prop/test/microwaveprop/propagation/band_weights_test.exs

defmodule Microwaveprop.Propagation.BandWeightsTest do
  # async: false because BandWeights caches in :persistent_term, which is
  # global to the BEAM. Each test resets the cache in setup so ordering
  # is irrelevant, but concurrent runs would still see each other.
  use ExUnit.Case, async: false

  alias Microwaveprop.Propagation.BandWeights

  @valid_json """
  {
    "generated_at": "2026-05-24T18:53:32+00:00",
    "schema_version": 1,
    "global_weights": {
      "humidity": 0.1262, "time_of_day": 0.038, "td_depression": 0.101,
      "refractivity": 0.0986, "sky": 0.0841, "season": 0.1134,
      "wind": 0.0841, "rain": 0.1431, "pwat": 0.1147, "pressure": 0.0967
    },
    "band_overrides": {
      "10000": {
        "weights": {
          "humidity": 0.20, "time_of_day": 0.04, "td_depression": 0.10,
          "refractivity": 0.10, "sky": 0.08, "season": 0.11,
          "wind": 0.08, "rain": 0.14, "pwat": 0.11, "pressure": 0.04
        },
        "n_samples": 54161,
        "source": "contacts"
      },
      "144": {
        "weights": {
          "humidity": 0.18, "time_of_day": 0.02, "td_depression": 0.15,
          "refractivity": 0.11, "sky": 0.06, "season": 0.12,
          "wind": 0.06, "rain": 0.01, "pwat": 0.17, "pressure": 0.12
        },
        "n_samples": 12927,
        "source": "pskr"
      }
    }
  }
  """

  setup do
    # Cache is global to the BEAM; reset before every test to avoid
    # bleed between cases.
    BandWeights.reset()
    prior_env = Application.get_env(:microwaveprop, :band_weights_json)

    on_exit(fn ->
      BandWeights.reset()

      if prior_env do
        Application.put_env(:microwaveprop, :band_weights_json, prior_env)
      else
        Application.delete_env(:microwaveprop, :band_weights_json)
      end
    end)

    :ok
  end

  describe "lookup/1 with a valid JSON file" do
    setup do
      path = Path.join(System.tmp_dir!(), "band_weights_#{System.unique_integer([:positive])}.json")
      File.write!(path, @valid_json)
      Application.put_env(:microwaveprop, :band_weights_json, path)
      on_exit(fn -> File.rm(path) end)
      %{path: path}
    end

    test "returns the override weights for a band present in the file" do
      result = BandWeights.lookup(10_000)
      assert result.humidity == 0.20
      assert result.pressure == 0.04
      # All 10 keys present.
      expected_keys =
        MapSet.new([
          :humidity,
          :time_of_day,
          :td_depression,
          :refractivity,
          :sky,
          :season,
          :wind,
          :rain,
          :pwat,
          :pressure
        ])

      assert MapSet.new(Map.keys(result)) == expected_keys
    end

    test "returns the override weights for a second band" do
      result = BandWeights.lookup(144)
      assert result.humidity == 0.18
    end

    test "returns nil for a band not present in the file" do
      assert BandWeights.lookup(75_000) == nil
    end

    test "is cheap on repeat calls (cached)" do
      first = BandWeights.lookup(10_000)
      # Delete the source file — second call must still succeed from cache.
      File.rm!(Application.fetch_env!(:microwaveprop, :band_weights_json))
      second = BandWeights.lookup(10_000)
      assert first == second
    end
  end

  describe "lookup/1 when the file is missing" do
    setup do
      Application.put_env(:microwaveprop, :band_weights_json, "/nonexistent/path/band_weights.json")
      :ok
    end

    test "returns nil for every band (does not raise)" do
      assert BandWeights.lookup(10_000) == nil
      assert BandWeights.lookup(50) == nil
    end
  end

  describe "lookup/1 when the loader is disabled in config" do
    setup do
      Application.put_env(:microwaveprop, :band_weights_json, false)
      :ok
    end

    test "returns nil for every band" do
      assert BandWeights.lookup(10_000) == nil
      assert BandWeights.lookup(144) == nil
    end
  end

  describe "lookup/1 with malformed JSON" do
    setup do
      path = Path.join(System.tmp_dir!(), "band_weights_bad_#{System.unique_integer([:positive])}.json")
      File.write!(path, "{ not valid json")
      Application.put_env(:microwaveprop, :band_weights_json, path)
      on_exit(fn -> File.rm(path) end)
      %{path: path}
    end

    test "returns nil for every band (logs but does not raise)" do
      assert BandWeights.lookup(10_000) == nil
    end
  end

  describe "all_overrides/0" do
    setup do
      path = Path.join(System.tmp_dir!(), "band_weights_#{System.unique_integer([:positive])}.json")
      File.write!(path, @valid_json)
      Application.put_env(:microwaveprop, :band_weights_json, path)
      on_exit(fn -> File.rm(path) end)
      :ok
    end

    test "returns a map of all band overrides keyed by freq_mhz integer" do
      result = BandWeights.all_overrides()
      assert Map.has_key?(result, 10_000)
      assert Map.has_key?(result, 144)
      assert result[10_000].humidity == 0.20
    end
  end
end