server {
    listen 80;
    listen [::]:80;
    server_name _;

    root /usr/share/nginx/html;
    index index.html;

    server_tokens off;

    gzip on;
    gzip_vary on;
    gzip_min_length 1024;
    gzip_proxied any;
    gzip_types
        text/plain
        text/css
        text/javascript
        application/javascript
        application/json
        application/xml
        image/svg+xml
        font/woff
        font/woff2;

    # NOTE: add_header does not inherit into a location that declares its own,
    # so the security headers are repeated in each block rather than set once
    # at server level (where they would be silently dropped).

    # Content-hashed build output. Safe to cache forever: a new deploy emits new
    # filenames, so a stale cache can never serve the wrong bundle.
    # `expires` is deliberately not used here -- it emits its own Cache-Control
    # and the two would conflict.
    location /assets/ {
        add_header Cache-Control "public, max-age=31536000, immutable" always;
        add_header X-Content-Type-Options "nosniff" always;
        access_log off;
        try_files $uri =404;
    }

    # The app shell. Must never be cached, or browsers keep booting the old
    # bundle after a deploy and users report "the update didn't work".
    location = /index.html {
        add_header Cache-Control "no-cache, no-store, must-revalidate" always;
        add_header X-Content-Type-Options "nosniff" always;
        add_header X-Frame-Options "SAMEORIGIN" always;
        add_header Referrer-Policy "strict-origin-when-cross-origin" always;
    }

    # SPA fallback. index.html carries the theme bootstrap script, so an
    # unknown route must still resolve to a normal 200 document.
    location / {
        add_header Cache-Control "no-cache" always;
        add_header X-Content-Type-Options "nosniff" always;
        add_header X-Frame-Options "SAMEORIGIN" always;
        add_header Referrer-Policy "strict-origin-when-cross-origin" always;
        try_files $uri $uri/ /index.html;
    }
}