Phoenix plug to rewrite phoenix_live_dashboard request_logger cookie to parent domain

rewrite_request_logger_cookie.ex

defmodule Dashboard.Plug.RewriteRequestLoggerCookie do
  alias Plug.Conn

  @behaviour Plug

  @impl true
  def init(opts) do
    cookie_key = opts[:cookie_key]

    unless cookie_key do
      raise ArgumentError, "expected cookie_key to be given"
    end

    cookie_key
  end

  @impl true
  def call(conn, cookie_key) do
    conn = Conn.fetch_cookies(conn)

    case conn.req_cookies[cookie_key] do
      nil ->
        conn

      cookie_value ->
        Conn.put_resp_cookie(
          conn,
          cookie_key,
          cookie_value,
          domain: parent_domain(conn.host)
        )
    end
  end

  defp parent_domain(host) do
    case Regex.named_captures(~r/[^\.]*\.(?<parent_domain>.*)$/, host) do
      %{"parent_domain" => parent_domain} -> parent_domain
      _ -> host
    end
  end
end