import 'package:flutter_test/flutter_test.dart';
import 'package:rippr/src/domain/models.dart';
import 'package:rippr/src/recording/ride_accumulator.dart';
import 'package:rippr/src/stats/ride_statistics.dart';

/// Ported from `com.rippr.AccumulatorTest`.
///
/// As in `ride_statistics_test.dart`, the one RNG-driven case uses the shared LCG rather
/// than either language's `Random`, so the fixture is identical across implementations.
class _Lcg {
  _Lcg(this._s);
  int _s;
  double nextDouble() {
    _s = _s * 6364136223846793005 + 1442695040888963407;
    final bits = (_s >>> 11) & ((1 << 53) - 1);
    return bits / (1 << 53);
  }
}

void main() {
  var nextId = 1;

  TrackPoint point({
    int segmentId = 1,
    required int ts,
    double lat = 51.0,
    double speed = 40.0,
    double alt = 1000.0,
  }) =>
      TrackPoint(
        id: nextId++,
        tripId: 1,
        segmentId: segmentId,
        timestamp: ts,
        latitude: lat,
        longitude: -114.0,
        speedKmh: speed,
        altitudeM: alt,
      );

  List<TrackPoint> run(int n,
          {int segmentId = 1, int startTs = 0, double startLat = 51.0}) =>
      List.generate(
        n,
        (i) => point(
            segmentId: segmentId,
            ts: startTs + i * 1000,
            lat: startLat + i * 0.0001),
      );

  setUp(() => nextId = 1);

  group('the cross-batch anchor — the subtle bug this class exists to avoid', () {
    test('distance across many small batches matches one big batch', () {
      final points = run(100);

      final batched = Accumulator();
      for (var i = 0; i < points.length; i += 7) {
        batched.fold(points.sublist(i, (i + 7).clamp(0, points.length)));
      }
      final single = Accumulator()..fold(points);

      expect(batched.distanceM, closeTo(single.distanceM, 1e-6),
          reason:
              'losing the anchor between flushes silently under-reports distance');
    });

    test('accumulated distance agrees with the batch statistics', () {
      final points = run(100);

      final acc = Accumulator();
      for (var i = 0; i < points.length; i += 25) {
        acc.fold(points.sublist(i, (i + 25).clamp(0, points.length)));
      }
      final summary = computeSummary(points);

      expect(acc.distanceM, closeTo(summary.distanceM, 0.5));
      expect(acc.movingMillis, summary.movingMillis);
      expect(acc.maxSpeedKmh, closeTo(summary.maxSpeedKmh, 1e-6));
      expect(acc.pointCount, summary.pointCount);
    });
  });

  group('segment boundaries', () {
    test('distance does not span a segment boundary', () {
      // Second segment starts a full degree of latitude away — a trailered gap.
      final acc = Accumulator();
      acc.fold(run(5, segmentId: 1, startLat: 51.0));
      acc.fold(run(5, segmentId: 2, startTs: 600000, startLat: 52.0));

      expect(acc.distanceM, lessThan(200.0),
          reason: 'the ~111 km gap leaked into distance: ${acc.distanceM} m');
    });

    test('onSegmentChanged clears the anchor even within one batch stream', () {
      final acc = Accumulator();
      acc.fold(run(5, segmentId: 1, startLat: 51.0));
      acc.onSegmentChanged();
      acc.fold(run(5, segmentId: 1, startTs: 600000, startLat: 52.0));

      expect(acc.distanceM, lessThan(200.0),
          reason: 'anchor was not cleared: ${acc.distanceM} m');
    });
  });

  group('moving time', () {
    test('moving time ignores samples below the speed noise floor', () {
      final acc = Accumulator();
      acc.fold(List.generate(30, (i) => point(ts: i * 1000, speed: 40.0)));
      acc.fold(
          List.generate(30, (i) => point(ts: (30 + i) * 1000, speed: 0.0)));

      expect(acc.movingMillis, 29000);
    });

    test('a long gap between fixes does not inject phantom moving time', () {
      final acc = Accumulator();
      acc.fold([
        point(ts: 0, speed: 90.0),
        point(ts: 120000, lat: 51.001, speed: 90.0),
      ]);
      expect(acc.movingMillis, 0);
    });
  });

  group('elevation', () {
    test('elevation gain is visible before the climb ends', () {
      // A steady ascent that never turns back down. Reading the committed total alone
      // would report zero, so the live figure has to include the pending run.
      final acc = Accumulator();
      acc.fold(List.generate(101, (i) => point(ts: i * 1000, alt: 1000.0 + i)));
      expect(acc.elevationGain(), closeTo(100.0, 6.0));
    });

    test('a parked bike does not accumulate phantom climbing', () {
      final rng = _Lcg(7);
      final acc = Accumulator();
      acc.fold(List.generate(
        600,
        (i) => point(
            ts: i * 1000,
            speed: 0.0,
            alt: 1000.0 + (rng.nextDouble() * 16.0 - 8.0)),
      ));
      expect(acc.elevationGain(), lessThan(60.0),
          reason: 'phantom climbing: ${acc.elevationGain()} m');
    });
  });

  group('restore', () {
    test('restore continues from persisted totals rather than starting over', () {
      final acc = Accumulator();
      acc.restore(
        distanceM: 5000.0,
        movingMillis: 300000,
        maxSpeedKmh: 95.0,
        elevationGainM: 120.0,
        pointCount: 600,
        lastPoint: null,
      );
      acc.fold(run(11));

      expect(acc.distanceM, greaterThan(5000.0), reason: 'distance went backwards');
      expect(acc.distanceM, closeTo(5111.2, 5.0));
      expect(acc.pointCount, 611);
      expect(acc.maxSpeedKmh, closeTo(95.0, 1e-6));
      expect(acc.elevationGain(), greaterThanOrEqualTo(120.0),
          reason: 'persisted elevation was lost');
    });

    test('restore keeps a higher persisted max speed', () {
      final acc = Accumulator();
      acc.restore(
        distanceM: 0.0,
        movingMillis: 0,
        maxSpeedKmh: 150.0,
        elevationGainM: 0.0,
        pointCount: 0,
        lastPoint: null,
      );
      acc.fold(run(5));
      expect(acc.maxSpeedKmh, closeTo(150.0, 1e-6));
    });
  });

  test('reset clears everything', () {
    final acc = Accumulator();
    acc.fold(run(20));
    acc.reset();

    expect(acc.distanceM, closeTo(0.0, 1e-9));
    expect(acc.movingMillis, 0);
    expect(acc.maxSpeedKmh, closeTo(0.0, 1e-9));
    expect(acc.pointCount, 0);
    expect(acc.elevationGain(), closeTo(0.0, 1e-9));
  });

  test('folding an empty batch is a no-op', () {
    final acc = Accumulator();
    acc.fold(const []);
    expect(acc.pointCount, 0);
    expect(acc.distanceM, closeTo(0.0, 1e-9));
  });
}