server {

    # MIME types for PWA
    include mime.types;
    types {
       application/manifest+json  webmanifest;
    }

    listen 80;
    server_name localhost;
    root /usr/share/nginx/html;
    index index.html;

    # Trust proxy headers from Caddy/upstream proxy
    set_real_ip_from 0.0.0.0/0;
    real_ip_header X-Forwarded-For;
    real_ip_recursive on;

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

    # Enable gzip compression
    gzip on;
    gzip_vary on;
    gzip_min_length 1024;
    gzip_proxied expired no-cache no-store private auth;
    gzip_types text/plain text/css text/xml text/javascript application/javascript application/xml+rss application/json application/manifest+json image/svg+xml;

    # Service worker - no cache, must revalidate
    location ~ ^/(sw\.js|workbox-.*\.js)$ {
        add_header Cache-Control "no-cache, no-store, must-revalidate" always;
        add_header Pragma "no-cache" always;
        add_header Expires "0" always;
        add_header Service-Worker-Allowed "/" always;
        types {
            application/javascript js;
        }
    }

    # PWA manifest - short cache with revalidation
    location ~ ^/manifest\.webmanifest$ {
        add_header Cache-Control "public, max-age=3600, must-revalidate" always;
        types {
            application/manifest+json webmanifest;
        }
    }

    # Handle client-side routing (SPA)
    location / {
        autoindex off;
        expires off;
        add_header Cache-Control "public, max-age=0, s-maxage=0, must-revalidate" always;
        try_files $uri $uri/ /index.html =404;
    }

    # API proxy to backend (configurable via API_BACKEND_URL env var)
    location /api/ {
        proxy_pass ${API_BACKEND_URL};
        proxy_set_header Host $http_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 $http_x_forwarded_proto;
        proxy_set_header X-Forwarded-Host $http_x_forwarded_host;
        proxy_redirect off;

        # Timeouts
        proxy_connect_timeout 60s;
        proxy_send_timeout 60s;
        proxy_read_timeout 60s;
    }

    # Cache static assets with immutable flag
    location ~* \.(css|js)$ {
        expires 1y;
        add_header Cache-Control "public, immutable" always;
        access_log off;
    }

    # Cache images and icons
    location ~* \.(png|jpg|jpeg|gif|ico|svg|webp)$ {
        expires 1y;
        add_header Cache-Control "public, immutable" always;
        access_log off;
    }

    # Cache fonts (if any are added later)
    location ~* \.(woff|woff2|ttf|eot|otf)$ {
        expires 1y;
        add_header Cache-Control "public, immutable" always;
        add_header Access-Control-Allow-Origin "*" always;
        access_log off;
    }

    # Other static files
    location ~* \.(xml|txt)$ {
        expires 1d;
        add_header Cache-Control "public, must-revalidate" always;
    }
}