upstream lottery_backend {
    # Primary backend (port 8080)
    server 127.0.0.1:8080 max_fails=3 fail_timeout=30s;
    # Standby backend (port 8082) - used during rolling updates
    # Uncomment the line below to switch traffic to new backend
    # server 127.0.0.1:8082 max_fails=3 fail_timeout=30s backup;
    
    # Health check configuration
    keepalive 32;
}

server {
    listen 80;
    server_name _;

    # Increase body size limit for API requests
    client_max_body_size 10M;

    # 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;

    # API endpoints
    location /api/ {
        proxy_pass http://lottery_backend;
        proxy_http_version 1.1;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection 'upgrade';
        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_cache_bypass $http_upgrade;
        
        # Timeouts
        proxy_connect_timeout 60s;
        proxy_send_timeout 60s;
        proxy_read_timeout 60s;
    }

    # Actuator endpoints (for health checks)
    location /actuator/ {
        proxy_pass http://lottery_backend;
        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;
    }

    # Ping endpoint
    location /ping {
        proxy_pass http://lottery_backend;
        proxy_http_version 1.1;
        proxy_set_header Host $host;
    }

    # Frontend (if serving static files)
    location / {
        root /usr/share/nginx/html;
        try_files $uri $uri/ /index.html;
        index index.html;
    }
}

# HTTPS configuration (uncomment and configure when SSL certificates are available)
# server {
#     listen 443 ssl http2;
#     server_name your-domain.com;
#
#     ssl_certificate /etc/nginx/ssl/cert.pem;
#     ssl_certificate_key /etc/nginx/ssl/key.pem;
#
#     # SSL configuration
#     ssl_protocols TLSv1.2 TLSv1.3;
#     ssl_ciphers HIGH:!aNULL:!MD5;
#     ssl_prefer_server_ciphers on;
#
#     # Same location blocks as HTTP server
#     # ...
# }