defmodule Mix.Tasks.Crumb.Install do
  import Macro, only: [underscore: 1]
  import Mix.Generator

  use Mix.Task

  @shortdoc "generates crumb migration file for your database"

  def run(_args) do
    path = Path.relative_to("priv/repo/migrations", Mix.Project.app_path)
    file = Path.join(path, "#{timestamp()}_#{underscore(AddVersions)}.exs")
    create_directory path

    create_file file, """
    defmodule Repo.Migrations.AddVersions do
      use Ecto.Migration
      def change do
        create table(:versions) do
          add :event,        :string
          add :item_type,    :string
          add :item_id,      :integer
          add :user_id,      :integer
          add :item_changes, :map
          add :meta,         :map
          add :inserted_at,  :utc_datetime, null: false
        end
        create index(:versions, [:event, :item_id, :item_type, :user_id])
      end
    end
    """
  end


  defp timestamp do
    {{y, m, d}, {hh, mm, ss}} = :calendar.universal_time()
    "#{y}#{pad(m)}#{pad(d)}#{pad(hh)}#{pad(mm)}#{pad(ss)}"
  end

  defp pad(i) when i < 10, do: << ?0, ?0 + i >>
  defp pad(i), do: to_string(i)
end