defmodule CMDC.Tool.AskUser do
  @moduledoc """
  向用户提问，等待用户回答后继续，对标 DeepAgents `ask_user` 工具。

  ## 执行流程

  1. 生成唯一 `ref`
  2. 广播 `{:ask_user, session_id, question, options, ref}` 事件
  3. 阻塞等待 `{:cmdc_event, session_id, {:user_responded, session_id, ref, response}}` 消息
  4. 超时（默认 5 分钟）则返回错误
  5. 将用户回答作为工具结果返回 LLM

  ## 选项参数（可选）

  `options` 字段支持预设选项列表，UI 可展示为单选/多选。
  为空列表时视为自由文本输入。

  ## 注意

  此工具会**阻塞当前工具执行 Task**，直到用户响应或超时。
  外部需通过 `CMDC.approve/2` 或发送对应事件来解除阻塞。
  """

  @behaviour CMDC.Tool

  @default_timeout 300_000

  @impl true
  def name, do: "ask_user"

  @impl true
  def description do
    "Ask the user a question and wait for their response before continuing. " <>
      "Use this when you need clarification, a decision, or information " <>
      "that cannot be inferred from context. " <>
      "Do NOT use this for simple yes/no decisions you can make yourself."
  end

  @impl true
  def meta(%{"question" => q}), do: "Ask: #{String.slice(q, 0, 54)}"
  def meta(_), do: "AskUser"

  @impl true
  def parameters do
    %{
      "type" => "object",
      "properties" => %{
        "question" => %{
          "type" => "string",
          "description" => "The question to ask the user. Be specific and concise."
        },
        "options" => %{
          "type" => "array",
          "items" => %{
            "type" => "object",
            "properties" => %{
              "id" => %{"type" => "string", "description" => "Option identifier"},
              "label" => %{"type" => "string", "description" => "Display text for the option"}
            },
            "required" => ["id", "label"]
          },
          "description" =>
            "Optional list of pre-defined answer options. " <>
              "If provided, user selects from these choices. " <>
              "If empty, free-form text input is expected."
        }
      },
      "required" => ["question"]
    }
  end

  @impl true
  def execute(%{"question" => question} = args, context) do
    session_id = context.session_id
    options = Map.get(args, "options", [])
    ref = generate_ref()
    timeout = @default_timeout

    CMDC.EventBus.subscribe(session_id)
    CMDC.EventBus.broadcast(session_id, {:ask_user, session_id, question, options, ref})

    result = wait_for_response(session_id, ref, timeout)
    CMDC.EventBus.unsubscribe(session_id)
    result
  end

  def execute(_args, _ctx), do: {:error, "Missing required parameter: question"}

  # ==========================================================================
  # 私有辅助
  # ==========================================================================

  defp wait_for_response(session_id, ref, timeout) do
    receive do
      {:cmdc_event, ^session_id, {:user_responded, ^session_id, ^ref, response}} ->
        {:ok, format_response(response)}

      {:cmdc_event, ^session_id, {:user_responded, ^session_id, ^ref, response, _meta}} ->
        {:ok, format_response(response)}
    after
      timeout ->
        {:error, "User did not respond within #{div(timeout, 1000)}s timeout"}
    end
  end

  defp format_response(response) when is_binary(response), do: response
  defp format_response(response) when is_list(response), do: Enum.join(response, ", ")
  defp format_response(response), do: inspect(response)

  defp generate_ref do
    :crypto.strong_rand_bytes(8) |> Base.encode16(case: :lower)
  end
end