// GDV Bridge Server - server.js
// Empfängt POST-Anfragen mit XML-Body und leitet sie per TCP an den GDV-Server weiter
// Installation: node server.js (Port 8080)

const http = require('http');
const net = require('net');

const PORT = process.env.PORT || 8080;
const GDV_HOST = process.env.GDV_HOST || '10.0.0.1'; // GDV-Server IP (hinter VPN)
const GDV_PORT = parseInt(process.env.GDV_PORT || '7302'); // GDV TCP-Port

const server = http.createServer((req, res) => {
  if (req.method === 'GET' && req.url === '/health') {
    res.writeHead(200, { 'Content-Type': 'application/json' });
    res.end(JSON.stringify({ status: 'ok', gdvTarget: GDV_HOST + ':' + GDV_PORT }));
    return;
  }

  if (req.method !== 'POST' || req.url !== '/check') {
    res.writeHead(405, { 'Content-Type': 'application/json' });
    res.end(JSON.stringify({ error: 'Nur POST /check erlaubt' }));
    return;
  }

  let body = '';
  req.on('data', chunk => { body += chunk.toString(); });

  req.on('end', () => {
    console.log('[Bridge] Anfrage empfangen, Länge:', body.length, 'bytes');
    console.log('[Bridge] Leite weiter an GDV:', GDV_HOST + ':' + GDV_PORT);

    const socket = new net.Socket();
    let responseData = '';
    let responded = false;

    const timeout = setTimeout(() => {
      if (!responded) {
        responded = true;
        socket.destroy();
        res.writeHead(504, { 'Content-Type': 'application/json' });
        res.end(JSON.stringify({ error: 'GDV-Server Timeout nach 15s' }));
      }
    }, 15000);

    socket.connect(GDV_PORT, GDV_HOST, () => {
      console.log('[Bridge] TCP-Verbindung zu GDV hergestellt');
      // XML mit Längenpräfix senden (GDV-Protokoll)
      const xmlBytes = Buffer.from(body, 'utf8');
      const lengthBuf = Buffer.alloc(4);
      lengthBuf.writeUInt32BE(xmlBytes.length, 0);
      socket.write(Buffer.concat([lengthBuf, xmlBytes]));
    });

    socket.on('data', data => {
      responseData += data.toString();
      // Prüfen ob vollständige XML-Antwort empfangen (enthält </Response> oder </ResponsibleInsuranceResponse>)
      if (responseData.includes('</Response>') || responseData.includes('</ResponsibleInsuranceResponse>')) {
        if (!responded) {
          responded = true;
          clearTimeout(timeout);
          socket.destroy();
          console.log('[Bridge] Antwort von GDV erhalten, sende zurück');
          res.writeHead(200, { 'Content-Type': 'application/xml; charset=UTF-8' });
          // Ersten 4 Bytes (Längenpräfix) überspringen falls vorhanden
          const cleanResponse = responseData.replace(/^[\x00-\x1F]{4}/, '');
          res.end(cleanResponse);
        }
      }
    });

    socket.on('error', err => {
      if (!responded) {
        responded = true;
        clearTimeout(timeout);
        console.error('[Bridge] TCP-Fehler:', err.message);
        res.writeHead(502, { 'Content-Type': 'application/json' });
        res.end(JSON.stringify({ error: 'GDV-TCP-Fehler: ' + err.message }));
      }
    });

    socket.on('close', () => {
      if (!responded && responseData) {
        responded = true;
        clearTimeout(timeout);
        res.writeHead(200, { 'Content-Type': 'application/xml; charset=UTF-8' });
        const cleanResponse = responseData.replace(/^[\x00-\x1F]{4}/, '');
        res.end(cleanResponse);
      }
    });
  });
});

server.listen(PORT, () => {
  console.log('[Bridge] GDV-Bridge läuft auf Port', PORT);
  console.log('[Bridge] Ziel-GDV-Server:', GDV_HOST + ':' + GDV_PORT);
});

# /etc/systemd/system/gdv-bridge.service
[Unit]
Description=GDV Bridge Server
After=network.target

[Service]
Type=simple
User=root
WorkingDirectory=/opt/gdv-bridge
Environment=PORT=8080
Environment=GDV_HOST=10.0.0.1
Environment=GDV_PORT=7302
ExecStart=/usr/bin/node server.js
Restart=always
RestartSec=5

[Install]
WantedBy=multi-user.target

# Auf dem Hetzner-Server ausführen:
mkdir -p /opt/gdv-bridge
cd /opt/gdv-bridge

# server.js erstellen (Inhalt aus dem Code-Block oben kopieren)
nano server.js

# systemd-Service einrichten
nano /etc/systemd/system/gdv-bridge.service
# (Inhalt aus dem Service-Block oben, GDV_HOST anpassen!)

# Service aktivieren & starten
systemctl daemon-reload
systemctl enable gdv-bridge
systemctl restart gdv-bridge

# Status prüfen
systemctl status gdv-bridge

# Verbindungstest (vom Server aus):
curl -X GET http://localhost:8080/health