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 text/javascript;
    gzip_min_length 1024;
    gzip_proxied any;
    gzip_comp_level 6;

    # 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;
    add_header Referrer-Policy "strict-origin-when-cross-origin" always;
    add_header Content-Security-Policy "default-src 'self'; script-src 'self' 'unsafe-inline' 'unsafe-eval' https://hcaptcha.com https://*.hcaptcha.com; style-src 'self' 'unsafe-inline' https://fonts.googleapis.com; img-src 'self' data: blob: https://hcaptcha.com https://*.hcaptcha.com; media-src 'self' blob:; connect-src 'self' https://hcaptcha.com https://*.hcaptcha.com; font-src 'self' https://fonts.gstatic.com; frame-src 'self' https://hcaptcha.com https://*.hcaptcha.com;" always;
    add_header Permissions-Policy "camera=(), microphone=(), geolocation=()" always;

    # API proxy to backend
    location /api/ {
        resolver 127.0.0.11 valid=10s;
        set $backend http://backend:8000;
        proxy_pass $backend;
        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;

        # Large file uploads
        client_max_body_size 500M;
        proxy_request_buffering off;
        proxy_read_timeout 600s;
    }

    # SCORM content — no frame-blocking headers, allow scripts
    location /uploads/scorm/ {
        resolver 127.0.0.11 valid=10s;
        set $backend http://backend:8000;
        proxy_pass $backend;
        proxy_set_header Host $host;
        proxy_hide_header X-Frame-Options;
        proxy_force_ranges on; # Pinned backend FileResponse does not implement byte ranges.
        # Local add_header prevents inheriting the app CSP; preserve backend SVG sandbox.
        add_header X-Content-Type-Options "nosniff" always;
    }

    # Uploaded images proxy to backend
    location /uploads/ {
        resolver 127.0.0.11 valid=10s;
        set $backend http://backend:8000;
        proxy_pass $backend;
        proxy_set_header Host $host;
        # Backend owns private/no-store and Vary; never cache protected media.
        proxy_force_ranges on;
        add_header X-Content-Type-Options "nosniff" always;
    }

    # Hashed build assets are immutable — a new build gets a new filename.
    location /assets/ {
        expires 1y;
        add_header Cache-Control "public, immutable" always;
        add_header X-Content-Type-Options "nosniff" always;
    }

    # index.html must never be cached, or a deploy keeps serving the old
    # bundle references and the app appears unchanged after a release.
    location = /index.html {
        add_header Cache-Control "no-cache, must-revalidate" always;
        add_header X-Content-Type-Options "nosniff" always;
    }

    # SPA fallback
    location / {
        add_header Cache-Control "no-cache, must-revalidate" always;
        try_files $uri $uri/ /index.html;
    }
}