defmodule Microwaveprop.Weather.Soundings do
  @moduledoc false

  import Ecto.Query

  alias Microwaveprop.Repo
  alias Microwaveprop.Weather.Sounding
  alias Microwaveprop.Weather.Station
  alias Microwaveprop.Weather.SurfaceObservation

  # Approximate km per degree latitude
  @km_per_deg_lat 111.0
  @sounding_search_radii_km [150, 300, 600, 1000]

  @spec upsert_sounding(Station.t(), map()) :: {:ok, Sounding.t()} | {:error, Ecto.Changeset.t()}
  def upsert_sounding(%Station{} = station, attrs) do
    attrs = Map.put(attrs, :station_id, station.id)

    %Sounding{}
    |> Sounding.changeset(attrs)
    |> Repo.insert(
      on_conflict:
        from(s in Sounding,
          update: [
            set: [
              profile: fragment("EXCLUDED.profile"),
              level_count: fragment("EXCLUDED.level_count"),
              surface_pressure_mb: fragment("EXCLUDED.surface_pressure_mb"),
              surface_temp_c: fragment("EXCLUDED.surface_temp_c"),
              surface_dewpoint_c: fragment("EXCLUDED.surface_dewpoint_c"),
              surface_refractivity: fragment("EXCLUDED.surface_refractivity"),
              min_refractivity_gradient: fragment("EXCLUDED.min_refractivity_gradient"),
              boundary_layer_depth_m: fragment("EXCLUDED.boundary_layer_depth_m"),
              precipitable_water_mm: fragment("EXCLUDED.precipitable_water_mm"),
              k_index: fragment("EXCLUDED.k_index"),
              lifted_index: fragment("EXCLUDED.lifted_index"),
              ducting_detected: fragment("EXCLUDED.ducting_detected"),
              duct_characteristics: fragment("EXCLUDED.duct_characteristics"),
              updated_at: fragment("EXCLUDED.updated_at")
            ]
          ],
          where:
            s.level_count != fragment("EXCLUDED.level_count") or
              s.surface_temp_c != fragment("EXCLUDED.surface_temp_c") or
              s.surface_refractivity != fragment("EXCLUDED.surface_refractivity")
        ),
      conflict_target: [:station_id, :observed_at],
      returning: true,
      stale_error_field: :id
    )
  end

  @spec has_sounding?(Ecto.UUID.t(), DateTime.t()) :: boolean()
  def has_sounding?(station_id, observed_at) do
    Sounding
    |> where([s], s.station_id == ^station_id and s.observed_at == ^observed_at)
    |> Repo.exists?()
  end

  @doc "Returns a MapSet of {station_id, observed_at} tuples that have soundings."
  @spec station_ids_with_soundings([Ecto.UUID.t()], [DateTime.t()]) :: MapSet.t({Ecto.UUID.t(), DateTime.t()})
  def station_ids_with_soundings(station_ids, sounding_times) do
    Sounding
    |> where([s], s.station_id in ^station_ids and s.observed_at in ^sounding_times)
    |> select([s], {s.station_id, s.observed_at})
    |> distinct(true)
    |> Repo.all()
    |> MapSet.new()
  end

  @spec sounding_times_around(DateTime.t()) :: [DateTime.t()]
  def sounding_times_around(dt) do
    date = DateTime.to_date(dt)

    times =
      if dt.hour < 12 do
        [
          DateTime.new!(Date.add(date, -1), ~T[12:00:00], "Etc/UTC"),
          DateTime.new!(date, ~T[00:00:00], "Etc/UTC")
        ]
      else
        [
          DateTime.new!(date, ~T[00:00:00], "Etc/UTC"),
          DateTime.new!(date, ~T[12:00:00], "Etc/UTC")
        ]
      end

    Enum.uniq(times)
  end

  @spec weather_for_contact(map(), keyword()) :: %{
          surface_observations: [SurfaceObservation.t()],
          soundings: [Sounding.t()]
        }
  def weather_for_contact(contact_params, opts \\ []) do
    lat = contact_params[:lat] || contact_params.lat
    lon = contact_params[:lon] || contact_params.lon
    timestamp = contact_params[:timestamp] || contact_params.timestamp

    radius_km = Keyword.get(opts, :radius_km, 150)
    time_window_hours = Keyword.get(opts, :time_window_hours, 6)

    # Bounding box in degrees
    dlat = radius_km / @km_per_deg_lat
    dlon = radius_km / (@km_per_deg_lat * :math.cos(lat * :math.pi() / 180))

    time_start = DateTime.shift(timestamp, hour: -time_window_hours)
    time_end = DateTime.shift(timestamp, hour: time_window_hours)

    station_ids =
      Station
      |> where(
        [s],
        s.lat >= ^(lat - dlat) and s.lat <= ^(lat + dlat) and
          s.lon >= ^(lon - dlon) and s.lon <= ^(lon + dlon)
      )
      |> select([s], s.id)

    surface_observations =
      SurfaceObservation
      |> where([o], o.station_id in subquery(station_ids))
      |> where([o], o.observed_at >= ^time_start and o.observed_at <= ^time_end)
      |> preload(:station)
      |> Repo.all()

    soundings =
      Sounding
      |> where([s], s.station_id in subquery(station_ids))
      |> where([s], s.observed_at >= ^time_start and s.observed_at <= ^time_end)
      |> preload(:station)
      |> Repo.all()

    %{surface_observations: surface_observations, soundings: soundings}
  end

  @doc """
  Search for soundings in widening radii around the given location, stopping
  at the first radius that returns any. Returns `%{soundings, radius_km,
  exhausted}` where `exhausted: true` means the widest radius also came up
  empty — the caller should trigger a fetch for missing data at that point.
  """
  @spec soundings_with_widening_radius(map()) :: %{
          soundings: [Sounding.t()],
          radius_km: pos_integer(),
          exhausted: boolean()
        }
  def soundings_with_widening_radius(params) do
    Enum.reduce_while(@sounding_search_radii_km, nil, fn radius_km, _acc ->
      result = weather_for_contact(params, radius_km: radius_km)

      if result.soundings == [] do
        {:cont, %{soundings: [], radius_km: radius_km, exhausted: true}}
      else
        {:halt, %{soundings: result.soundings, radius_km: radius_km, exhausted: false}}
      end
    end)
  end

  @doc """
  Nearest sounding to (`lat`, `lon`) within `radius_km` km and a ±3-hour
  window around `timestamp`. Joins `weather_stations` to `soundings` so
  the caller gets the raw sounding row (station_id set, derived duct
  fields populated) back.

  Returns `{:ok, sounding}` or `{:error, :not_found}`. Use this in the
  path calculator to surface the nearest RAOB's `ducting_detected` flag
  as an independent check on HRRR's pressure-level duct signal, which
  under-reads thin surface ducts.
  """
  @spec nearest_sounding_to(float(), float(), DateTime.t(), keyword()) ::
          {:ok, Sounding.t()} | {:error, :not_found}
  def nearest_sounding_to(lat, lon, timestamp, opts \\ []) do
    radius_km = Keyword.get(opts, :radius_km, 300)
    hours = Keyword.get(opts, :hours, 3)

    # 1 deg lat ≈ 111 km; lon scaled by cos(lat).
    dlat = radius_km / 111.0
    dlon = radius_km / (111.0 * max(0.1, :math.cos(lat * :math.pi() / 180.0)))
    time_start = DateTime.shift(timestamp, hour: -hours)
    time_end = DateTime.shift(timestamp, hour: hours)

    from(s in Sounding,
      join: station in assoc(s, :station),
      where:
        station.lat >= ^(lat - dlat) and station.lat <= ^(lat + dlat) and
          station.lon >= ^(lon - dlon) and station.lon <= ^(lon + dlon) and
          s.observed_at >= ^time_start and s.observed_at <= ^time_end,
      order_by:
        fragment(
          "SQRT(POW(? - ?, 2) + POW(? - ?, 2)) + ABS(EXTRACT(EPOCH FROM ? - ?)) / 86400.0",
          station.lat,
          ^lat,
          station.lon,
          ^lon,
          s.observed_at,
          ^timestamp
        ),
      limit: 1,
      preload: [:station]
    )
    |> Repo.one()
    |> case do
      nil -> {:error, :not_found}
      sounding -> {:ok, sounding}
    end
  end
end