project-user-m2m

project-user-m2m.ex

  def join_project(%Project{} = project, %User{} = me) do
    project = Repo.preload(project, :users)
    users =
      project.users ++ [me]
      |> Enum.map(&Ecto.Changeset.change/1)

    event
    |> change_project()
    |> put_assoc(:users, users)
    |> Repo.update()
  end

  def leave_project(%Project{} = project, %User{} = me) do
    project = Repo.preload(project, :users)

    Multi.new()
    |> Multi.run(:remove_m2m, fn _, _ ->
      case Repo.get_by(ProjectUser, project_id: project.id, user_id: me.id) do
        %ProjectUser{} = pu -> Repo.delete(pu)
        nil -> nil
      end

      {:ok, nil}
    end)
    |> Multi.run(:update_users, fn _, _ ->
      users =
        project.users -- [me]
        |> Enum.map(&Ecto.Changeset.change/1)

      {:ok, users}
    end)
    |> Multi.run(:update_project, fn _, %{update_users: users} ->
      project
      |> change_project()
      |> put_assoc(:users, users)
      |> Repo.update()
    end)
    |> Repo.transaction()
    |> case do
      {:ok, %{update_project: project}} -> {:ok, project}
      {:error, :update_project, changeset, _} -> {:error, changeset}
    end
  end