events {
    worker_connections 1024;
}

http {
    # Upstream API servers - Docker will resolve 'api' to all instances
    upstream api_servers {
        # Load balancing method: least_conn sends to least busy server
        # Other options: round_robin (default), ip_hash, random
        least_conn;

        # Docker Compose service discovery
        server api:8000;

        # When scaling manually, you'd list servers like:
        # server api_1:8000;
        # server api_2:8000;
        # server api_3:8000;
    }

    # Rate limiting zone: 10 requests per second per IP
    limit_req_zone $binary_remote_addr zone=api_limit:10m rate=10r/s;

    server {
        listen 80;
        server_name localhost;

        # Health check endpoint
        location /health {
            access_log off;
            return 200 "OK\n";
            add_header Content-Type text/plain;
        }

        # API endpoints
        location / {
            # Apply rate limiting with burst
            limit_req zone=api_limit burst=20 nodelay;

            proxy_pass http://api_servers;
            proxy_http_version 1.1;

            # Pass client info to backend
            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;

            # Timeouts
            proxy_connect_timeout 5s;
            proxy_send_timeout 10s;
            proxy_read_timeout 10s;
        }
    }
}