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

    gzip on;
    gzip_vary on;
    gzip_min_length 1024;
    gzip_types text/plain text/css text/xml text/javascript application/x-javascript application/xml+rss application/javascript application/json;

    add_header X-Frame-Options "SAMEORIGIN" always;
    add_header X-Content-Type-Options "nosniff" always;
    add_header X-XSS-Protection "1; mode=block" always;

    # Re-resolve Docker DNS so backend IP changes after recreate don't stick as 502
    resolver 127.0.0.11 valid=10s ipv6=off;

    # Frontend → /api/backend/* → Hono. Variable upstream + rewrite avoids stale DNS
    # and still strips the /api/backend prefix.
    location /api/backend/ {
        rewrite ^/api/backend/(.*)$ /$1 break;
        set $backend_upstream backend:3001;
        proxy_pass http://$backend_upstream;
        proxy_http_version 1.1;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection 'upgrade';
        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_cache_bypass $http_upgrade;
        proxy_connect_timeout 5s;
        proxy_read_timeout 180s;
        proxy_send_timeout 180s;
    }

    location = /api/backend {
        return 301 /api/backend/;
    }

    location / {
        try_files $uri $uri/ /index.html;
    }

    location ~* \.(js|css|png|jpg|jpeg|gif|ico|svg|woff|woff2|ttf|eot)$ {
        expires 1y;
        add_header Cache-Control "public, immutable";
    }

    location ~* \.html$ {
        expires -1;
        add_header Cache-Control "no-store, no-cache, must-revalidate";
    }

    location /health {
        access_log off;
        return 200 "healthy\n";
        add_header Content-Type text/plain;
    }
}