events {
    worker_connections 1024;
}

http {
    include /etc/nginx/mime.types;
    default_type application/octet-stream;

    # Use Docker's internal DNS resolver with short TTL to handle container IP changes
    resolver 127.0.0.11 valid=10s ipv6=off;

    # Rate limiting
    limit_req_zone $binary_remote_addr zone=general:10m rate=10r/s;
    limit_req_zone $binary_remote_addr zone=auth:10m rate=10r/s;

    server {
        listen 80;
        server_name localhost;

        # Security headers
        add_header X-Frame-Options "SAMEORIGIN" always;
        add_header X-Content-Type-Options "nosniff" always;
        add_header X-XSS-Protection "1; mode=block" always;
        add_header Referrer-Policy "strict-origin-when-cross-origin" always;

        # Frontend — serve static files directly, fall back to index.html for SPA routes
        root /usr/share/nginx/html;
        index index.html;

        location / {
            limit_req zone=general burst=20 nodelay;
            try_files $uri $uri/ /index.html;
        }

        # Backend API
        location /api/ {
            limit_req zone=general burst=20 nodelay;
            set $backend_upstream http://backend:3001;
            proxy_pass $backend_upstream;
            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;
            proxy_http_version 1.1;
            proxy_set_header Connection "";
        }

        # Auth endpoints - stricter rate limiting
        location /api/auth/ {
            limit_req zone=auth burst=5 nodelay;
            set $backend_upstream http://backend:3001;
            proxy_pass $backend_upstream;
            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;
        }

        # Health check
        location /health {
            set $backend_upstream http://backend:3001;
            proxy_pass $backend_upstream/api/health;
            access_log off;
        }
    }
}