events {
    worker_connections 1024;
}

http {
    upstream frontend {
        server frontend:3000;
    }

    upstream backend {
        server backend:3001;
    }

    # Rate limiting
    limit_req_zone $binary_remote_addr zone=api:10m rate=10r/s;
    limit_req_zone $binary_remote_addr zone=frontend:10m rate=30r/s;

    # Gzip compression
    gzip on;
    gzip_vary on;
    gzip_min_length 1024;
    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/atom+xml
        image/svg+xml;

    # Security headers
    add_header X-Frame-Options "SAMEORIGIN" always;
    add_header X-XSS-Protection "1; mode=block" always;
    add_header X-Content-Type-Options "nosniff" always;
    add_header Referrer-Policy "no-referrer-when-downgrade" always;
    add_header Content-Security-Policy "default-src 'self' http: https: data: blob: 'unsafe-inline'" always;

    server {
        listen 80;
        server_name _;
        
        # Redirect HTTP to HTTPS
        return 301 https://$host$request_uri;
    }

    server {
        listen 443 ssl http2;
        server_name _;

        # SSL configuration
        # These paths match Let's Encrypt certificate files copied in the CI/CD setup guide
        ssl_certificate /etc/nginx/ssl/fullchain.pem;
        ssl_certificate_key /etc/nginx/ssl/privkey.pem;
        ssl_protocols TLSv1.2 TLSv1.3;
        ssl_ciphers ECDHE-RSA-AES256-GCM-SHA512:DHE-RSA-AES256-GCM-SHA512:ECDHE-RSA-AES256-GCM-SHA384:DHE-RSA-AES256-GCM-SHA384;
        ssl_prefer_server_ciphers off;
        ssl_session_cache shared:SSL:10m;
        ssl_session_timeout 10m;

        # Frontend routes
        location / {
            limit_req zone=frontend burst=20 nodelay;
            
            proxy_pass http://frontend;
            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;
        }

        # API routes
        location /api/ {
            limit_req zone=api burst=10 nodelay;
            
            proxy_pass http://backend/;
            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;
            
            # CORS headers
            add_header Access-Control-Allow-Origin * always;
            add_header Access-Control-Allow-Methods "GET, POST, PUT, DELETE, OPTIONS" always;
            add_header Access-Control-Allow-Headers "DNT,User-Agent,X-Requested-With,If-Modified-Since,Cache-Control,Content-Type,Range,Authorization" always;
            
            if ($request_method = 'OPTIONS') {
                add_header Access-Control-Allow-Origin *;
                add_header Access-Control-Allow-Methods "GET, POST, PUT, DELETE, OPTIONS";
                add_header Access-Control-Allow-Headers "DNT,User-Agent,X-Requested-With,If-Modified-Since,Cache-Control,Content-Type,Range,Authorization";
                add_header Access-Control-Max-Age 1728000;
                add_header Content-Type 'text/plain; charset=utf-8';
                add_header Content-Length 0;
                return 204;
            }
        }

        # Health check endpoint
        location /health {
            access_log off;
            proxy_pass http://backend/health;
            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;
            add_header Content-Type application/json;
        }
    }
}