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

    # Gzip compression
    gzip on;
    gzip_vary on;
    gzip_min_length 1024;
    gzip_types text/plain text/css text/xml text/javascript application/javascript application/xml+rss application/json;

    # Security headers.
    # NOTE: nginx does not inherit `add_header` into a location that declares its
    # own add_header, so the asset/worker locations below repeat them.
    add_header X-Frame-Options "SAMEORIGIN" always;
    add_header X-Content-Type-Options "nosniff" always;
    add_header X-XSS-Protection "1; mode=block" always;

    # PDF.js worker: serve the tracked .mjs with a JS MIME type
    location = /pdf.worker.min.mjs {
        default_type application/javascript;
        expires 1y;
        add_header Cache-Control "public, immutable";
        add_header X-Content-Type-Options "nosniff" always;
    }

    # Hashed assets are immutable (safe to cache for a long time)
    location ~* \.(js|mjs|css|png|jpg|jpeg|gif|ico|svg|woff|woff2|ttf|eot)$ {
        expires 1y;
        add_header Cache-Control "public, immutable";
        add_header X-Content-Type-Options "nosniff" always;
    }

    # SPA shell: never cache it, it references hashed chunks removed on deploy.
    # `expires -1` emits `Cache-Control: no-cache` without using add_header, so
    # the server-level security headers above are still inherited.
    location = /index.html {
        expires -1;
    }

    # All routes fall back to index.html (SPA)
    location / {
        expires -1;
        try_files $uri $uri/ /index.html;
    }
}