Caddyfile

www.{$CADDY_HOST} {
    tls {$CADDY_TLS_EMAIL}
    gzip
    root /var/www/nerd_herder

    redir 302 {
        # Caddy is dumb and has no way of redirecting only the index without this if statment.
        if {path} is /
        / /app/
    }

    rewrite /app {
        to {path} {path}/ /
    }

    rewrite /favicon {
        to {path}
    }

    # First attempt to load the file (via {path}), if that fails re-write to the proxy URL
    rewrite {
        to {path} /proxy/{uri}
    }

    # Proxy to nerd_herder service via /proxy, but drop the /proxy prefix
    proxy /proxy nerd_herder:8080 {
        transparent
        without /proxy
    }
}

{$CADDY_HOST} {
    redir https://www.{$CADDY_HOST}{uri}
}