fix: issue #20 cmd-J panel tab strip visibility and output panel parity

lib/bds/scripting/lua.ex

@@ -6,16 +6,20 @@ defmodule BDS.Scripting.Lua do
   and opt-in.
   """
 
+  require Logger
+
   @type source :: String.t()
   @type entrypoint :: String.t()
   @type args :: [term()]
   @type progress_event :: map()
   @type progress_callback :: (progress_event() -> any())
+  @type output_callback :: (String.t() -> any())
   @type execution_option ::
           {:timeout, non_neg_integer() | :infinity}
           | {:max_reductions, pos_integer() | :none}
           | {:spawn_opts, [term()]}
           | {:on_progress, progress_callback()}
+          | {:on_output, output_callback()}
           | {:capabilities, map()}
 
   @callback validate(source()) :: :ok | {:error, term()}
@@ -48,12 +52,65 @@ defmodule BDS.Scripting.Lua do
     end
   end
 
+  @doc """
+  Returns the sink script output (`print`, `bds.app.log`) is routed to: the
+  `:on_output` callback when given, otherwise a Logger-based default so script
+  output never leaks onto the console (where it would corrupt the TUI).
+  """
+  @spec output_sink(keyword()) :: output_callback()
+  def output_sink(opts) when is_list(opts) do
+    case Keyword.get(opts, :on_output) do
+      callback when is_function(callback, 1) ->
+        callback
+
+      _other ->
+        fn text -> Logger.debug("script output: #{text}") end
+    end
+  end
+
+  @doc """
+  Builds the Lua-callable function shared by the global `print` override and
+  the `bds.app.log` capability: joins all arguments with spaces and forwards
+  the line to the output sink.
+  """
+  @spec output_function(keyword(), [term()]) :: (list(), lua_state() -> {list(), lua_state()})
+  def output_function(opts, return_values \\ []) when is_list(opts) and is_list(return_values) do
+    sink = output_sink(opts)
+
+    fn args, current_state ->
+      line =
+        args
+        |> :luerl.decode_list(current_state)
+        |> Enum.map_join(" ", &format_lua_value/1)
+
+      sink.(line)
+      :luerl.encode_list(return_values, current_state)
+    end
+  end
+
+  @doc "Formats a decoded Lua value the way Lua's `tostring` would present it."
+  @spec format_lua_value(term()) :: String.t()
+  def format_lua_value(nil), do: "nil"
+  def format_lua_value(true), do: "true"
+  def format_lua_value(false), do: "false"
+  def format_lua_value(value) when is_binary(value), do: value
+
+  def format_lua_value(value) when is_float(value) do
+    if Float.round(value, 0) == value,
+      do: "#{trunc(value)}.0",
+      else: to_string(value)
+  end
+
+  def format_lua_value(value) when is_integer(value), do: Integer.to_string(value)
+  def format_lua_value(value), do: inspect(value)
+
   defp initial_state(opts) do
     state = :luerl_sandbox.init()
     capabilities = Keyword.get(opts, :capabilities, %{})
 
     with {:ok, state} <- :luerl.set_table_keys_dec(["bds"], %{}, state),
          {:ok, state} <- install_progress_callback(state, Keyword.get(opts, :on_progress)),
+         {:ok, state} <- install_print_override(state, opts),
          {:ok, state} <- install_capabilities(state, capabilities) do
       {:ok, state}
     end
@@ -85,6 +142,15 @@ defmodule BDS.Scripting.Lua do
   defp install_progress_callback(_state, callback),
     do: {:error, {:invalid_progress_callback, callback}}
 
+  # Replaces the built-in `print` (which would write straight to the BEAM
+  # console) with a function routed to the output sink.
+  defp install_print_override(state, opts) do
+    case :luerl.set_table_keys_dec(["print"], output_function(opts), state) do
+      {:ok, next_state} -> {:ok, next_state}
+      error -> {:error, {:print_override_install_failed, error}}
+    end
+  end
+
   defp install_capabilities(state, capabilities) when capabilities in [%{}, []], do: {:ok, state}
 
   defp install_capabilities(state, capabilities) when is_map(capabilities) do