defmodule ArcadiaCloud.Provisioning.Steps.LinkDeploymentResource do
  @moduledoc """
  Attaches the freshly-registered cloud resource (set by RegisterDroplet
  as `cloud_resource_id` in context) to the saga's deployment: stamps
  `deployment_id` and `tenant_id` onto the `cloud_resources` row.

  This is what makes the resource show up under the deployment in
  inventory and bill against the right tenant.

  Idempotent: re-running just re-writes the same two columns.

  Compensation: clears `deployment_id` and `tenant_id` back to nil. The
  resource row itself (and the droplet) are undone by RegisterDroplet /
  CreateDroplet compensation.
  """

  @behaviour ArcadiaCloud.Provisioning.Step

  import Ecto.Query

  alias ArcadiaCloud.Deployments
  alias ArcadiaCloud.Cloud.CloudResource
  alias ArcadiaCloud.Provisioning.SagaState
  alias ArcadiaCloud.Repo

  @impl true
  def name, do: "link_deployment_resource"

  @impl true
  def execute(state) do
    with {:ok, resource_id} <- fetch(state, :cloud_resource_id),
         {:ok, deployment} <- fetch_deployment(state) do
      {_, _} =
        from(r in CloudResource, where: r.id == ^resource_id)
        |> Repo.update_all(
          set: [
            deployment_id: deployment.id,
            tenant_id: deployment.tenant_id,
            updated_at: DateTime.utc_now() |> DateTime.truncate(:second)
          ]
        )

      {:ok, state}
    end
  end

  @impl true
  def compensate(state) do
    case SagaState.get_output(state, :cloud_resource_id) do
      nil ->
        :ok

      resource_id ->
        from(r in CloudResource, where: r.id == ^resource_id)
        |> Repo.update_all(set: [deployment_id: nil, tenant_id: nil])

        :ok
    end
  end

  defp fetch(state, key) do
    case SagaState.get_output(state, key) do
      nil -> {:error, {:missing_context, key}}
      value -> {:ok, value}
    end
  end

  defp fetch_deployment(state) do
    case state.saga && state.saga.deployment_id do
      nil ->
        {:error, :saga_has_no_deployment}

      id ->
        case Deployments.get_deployment(id) do
          nil -> {:error, :deployment_not_found}
          deployment -> {:ok, deployment}
        end
    end
  end
end