server {
    listen 80;
    server_name localhost;
    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 X-XSS-Protection "1; mode=block" always;
    add_header Referrer-Policy "strict-origin-when-cross-origin" always;

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

    # Health check endpoint
    location /health {
        proxy_pass http://127.0.0.1:8001/health;
        proxy_set_header Host $host;
    }

    # Proxy /api requests to localhost backend
    location /api/ {
        proxy_pass http://127.0.0.1:8001/api/;
        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_read_timeout 300s;
        proxy_connect_timeout 75s;
    }

    # Proxy websockets/docs if needed
    location /docs {
        proxy_pass http://127.0.0.1:8001/docs;
    }

    location /openapi.json {
        proxy_pass http://127.0.0.1:8001/openapi.json;
    }

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

    # Gzip compression
    gzip on;
    gzip_vary on;
    gzip_min_length 1024;
    gzip_proxied any;
    gzip_types text/plain text/css text/xml text/javascript application/javascript application/json application/xml;
}