
    
    // Versuche ping-Kommando
    $safeDomain = escapeshellarg($domain);
    $pingResult = @shell_exec("ping -c 3 -W 2 {$safeDomain} 2>/dev/null");
    
    if ($pingResult) {
        // Prüfe auf erfolgreiche Antworten
        if (preg_match('/(\d+)% packet loss/', $pingResult, $lossMatch)) {
            $result['packet_loss'] = (int)$lossMatch[1];
            $result['reachable'] = $result['packet_loss'] < 100;
        }
        
        // Durchschnittliche Zeit extrahieren
        if (preg_match('/avg.*?=.*?[\d.]+\/([\d.]+)\//', $pingResult, $timeMatch)) {
            $result['response_time_ms'] = (float)$timeMatch[1];
        } elseif (preg_match('/time[=<]([\d.]+)\s*ms/', $pingResult, $timeMatch)) {
            $result['response_time_ms'] = (float)$timeMatch[1];
        }
    }
    
    return $result;
}

/**
 * HTTP(S)-Verbindung prüfen
 */
function checkHttpConnection(string $domain, bool $https = false): array {
    $protocol = $https ? 'https' : 'http';
    $port = $https ? 443 : 80;
    $url = "{$protocol}://{$domain}";
    
    $result = [
        'reachable' => false,
        'status_code' => null,
        'response_time_ms' => null,
        'redirect_url' => null,
        'server' => null
    ];
    
    $start = microtime(true);
    
    // cURL verwenden
    $ch = curl_init();
    curl_setopt_array($ch, [
        CURLOPT_URL => $url,
        CURLOPT_RETURNTRANSFER => true,
        CURLOPT_HEADER => true,
        CURLOPT_NOBODY => true,
        CURLOPT_TIMEOUT => 10,
        CURLOPT_CONNECTTIMEOUT => 5,
        CURLOPT_FOLLOWLOCATION => false,
        CURLOPT_SSL_VERIFYPEER => false,
        CURLOPT_SSL_VERIFYHOST => 0,
        CURLOPT_USERAGENT => 'HexaDNS Ping Check/1.0'
    ]);
    
    $response = curl_exec($ch);
    $result['response_time_ms'] = round((microtime(true) - $start) * 1000, 2);
    
    if ($response !== false) {
        $result['status_code'] = curl_getinfo($ch, CURLINFO_HTTP_CODE);
        $result['reachable'] = $result['status_code'] > 0;
        
        // Redirect-URL
        $redirectUrl = curl_getinfo($ch, CURLINFO_REDIRECT_URL);
        if (!empty($redirectUrl)) {
            $result['redirect_url'] = $redirectUrl;
        }
        
        // Server-Header
        if (preg_match('/Server:\s*([^\r\n]+)/i', $response, $serverMatch)) {
            $result['server'] = trim($serverMatch[1]);
        }
    } else {
        $result['error'] = curl_error($ch);
    }
    
    curl_close($ch);
    
    return $result;
}