/**
 * Date utility functions
 */

/**
 * Format date from YYYY-MM-DD to DD.MM.YYYY
 * @param {string} dateStr - Date in YYYY-MM-DD format
 * @returns {string} - Date in DD.MM.YYYY format
 */
export function formatDateDisplay(dateStr) {
  const [year, month, day] = dateStr.split('-');
  return `${day}.${month}.${year}`;
}

/**
 * Format date from DD.MM.YYYY to YYYY-MM-DD
 * @param {string} dateStr - Date in DD.MM.YYYY format
 * @returns {string} - Date in YYYY-MM-DD format
 */
export function formatDateISO(dateStr) {
  const [day, month, year] = dateStr.split('.');
  return `${year}-${month}-${day}`;
}

/**
 * Get today's date in YYYY-MM-DD format
 * @returns {string} - Today's date
 */
export function getTodayISO() {
  const today = new Date();
  const year = today.getFullYear();
  const month = String(today.getMonth() + 1).padStart(2, '0');
  const day = String(today.getDate()).padStart(2, '0');
  return `${year}-${month}-${day}`;
}

/**
 * Get day of week name in German
 * @param {Date} date - Date object
 * @returns {string} - German day name (Mo, Di, Mi, etc.)
 */
export function getDayOfWeek(date) {
  const days = ['So', 'Mo', 'Di', 'Mi', 'Do', 'Fr', 'Sa'];
  return days[date.getDay()];
}

/**
 * Get month name in German
 * @param {number} monthIndex - Month index (0-11)
 * @returns {string} - German month name
 */
export function getMonthName(monthIndex) {
  const months = [
    'Januar', 'Februar', 'März', 'April', 'Mai', 'Juni',
    'Juli', 'August', 'September', 'Oktober', 'November', 'Dezember'
  ];
  return months[monthIndex];
}

/**
 * Check if date is weekend or holiday
 * @param {Date} date - Date object
 * @returns {boolean} - True if weekend or holiday
 */
export function isWeekendOrHoliday(date) {
  const dayOfWeek = date.getDay();
  return dayOfWeek === 0 || dayOfWeek === 6; // Sunday or Saturday
}