defmodule ArcadiaCloud.Provisioning.Steps.WaitDropletActive do
  @moduledoc """
  Polls a droplet (created by a prior CreateDroplet step) until its
  status is "active". Reads `droplet_id` from saga context.

  No compensation — waiting has no side effect to undo. If the saga
  rolls back, the prior CreateDroplet step's compensate destroys the
  droplet regardless of whether it ever reached active.
  """

  @behaviour ArcadiaCloud.Provisioning.Step

  alias ArcadiaCloud.DigitalOcean.Client
  alias ArcadiaCloud.Provisioning.SagaState

  @poll_interval_ms 5_000
  @poll_max_attempts 96

  @impl true
  def name, do: "wait_droplet_active"

  @impl true
  def execute(state) do
    case SagaState.get_output(state, :droplet_id) do
      nil -> {:error, :no_droplet_id_in_context}
      droplet_id -> poll(state, droplet_id, 1)
    end
  end

  defp poll(_state, _droplet_id, attempt) when attempt > @poll_max_attempts do
    {:error, :droplet_active_timeout}
  end

  defp poll(state, droplet_id, attempt) do
    case Client.get_droplet(droplet_id) do
      {:ok, %{"status" => "active"} = droplet} ->
        public_ip = extract_public_ip(droplet)
        {:ok, SagaState.put_output(state, :droplet_public_ip, public_ip)}

      {:ok, %{"status" => status}} when status in ["new", "off"] ->
        Process.sleep(@poll_interval_ms)
        poll(state, droplet_id, attempt + 1)

      {:ok, %{"status" => other}} ->
        {:error, {:unexpected_droplet_status, other}}

      {:error, reason} ->
        {:error, reason}
    end
  end

  defp extract_public_ip(droplet) do
    droplet
    |> get_in(["networks", "v4"])
    |> List.wrap()
    |> Enum.find(%{}, &(&1["type"] == "public"))
    |> Map.get("ip_address")
  end
end