defmodule Microwaveprop.Rover.RoadProximityTest do
  use ExUnit.Case, async: true

  alias Microwaveprop.Rover.RoadProximity

  describe "road_distances/3" do
    test "returns distances when segments are available" do
      cells = [%{lat: 33.0, lon: -97.0}]
      bbox = %{"south" => 32.5, "north" => 33.5, "west" => -98.0, "east" => -96.0}

      # One segment 0.5° (~55 km) from the cell
      fetch = fn _bbox -> {:ok, [{{33.0, -96.5}, {33.0, -96.0}}]} end

      {:ok, distances} = RoadProximity.road_distances(cells, bbox, fetch: fetch)
      assert is_map(distances)
      assert Map.has_key?(distances, {33.0, -97.0})
      assert distances[{33.0, -97.0}] > 0
    end

    test "returns nanometres for point exactly on the road" do
      cells = [%{lat: 33.0, lon: -97.0}]
      bbox = %{"south" => 32.5, "north" => 33.5, "west" => -98.0, "east" => -96.0}

      # Segment passes through the cell point
      fetch = fn _bbox -> {:ok, [{{33.0, -98.0}, {33.0, -96.0}}]} end

      {:ok, distances} = RoadProximity.road_distances(cells, bbox, fetch: fetch)
      assert_in_delta distances[{33.0, -97.0}], 0.0, 0.001
    end

    test "returns {:error, :no_roads} when no segments found" do
      cells = [%{lat: 33.0, lon: -97.0}]
      bbox = %{"south" => 32.5, "north" => 33.5, "west" => -98.0, "east" => -96.0}

      assert {:error, :no_roads} = RoadProximity.road_distances(cells, bbox, fetch: fn _ -> {:ok, []} end)
    end

    test "propagates fetch errors" do
      cells = [%{lat: 33.0, lon: -97.0}]
      bbox = %{"south" => 32.5, "north" => 33.5, "west" => -98.0, "east" => -96.0}

      assert {:error, :overpass_timeout} =
               RoadProximity.road_distances(cells, bbox, fetch: fn _ -> {:error, :overpass_timeout} end)
    end

    test "multiple cells each get their nearest road distance" do
      cells = [
        %{lat: 33.0, lon: -97.0},
        %{lat: 33.5, lon: -97.0},
        %{lat: 34.0, lon: -97.0}
      ]

      bbox = %{"south" => 32.5, "north" => 34.5, "west" => -98.0, "east" => -96.0}

      # Road runs east-west at lat=33.0
      fetch = fn _bbox ->
        {:ok, [{{33.0, -98.0}, {33.0, -96.0}}]}
      end

      {:ok, distances} = RoadProximity.road_distances(cells, bbox, fetch: fetch)
      # Cell at lat=33.0 is ON the road, lat=33.5 is ~55 km north, lat=34.0 is ~111 km north
      assert distances[{33.0, -97.0}] < distances[{33.5, -97.0}]
      assert distances[{33.5, -97.0}] < distances[{34.0, -97.0}]
    end

    test "segments_from_elements excludes non-way or short geometry" do
      # Tested implicitly through road_distances with injected fetch.
      # The internal segments_from_elements/1 is exercised by:
      # road_distances → fetch → {:ok, segments}
      # where segments are directly provided.
    end
  end
end