defmodule Microwaveprop.Workers.RoverPathProfileWorker do
  @moduledoc """
  Computes a terrain path profile for one rover-location → station
  pairing inside a `RoverPlanning.Mission`. Mirrors the synchronous
  `MicrowavepropWeb.PathLive` compute pipeline (elevation profile +
  ITU-R P.526 analysis at the mission's band + heights) and stores
  the result as JSON on the matching `RoverPlanning.Path`.

  The HRRR-along-path step from `/path` is intentionally skipped here:
  it depends on real-time profile grids that aren't worth pinning to a
  stored mission result. The rendered show page can re-fetch live
  weather on demand if needed.
  """
  use Oban.Worker,
    queue: :terrain,
    max_attempts: 5,
    unique: [
      period: 300,
      keys: [:mission_id, :rover_location_id, :station_id],
      states: [:available, :scheduled, :executing, :retryable]
    ]

  import Ecto.Query

  alias Microwaveprop.Geo
  alias Microwaveprop.Propagation.ScoresFile
  alias Microwaveprop.Repo
  alias Microwaveprop.RoverPlanning.Path
  alias Microwaveprop.Terrain.ElevationClient
  alias Microwaveprop.Terrain.TerrainAnalysis

  require Logger

  @impl Oban.Worker
  def backoff(%Oban.Job{attempt: attempt}) do
    min(60 * Integer.pow(2, attempt - 1), 3600)
  end

  @impl Oban.Worker
  def perform(%Oban.Job{
        args: %{"mission_id" => mission_id, "rover_location_id" => rover_location_id, "station_id" => station_id}
      }) do
    case load_path(mission_id, rover_location_id, station_id) do
      nil ->
        :ok

      %Path{status: :complete} ->
        :ok

      %Path{} = path ->
        run(path)
    end
  end

  defp load_path(mission_id, rover_location_id, station_id) do
    Path
    |> where([p], p.mission_id == ^mission_id)
    |> where([p], p.rover_location_id == ^rover_location_id)
    |> where([p], p.station_id == ^station_id)
    |> preload([:rover_location, :station, :mission])
    |> Repo.one()
  end

  defp run(%Path{rover_location: rover, station: station, mission: mission} = path) do
    mark_status(path, :computing)

    rover_height_m = (mission.rover_height_ft || 8.0) * 0.3048
    station_height_m = (mission.station_height_ft || 30.0) * 0.3048
    freq_ghz = mission.band_mhz / 1000
    dist_km = Geo.haversine_km(rover.lat, rover.lon, station.lat, station.lon)
    bearing = Geo.bearing_deg(rover.lat, rover.lon, station.lat, station.lon)

    case ElevationClient.fetch_elevation_profile(
           rover.lat,
           rover.lon,
           station.lat,
           station.lon,
           64,
           download: true
         ) do
      {:ok, profile} ->
        analysis =
          TerrainAnalysis.analyse(profile, dist_km, freq_ghz,
            ant_ht_a: rover_height_m,
            ant_ht_b: station_height_m
          )

        midlat = (rover.lat + station.lat) / 2
        midlon = (rover.lon + station.lon) / 2
        propagation_score = lookup_propagation_score(mission.band_mhz, midlat, midlon)

        store_complete(path, profile, analysis, dist_km, bearing, propagation_score)

      {:error, reason} ->
        store_failed(path, "elevation profile failed: #{inspect(reason)}")
    end
  rescue
    e ->
      Logger.error("RoverPathProfileWorker crashed for path=#{path.id}: #{Exception.message(e)}")
      store_failed(path, "exception: #{Exception.message(e)}")
      reraise e, __STACKTRACE__
  end

  defp store_complete(path, profile, analysis, dist_km, bearing, propagation_score) do
    points =
      Enum.map(profile, fn p ->
        %{
          "lat" => p.lat,
          "lon" => p.lon,
          "d" => p.d,
          "elev" => p.elev,
          "dist_km" => p.dist_km
        }
      end)

    result = %{
      "distance_km" => dist_km,
      "bearing_deg" => bearing,
      "max_elevation_m" => analysis.max_elevation_m,
      "min_clearance_m" => analysis.min_clearance_m,
      "diffraction_db" => analysis.diffraction_db,
      "fresnel_hit_count" => analysis.fresnel_hit_count,
      "obstructed_count" => analysis.obstructed_count,
      "verdict" => to_string(analysis.verdict),
      "sample_count" => length(profile),
      "propagation_score" => propagation_score,
      "path_points" => points
    }

    path
    |> Path.changeset(%{
      status: :complete,
      result: result,
      error: nil,
      computed_at: DateTime.truncate(DateTime.utc_now(), :second)
    })
    |> Repo.update()
    |> case do
      {:ok, updated} ->
        broadcast(updated)
        :ok

      {:error, cs} ->
        {:error, "store update failed: #{inspect(cs.errors)}"}
    end
  end

  defp store_failed(path, message) do
    path
    |> Path.changeset(%{
      status: :failed,
      error: message,
      computed_at: DateTime.truncate(DateTime.utc_now(), :second)
    })
    |> Repo.update()
    |> case do
      {:ok, updated} ->
        broadcast(updated)
        {:error, message}

      {:error, cs} ->
        {:error, "store update failed: #{inspect(cs.errors)}"}
    end
  end

  defp mark_status(path, status) do
    path
    |> Path.changeset(%{status: status})
    |> Repo.update()
    |> case do
      {:ok, _} -> :ok
      _ -> :ok
    end
  end

  # Look up the propagation grid score (0-100) for the midpoint of a
  # path at the most recent forecast time available on disk. Returns
  # nil when no scores file exists for this band yet — callers (the
  # show page, primarily) render that as "—" without distinguishing
  # "no data" from "score really is 0".
  defp lookup_propagation_score(band_mhz, lat, lon) do
    case ScoresFile.list_valid_times(band_mhz) do
      [] ->
        nil

      times ->
        now = DateTime.utc_now()
        time = Enum.min_by(times, &abs(DateTime.diff(&1, now)))
        ScoresFile.read_point(band_mhz, time, lat, lon)
    end
  end

  defp broadcast(%Path{mission_id: mission_id} = path) do
    Phoenix.PubSub.broadcast(
      Microwaveprop.PubSub,
      "rover_planning:#{mission_id}",
      {:rover_path_updated, path.id}
    )
  end
end