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;

    # Gzip compression
    gzip on;
    gzip_vary on;
    gzip_min_length 1000;
    gzip_comp_level 6;
    gzip_types text/plain text/css application/json application/javascript text/xml application/xml application/xml+rss text/javascript image/svg+xml;

    # Static asset caching (hashed filenames = immutable)
    location ~* \.(js|css|png|jpg|jpeg|gif|ico|svg|woff|woff2|ttf|eot|map)$ {
        expires 1y;
        add_header Cache-Control "public, immutable";
        access_log off;
    }

    # API proxy to backend
    location /api/ {
        proxy_pass http://backend:5000/api/;
        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_read_timeout 600s;  # 10 minutes for long-running backtests
        proxy_connect_timeout 75s;
        proxy_send_timeout 600s;  # 10 minutes for sending response
        # Allow large file uploads (e.g. indicator import)
        client_max_body_size 10m;
    }

    # SPA routing support (all routes fall back to index.html)
    location / {
        try_files $uri $uri/ /index.html;
    }

    # Health check endpoint
    location /health {
        return 200 'OK';
        add_header Content-Type text/plain;
        access_log off;
    }
}