defmodule Microwaveprop.Workers.IemreFetchWorker do
  @moduledoc false
  use Oban.Pro.Worker,
    queue: :iemre,
    max_attempts: 20,
    unique: [period: 300, fields: [:args], states: :scheduled]

  alias Microwaveprop.Weather
  alias Microwaveprop.Weather.IemClient

  require Logger

  @impl Oban.Worker
  def backoff(%Oban.Job{attempt: attempt}) do
    min(120 * Integer.pow(2, attempt - 1), _six_hours = 21_600)
  end

  @impl Oban.Pro.Worker
  def process(%Oban.Job{args: args}) do
    %{"lat" => lat, "lon" => lon, "date" => date_str} = args
    date = Date.from_iso8601!(date_str)

    if Weather.has_iemre_observation?(lat, lon, date) do
      Logger.info("IEMRE observation already exists for #{lat},#{lon} @ #{date_str}")
      :ok
    else
      Logger.info("Fetching IEMRE data for #{lat},#{lon} @ #{date_str}")
      fetch_and_store_iemre(lat, lon, date, date_str)
    end
  end

  defp fetch_and_store_iemre(lat, lon, date, date_str) do
    case IemClient.fetch_iemre(lat, lon, date) do
      {:ok, []} ->
        # Store stub so this lat/lon/date isn't retried on future backfills
        _ = Weather.upsert_iemre_observation(%{lat: lat, lon: lon, date: date, hourly: []})
        Logger.info("IEMRE: no data available for #{lat},#{lon} @ #{date_str}, stored stub")
        :ok

      {:ok, data} ->
        _ =
          Weather.upsert_iemre_observation(%{
            lat: lat,
            lon: lon,
            date: date,
            hourly: data
          })

        Logger.info("IEMRE observation saved for #{lat},#{lon} @ #{date_str} (#{length(data)} hours)")
        :ok

      {:error, reason} ->
        handle_error(reason, lat, lon, date, date_str)
    end
  end

  defp handle_error(reason, lat, lon, date, date_str) do
    case classify_failure(reason) do
      :transient ->
        Logger.error("IEMRE transient error for #{lat},#{lon} @ #{date_str}: #{inspect(reason)}")
        {:error, reason}

      :permanent ->
        # Permanent upstream failure (e.g. 404, 422 out-of-grid). Stub
        # the bucket so future backfill enqueues skip the fetch and
        # let ContactWeatherEnqueueWorker reconcile the contacts'
        # :queued → :complete transition via the empty-jobs branch.
        _ = Weather.upsert_iemre_observation(%{lat: lat, lon: lon, date: date, hourly: []})

        Logger.warning("IEMRE permanent failure for #{lat},#{lon} @ #{date_str}: #{inspect(reason)}, stored stub")

        {:cancel, reason}
    end
  end

  # Network/transport exceptions are always transient; retry.
  defp classify_failure(%{__exception__: true}), do: :transient

  # IEM surfaces the HTTP status in the reason string. Split the integer
  # back out and pattern-match rate-limit / 5xx codes as transient.
  defp classify_failure("IEM IEMRE HTTP " <> status) do
    case Integer.parse(status) do
      {code, _} when code in [429, 500, 502, 503, 504] -> :transient
      _ -> :permanent
    end
  end

  # Anything else (404, 422, unexpected shapes) is permanent — cancel
  # the job and stub the bucket.
  defp classify_failure(_), do: :permanent
end