defmodule Microwaveprop.CanopyTest do
  use ExUnit.Case, async: true

  alias Microwaveprop.Canopy

  @samples 4

  setup do
    tiles_dir = Path.join(System.tmp_dir!(), "canopy_test_#{:erlang.unique_integer([:positive])}")
    File.mkdir_p!(tiles_dir)
    on_exit(fn -> File.rm_rf!(tiles_dir) end)
    {:ok, tiles_dir: tiles_dir}
  end

  defp write_tile(tiles_dir, lat, lon, heights) do
    path = Path.join(tiles_dir, Canopy.tile_filename(lat, lon))
    File.write!(path, IO.iodata_to_binary(heights))
    path
  end

  test "tile_filename/2 follows SRTM naming convention" do
    assert Canopy.tile_filename(32.5, -97.5) == "N32W098.canopy"
    assert Canopy.tile_filename(33.0, -96.0) == "N33W096.canopy"
  end

  test "lookup/3 returns 0 when tile is missing", %{tiles_dir: tiles_dir} do
    assert Canopy.lookup(32.5, -97.5, tiles_dir, samples: @samples) == 0
  end

  test "lookup/3 returns the height at the matching pixel", %{tiles_dir: tiles_dir} do
    # 4x4 grid, row 0 = north edge, so:
    # row 0 = lat 33 (N edge)
    # row 3 = lat 32 (S edge)
    heights =
      List.flatten([
        [10, 11, 12, 13],
        [20, 21, 22, 23],
        [30, 31, 32, 33],
        [40, 41, 42, 43]
      ])

    write_tile(tiles_dir, 32.5, -97.5, heights)

    # Interior near NW (row 0, col 0) -> 10
    assert Canopy.lookup(32.999, -97.999, tiles_dir, samples: @samples) == 10
    # Interior near NE (row 0, col 3) -> 13
    assert Canopy.lookup(32.999, -97.001, tiles_dir, samples: @samples) == 13
    # Interior near SW (row 3, col 0) -> 40
    assert Canopy.lookup(32.001, -97.999, tiles_dir, samples: @samples) == 40
    # Interior near SE (row 3, col 3) -> 43
    assert Canopy.lookup(32.001, -97.001, tiles_dir, samples: @samples) == 43
  end

  test "lookup_many/2 batches lookups grouping by tile", %{tiles_dir: tiles_dir} do
    heights = List.duplicate(25, @samples * @samples)
    write_tile(tiles_dir, 32.5, -97.5, heights)

    points = [{32.5, -97.5}, {32.1, -97.9}]
    result = Canopy.lookup_many(points, tiles_dir, samples: @samples)

    assert result[{32.5, -97.5}] == 25
    assert result[{32.1, -97.9}] == 25
    # Point in a tile that doesn't exist is 0.
    assert Canopy.lookup_many([{40.0, -90.0}], tiles_dir, samples: @samples)[{40.0, -90.0}] == 0
  end
end