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

    # Docker DNS resolver for dynamic service discovery (required for Swarm/Compose)
    resolver 127.0.0.11 valid=10s ipv6=off;
    resolver_timeout 5s;

    # Allow larger file uploads (up to 1GB for video support)
    client_max_body_size 1G;
    client_body_timeout 300s;

    # Gzip compression
    gzip on;
    gzip_vary on;
    gzip_min_length 1024;
    gzip_types text/plain text/css text/xml text/javascript application/javascript application/xml+rss application/json;

    # Security headers
    add_header X-Frame-Options "SAMEORIGIN" always;
    add_header X-Content-Type-Options "nosniff" always;
    add_header Referrer-Policy "strict-origin-when-cross-origin" always;
    add_header Permissions-Policy "camera=(), microphone=(), geolocation=(), payment=()" always;
    add_header Content-Security-Policy "default-src 'self'; script-src 'self' https://www.google.com https://www.gstatic.com; style-src 'self' 'unsafe-inline' https:; img-src 'self' data: https: blob:; connect-src 'self' https://www.google.com https://www.gstatic.com; font-src 'self' https: data:; object-src 'none'; media-src 'self'; frame-src 'self' https://www.google.com" always;

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

    # Cache static assets
    location ~* \.(js|css|png|jpg|jpeg|gif|ico|svg|woff|woff2|ttf|eot)$ {
        expires 1y;
        add_header Cache-Control "public, immutable";
        # Re-apply security headers (add_header in location block overrides server-level)
        add_header X-Frame-Options "SAMEORIGIN" always;
        add_header X-Content-Type-Options "nosniff" always;
        add_header Referrer-Policy "strict-origin-when-cross-origin" always;
        add_header Content-Security-Policy "default-src 'self'; script-src 'self' https://www.google.com https://www.gstatic.com; style-src 'self' 'unsafe-inline' https:; img-src 'self' data: https: blob:; connect-src 'self' https://www.google.com https://www.gstatic.com; font-src 'self' https: data:; object-src 'none'; media-src 'self'; frame-src 'self' https://www.google.com" always;
    }

    # Cache index.html with revalidation
    location = /index.html {
        add_header Cache-Control "no-cache, no-store, must-revalidate";
        add_header Pragma "no-cache";
        add_header Expires "0";
        # Re-apply security headers
        add_header X-Frame-Options "SAMEORIGIN" always;
        add_header X-Content-Type-Options "nosniff" always;
        add_header Referrer-Policy "strict-origin-when-cross-origin" always;
        add_header Content-Security-Policy "default-src 'self'; script-src 'self' https://www.google.com https://www.gstatic.com; style-src 'self' 'unsafe-inline' https:; img-src 'self' data: https: blob:; connect-src 'self' https://www.google.com https://www.gstatic.com; font-src 'self' https: data:; object-src 'none'; media-src 'self'; frame-src 'self' https://www.google.com" always;
    }

    # API proxy
    location /api {
        # Use variable to force DNS resolution per request (required for Docker Swarm)
        set $backend_upstream backend;
        proxy_pass http://$backend_upstream:3000;
        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 86400;

        # Allow larger uploads for API endpoints (up to 1GB for video support)
        client_max_body_size 1G;
        client_body_timeout 300s;
    }

    # Photo serving proxy
    location /photos {
        set $backend_upstream backend;
        proxy_pass http://$backend_upstream:3000;
        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;

        # Cache photos
        proxy_cache_valid 200 302 1d;
        proxy_cache_valid 404 1m;
    }

    # Thumbnail serving proxy
    location /thumbnails {
        set $backend_upstream backend;
        proxy_pass http://$backend_upstream:3000;
        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;

        # Cache thumbnails
        proxy_cache_valid 200 302 7d;
        proxy_cache_valid 404 1m;
    }

    # Uploads serving proxy (logos, favicons, watermarks)
    # ^~ modifier stops regex matching, ensuring uploads are proxied not served locally
    location ^~ /uploads {
        set $backend_upstream backend;
        proxy_pass http://$backend_upstream:3000;
        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;

        # Cache uploads
        proxy_cache_valid 200 302 7d;
        proxy_cache_valid 404 1m;
    }

    # Dynamic robots.txt served by backend
    location = /robots.txt {
        set $backend_upstream backend;
        proxy_pass http://$backend_upstream:3000/robots.txt;
        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;
    }

    # Delegate root requests to backend for public landing page handling
    location = / {
        # Use variable to force DNS resolution per request (required for Docker Swarm)
        set $backend_upstream backend;
        proxy_pass http://$backend_upstream:3000/;
        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_read_timeout 60s;
    }

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

    # Deny access to hidden files
    location ~ /\. {
        deny all;
    }
}