import '../models/user_profile.dart';
import '../models/cycle_entry.dart';

class CycleService {
  /// Calculates the current cycle information based on user profile
  static Map<String, dynamic> calculateCycleInfo(UserProfile? user) {
    if (user?.lastPeriodStartDate == null) {
      return {
        'phase': CyclePhase.follicular,
        'dayOfCycle': 1,
        'daysUntilPeriod': user?.averageCycleLength ?? 28,
        'isPeriodExpected': false,
      };
    }

    final lastPeriod = user!.lastPeriodStartDate!;
    final cycleLength = user.averageCycleLength;
    final now = DateTime.now();
    
    // Normalize dates to midnight for accurate day counting
    final startOfToday = DateTime(now.year, now.month, now.day);
    final startOfLastPeriod = DateTime(lastPeriod.year, lastPeriod.month, lastPeriod.day);
    
    final daysSinceLastPeriod = startOfToday.difference(startOfLastPeriod).inDays + 1;
    
    // Handle cases where last period was long ago (more than one cycle)
    final dayOfCycle = ((daysSinceLastPeriod - 1) % cycleLength) + 1;
    final daysUntilPeriod = cycleLength - dayOfCycle;

    CyclePhase phase;
    if (dayOfCycle <= 5) {
      phase = CyclePhase.menstrual;
    } else if (dayOfCycle <= 13) {
      phase = CyclePhase.follicular;
    } else if (dayOfCycle <= 16) {
      phase = CyclePhase.ovulation;
    } else {
      phase = CyclePhase.luteal;
    }

    return {
      'phase': phase,
      'dayOfCycle': dayOfCycle,
      'daysUntilPeriod': daysUntilPeriod,
      'isPeriodExpected': daysUntilPeriod <= 0 || dayOfCycle <= 5,
    };
  }

  /// Format cycle day for display
  static String getDayOfCycleDisplay(int day) => 'Day $day';

  /// Get phase description
  static String getPhaseDescription(CyclePhase phase) {
    switch (phase) {
      case CyclePhase.menstrual:
        return 'Your body is resting and clearing. Be gentle with yourself.';
      case CyclePhase.follicular:
        return 'Energy and optimism are rising. A great time for new projects.';
      case CyclePhase.ovulation:
        return 'You are at your peak energy and fertility.';
      case CyclePhase.luteal:
        return 'Progesterone is rising. You may feel more introverted or sensitive.';
    }
  }
}