defmodule Microwaveprop.Propagation do
  @moduledoc false

  import Ecto.Query

  alias Microwaveprop.Propagation.BandConfig
  alias Microwaveprop.Propagation.RunTiming
  alias Microwaveprop.Propagation.Scorer
  alias Microwaveprop.Propagation.ScoreStore
  alias Microwaveprop.Repo

  # ── ML Model Lifecycle ──────────────────────────────────────────────

  alias Microwaveprop.Weather.SoundingParams

  require Logger

  @ml_key :propagation_ml
  @ml_module Microwaveprop.Propagation.Model

  @doc """
  Loads the ML model from disk, compiles the predict function, and caches both
  in persistent_term. No-op if the model file doesn't exist or ML deps unavailable.
  """
  @spec load_ml_model() :: :ok
  def load_ml_model do
    if Code.ensure_loaded?(@ml_module) do
      # credo:disable-for-next-line Credo.Check.Refactor.Apply
      case apply(@ml_module, :load, []) do
        {:ok, params} ->
          # credo:disable-for-next-line Credo.Check.Refactor.Apply
          predict_fn = apply(@ml_module, :compile_predict, [])
          :persistent_term.put(@ml_key, {predict_fn, params})
          Logger.info("PropagationML: model loaded and compiled")
          :ok

        :error ->
          Logger.info("PropagationML: no model file found, using algorithm scorer only")
          :ok
      end
    else
      Logger.info("PropagationML: ML dependencies not available")

      # ── Scoring ─────────────────────────────────────────────────────────
      :ok
    end
  end

  @doc "Returns cached {predict_fn, params} tuple, or nil if not loaded."
  @spec ml_model() :: {function(), term()} | nil
  def ml_model do
    :persistent_term.get(@ml_key, nil)
  end

  @doc """
  Score a single grid point across all bands using HRRR profile data.
  Uses ML model if loaded, falls back to algorithm scorer.
  Returns a list of %{band_mhz, score, factors} maps.
  """
  @spec score_grid_point(map(), DateTime.t(), float(), float()) ::
          [%{band_mhz: non_neg_integer(), score: non_neg_integer(), factors: map()}]
  def score_grid_point(hrrr_profile, valid_time, latitude, longitude) do
    derived = derive_from_hrrr(hrrr_profile)

    temp_c = hrrr_profile.surface_temp_c
    dewpoint_c = hrrr_profile.surface_dewpoint_c

    # Skip points with missing or physically impossible surface data
    if is_nil(temp_c) or is_nil(dewpoint_c) or temp_c < -80 or temp_c > 60 or
         dewpoint_c < -80 or dewpoint_c > 50 do
      []
    else
      score_grid_point_with_data(hrrr_profile, valid_time, temp_c, dewpoint_c, derived, latitude, longitude)
    end
  end

  defp score_grid_point_with_data(hrrr_profile, valid_time, temp_c, dewpoint_c, derived, latitude, longitude) do
    # Algorithm is the primary scorer — always used for the map score.
    # ML score stored in factors as :ml_score for comparison/analysis.
    score_with_algorithm(hrrr_profile, valid_time, temp_c, dewpoint_c, derived, latitude, longitude)
  end

  defp score_with_algorithm(hrrr_profile, valid_time, temp_c, dewpoint_c, derived, latitude, longitude) do
    temp_f = Scorer.c_to_f(temp_c)
    dewpoint_f = Scorer.c_to_f(dewpoint_c)

    conditions = %{
      abs_humidity: Scorer.absolute_humidity(temp_c, dewpoint_c),
      temp_f: temp_f,
      dewpoint_f: dewpoint_f,
      wind_speed_kts: Scorer.wind_speed_kts(hrrr_profile[:wind_u], hrrr_profile[:wind_v]),
      sky_cover_pct: hrrr_profile[:cloud_cover_pct],
      utc_hour: valid_time.hour,
      utc_minute: valid_time.minute,
      month: valid_time.month,
      latitude: latitude,
      longitude: longitude,
      pressure_mb: hrrr_profile.surface_pressure_mb,
      prev_pressure_mb: nil,
      rain_rate_mmhr: merged_rain_rate(hrrr_profile),
      min_refractivity_gradient: hrrr_profile[:native_min_gradient] || derived[:min_refractivity_gradient],
      bl_depth_m: hrrr_profile[:hpbl_m],
      pwat_mm: hrrr_profile[:pwat_mm],
      best_duct_band_ghz: hrrr_profile[:best_duct_freq_ghz] || hrrr_profile[:best_duct_band_ghz],
      bulk_richardson: hrrr_profile[:bulk_richardson]
    }

    # Hoist the four band-invariant factors out of the 17-band inner
    # loop. time_of_day / sky / wind / pressure depend on conditions
    # alone, not the band — precomputing once per point drops ~30% of
    # the scoring wall time on the hourly chain.
    conditions = Map.merge(conditions, Scorer.precompute_band_invariants(conditions))

    duct_info =
      if hrrr_profile[:duct_count] && hrrr_profile[:duct_count] > 0 do
        %{
          duct_count: hrrr_profile[:duct_count],
          best_duct_freq_ghz: hrrr_profile[:best_duct_freq_ghz],
          max_duct_thickness_m: hrrr_profile[:max_duct_thickness_m],
          ducts: hrrr_profile[:ducts] || []
        }
      end

    link_degradation = hrrr_profile[:commercial_link_degradation]
    # Kp is grid-point-invariant within a cycle. Callers populate
    # `:kp_index` once per scoring run (see SpaceWeather.latest_kp/0)
    # so we never query the DB inside the per-point band loop. Nil
    # means no aurora boost — the same fallback that quiet
    # geomagnetic conditions produce.
    kp_index = hrrr_profile[:kp_index]

    Enum.map(BandConfig.all_bands(), fn band_config ->
      conditions
      |> Scorer.composite_score(band_config)
      |> finalize_band_result(band_config, link_degradation, kp_index, duct_info)
    end)
  end

  # Apply terminal boosts and stash diagnostic factor entries. Split
  # out of `score_with_algorithm/7` to keep its cyclomatic complexity
  # within credo's per-function limit; this helper owns the
  # band-level conditional plumbing instead.
  defp finalize_band_result(result, band_config, link_degradation, kp_index, duct_info) do
    boosted_score =
      result.score
      |> maybe_apply_link_boost(link_degradation)
      |> Scorer.aurora_boost(kp_index, band_config)

    result
    |> Map.put(:score, boosted_score)
    |> Map.put(:band_mhz, band_config.freq_mhz)
    |> maybe_put_factor(:commercial_link_degradation, link_degradation)
    |> maybe_put_kp_factor(kp_index, band_config)
    |> maybe_put_factor(:duct_info, duct_info)
  end

  defp maybe_apply_link_boost(score, nil), do: score
  defp maybe_apply_link_boost(score, link_degradation), do: Scorer.commercial_link_boost(score, link_degradation)

  defp maybe_put_factor(result, _key, nil), do: result
  defp maybe_put_factor(result, key, value), do: put_in(result, [:factors, key], value)

  defp maybe_put_kp_factor(result, nil, _band_config), do: result
  defp maybe_put_kp_factor(result, _kp, %{freq_mhz: f}) when f > 432, do: result
  defp maybe_put_kp_factor(result, kp, _band_config), do: put_in(result, [:factors, :kp_index], kp)

  # Pick the heavier of HRRR's hourly accumulation-derived rate and NEXRAD's
  # reflectivity-derived rate. NEXRAD catches fast-moving convective cells that
  # fall between HRRR hourly analyses; HRRR catches broad stratiform rain that
  # NEXRAD reports as low dBZ. Taking max lets either source trigger the rain
  # penalty without double-counting.
  defp merged_rain_rate(hrrr_profile) do
    hrrr_rate = Scorer.precip_to_rate_mmhr(hrrr_profile[:precip_mm])
    nexrad_rate = Scorer.dbz_to_rain_rate_mmhr(hrrr_profile[:nexrad_max_reflectivity_dbz])
    max(hrrr_rate, nexrad_rate)
  end

  defdelegate replace_scores(scores, valid_time), to: ScoreStore
  defdelegate prune_old_scores(), to: ScoreStore
  defdelegate retain_scores_window(run_time), to: ScoreStore
  defdelegate available_valid_times(band_mhz), to: ScoreStore
  # ── Delegates to ScoreStore (file I/O + cache) ──────────────────────
  defdelegate hot_cache_window(), to: ScoreStore
  defdelegate scores_at(band_mhz, valid_time, bounds \\ nil), to: ScoreStore
  defdelegate scores_at_fresh(band_mhz, valid_time, bounds \\ nil), to: ScoreStore
  defdelegate warm_cache_and_broadcast(band_mhz, valid_time), to: ScoreStore
  defdelegate latest_scores(band_mhz, bounds \\ nil), to: ScoreStore
  defdelegate point_forecast(band_mhz, lat, lon), to: ScoreStore
  defdelegate point_detail(band_mhz, lat, lon, valid_time \\ nil), to: ScoreStore
  defdelegate latest_valid_time(), to: ScoreStore

  # ── Scoring helpers called from ScoreStore ──────────────────────────
  defdelegate latest_valid_time(band_mhz), to: ScoreStore

  @doc """
  Rebuild the factor breakdown for a clicked grid cell by rescoring
  the persisted HRRR profile. Made public so ScoreStore can call it
  after reading the profile from disk.
  """
  @spec factors_from_profile(non_neg_integer(), DateTime.t(), map(), float(), float()) :: map()
  def factors_from_profile(band_mhz, valid_time, profile, lat, lon) do
    profile
    |> Map.put(:kp_index, current_kp_index())
    |> score_grid_point(valid_time, lat, lon)
    |> Enum.find(fn r -> r.band_mhz == band_mhz end)
    |> case do
      %{factors: factors} when is_map(factors) -> factors
      _ -> %{}
    end
  end

  # Latest geomagnetic Kp from SWPC, used by the aurora boost. Returns
  # nil if SpaceWeather hasn't been ingested yet (boost falls back to
  # quiet-conditions no-op). Prefer the integer `kp_index` over
  # `estimated_kp` so the threshold edges in `Scorer.aurora_boost/3`
  # are deterministic during the 3-hour window between official Kp
  # publications.
  defp current_kp_index do
    case Microwaveprop.SpaceWeather.latest_kp() do
      %{kp_index: kp} when is_integer(kp) -> kp
      %{estimated_kp: kp} when is_number(kp) -> trunc(kp)
      _ -> nil
    end

    # ── Run timings ─────────────────────────────────────────────────────
  end

  @doc """
  Record wall-clock duration for a single forecast-hour chain step.

  Called by `PropagationGridWorker` at the end of every step (success or
  failure) so the timing history survives pod restarts and can be
  inspected later to see which steps are slow or flaky.
  """
  @spec record_run_timing(map()) ::
          {:ok, RunTiming.t()} | {:error, Ecto.Changeset.t()}
  def record_run_timing(attrs) do
    %RunTiming{}
    |> RunTiming.changeset(attrs)
    |> Repo.insert()
  end

  @doc """
  List the most-recently-started run-timing rows, newest first.

  Defaults to 100 rows; pass `:limit` to override.
  """
  @spec list_recent_run_timings(keyword()) :: [RunTiming.t()]
  def list_recent_run_timings(opts \\ []) do
    limit = Keyword.get(opts, :limit, 100)

    RunTiming
    |> order_by(desc: :started_at)
    |> limit(^limit)
    |> Repo.all()
  end

  # ── Derived factors ─────────────────────────────────────────────────

  # Prefer the persisted scalar — `hrrr_profiles` already stored this at
  # ingestion time and AsosAdjustmentWorker loads 92k rows per tick without
  # the JSONB `profile` column to avoid a Jason.decode! storm on the DB pool.
  defp derive_from_hrrr(%{min_refractivity_gradient: grad}) when is_number(grad) do
    %{min_refractivity_gradient: grad * 1.0}
  end

  defp derive_from_hrrr(%{profile: [_, _, _ | _] = profile}) do
    case SoundingParams.derive(profile) do
      nil -> %{}
      derived -> %{min_refractivity_gradient: derived.min_refractivity_gradient}
    end
  end

  defp derive_from_hrrr(_), do: %{}
end