user nginx;
worker_processes auto;
error_log /var/log/nginx/error.log warn;
pid /var/run/nginx.pid;

events {
    worker_connections 1024;
    use epoll;
}

http {
    include /etc/nginx/mime.types;
    default_type application/octet-stream;

    # Logging
    log_format main '$remote_addr - $remote_user [$time_local] "$request" '
                    '$status $body_bytes_sent "$http_referer" '
                    '"$http_user_agent" "$http_x_forwarded_for"';
    access_log /var/log/nginx/access.log main;

    # Performance
    sendfile on;
    tcp_nopush on;
    tcp_nodelay on;
    keepalive_timeout 65;
    types_hash_max_size 2048;
    client_max_body_size 50M;

    # Gzip compression
    gzip on;
    gzip_vary on;
    gzip_proxied any;
    gzip_comp_level 6;
    gzip_types text/plain text/css text/xml text/javascript 
               application/json application/javascript application/xml+rss 
               application/rss+xml font/truetype font/opentype 
               application/vnd.ms-fontobject image/svg+xml;

    # 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;

    # Rate limiting zones
    limit_req_zone $binary_remote_addr zone=general:10m rate=10r/s;
    limit_req_zone $binary_remote_addr zone=api:10m rate=20r/s;

    # Cache settings
    proxy_cache_path /var/cache/nginx levels=1:2 keys_zone=static_cache:10m max_size=100m inactive=60m;
    proxy_cache_key "$scheme$request_method$host$request_uri";

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

        # Security: Hide nginx version
        server_tokens off;

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

        # API proxy (if backend is separate)
        location /api/ {
            # Rate limiting
            limit_req zone=api burst=20 nodelay;

            # Proxy settings
            proxy_pass http://backend:5000/;
            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;

            # Timeouts
            proxy_connect_timeout 30s;
            proxy_send_timeout 30s;
            proxy_read_timeout 30s;
        }

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

        # Service Worker (no cache)
        location = /service-worker.js {
            add_header Cache-Control "no-cache, no-store, must-revalidate";
            add_header Pragma "no-cache";
            add_header Expires 0;
        }

        # React Router - redirect all to index.html
        location / {
            limit_req zone=general burst=10 nodelay;
            try_files $uri $uri/ /index.html;
            add_header Cache-Control "no-cache, must-revalidate";
        }

        # Error pages
        error_page 404 /index.html;
        error_page 500 502 503 504 /50x.html;
        location = /50x.html {
            root /usr/share/nginx/html;
        }
    }
}