prop/test/microwaveprop/propagation/grid_test.exs

defmodule Microwaveprop.Propagation.GridTest do
  use ExUnit.Case, async: true

  alias Microwaveprop.Propagation.Grid

  describe "conus_points/0" do
    test "generates grid at 0.125 degree resolution" do
      points = Grid.conus_points()
      assert Enum.count_until(points, 5001) == 5001
      assert Enum.count_until(points, 100) < 100_000
    end

    test "all points within CONUS bounds" do
      Enum.each(Grid.conus_points(), fn {lat, lon} ->
        assert lat >= 25.0 and lat <= 50.0
        assert lon >= -125.0 and lon <= -66.0
      end)
    end

    test "points are on 0.125 degree grid" do
      Enum.each(Grid.conus_points(), fn {lat, lon} ->
        assert Float.round(lat * 8, 0) == lat * 8
        assert Float.round(lon * 8, 0) == lon * 8
      end)
    end

    test "first point is at SW corner" do
      [{lat, lon} | _] = Grid.conus_points()
      assert lat == 25.0
      assert lon == -125.0
    end

    test "last point is at NE corner" do
      points = Grid.conus_points()
      {lat, lon} = List.last(points)
      assert lat == 50.0
      assert lon == -66.0
    end
  end

  describe "step/0" do
    test "returns 0.125" do
      assert Grid.step() == 0.125
    end
  end

  describe "bounds/0" do
    test "returns CONUS bounding box" do
      bounds = Grid.bounds()
      assert bounds.lat_min == 25.0
      assert bounds.lat_max == 50.0
      assert bounds.lon_min == -125.0
      assert bounds.lon_max == -66.0
    end
  end

  describe "contains?/1" do
    test "true for DFW (firmly inside the box)" do
      assert Grid.contains?(%{"lat" => 32.9, "lon" => -97.0})
    end

    test "true for every corner of the CONUS bounding box (inclusive)" do
      assert Grid.contains?(%{"lat" => 25.0, "lon" => -125.0})
      assert Grid.contains?(%{"lat" => 50.0, "lon" => -66.0})
      assert Grid.contains?(%{"lat" => 25.0, "lon" => -66.0})
      assert Grid.contains?(%{"lat" => 50.0, "lon" => -125.0})
    end

    test "false for OCONUS positions (UK, Winnipeg, Alberta, etc.)" do
      # 27 stuck hrrr-queued contacts in prod landed on points like
      # these. Add them as regression fixtures.
      refute Grid.contains?(%{"lat" => 51.4, "lon" => 0.47})
      refute Grid.contains?(%{"lat" => 51.39, "lon" => -114.04})
      refute Grid.contains?(%{"lat" => 50.1875, "lon" => -97.625})
    end

    test "false for nil pos or missing keys" do
      refute Grid.contains?(nil)
      refute Grid.contains?(%{})
      refute Grid.contains?(%{"lat" => 32.9})
      refute Grid.contains?(%{"lon" => -97.0})
    end

    test "false when lat or lon is nil" do
      refute Grid.contains?(%{"lat" => nil, "lon" => -97.0})
      refute Grid.contains?(%{"lat" => 32.9, "lon" => nil})
    end
  end

  describe "wgrib2_grid_spec/0" do
    test "lon_start / lat_start match the bounding box SW corner" do
      spec = Grid.wgrib2_grid_spec()
      assert spec.lon_start == -125.0
      assert spec.lat_start == 25.0
    end

    test "grid step matches Grid.step/0 on both axes" do
      spec = Grid.wgrib2_grid_spec()
      assert spec.lon_step == Grid.step()
      assert spec.lat_step == Grid.step()
    end

    test "lon_count and lat_count span the full CONUS box inclusive" do
      spec = Grid.wgrib2_grid_spec()
      # (lon_max - lon_min) / step + 1 = (-66 - -125) / 0.125 + 1 = 473
      assert spec.lon_count == 473
      # (lat_max - lat_min) / step + 1 = (50 - 25) / 0.125 + 1 = 201
      assert spec.lat_count == 201
    end

    test "total cells in wgrib2_grid_spec matches conus_points length" do
      spec = Grid.wgrib2_grid_spec()
      points = Grid.conus_points()
      assert length(points) == spec.lon_count * spec.lat_count
    end
  end

  describe "hrdps_only_points/0" do
    test "covers cells north of HRRR's lat_max" do
      points = Grid.hrdps_only_points()
      # At least one cell strictly north of HRRR's lat_max=50
      assert Enum.any?(points, fn {lat, _lon} -> lat > 50.0 end)
    end

    test "is disjoint from conus_points/0" do
      conus = MapSet.new(Grid.conus_points())
      hrdps = MapSet.new(Grid.hrdps_only_points())
      assert MapSet.disjoint?(conus, hrdps), "hrdps_only_points must not overlap conus_points"
    end

    test "all points within HRDPS bbox" do
      Enum.each(Grid.hrdps_only_points(), fn {lat, lon} ->
        assert lat >= 49.0 and lat <= 60.0
        assert lon >= -141.0 and lon <= -52.0
      end)
    end

    test "points are on 0.125 degree grid" do
      Enum.each(Grid.hrdps_only_points(), fn {lat, lon} ->
        assert Float.round(lat * 8, 0) == lat * 8
        assert Float.round(lon * 8, 0) == lon * 8
      end)
    end

    test "no point is inside the CONUS bounding box" do
      Enum.each(Grid.hrdps_only_points(), fn {lat, lon} ->
        in_conus = lat >= 25.0 and lat <= 50.0 and lon >= -125.0 and lon <= -66.0
        refute in_conus, "point #{lat},#{lon} is inside CONUS bbox"
      end)
    end
  end

  describe "point_source/1" do
    test "classifies cells inside CONUS as :hrrr" do
      assert Grid.point_source({32.9, -97.0}) == :hrrr
      assert Grid.point_source({49.0, -98.0}) == :hrrr
    end

    test "classifies Canadian cells outside HRRR as :hrdps" do
      assert Grid.point_source({53.32, -60.42}) == :hrdps
      assert Grid.point_source({50.125, -97.0}) == :hrdps
    end

    test "classifies points outside both bboxes as :neither" do
      assert Grid.point_source({-30.0, 150.0}) == :neither
      assert Grid.point_source({65.0, -90.0}) == :neither
    end

    test "accepts %{lat: _, lon: _} maps as well as tuples" do
      assert Grid.point_source(%{lat: 32.9, lon: -97.0}) == :hrrr
      assert Grid.point_source(%{lat: 53.32, lon: -60.42}) == :hrdps
    end
  end
end