import 'package:flutter_timezone/flutter_timezone.dart';
import 'package:timezone/data/latest.dart' as tzdata;
import 'package:timezone/timezone.dart' as tz;

class TimeService {
  static const String estLocationName = 'America/New_York';

  static bool _initialized = false;

  static Future<void> initialize() async {
    if (_initialized) {
      return;
    }

    tzdata.initializeTimeZones();
    final localName = await FlutterTimezone.getLocalTimezone();
    tz.setLocalLocation(tz.getLocation(localName));
    _initialized = true;
  }

  static tz.Location get est => tz.getLocation(estLocationName);

  static tz.TZDateTime estNow() => tz.TZDateTime.now(est);

  static DateTime localNow() => tz.TZDateTime.now(tz.local);

  static tz.TZDateTime estDeadlinePassedAt(int year, int month) {
    return tz.TZDateTime(est, year, month, 2, 0, 0);
  }

  static tz.TZDateTime estFirstReminderAt(int year, int month) {
    return tz.TZDateTime(est, year, month, 2, 0, 5);
  }

  static bool isOnTimeByDeadline(DateTime paidAtUtc, int year, int month) {
    final estPaidAt = tz.TZDateTime.from(paidAtUtc, est);
    final cutoff = tz.TZDateTime(est, year, month, 1, 23, 59, 59, 999);
    return !estPaidAt.isAfter(cutoff);
  }

  static DateTime applyQuietHours({
    required DateTime localTime,
    required int quietHourStart,
    required int fallbackHour,
  }) {
    if (localTime.hour >= quietHourStart) {
      return DateTime(
        localTime.year,
        localTime.month,
        localTime.day + 1,
        fallbackHour,
      );
    }

    return localTime;
  }

  static DateTime nextEligibleLocal({
    required DateTime candidate,
    required int quietHourStart,
    required int fallbackHour,
  }) {
    final now = localNow();
    var result = candidate;

    if (result.isBefore(now)) {
      result = now.add(const Duration(minutes: 1));
    }

    if (result.hour >= quietHourStart) {
      result = DateTime(
        result.year,
        result.month,
        result.day + 1,
        fallbackHour,
      );
    }

    return result;
  }

  static bool monthAtOrAfter({
    required int year,
    required int month,
    required int pivotYear,
    required int pivotMonth,
  }) {
    return year > pivotYear || (year == pivotYear && month >= pivotMonth);
  }

  static bool monthBefore({
    required int year,
    required int month,
    required int otherYear,
    required int otherMonth,
  }) {
    return year < otherYear || (year == otherYear && month < otherMonth);
  }

  static String monthKey(int year, int month) {
    return '$year-${month.toString().padLeft(2, '0')}';
  }
}