map $http_upgrade $connection_upgrade {
    default upgrade;
    ''      close;
}

server {
    listen 80;
    server_name _;

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

    # Security headers
    add_header X-Frame-Options        "SAMEORIGIN" always;
    add_header X-Content-Type-Options "nosniff"    always;
    add_header Referrer-Policy        "no-referrer-when-downgrade" always;
    add_header X-XSS-Protection       "1; mode=block" always;

    # Gzip
    gzip              on;
    gzip_vary         on;
    gzip_min_length   1024;
    gzip_comp_level   6;
    gzip_types
        text/plain
        text/css
        text/javascript
        application/javascript
        application/json
        application/xml
        image/svg+xml
        font/ttf
        font/otf
        font/woff
        font/woff2;

    # SPA fallback
    location / {
        try_files $uri $uri/ /index.html;
    }

    # Hashed static assets — агрессивный кэш
    location /static/ {
        expires 1y;
        access_log off;
        add_header Cache-Control "public, immutable";
        try_files $uri =404;
    }

    # HTML не кэшируется (чтобы обновления прилетали сразу)
    location = /index.html {
        add_header Cache-Control "no-store, no-cache, must-revalidate" always;
        expires -1;
    }

    # API + WebSocket → backend
    location /api/ {
        proxy_pass ${BACKEND_URL};
        proxy_http_version 1.1;

        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;

        proxy_set_header Upgrade    $http_upgrade;
        proxy_set_header Connection $connection_upgrade;

        proxy_connect_timeout 10s;
        proxy_read_timeout    300s;
        proxy_send_timeout    300s;
    }

    # Загруженные аватары → backend
    location /static/avatars/ {
        proxy_pass ${BACKEND_URL};
        proxy_set_header Host            $host;
        proxy_set_header X-Real-IP       $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    }

    error_page 404 /index.html;
}