rippr/test/geo_test.dart

import 'dart:math' as math;

import 'package:flutter_test/flutter_test.dart';
import 'package:rippr/src/geo/geo.dart';

/// Ported from `com.rippr.geo.GeoTest` (native Android v2.0.1).
///
/// Every case and every tolerance is carried over unchanged. Where the Kotlin
/// suite encoded a hard-won correction — notably the Calgary–Edmonton
/// great-circle figure, which was verified by hand after the *test* turned out to
/// be wrong rather than the code — that correction travels with it.
void main() {
  const calgary = LatLon(51.0447, -114.0719);
  const edmonton = LatLon(53.5461, -113.4938);

  List<LatLon> line(int n) =>
      List.generate(n, (i) => LatLon(51.0 + i * 0.001, -114.0));

  group('haversine', () {
    test('matches a known long-distance reference', () {
      // Calgary to Edmonton, great-circle. Cross-checked by hand: 2.5014° of
      // latitude is ~278.1 km, and 0.5781° of longitude at ~52.3° is ~39.3 km,
      // giving sqrt(278.1² + 39.3²) ≈ 280.9 km. (Road distance is ~300 km — not
      // the same thing.)
      final d = haversineBetween(calgary, edmonton);
      expect(d, closeTo(280900.0, 280900.0 * 0.005));
    });

    test('one degree of latitude is about 111 km anywhere', () {
      final atEquator = haversineMeters(0.0, 0.0, 1.0, 0.0);
      final atLatitude60 = haversineMeters(60.0, 0.0, 61.0, 0.0);
      expect(atEquator, closeTo(111195.0, 200.0));
      expect(atLatitude60, closeTo(atEquator, 200.0),
          reason: 'latitude spacing does not vary with longitude');
    });

    test('a degree of longitude shrinks with latitude', () {
      final atEquator = haversineMeters(0.0, 0.0, 0.0, 1.0);
      final atLatitude60 = haversineMeters(60.0, 0.0, 60.0, 1.0);
      // cos(60°) = 0.5, so it should be about half.
      expect(atLatitude60, closeTo(atEquator / 2, 500.0));
    });

    test('identical points are zero distance', () {
      expect(haversineBetween(calgary, calgary), closeTo(0.0, 1e-9));
    });

    test('short hops between consecutive fixes stay accurate', () {
      // ~11 m north, the scale of a 2 Hz fix at road speed.
      final d = haversineMeters(51.0447, -114.0719, 51.04480, -114.0719);
      expect(d, closeTo(11.1, 0.5));
    });

    test('distance is symmetric', () {
      expect(
        haversineBetween(calgary, edmonton),
        closeTo(haversineBetween(edmonton, calgary), 1e-6),
      );
    });

    test('handles an antimeridian crossing without exploding', () {
      // 0.02° apart in longitude, straddling +/-180.
      final d = haversineMeters(0.0, 179.99, 0.0, -179.99);
      expect(d, lessThan(3000), reason: 'expected a short hop, got $d m');
    });
  });

  group('douglas-peucker', () {
    test('a straight line collapses to its endpoints', () {
      final simplified = simplify(line(50), 5.0);
      expect(simplified.length, 2);
      expect(simplified.first, line(50).first);
      expect(simplified.last, line(50).last);
    });

    test('endpoints always survive', () {
      final zigzag = List.generate(
        30,
        (i) => LatLon(51.0 + i * 0.001, -114.0 + (i % 2 == 0 ? 0.0 : 0.002)),
      );
      final simplified = simplify(zigzag, 5.0);
      expect(simplified.first, zigzag.first);
      expect(simplified.last, zigzag.last);
    });

    test('deviation above epsilon is preserved', () {
      // Middle point sits ~110 m off the line between its neighbours.
      const points = [
        LatLon(51.000, -114.0),
        LatLon(51.001, -113.999),
        LatLon(51.002, -114.0),
      ];
      expect(simplify(points, 5.0).length, 3);
    });

    test('deviation below epsilon is dropped', () {
      const points = [
        LatLon(51.000, -114.0),
        LatLon(51.001, -114.00001), // under a metre off the line
        LatLon(51.002, -114.0),
      ];
      expect(simplify(points, 5.0).length, 2);
    });

    test('epsilon of zero returns the input untouched', () {
      final input = line(20);
      expect(simplify(input, 0.0), input);
    });

    test('inputs of two or fewer are returned as-is', () {
      expect(simplify(const <LatLon>[], 5.0).length, 0);
      expect(simplify(line(1), 5.0).length, 1);
      expect(simplify(line(2), 5.0).length, 2);
    });

    test('handles a full ride without stack overflow and stays fast', () {
      // Three hours at 2 Hz, the real scale this has to survive.
      final ride = List.generate(
        21600,
        (i) => LatLon(51.0 + i * 0.00001, -114.0 + math.sin(i / 100.0) * 0.001),
      );
      final started = DateTime.now();
      final simplified = simplify(ride, 5.0);
      final elapsedMs = DateTime.now().difference(started).inMilliseconds;

      expect(simplified.length, lessThan(ride.length),
          reason: 'simplification should reduce the point count');
      expect(simplified.first, ride.first);
      expect(simplified.last, ride.last);
      expect(elapsedMs, lessThan(1000),
          reason: 'took ${elapsedMs}ms, expected well under a second');
    });
  });

  group('perpendicular distance', () {
    test('a point on the segment has zero perpendicular distance', () {
      final d = perpendicularDistanceMeters(
        const LatLon(51.001, -114.0),
        const LatLon(51.000, -114.0),
        const LatLon(51.002, -114.0),
      );
      expect(d.abs(), lessThan(0.01), reason: 'expected ~0, got $d');
    });

    test('a point beyond the end measures to the endpoint, not the infinite line',
        () {
      // Directly past the segment's end along the same bearing.
      final d = perpendicularDistanceMeters(
        const LatLon(51.003, -114.0),
        const LatLon(51.000, -114.0),
        const LatLon(51.002, -114.0),
      );
      expect(d, closeTo(111.0, 5.0),
          reason: 'should be the ~111 m to the endpoint');
    });

    test('a degenerate segment falls back to point distance', () {
      const a = LatLon(51.0, -114.0);
      final d = perpendicularDistanceMeters(const LatLon(51.001, -114.0), a, a);
      expect(d, closeTo(111.0, 5.0));
    });
  });

  group('bounds', () {
    test('bounds is null for an empty path', () {
      expect(bounds(const <LatLon>[]), isNull);
    });

    test('bounds spans mixed-sign coordinates', () {
      final b = bounds(const [
        LatLon(-10.0, -20.0),
        LatLon(30.0, 40.0),
        LatLon(5.0, 0.0),
      ])!;
      expect(b.minLat, closeTo(-10.0, 1e-9));
      expect(b.maxLat, closeTo(30.0, 1e-9));
      expect(b.minLon, closeTo(-20.0, 1e-9));
      expect(b.maxLon, closeTo(40.0, 1e-9));
      expect(b.centerLat, closeTo(10.0, 1e-9));
    });

    test('a stationary ride reports degenerate bounds', () {
      final b = bounds(List.filled(10, calgary))!;
      expect(b.isDegenerate, isTrue,
          reason: 'map auto-fit must special-case this');
    });

    test('a real path is not degenerate', () {
      expect(bounds(line(10))!.isDegenerate, isFalse);
    });
  });

  group('path length', () {
    test('path length sums consecutive hops', () {
      final points = line(11); // ten hops of 0.001 degrees latitude
      expect(pathLengthMeters(points), closeTo(10 * 111.19, 20.0));
    });

    test('path length of fewer than two points is zero', () {
      expect(pathLengthMeters(const <LatLon>[]), closeTo(0.0, 1e-9));
      expect(pathLengthMeters(const [calgary]), closeTo(0.0, 1e-9));
    });
  });
}