server {
    listen 80;
    server_name _;   # accept any hostname (update to your domain for production)

    # Security headers
    add_header X-Frame-Options "SAMEORIGIN" always;
    add_header X-Content-Type-Options "nosniff" always;
    add_header Referrer-Policy "strict-origin-when-cross-origin" always;

    # Proxy to Next.js app
    location / {
        proxy_pass http://app:3000;
        proxy_http_version 1.1;

        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-Forwarded-Proto $scheme;

        # WebSocket support (for dev HMR; optional in production)
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection "upgrade";

        proxy_cache_bypass $http_upgrade;
        proxy_read_timeout 86400;
    }

    # Static file optimization
    location /_next/static {
        proxy_pass http://app:3000;
        proxy_cache_valid 200 365d;
        add_header Cache-Control "public, immutable";
    }
}