import 'package:flutter_test/flutter_test.dart';
import 'package:tasq/utils/task_duration.dart';

DurationEvent _ev(DateTime at, String action) =>
    (createdAt: at, actionType: action);

void main() {
  final base = DateTime.utc(2026, 1, 1, 9, 0);

  group('computeEffectiveDuration', () {
    test('no pause events → full span from fallbackStartedAt to endAt', () {
      final worked = computeEffectiveDuration(
        fallbackStartedAt: base,
        endAt: base.add(const Duration(hours: 2)),
        events: const [],
      );
      expect(worked, const Duration(hours: 2));
    });

    test('resolves start from the "started" event over the fallback', () {
      final started = base.add(const Duration(minutes: 30));
      // events are newest-first (DESC)
      final events = [_ev(started, 'started')];
      final worked = computeEffectiveDuration(
        fallbackStartedAt: base, // earlier fallback should be ignored
        endAt: started.add(const Duration(hours: 1)),
        events: events,
      );
      expect(worked, const Duration(hours: 1));
    });

    test('subtracts a completed paused interval', () {
      final started = base;
      final paused = base.add(const Duration(minutes: 20));
      final resumed = base.add(const Duration(minutes: 50)); // 30m paused
      final end = base.add(const Duration(hours: 2));
      // DESC order
      final events = [
        _ev(resumed, 'resumed'),
        _ev(paused, 'paused'),
        _ev(started, 'started'),
      ];
      final worked = computeEffectiveDuration(
        fallbackStartedAt: started,
        endAt: end,
        events: events,
      );
      expect(worked, const Duration(hours: 2) - const Duration(minutes: 30));
    });

    test('counts an open pause interval still active at endAt', () {
      final started = base;
      final paused = base.add(const Duration(minutes: 40));
      final end = base.add(const Duration(hours: 1)); // 20m still paused
      final events = [
        _ev(paused, 'paused'),
        _ev(started, 'started'),
      ];
      final worked = computeEffectiveDuration(
        fallbackStartedAt: started,
        endAt: end,
        events: events,
      );
      expect(worked, const Duration(minutes: 40));
    });

    test('returns zero when there is no resolvable start', () {
      final worked = computeEffectiveDuration(
        fallbackStartedAt: null,
        endAt: base,
        events: const [],
      );
      expect(worked, Duration.zero);
    });

    test('returns zero when endAt is before start', () {
      final worked = computeEffectiveDuration(
        fallbackStartedAt: base,
        endAt: base.subtract(const Duration(minutes: 5)),
        events: const [],
      );
      expect(worked, Duration.zero);
    });
  });
}