server {
    listen 80;
    server_name localhost;

    root /usr/share/nginx/html;
    index index.html;

    location / {
        try_files $uri $uri/ /index.html;
    }

    location /api/ {
        # Try to proxy to backend first
        proxy_pass http://backend:3000;
        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;

        # Allow larger file uploads (50MB)
        client_max_body_size 50M;

        # If backend is unavailable, serve mock data
        error_page 502 503 504 = @fallback;
    }

    location @fallback {
        # Serve mock data from frontend
        rewrite ^/api/(.*)$ /mock/$1 break;
        try_files $uri /index.html;

        # Add header to indicate mock data is being used
        add_header X-Mock-Data "true";
        add_header X-Backend-Status "unavailable";
    }

    # Handle auth endpoints
    location /auth/ {
        proxy_pass http://backend:3000;
        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;

        # Auth endpoints should fail if backend is down
        error_page 502 503 504 = /auth-unavailable.html;
    }

    # Handle static assets
    location /assets/ {
        expires 1y;
        add_header Cache-Control "public";
    }
}