Add Kino.Proxy module

lib/kino/bridge.ex

@@ -250,6 +250,15 @@ defmodule Kino.Bridge do
     match?({:ok, _}, io_request(:livebook_get_evaluation_file))
   end
 
+  @doc """
+  Requests the child spec for proxy handler with the given function.
+  """
+  @spec get_proxy_handler_child_spec((Plug.Conn.t() -> Plug.Conn.t())) ::
+          {:ok, {module(), term()}} | request_error()
+  def get_proxy_handler_child_spec(fun) do
+    io_request({:livebook_get_proxy_handler_child_spec, fun})
+  end
+
   defp io_request(request) do
     gl = Process.group_leader()
     ref = Process.monitor(gl)

lib/kino/proxy.ex

@@ -0,0 +1,21 @@
+defmodule Kino.Proxy do
+  @moduledoc """
+  Functionality for handling proxy requests forwarded from Livebook.
+
+  TODO: Write an extensive docs here.
+  """
+
+  @doc """
+  Persists the function to be listened by the proxy handler.
+  """
+  @spec listen((Plug.Conn.t() -> Plug.Conn.t())) :: DynamicSupervisor.on_start_child()
+  def listen(fun) when is_function(fun, 1) do
+    case Kino.Bridge.get_proxy_handler_child_spec(fun) do
+      {:ok, child_spec} ->
+        Kino.start_child(child_spec)
+
+      {:request_error, reason} ->
+        raise "failed to access the proxy handler child spec, reason: #{inspect(reason)}"
+    end
+  end
+end