cmdc_tui

defmodule CmdcTui.Panels.TodoPanel do
  @moduledoc """
  Todo 面板 — 侧栏 Checkbox + WidgetList。

  ## 功能

  - pending：白色方框
  - in_progress：黄色 + `▶` 前缀标记
  - completed：绿色 + 勾选
  - cancelled：灰色删除线效果（前缀 `✗`）
  - header 显示 "X/N 完成" 统计
  - 内容超 30 字符时截断并加 `…`
  """

  alias ExRatatui.Style
  alias ExRatatui.Layout.Rect
  alias ExRatatui.Widgets.{Block, Checkbox, Paragraph, WidgetList}

  @doc "渲染 Todo 面板。"
  @spec render(CmdcTui.State.t(), Rect.t()) :: [{ExRatatui.widget(), Rect.t()}]
  def render(%{todos: []} = _state, area) do
    render_empty(area)
  end

  def render(state, area) do
    {done, total} = count_stats(state.todos)
    items = Enum.map(state.todos, &todo_item/1)

    widget = %WidgetList{
      items: items,
      block: %Block{
        title: "Todo #{done}/#{total} [Tab]",
        borders: [:all],
        border_type: :rounded,
        border_style: todo_border_style(state.todos)
      }
    }

    [{widget, area}]
  end

  # ==========================================================================
  # 私有
  # ==========================================================================

  defp render_empty(area) do
    items = [
      {%Paragraph{text: "  (empty)", style: %Style{fg: :dark_gray}}, 1}
    ]

    widget = %WidgetList{
      items: items,
      block: %Block{
        title: "Todo [Tab]",
        borders: [:all],
        border_type: :rounded,
        border_style: %Style{fg: :dark_gray}
      }
    }

    [{widget, area}]
  end

  defp todo_item(todo) do
    content = get_field(todo, :content, "content", "")
    status = get_field(todo, :status, "status", "pending")

    {label, checked, style} = item_attrs(status, content)

    checkbox = %Checkbox{
      label: label,
      checked: checked,
      style: style
    }

    {checkbox, 1}
  end

  defp item_attrs(status, content) when status in [:completed, "completed"] do
    {truncate(content, 35), true, %Style{fg: :green}}
  end

  defp item_attrs(status, content) when status in [:in_progress, "in_progress"] do
    {"▶ #{truncate(content, 33)}", false, %Style{fg: :yellow, modifiers: [:bold]}}
  end

  defp item_attrs(status, content) when status in [:cancelled, "cancelled"] do
    {"✗ #{truncate(content, 33)}", false, %Style{fg: :dark_gray}}
  end

  defp item_attrs(_status, content) do
    {truncate(content, 35), false, %Style{fg: :white}}
  end

  defp count_stats(todos) do
    done =
      Enum.count(todos, fn t ->
        get_field(t, :status, "status", "pending") in [:completed, "completed"]
      end)

    {done, length(todos)}
  end

  defp todo_border_style(todos) do
    in_progress =
      Enum.any?(todos, fn t ->
        get_field(t, :status, "status", "pending") in [:in_progress, "in_progress"]
      end)

    if in_progress, do: %Style{fg: :yellow}, else: %Style{fg: :dark_gray}
  end

  defp truncate(text, max_len) when byte_size(text) > max_len do
    String.slice(text, 0, max_len - 1) <> "…"
  end

  defp truncate(text, _), do: text

  # 同时支持 atom key 和 string key（兼容不同序列化来源）
  defp get_field(map, atom_key, string_key, default) do
    Map.get(map, atom_key, Map.get(map, string_key, default))
  end
end