mattermost

defmodule Mattermost.Plug do
  @moduledoc """
  A plug for receiving Mattermost slash command webhooks.

  Mount this inside your Phoenix router. The `:handler` option is the module
  implementing `Mattermost.Bot`.

      # lib/my_app_web/router.ex
      scope "/agent" do
        forward "/commands", Mattermost.Plug, handler: MyApp.Bot
      end

  Then in Mattermost, set each slash command's Request URL to:

      https://your-domain.com/agent/commands/TRIGGER_WORD

  The last path segment becomes the `command` argument in `handle_command/3`.
  Mattermost POSTs form-encoded params: `text`, `channel_id`, `user_id`,
  `user_name`, `team_id`, etc.
  """

  @behaviour Plug

  import Plug.Conn
  require Logger

  @impl Plug
  def init(opts), do: opts

  @impl Plug
  def call(conn, opts) do
    handler = Keyword.fetch!(opts, :handler)

    conn = Plug.Parsers.call(conn, Plug.Parsers.init(parsers: [:urlencoded], pass: ["*/*"]))

    params = conn.body_params
    command = List.last(conn.path_info)
    text = params["text"] || ""
    channel_id = params["channel_id"]
    user_id = params["user_id"]

    Logger.debug("[Mattermost.Plug] /#{command} from user #{user_id}")

    ctx = %Mattermost.Context{
      config: Mattermost.from_env(),
      channel_id: channel_id,
      user_id: user_id,
      post: nil
    }

    safe_dispatch(handler, command, text, ctx)

    conn
    |> put_resp_content_type("application/json")
    |> send_resp(200, "{}")
  end

  defp safe_dispatch(handler, command, text, ctx) do
    handler.handle_command(command, text, ctx)
  rescue
    error ->
      Logger.error("[Mattermost.Plug] Error in #{handler}.handle_command/3: #{inspect(error)}")
  end
end