cmdc_tui

defmodule CmdcTui.App do
  @moduledoc """
  CMDC TUI 主应用模块 — ExRatatui.App behaviour 实现。

  使用 ExRatatui.Server（GenServer）管理终端事件循环，
  `poll_event` 在 DirtyIO scheduler 上阻塞，不影响 `handle_info` 接收 CMDC 事件，
  按键到达后立刻 dispatch → render，零额外延迟。

  ## 布局

  ```
  ┌────────────────────────────┬───────────────┐
  │                            │   ToolPanel   │
  │       ChatPanel            │   /TodoPanel  │
  │  (messages + textarea)     │   (Tab 切换)   │
  │                            │               │
  ├────────────────────────────┴───────────────┤
  │                 StatusBar                   │
  └─────────────────────────────────────────────┘
  ```

  ## State 管理

  集中式 state，Panel 模块为纯渲染函数，不持有独立状态。
  EventBus 事件通过 `handle_info` 统一更新 state 并触发 re-render。
  """

  use ExRatatui.App

  alias ExRatatui.{Layout, Style}
  alias ExRatatui.Layout.Rect
  alias ExRatatui.Widgets.{Block, Clear, Paragraph, Textarea}

  alias CmdcTui.{
    Panels.ChatPanel,
    Panels.ToolPanel,
    Panels.TodoPanel,
    Panels.StatusBar,
    Dialogs.ApprovalDialog,
    Dialogs.AskUserDialog,
    Dialogs.CommandPalette,
    Dialogs.SlashAutocomplete
  }

  @sidebar_width_ratio 30
  @status_bar_height 1
  @input_height 4

  # ==========================================================================
  # ExRatatui.App Callbacks
  # ==========================================================================

  @impl true
  def mount(opts) do
    textarea = ExRatatui.textarea_new()
    opts = Keyword.put(opts, :textarea, textarea)
    state = CmdcTui.State.new(opts)

    if state.session do
      CMDC.subscribe(state.session)
    end

    {:ok, state}
  end

  @impl true
  def render(state, frame) do
    state = tick_throbber(state)
    area = %Rect{x: 0, y: 0, width: frame.width, height: frame.height}

    if frame.width < 40 or frame.height < 10 do
      render_too_small(area)
    else
      render_layout(state, area)
    end
  end

  @impl true
  def handle_event(%ExRatatui.Event.Key{code: "c", modifiers: ["ctrl"]}, state) do
    {:stop, state}
  end

  def handle_event(%ExRatatui.Event.Key{} = key, state) do
    case CmdcTui.KeyHandler.handle(key, state) do
      {:stop, state} ->
        {:stop, state}

      {:noreply, state} ->
        # 处理完第一个按键后，非阻塞消费所有积压的后续按键，
        # 这样 Server 只渲染一帧，避免每键一帧的延迟
        {:noreply, drain_pending_keys(state)}
    end
  end

  def handle_event(%ExRatatui.Event.Resize{}, state) do
    {:noreply, state}
  end

  def handle_event(_event, state) do
    {:noreply, state}
  end

  @impl true
  def handle_info({:cmdc_event, _session_id, event}, state) do
    state = CmdcTui.EventRouter.route(event, state)
    {:noreply, state}
  end

  def handle_info(_msg, state), do: {:noreply, state}

  @impl true
  def terminate(_reason, state) do
    if state.session do
      CMDC.unsubscribe(state.session)
    end

    :ok
  end

  # ==========================================================================
  # Layout
  # ==========================================================================

  defp render_layout(state, area) do
    [main_area, status_area] =
      Layout.split(area, :vertical, [
        {:min, 8},
        {:length, @status_bar_height}
      ])

    show_sidebar = area.width >= 80

    base_widgets =
      if show_sidebar do
        render_with_sidebar(state, main_area, status_area)
      else
        render_no_sidebar(state, main_area, status_area)
      end

    dialog_widgets =
      ApprovalDialog.render(state, area) ++
        AskUserDialog.render(state, area) ++
        CommandPalette.render(state, area) ++
        SlashAutocomplete.render(state, area)

    [{%Clear{}, area} | base_widgets ++ dialog_widgets]
  end

  defp render_with_sidebar(state, main_area, status_area) do
    [chat_area, sidebar_area] =
      Layout.split(main_area, :horizontal, [
        {:percentage, 100 - @sidebar_width_ratio},
        {:percentage, @sidebar_width_ratio}
      ])

    chat_widgets = render_chat_area(state, chat_area)
    sidebar_widgets = render_sidebar(state, sidebar_area)
    status_widgets = StatusBar.render(state, status_area)

    chat_widgets ++ sidebar_widgets ++ status_widgets
  end

  defp render_no_sidebar(state, main_area, status_area) do
    chat_widgets = render_chat_area(state, main_area)
    status_widgets = StatusBar.render(state, status_area)

    chat_widgets ++ status_widgets
  end

  defp render_chat_area(state, area) do
    [messages_area, input_area] =
      Layout.split(area, :vertical, [
        {:min, 3},
        {:length, @input_height}
      ])

    message_widgets = ChatPanel.render_messages(state, messages_area)
    input_widgets = render_input(state, input_area)

    message_widgets ++ input_widgets
  end

  defp render_input(state, area) do
    if is_nil(state.textarea) do
      placeholder = %Paragraph{
        text: "输入消息... (Enter 发送, Shift+Enter 换行, / 命令)",
        style: %Style{fg: :dark_gray}
      }

      [{placeholder, area}]
    else
      textarea = %Textarea{
        state: state.textarea,
        style: %Style{fg: :white},
        cursor_style: %Style{bg: :white, fg: :black},
        placeholder: "输入消息... (Enter 发送, Shift+Enter 换行, / 命令)",
        placeholder_style: %Style{fg: :dark_gray},
        block: %Block{
          title: input_title(state),
          borders: [:all],
          border_type: :rounded,
          border_style: input_border_style(state)
        }
      }

      [{textarea, area}]
    end
  end

  defp input_title(%{agent_status: :streaming}), do: "输入 (streaming...)"
  defp input_title(%{agent_status: :running}), do: "输入 (thinking...)"
  defp input_title(_state), do: "输入"

  defp input_border_style(%{agent_status: s}) when s in [:streaming, :running],
    do: %Style{fg: :yellow}

  defp input_border_style(_state), do: %Style{fg: :blue}

  defp render_sidebar(state, area) do
    case state.sidebar_tab do
      :tools -> ToolPanel.render(state, area)
      :todos -> TodoPanel.render(state, area)
    end
  end

  defp render_too_small(area) do
    msg = %Paragraph{
      text: "终端过小，请调整窗口大小 (需要 ≥ 40×10)",
      style: %Style{fg: :red, modifiers: [:bold]}
    }

    [{msg, area}]
  end

  # ==========================================================================
  # Private Helpers
  # ==========================================================================

  defp tick_throbber(%{agent_status: s} = state) when s in [:streaming, :running] do
    %{state | throbber_step: state.throbber_step + 1}
  end

  defp tick_throbber(state), do: state

  # 非阻塞排尽所有积压的按键事件，合并到同一帧渲染
  defp drain_pending_keys(state) do
    case ExRatatui.poll_event(0) do
      %ExRatatui.Event.Key{code: "c", modifiers: ["ctrl"]} ->
        state

      %ExRatatui.Event.Key{} = key ->
        case CmdcTui.KeyHandler.handle(key, state) do
          {:noreply, new_state} -> drain_pending_keys(new_state)
          {:stop, new_state} -> new_state
        end

      _ ->
        state
    end
  end
end