server {
    listen 80;
    server_name _;
    root /usr/share/nginx/html;
    index index.html;

    # Gzip compression
    gzip on;
    gzip_types text/plain text/css application/json application/javascript text/xml application/xml application/xml+rss text/javascript;

    # Main location - no cache for HTML
    location / {
        try_files $uri $uri/ /index.html;
        add_header Cache-Control "no-cache, no-store, must-revalidate";
        add_header Pragma "no-cache";
        add_header Expires "0";
    }

    # API proxy to backend service
    # For Kubernetes: set BACKEND_HOST env var or use service name
    # For Docker Compose: backend service name is 'backend'
    location /api/ {
        # Docker's embedded DNS server
        resolver 127.0.0.11 valid=30s;
        
        # In Kubernetes, this will be: oramap-backend:3000
        # In Docker Compose, this will be: backend:3000
        # Default to backend:3000
        set $backend_host backend;
        if ($http_x_backend_host != "") {
            set $backend_host $http_x_backend_host;
        }
        
        proxy_pass http://$backend_host:3000;
        proxy_http_version 1.1;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection 'upgrade';
        proxy_set_header Host $host;
        proxy_cache_bypass $http_upgrade;
        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;
    }

    # No cache for CSS and JS to allow quick updates
    location ~* \.(css|js)$ {
        add_header Cache-Control "no-cache, no-store, must-revalidate";
        add_header Pragma "no-cache";
        add_header Expires "0";
    }

    # Cache images only
    location ~* \.(jpg|jpeg|png|gif|ico|svg)$ {
        expires 7d;
        add_header Cache-Control "public, max-age=604800";
    }
}