defmodule CodeNameRaven.ChannelDisplay do
  @moduledoc """
  Behaviour for notification channel display modules.

  Renders a channel's own dashboard panel (e.g. delivery history). Paired
  with a `CodeNameRaven.Channel` module the same way `CodeNameRaven.Display`
  pairs with `CodeNameRaven.Monitor` — self-bundled in one module, or as a
  separate package-sibling module declaring `compatible_channels/0`.
  """

  @callback display_name() :: String.t()
  @callback compatible_channels() :: [module()]
  @callback prepare_assigns(map()) :: map()
  @callback render(map()) :: Phoenix.LiveView.Rendered.t()

  defmacro __using__(_opts) do
    quote do
      @behaviour CodeNameRaven.ChannelDisplay
      use Phoenix.Component

      @impl true
      def display_name do
        __MODULE__
        |> Module.split()
        |> List.last()
        |> Macro.underscore()
        |> String.replace("_", " ")
        |> String.split()
        |> Enum.map_join(" ", &String.capitalize/1)
      end

      @impl true
      def prepare_assigns(assigns), do: assigns

      defoverridable display_name: 0, prepare_assigns: 1
    end
  end

  @doc "Returns true if the module implements the ChannelDisplay behaviour."
  def channel_display_module?(module) do
    Code.ensure_loaded?(module) and
      function_exported?(module, :compatible_channels, 0) and
      function_exported?(module, :render, 1)
  end
end