defmodule CMDCGateway.CallbackTool do
  @moduledoc """
  HTTP 回调工具代理。

  外部系统通过 `POST /v1/sessions/:id/tools` 注册自定义工具，
  Agent 调用时 Gateway 向 `callback_url` 发 POST 请求，代理执行结果。

  ## 注册请求体

      {
        "name": "query_database",
        "description": "Run a SQL query on the production database",
        "parameters": {
          "type": "object",
          "properties": {
            "query": {"type": "string", "description": "SQL query to execute"}
          },
          "required": ["query"]
        },
        "callbackUrl": "https://my-service.example.com/tools/query",
        "timeoutMs": 30000
      }

  ## 回调请求格式

  Gateway 向 callbackUrl 发 POST：

      {
        "callId": "tc_abc123",
        "toolName": "query_database",
        "args": {"query": "SELECT * FROM users LIMIT 10"},
        "sessionId": "s-001"
      }

  ## 回调响应格式

      {"result": "10 rows returned..."}
      // 或错误
      {"error": "Connection refused"}
  """

  @registry_table :"#{__MODULE__}.Registry"

  @type tool_spec :: %{
          name: String.t(),
          description: String.t(),
          parameters: map(),
          callback_url: String.t(),
          timeout_ms: pos_integer()
        }

  # ==========================================================================
  # Public API
  # ==========================================================================

  @doc "初始化 ETS 注册表（由 Application 调用）。"
  @spec init_registry() :: :ok
  def init_registry do
    if :ets.info(@registry_table) == :undefined do
      :ets.new(@registry_table, [:named_table, :bag, :public, read_concurrency: true])
    end

    :ok
  end

  @doc """
  为指定 session 注册一个回调工具。

  返回动态生成的 Tool 模块原子。
  """
  @spec register(String.t(), map()) :: {:ok, module()} | {:error, term()}
  def register(session_id, %{"name" => name, "callbackUrl" => callback_url} = spec) do
    tool_spec = %{
      name: name,
      description: Map.get(spec, "description", "External tool: #{name}"),
      parameters: Map.get(spec, "parameters", %{"type" => "object", "properties" => %{}}),
      callback_url: callback_url,
      timeout_ms: Map.get(spec, "timeoutMs", 30_000)
    }

    tool_module = generate_tool_module(session_id, tool_spec)
    :ets.insert(@registry_table, {session_id, name, tool_module, tool_spec})
    {:ok, tool_module}
  end

  def register(_session_id, _spec), do: {:error, "Missing required fields: name, callbackUrl"}

  @doc "获取指定 session 的所有已注册回调工具模块。"
  @spec list_tools(String.t()) :: [module()]
  def list_tools(session_id) do
    if :ets.info(@registry_table) != :undefined do
      @registry_table
      |> :ets.lookup(session_id)
      |> Enum.map(fn {_sid, _name, module, _spec} -> module end)
    else
      []
    end
  end

  @doc "清理指定 session 的所有回调工具。"
  @spec cleanup(String.t()) :: :ok
  def cleanup(session_id) do
    if :ets.info(@registry_table) != :undefined do
      :ets.match_delete(@registry_table, {session_id, :_, :_, :_})
    end

    :ok
  end

  @doc """
  执行 HTTP 回调。

  向 `callback_url` 发送 POST 请求，传递工具调用参数，返回结果。
  """
  @spec execute_callback(tool_spec(), String.t(), String.t(), map()) ::
          {:ok, String.t()} | {:error, String.t()}
  def execute_callback(tool_spec, session_id, call_id, args) do
    body = %{
      callId: call_id,
      toolName: tool_spec.name,
      args: args,
      sessionId: session_id
    }

    tool_spec.callback_url
    |> Req.post(json: body, receive_timeout: tool_spec.timeout_ms, retry: false)
    |> handle_callback_response()
  end

  defp handle_callback_response({:ok, %Req.Response{status: status, body: body}})
       when status in 200..299 do
    body |> extract_result() |> normalize_result()
  end

  defp handle_callback_response({:ok, %Req.Response{status: status, body: body}}) do
    {:error, "Callback returned HTTP #{status}: #{inspect(body)}"}
  end

  defp handle_callback_response({:error, reason}) do
    {:error, "Callback request failed: #{inspect(reason)}"}
  end

  defp extract_result(%{"result" => r}), do: r
  defp extract_result(%{"error" => e}), do: {:error, e}
  defp extract_result(r) when is_binary(r), do: r
  defp extract_result(r), do: inspect(r)

  defp normalize_result({:error, e}), do: {:error, to_string(e)}
  defp normalize_result(r), do: {:ok, to_string(r)}

  # ==========================================================================
  # Private — Dynamic Tool Module Generation
  # ==========================================================================

  defp generate_tool_module(session_id, tool_spec) do
    module_name =
      Module.concat([
        CMDCGateway.CallbackTool.Dynamic,
        "S_#{safe_name(session_id)}_T_#{safe_name(tool_spec.name)}"
      ])

    if :erlang.module_loaded(module_name) do
      :code.purge(module_name)
      :code.delete(module_name)
    end

    spec = tool_spec

    contents =
      quote do
        @moduledoc false
        @behaviour CMDC.Tool

        @tool_spec unquote(Macro.escape(spec))
        @session_id unquote(session_id)

        @impl true
        def name, do: @tool_spec.name

        @impl true
        def description, do: @tool_spec.description

        @impl true
        def parameters, do: @tool_spec.parameters

        @impl true
        def execute(args, ctx) do
          call_id = Map.get(ctx, :call_id, "unknown")
          sid = Map.get(ctx, :session_id, @session_id)
          CMDCGateway.CallbackTool.execute_callback(@tool_spec, sid, call_id, args)
        end
      end

    Module.create(module_name, contents, Macro.Env.location(__ENV__))
    module_name
  end

  defp safe_name(str) do
    str
    |> String.replace(~r/[^a-zA-Z0-9]/, "_")
    |> String.slice(0, 40)
  end
end