defmodule Mix.Tasks.HrrrClimatology do
  @shortdoc "Build surface temperature climatology from hrrr_profiles"
  @moduledoc """
  Aggregates `hrrr_profiles.surface_temp_c` by (lat, lon, month, hour)
  into `hrrr_climatology` for use by the temperature-anomaly feature.

  With 42M+ grid-point profiles, this runs a single SQL GROUP BY and
  bulk-inserts the results. Idempotent via ON CONFLICT.

      mix hrrr_climatology                  # build from all grid-point profiles
      mix hrrr_climatology --min-samples 5  # require at least 5 observations per cell
  """
  use Mix.Task

  alias Microwaveprop.Repo

  @impl Mix.Task
  def run(argv) do
    Mix.Task.run("app.start")

    {opts, _, _} = OptionParser.parse(argv, switches: [min_samples: :integer])
    min_samples = Keyword.get(opts, :min_samples, 3)

    Mix.shell().info("Building climatology (min_samples=#{min_samples})...")

    # Single SQL: aggregate and upsert in one shot
    {count, _} =
      Repo.query!(
        """
        INSERT INTO hrrr_climatology (id, lat, lon, month, hour,
                                      mean_surface_temp_c, stddev_surface_temp_c, sample_count)
        SELECT gen_random_uuid(), lat, lon,
               EXTRACT(MONTH FROM valid_time)::int AS month,
               EXTRACT(HOUR FROM valid_time)::int AS hour,
               AVG(surface_temp_c),
               STDDEV_SAMP(surface_temp_c),
               COUNT(*)
        FROM hrrr_profiles
        WHERE surface_temp_c IS NOT NULL
          AND is_grid_point = true
        GROUP BY lat, lon,
                 EXTRACT(MONTH FROM valid_time)::int,
                 EXTRACT(HOUR FROM valid_time)::int
        HAVING COUNT(*) >= $1
        ON CONFLICT (lat, lon, month, hour)
        DO UPDATE SET
          mean_surface_temp_c = EXCLUDED.mean_surface_temp_c,
          stddev_surface_temp_c = EXCLUDED.stddev_surface_temp_c,
          sample_count = EXCLUDED.sample_count
        """,
        [min_samples],
        timeout: 600_000
      )

    Mix.shell().info("Upserted #{count} climatology records.")
  end
end