neiam /gitgud

defmodule GitGud.Repo.Migrations.CreateEvents do
  use Ecto.Migration

  # An append-only log of what happened to an issue or pull request:
  # pushes, title edits, state flips, labels, moderation. Polymorphic
  # over `target_type` the same way `labelings` is, rather than one
  # table per target — the history pages read them identically and the
  # alternative is two schemas that differ only in a foreign key.
  #
  # `actor_id` is nullable on purpose: pushes are recorded by a worker
  # with no user attached, and federated actions arrive from a remote
  # actor rather than a local one.
  def change do
    create table(:events) do
      add :target_type, :string, null: false
      add :target_id, :bigint, null: false
      add :kind, :string, null: false
      # Per-kind payload — old/new titles, sha pair, label name, etc.
      # Shapes are documented on GitGud.Events.
      add :data, :map, null: false, default: %{}

      add :actor_id, references(:users, on_delete: :nilify_all)

      timestamps(type: :utc_datetime, updated_at: false)
    end

    # The only read: one target's history, oldest first.
    create index(:events, [:target_type, :target_id, :inserted_at])
  end
end