defmodule Microwaveprop.Workers.PropagationGridWorker do
  @moduledoc """
  Hourly Oban worker that downloads HRRR data (analysis + forecast hours)
  and computes propagation scores across the CONUS grid for all bands.
  Fetches f00-f18 to provide 18-hour forecast timeline.
  """

  # `unique.period` matches the 3-hour cron so a retrying job can't be
  # duplicated by the next cron firing.
  use Oban.Worker,
    queue: :propagation,
    max_attempts: 3,
    unique: [period: 10_800, states: [:available, :scheduled, :executing, :retryable]]

  alias Microwaveprop.Commercial
  alias Microwaveprop.Propagation
  alias Microwaveprop.Propagation.BandConfig
  alias Microwaveprop.Propagation.Grid
  alias Microwaveprop.Propagation.ScoreCache
  alias Microwaveprop.Weather
  alias Microwaveprop.Weather.GridCache
  alias Microwaveprop.Weather.HrrrClient
  alias Microwaveprop.Weather.HrrrNativeClient
  alias Microwaveprop.Weather.NexradClient
  alias Microwaveprop.Weather.SoundingParams

  require Logger

  # Hard ceiling per run. A healthy run is ~60 min (19 forecast hours × ~3 min
  # each). 90 min gives 1.5× headroom and is under the 3-hour cron cadence, so
  # a stuck wgrib2/HTTP call can't block the queue indefinitely. Oban kills
  # the executing process on timeout, which closes linked ports and cascades
  # SIGKILL to any child wgrib2 subprocess.
  @run_timeout_ms 90 * 60 * 1000

  @impl Oban.Worker
  def timeout(_job), do: @run_timeout_ms

  @max_forecast_hour 18

  @impl Oban.Worker
  def perform(%Oban.Job{}) do
    t_start = System.monotonic_time(:millisecond)

    # HRRR takes ~45min to publish after the hour. Use 2 hours ago to ensure availability.
    two_hours_ago = DateTime.add(DateTime.utc_now(), -2, :hour)
    run_time = two_hours_ago |> HrrrClient.nearest_hrrr_hour() |> DateTime.truncate(:second)
    points = Grid.conus_points()

    Logger.info("PropagationGrid: run_time=#{run_time}, #{length(points)} points, f00-f#{@max_forecast_hour}")

    for_result =
      for fh <- 0..@max_forecast_hour do
        valid_time = DateTime.add(run_time, fh * 3600, :second)
        result = process_forecast_hour(points, run_time, fh, valid_time)
        # Reclaim grid_data/profiles from this forecast hour before starting the next
        :erlang.garbage_collect()

        case result do
          :ok -> valid_time
          _ -> nil
        end
      end

    valid_times = Enum.reject(for_result, &is_nil/1)

    if valid_times != [] do
      Phoenix.PubSub.broadcast(
        Microwaveprop.PubSub,
        "propagation:updated",
        {:propagation_updated, valid_times}
      )
    end

    total_ms = System.monotonic_time(:millisecond) - t_start
    Logger.info("PropagationGrid: total time #{format_duration(total_ms)} (#{length(valid_times)} forecast hours)")

    Weather.prune_old_grid_profiles()
    Propagation.prune_old_scores()

    :ok
  end

  defp process_forecast_hour(points, run_time, forecast_hour, valid_time) do
    label = "f#{String.pad_leading(Integer.to_string(forecast_hour), 2, "0")}"

    case timed(label, fn ->
           HrrrClient.fetch_grid(points, run_time, forecast_hour: forecast_hour)
         end) do
      {:ok, grid_data} ->
        store_hrrr_profiles(grid_data, valid_time)
        :erlang.garbage_collect()

        # Fetch native duct metrics and merge into grid_data for scoring
        grid_data = merge_native_duct_data(grid_data, run_time, forecast_hour)
        :erlang.garbage_collect()

        # NEXRAD current-hour composite reflectivity catches fast-moving
        # convective cells between HRRR hourly analyses. Only useful for
        # f00 — forecast hours can't see the future radar image.
        grid_data =
          if forecast_hour == 0 do
            merge_nexrad_data(grid_data, valid_time)
          else
            grid_data
          end

        # Commercial-link inverse sensor — only meaningful for f00 because
        # the measurement is of the current atmospheric state, not a forecast.
        grid_data =
          if forecast_hour == 0 do
            merge_commercial_link_data(grid_data, valid_time)
          else
            grid_data
          end

        :erlang.garbage_collect()

        # Build weather cache rows from in-memory grid_data — avoids the ~20s
        # JSONB round trip that was crashing the worker before f01–f18 could run.
        rows = Weather.build_grid_cache_rows(grid_data, valid_time)
        GridCache.broadcast_put(valid_time, rows)

        Phoenix.PubSub.broadcast(
          Microwaveprop.PubSub,
          "weather:updated",
          {:weather_updated, valid_time}
        )

        scores = compute_scores(grid_data, valid_time)

        case Propagation.upsert_scores(scores, prune: false) do
          {:ok, count} ->
            Logger.info("PropagationGrid: #{label} → #{count} scores for #{valid_time}")
            warm_cache(valid_time)
            :ok

          error ->
            Logger.error("PropagationGrid: #{label} upsert failed: #{inspect(error)}")
            error
        end

      error ->
        Logger.warning("PropagationGrid: #{label} fetch failed: #{inspect(error)}")
        error
    end
  end

  defp warm_cache(valid_time) do
    Enum.each(BandConfig.all_bands(), fn band ->
      Propagation.warm_cache_and_broadcast(band.freq_mhz, valid_time)
    end)

    ScoreCache.prune_older_than(DateTime.add(DateTime.utc_now(), -2, :hour))
  end

  defp timed(label, fun) do
    t0 = System.monotonic_time(:millisecond)
    result = fun.()
    elapsed = System.monotonic_time(:millisecond) - t0
    Logger.info("PropagationGrid: #{label} took #{format_duration(elapsed)}")
    result
  end

  defp format_duration(ms) when ms < 1000, do: "#{ms}ms"
  defp format_duration(ms), do: "#{Float.round(ms / 1000, 1)}s"

  defp store_hrrr_profiles(grid_data, valid_time) do
    count =
      grid_data
      |> Stream.flat_map(fn {{lat, lon}, profile} ->
        build_profile_attrs_for_grid(lat, lon, valid_time, profile)
      end)
      |> Stream.chunk_every(500)
      |> Enum.reduce(0, fn chunk, acc ->
        Weather.upsert_hrrr_profiles_batch(chunk)
        acc + length(chunk)
      end)

    Logger.info("PropagationGrid: stored #{count} HRRR profiles")
  end

  defp build_profile_attrs_for_grid(lat, lon, valid_time, profile) do
    temp = profile.surface_temp_c

    if temp && temp > -80 && temp < 60 do
      params =
        if is_list(profile.profile) and length(profile.profile) >= 3,
          do: SoundingParams.derive(profile.profile)

      attrs = %{
        valid_time: valid_time,
        lat: lat,
        lon: lon,
        run_time: profile.run_time,
        profile: profile.profile || [],
        hpbl_m: profile.hpbl_m,
        pwat_mm: profile.pwat_mm,
        surface_temp_c: profile.surface_temp_c,
        surface_dewpoint_c: profile.surface_dewpoint_c,
        surface_pressure_mb: profile.surface_pressure_mb
      }

      attrs =
        if params do
          Map.merge(attrs, %{
            surface_refractivity: params.surface_refractivity,
            min_refractivity_gradient: params.min_refractivity_gradient,
            ducting_detected: params.ducting_detected,
            duct_characteristics: params.duct_characteristics
          })
        else
          attrs
        end

      [attrs]
    else
      []
    end
  end

  defp merge_native_duct_data(grid_data, run_time, forecast_hour) do
    hour_dt = HrrrClient.nearest_hrrr_hour(run_time)
    date = DateTime.to_date(hour_dt)
    hour = hour_dt.hour
    grid_spec = Grid.wgrib2_grid_spec()

    case timed("native", fn ->
           HrrrNativeClient.fetch_native_duct_grid(date, hour, grid_spec, forecast_hour)
         end) do
      {:ok, duct_grid} ->
        Logger.info("PropagationGrid: merged #{map_size(duct_grid)} native duct cells")
        apply_duct_grid(grid_data, duct_grid)

      {:error, reason} ->
        Logger.warning("PropagationGrid: native duct fetch failed (continuing without): #{inspect(reason)}")
        grid_data
    end
  end

  defp apply_duct_grid(grid_data, duct_grid) do
    Map.new(grid_data, fn {point, profile} ->
      case Map.get(duct_grid, point) do
        nil -> {point, profile}
        duct -> {point, Map.merge(profile, duct)}
      end
    end)
  end

  defp merge_commercial_link_data(grid_data, valid_time) do
    # Compute link degradation once per distinct link cluster and cache by
    # point. Commercial links only cluster around DFW so most grid points see
    # nil — cheap no-op path dominates.
    boosted =
      Enum.count(grid_data, fn {{lat, lon}, _profile} ->
        degradation = Commercial.link_degradation_at({lat, lon}, valid_time)
        not is_nil(degradation)
      end)

    if boosted > 0 do
      Logger.info("PropagationGrid: commercial-link degradation available for #{boosted} grid cells")
    end

    Map.new(grid_data, fn {{lat, lon} = point, profile} ->
      case Commercial.link_degradation_at({lat, lon}, valid_time) do
        nil -> {point, profile}
        degradation -> {point, Map.put(profile, :commercial_link_degradation, degradation)}
      end
    end)
  end

  defp merge_nexrad_data(grid_data, valid_time) do
    points = Map.keys(grid_data)

    case timed("nexrad", fn -> NexradClient.fetch_frame(valid_time, points) end) do
      {:ok, observations} ->
        apply_nexrad_observations(grid_data, observations)

      {:error, reason} ->
        Logger.warning("PropagationGrid: NEXRAD fetch failed (continuing without): #{inspect(reason)}")
        grid_data
    end
  end

  defp apply_nexrad_observations(grid_data, observations) do
    index = Map.new(observations, fn obs -> {{obs.lat, obs.lon}, obs.max_reflectivity_dbz} end)
    non_zero = Enum.count(index, fn {_pt, dbz} -> dbz > 0 end)
    Logger.info("PropagationGrid: NEXRAD merged (#{non_zero} cells with precip)")

    Map.new(grid_data, fn {point, profile} ->
      case Map.get(index, point) do
        nil -> {point, profile}
        dbz -> {point, Map.put(profile, :nexrad_max_reflectivity_dbz, dbz)}
      end
    end)
  end

  defp compute_scores(grid_data, valid_time) do
    # Algorithm is the primary scorer. ML score stored in factors for comparison.
    compute_scores_algorithm(grid_data, valid_time)
  end

  defp compute_scores_algorithm(grid_data, valid_time) do
    grid_data
    |> Task.async_stream(
      fn {{lat, lon}, profile} ->
        band_scores = Propagation.score_grid_point(profile, valid_time, lat, lon)

        Enum.map(band_scores, fn r ->
          %{lat: lat, lon: lon, valid_time: valid_time, band_mhz: r.band_mhz, score: r.score, factors: r.factors}
        end)
      end,
      max_concurrency: System.schedulers_online() * 2,
      timeout: 30_000
    )
    |> Stream.flat_map(fn
      {:ok, results} -> results
      {:exit, _reason} -> []
    end)
  end
end