import 'package:flutter_test/flutter_test.dart';
import 'package:glp1_companion/features/medication/domain/entities/dose_entry.dart';
import 'package:glp1_companion/features/medication/domain/usecases/calculate_serum_level.dart';

DoseEntry _dose({
  required String compound,
  required double mg,
  required DateTime administeredAt,
}) =>
    DoseEntry(
      compoundName: compound,
      doseMg: mg,
      administeredAt: administeredAt,
    );

void main() {
  const calculator = CalculateSerumLevel();
  final now = DateTime(2026, 10, 16, 12);

  group('CalculateSerumLevel', () {
    test('empty history yields zero concentration', () {
      expect(calculator.evaluate(doses: const [], at: now), 0);
    });

    test('a fresh dose contributes its full amount', () {
      final doses = [
        _dose(compound: 'Semaglutide', mg: 1, administeredAt: now),
      ];
      expect(calculator.evaluate(doses: doses, at: now), closeTo(1, 1e-9));
    });

    test('dose halves exactly after one half-life', () {
      final doses = [
        _dose(
          compound: 'Semaglutide',
          mg: 2,
          administeredAt: now.subtract(const Duration(hours: 168)),
        ),
      ];
      expect(calculator.evaluate(doses: doses, at: now), closeTo(1, 1e-9));
    });

    test('follows the published half-life per compound', () {
      // Tirzepatide: 2.5 mg after 120 h (one half-life) -> 1.25 mg.
      final tirzepatide = [
        _dose(
          compound: 'Tirzepatide',
          mg: 2.5,
          administeredAt: now.subtract(const Duration(hours: 120)),
        ),
      ];
      expect(calculator.evaluate(doses: tirzepatide, at: now), closeTo(1.25, 1e-9));

      // Liraglutide: 1.8 mg after 13 h (one half-life) -> 0.9 mg.
      final liraglutide = [
        _dose(
          compound: 'Liraglutide',
          mg: 1.8,
          administeredAt: now.subtract(const Duration(hours: 13)),
        ),
      ];
      expect(calculator.evaluate(doses: liraglutide, at: now), closeTo(0.9, 1e-9));
    });

    test('accumulates contributions across multiple doses', () {
      final doses = [
        _dose(
          compound: 'Semaglutide',
          mg: 1,
          administeredAt: now.subtract(const Duration(hours: 168)),
        ),
        _dose(
          compound: 'Semaglutide',
          mg: 1,
          administeredAt: now.subtract(const Duration(hours: 336)),
        ),
      ];
      // 1 * 0.5 + 1 * 0.25 = 0.75 mg.
      expect(calculator.evaluate(doses: doses, at: now), closeTo(0.75, 1e-9));
    });

    test('ignores doses timestamped in the future', () {
      final doses = [
        _dose(compound: 'Semaglutide', mg: 1, administeredAt: now),
        _dose(
          compound: 'Semaglutide',
          mg: 5,
          administeredAt: now.add(const Duration(hours: 24)),
        ),
      ];
      expect(calculator.evaluate(doses: doses, at: now), closeTo(1, 1e-9));
    });

    test('unknown compounds fall back to the default half-life', () {
      final doses = [
        _dose(
          compound: 'Compounded GLP-1',
          mg: 4,
          administeredAt: now.subtract(const Duration(hours: 168)),
        ),
      ];
      expect(calculator.evaluate(doses: doses, at: now), closeTo(2, 1e-9));
    });

    test('brand names resolve to their compound half-life', () {
      // "Ozempic" is semaglutide (168 h): 4 mg after 168 h -> 2 mg.
      final doses = [
        _dose(
          compound: 'Ozempic',
          mg: 4,
          administeredAt: now.subtract(const Duration(hours: 168)),
        ),
      ];
      expect(calculator.evaluate(doses: doses, at: now), closeTo(2, 1e-9));
    });

    test('call() mirrors evaluate()', () {
      final doses = [
        _dose(compound: 'Tirzepatide', mg: 3, administeredAt: now),
      ];
      expect(
        calculator(doses: doses, at: now),
        calculator.evaluate(doses: doses, at: now),
      );
    });

    test('halfLifeHours override forces a single half-life', () {
      final doses = [
        _dose(compound: 'Tirzepatide', mg: 2, administeredAt: now),
      ];
      expect(
        calculator.evaluate(
          doses: doses,
          at: now.add(const Duration(hours: 20)),
          halfLifeHours: 20,
        ),
        closeTo(1, 1e-9),
      );
    });
  });
}