defmodule Skeleton.Permission.Controller do
  import Plug.Conn

  # Callbacks

  defmacro __using__(opts) do
    alias Skeleton.Permission.Controller

    quote do
      @permission_module unquote(opts[:permission]) || raise("Permission required")

      def check_permission(%{halted: true} = conn, _, _, _), do: conn

      def check_permission(conn, permission, permission_name, ctx_fun) do
        Controller.do_check_permission(conn, @permission_module, permission, permission_name, ctx_fun)
      end

      def check_permission(%{halted: true} = conn, _, _), do: conn

      def check_permission(conn, permission, permission_name) do
        Controller.do_check_permission(conn, @permission_module, permission, permission_name, fn _, ctx ->
          ctx
        end)
      end

      # Permit params

      def permit_params(%{halted: true} = conn, _, _), do: conn

      def permit_params(conn, permission, permission_name) do
        Controller.do_permit_params(conn, @permission_module, permission, permission_name)
      end
    end
  end

  # Do check permission

  def do_check_permission(conn, permission_module, permission, permission_name, ctx_fun) do
    context =
      conn
      |> build_permission_context(permission_module, permission, ctx_fun)
      |> permission.preload_data([permission_name])

    if permission.check(permission_name, context) do
      conn
    else
      unauthorized(conn)
    end
  end

  # Do permit params

  def do_permit_params(conn, permission_module, permission, permission_name) do
    context = build_permission_context(conn, permission_module, permission, fn _, ctx -> ctx end)
    permitted_params = permission.permit(permission_name, context)
    Map.put(conn, :params, permitted_params)
  end

  # Do build context

  def build_permission_context(conn, permission_module, permission, ctx_fun) do
    default_context = permission_module.context(conn)
    permission_context = permission.context(conn, default_context)

    ctx_fun.(conn, Map.merge(default_context, permission_context))
  end

  # Return unauthorized

  def unauthorized(conn) do
    conn |> put_status(:unauthorized) |> halt()
  end

  def forbidden(conn) do
    conn |> put_status(:forbidden) |> halt()
  end
end