if Code.ensure_loaded?(Ecto.Adapters.SQL) do
  defmodule Ecto.Adapters.QuackDB do
    @moduledoc """
    Minimal Ecto SQL adapter for QuackDB.

    The first Ecto milestone intentionally supports raw SQL through
    `Ecto.Adapters.SQL.query/4` and repository `query/3` helpers only. Schema
    query generation, migrations, storage callbacks, and write planning are not
    implemented yet.

    ## Configuration

        config :my_app, MyApp.AnalyticsRepo,
          adapter: Ecto.Adapters.QuackDB,
          uri: "http://[::1]:9494",
          token: "super_secret"

    """

    use Ecto.Adapters.SQL,
      driver: :quackdb

    @impl Ecto.Adapter.Migration
    def supports_ddl_transaction?, do: true

    @impl Ecto.Adapter.Migration
    def lock_for_migrations(_meta, _options, _fun) do
      unsupported!(
        :migrations,
        "Ecto migrations are not supported yet; use Repo.query/3 for raw SQL"
      )
    end

    @impl Ecto.Adapter.Schema
    def autogenerate(:id), do: nil
    def autogenerate(:embed_id), do: Ecto.UUID.generate()
    def autogenerate(:binary_id), do: Ecto.UUID.bingenerate()

    defp unsupported!(feature, message) do
      raise QuackDB.Error.new(:ecto_feature_not_supported, message,
              source: :client,
              metadata: %{feature: feature}
            )
    end
  end
end