Calendar/src/v2/core/DateService.ts

import dayjs from 'dayjs';
import utc from 'dayjs/plugin/utc';
import timezone from 'dayjs/plugin/timezone';
import isoWeek from 'dayjs/plugin/isoWeek';
import { ITimeFormatConfig } from './ITimeFormatConfig';

// Enable dayjs plugins
dayjs.extend(utc);
dayjs.extend(timezone);
dayjs.extend(isoWeek);

export class DateService {
  private timezone: string;

  constructor(private config: ITimeFormatConfig) {
    this.timezone = config.timezone;
  }

  parseISO(isoString: string): Date {
    return dayjs(isoString).toDate();
  }

  getDayName(date: Date, format: 'short' | 'long' = 'short'): string {
    return new Intl.DateTimeFormat(this.config.locale, { weekday: format }).format(date);
  }

  getWeekDates(offset = 0, days = 7): string[] {
    const monday = dayjs().startOf('week').add(1, 'day').add(offset, 'week');
    return Array.from({ length: days }, (_, i) =>
      monday.add(i, 'day').format('YYYY-MM-DD')
    );
  }

  // ============================================
  // FORMATTING
  // ============================================

  formatTime(date: Date, showSeconds = false): string {
    const pattern = showSeconds ? 'HH:mm:ss' : 'HH:mm';
    return dayjs(date).format(pattern);
  }

  formatTimeRange(start: Date, end: Date): string {
    return `${this.formatTime(start)} - ${this.formatTime(end)}`;
  }

  formatDate(date: Date): string {
    return dayjs(date).format('YYYY-MM-DD');
  }

  getDateKey(date: Date): string {
    return this.formatDate(date);
  }

  // ============================================
  // TIME CALCULATIONS
  // ============================================

  timeToMinutes(timeString: string): number {
    const parts = timeString.split(':').map(Number);
    const hours = parts[0] || 0;
    const minutes = parts[1] || 0;
    return hours * 60 + minutes;
  }

  minutesToTime(totalMinutes: number): string {
    const hours = Math.floor(totalMinutes / 60);
    const minutes = totalMinutes % 60;
    return dayjs().hour(hours).minute(minutes).format('HH:mm');
  }

  getMinutesSinceMidnight(date: Date): number {
    const d = dayjs(date);
    return d.hour() * 60 + d.minute();
  }

  // ============================================
  // UTC CONVERSIONS
  // ============================================

  toUTC(localDate: Date): string {
    return dayjs.tz(localDate, this.timezone).utc().toISOString();
  }

  fromUTC(utcString: string): Date {
    return dayjs.utc(utcString).tz(this.timezone).toDate();
  }

  // ============================================
  // DATE CREATION
  // ============================================

  createDateAtTime(baseDate: Date | string, timeString: string): Date {
    const totalMinutes = this.timeToMinutes(timeString);
    const hours = Math.floor(totalMinutes / 60);
    const minutes = totalMinutes % 60;
    return dayjs(baseDate).startOf('day').hour(hours).minute(minutes).toDate();
  }

  getISOWeekDay(date: Date | string): number {
    return dayjs(date).isoWeekday();  // 1=Monday, 7=Sunday
  }
}