cmdc_gateway

defmodule CMDCGateway.Application do
  @moduledoc """
  Gateway OTP Application。

  独立启动时（`mix run --no-halt`）自动读取环境变量配置 Cowboy HTTP + WebSocket。

  ## 环境变量

  | 变量 | 说明 | 默认 |
  |------|------|------|
  | `GATEWAY_PORT` | HTTP 端口 | `4000` |
  | `GATEWAY_API_KEYS` | 逗号分隔的合法 API Key | 无（为空则跳过认证） |

  ## 嵌入模式

  设置 `config :cmdc_gateway, :standalone, false` 后 Application
  仅启动 SessionStore / RateLimiter / Meter，由宿主应用自行启动 Cowboy。
  """

  use Application
  require Logger

  @default_port 4000

  @impl true
  def start(_type, _args) do
    CMDCGateway.CallbackTool.init_registry()
    configure_from_env()

    children =
      [
        CMDCGateway.SessionStore,
        CMDCGateway.RateLimiter,
        CMDCGateway.Meter,
        CMDCGateway.TaskStore,
        webhook_dispatcher_spec(),
        {DynamicSupervisor, name: CMDCGateway.AgentSupervisor, strategy: :one_for_one}
      ] ++ cowboy_children()

    opts = [strategy: :one_for_one, name: CMDCGateway.Supervisor]
    Supervisor.start_link(children, opts)
  end

  # ==========================================================================
  # Private
  # ==========================================================================

  defp configure_from_env do
    if api_keys_str = System.get_env("GATEWAY_API_KEYS") do
      keys =
        api_keys_str
        |> String.split(",", trim: true)
        |> Enum.map(&String.trim/1)

      Application.put_env(:cmdc_gateway, CMDCGateway.Plugs.Auth, api_keys: keys)
    end
  end

  defp cowboy_children do
    standalone? = Application.get_env(:cmdc_gateway, :standalone, true)

    if standalone? do
      port = get_port()
      Logger.info("[CMDCGateway] Starting on port #{port} (HTTP + WebSocket)")

      plug_opts = CMDCGateway.Router.init([])

      dispatch = [
        {:_,
         [
           {"/v1/sessions/:session_id/ws", CMDCGateway.WSHandler, []},
           {:_, Plug.Cowboy.Handler, {CMDCGateway.Router, plug_opts}}
         ]}
      ]

      [
        {Plug.Cowboy,
         scheme: :http,
         plug: CMDCGateway.Router,
         options: [
           port: port,
           dispatch: dispatch,
           protocol_options: [idle_timeout: 300_000]
         ]}
      ]
    else
      []
    end
  end

  defp get_port do
    case System.get_env("GATEWAY_PORT") do
      nil -> @default_port
      str -> String.to_integer(str)
    end
  end

  # ==========================================================================
  # Webhook Dispatcher — dead-letter 重试调度
  # ==========================================================================
  #
  # 默认配置：
  #   - enabled?: true（环境变量 WEBHOOK_DLQ_ENABLED=false 关闭）
  #   - backend: DETS（环境变量 WEBHOOK_DLQ_FILE 指定文件，默认 webhook_dlq.dets）
  #   - tick_interval_ms: 30_000（30s）
  #   - max_retries: 10
  #
  # 应用层覆盖：在 config.exs 设置
  #
  #   config :cmdc_gateway, CMDCGateway.Webhook.Dispatcher,
  #     enabled?: true,
  #     backend: CMDCGateway.Webhook.DeadLetter.DETS,
  #     backend_opts: [file: ~c"/var/cmdc/webhook_dlq.dets"],
  #     tick_interval_ms: 60_000,
  #     max_retries: 10
  defp webhook_dispatcher_spec do
    app_opts = Application.get_env(:cmdc_gateway, CMDCGateway.Webhook.Dispatcher, [])

    enabled? =
      Keyword.get_lazy(app_opts, :enabled?, fn ->
        case System.get_env("WEBHOOK_DLQ_ENABLED") do
          nil -> true
          v -> String.downcase(v) not in ["false", "0", "off", "no"]
        end
      end)

    backend = Keyword.get(app_opts, :backend, CMDCGateway.Webhook.DeadLetter.DETS)

    backend_opts =
      Keyword.get_lazy(app_opts, :backend_opts, fn ->
        file =
          System.get_env("WEBHOOK_DLQ_FILE") ||
            Path.join(System.tmp_dir!(), "cmdc_gateway_webhook_dlq.dets")

        [file: String.to_charlist(file)]
      end)

    final_opts = [
      backend: backend,
      backend_opts: backend_opts,
      enabled?: enabled?,
      tick_interval_ms: Keyword.get(app_opts, :tick_interval_ms, 30_000),
      max_retries: Keyword.get(app_opts, :max_retries, 10)
    ]

    {CMDCGateway.Webhook.Dispatcher, final_opts}
  end
end