Battle-for-Tismo/tests/hex_test.js

import { TestCase } from "./framework/test_case.js";
import {
  MapTopology,
  mapToLocal,
  localToMap,
  nearestCopyPoint,
  flightLine,
  flightDistanceTiles,
  key,
  parseKey,
  COL_STEP,
  HEX_H,
} from "../shared/hex.js";

export class HexTest extends TestCase {
  flat() {
    return new MapTopology({ x: 10, y: 10 }, false);
  }

  cylinder() {
    return new MapTopology({ x: 10, y: 10 }, true);
  }

  test_topology_type_width_and_period() {
    this.assertFalse(this.flat().isCylindrical());
    this.assertApprox(this.flat().periodPixels(), 0, 1e-9);
    const cylinder = this.cylinder();
    this.assertTrue(cylinder.isCylindrical());
    this.assertEqual(cylinder.width, 10);
    this.assertApprox(cylinder.periodPixels(), COL_STEP * 10, 1e-9);
  }

  test_wrap_x_folds_only_on_a_cylinder() {
    const flatTopology = this.flat();
    this.assertEqual(flatTopology.wrapX(25), 25);
    this.assertEqual(flatTopology.wrapCoords(25, -3), { x: 25, y: -3 });
    const topology = this.cylinder();
    // Origin is -5, so the valid x range is -5..4.
    this.assertEqual(topology.wrapX(-5), -5);
    this.assertEqual(topology.wrapX(4), 4);
    this.assertEqual(topology.wrapX(5), -5);
    this.assertEqual(topology.wrapX(-6), 4);
  }

  test_wrapped_delta_takes_the_short_route() {
    this.assertEqual(this.flat().wrappedDelta({ x: -5, y: 0 }, { x: 4, y: 0 }), { x: 9, y: 0 });
    this.assertEqual(this.cylinder().wrappedDelta({ x: -5, y: 0 }, { x: 4, y: 0 }), { x: -1, y: 0 });
    this.assertApprox(this.cylinder().tileDistance({ x: -5, y: 0 }, { x: 4, y: 0 }), 1.0, 1e-9);

    const topology = this.cylinder();
    const delta = topology.pixelDelta({ x: 0, y: 0 }, { x: -4, y: 0 });
    const expected = mapToLocal(-4, 0);
    this.assertApprox(delta.x, expected.x, 1e-9);
    this.assertApprox(delta.y, expected.y, 1e-9);
  }

  test_neighbours_are_six_adjacent_cells_that_wrap() {
    const topology = this.flat();
    const neighbours = topology.neighbours(0, 0).map((c) => key(c.x, c.y)).sort();
    this.assertEqual(neighbours, ["-1,-1", "-1,0", "0,-1", "0,1", "1,-1", "1,0"]);

    const centre = mapToLocal(0, 0);
    for (const neighbour of topology.neighbours(0, 0)) {
      const delta = topology.pixelDelta({ x: 0, y: 0 }, neighbour);
      const distance = Math.hypot(delta.x, delta.y);
      this.assert(distance > 0 && distance <= HEX_H + 1e-9, `distance ${distance}`);
      const local = mapToLocal(neighbour.x, neighbour.y);
      this.assertApprox(local.x - centre.x, delta.x, 1e-9);
      this.assertApprox(local.y - centre.y, delta.y, 1e-9);
    }

    const cylinder = this.cylinder();
    for (const neighbour of cylinder.neighbours(-5, 0)) {
      this.assert(neighbour.x >= -5 && neighbour.x <= 4, `x ${neighbour.x} outside map`);
    }
    this.assertTrue(
      cylinder.neighbours(-5, 0).some((c) => c.x === 4),
      "the west neighbour of the seam wraps to the east edge"
    );
  }

  test_local_to_map_inverts_map_to_local() {
    const flat = this.flat();
    for (const coords of [{ x: 0, y: 0 }, { x: 3, y: -4 }, { x: -7, y: 2 }]) {
      this.assertEqual(localToMap(mapToLocal(coords.x, coords.y), flat), coords);
    }
    // A pixel a few units off a centre still resolves to that tile.
    const centre = mapToLocal(2, 3);
    this.assertEqual(localToMap({ x: centre.x + 4, y: centre.y - 3 }, flat), { x: 2, y: 3 });
    // On a cylinder the resolved tile folds back into range.
    this.assertEqual(localToMap(mapToLocal(5, 0), this.cylinder()), { x: -5, y: 0 });
  }

  test_nearest_copy_point_folds_by_whole_periods() {
    const point = mapToLocal(0, 0);
    const period = this.cylinder().periodPixels();
    const reference = { x: point.x - period * 1.2, y: 0 };
    const copy = nearestCopyPoint(point, reference, this.cylinder());
    this.assertApprox(copy.x, point.x - period, 1e-9);
    this.assertEqual(copy.y, point.y);
    // A flat map returns the point untouched.
    this.assertEqual(nearestCopyPoint(point, reference, this.flat()), point);
  }

  test_flight_line_takes_the_shortest_wrapped_copy() {
    const topology = this.cylinder();
    const from = mapToLocal(-5, 0);
    // -5 and 4 are neighbours across the seam, one map period apart.
    const line = flightLine(from, { x: 4, y: 0 }, topology);
    this.assertEqual(line.length, 2);
    this.assertEqual(line[0], from);
    // Adjacent columns are offset by half a hex, so a neighbour hop is a
    // diagonal of hypot(COL_STEP, HEX_H/2), not a bare COL_STEP.
    const hop = Math.hypot(COL_STEP, HEX_H / 2);
    this.assertApprox(
      Math.hypot(line[1].x - line[0].x, line[1].y - line[0].y),
      hop,
      1e-6,
      "the flight leaves one edge and re-enters the other"
    );
  }

  test_flight_distance_measures_tiles_along_the_line() {
    const maxStep = HEX_H;
    const hop = Math.hypot(COL_STEP, HEX_H / 2);
    this.assertApprox(
      flightDistanceTiles({ x: 0, y: 0 }, { x: 1, y: 0 }, this.flat(), maxStep),
      hop / maxStep,
      1e-9
    );
    // Across the seam on a cylinder it is the short hop, not the long way.
    this.assertApprox(
      flightDistanceTiles({ x: -5, y: 0 }, { x: 4, y: 0 }, this.cylinder(), maxStep),
      hop / maxStep,
      1e-9
    );
  }

  test_key_and_parse_key_round_trip_and_odd_column_offset() {
    for (const coords of [{ x: 0, y: 0 }, { x: 3, y: -4 }, { x: -12, y: 7 }]) {
      this.assertEqual(parseKey(key(coords.x, coords.y)), coords);
    }
    const even = mapToLocal(0, 0);
    const odd = mapToLocal(1, 0);
    this.assertApprox(odd.x - even.x, COL_STEP, 1e-9);
    this.assertApprox(odd.y - even.y, HEX_H / 2, 1e-9);
  }
}