/**
 * Utility Functions
 * Date/Time formatting, rounding, duration formatting
 */

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

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

/**
 * Get today's date in YYYY-MM-DD format
 */
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}`;
}

/**
 * Round time down to nearest 15 minutes
 */
function roundDownTo15Min(date) {
  const minutes = date.getMinutes();
  const roundedMinutes = Math.floor(minutes / 15) * 15;
  date.setMinutes(roundedMinutes);
  date.setSeconds(0);
  date.setMilliseconds(0);
  return date;
}

/**
 * Round time up to nearest 15 minutes
 */
function roundUpTo15Min(date) {
  const minutes = date.getMinutes();
  const roundedMinutes = Math.ceil(minutes / 15) * 15;
  date.setMinutes(roundedMinutes);
  date.setSeconds(0);
  date.setMilliseconds(0);
  return date;
}

/**
 * Format time as HH:MM
 */
function formatTime(date) {
  const hours = String(date.getHours()).padStart(2, '0');
  const minutes = String(date.getMinutes()).padStart(2, '0');
  return `${hours}:${minutes}`;
}

/**
 * Format seconds to HH:MM:SS
 */
function formatDuration(seconds) {
  const hrs = Math.floor(seconds / 3600);
  const mins = Math.floor((seconds % 3600) / 60);
  const secs = seconds % 60;
  return `${String(hrs).padStart(2, '0')}:${String(mins).padStart(2, '0')}:${String(secs).padStart(2, '0')}`;
}

/**
 * Show toast notification
 */
function showNotification(message, type = 'info') {
  const container = document.getElementById('toastContainer');
  
  // Create toast element
  const toast = document.createElement('div');
  toast.className = `toast toast-${type}`;
  
  // Icon based on type
  const icons = {
    success: '✓',
    error: '✕',
    info: 'ℹ'
  };
  
  toast.innerHTML = `
    <span class="toast-icon">${icons[type] || 'ℹ'}</span>
    <span>${message}</span>
  `;
  
  container.appendChild(toast);
  
  // Auto-remove after 3 seconds
  setTimeout(() => {
    toast.classList.add('hiding');
    setTimeout(() => {
      container.removeChild(toast);
    }, 300);
  }, 3000);
}

/**
 * Get day of week abbreviation in German
 */
function getDayOfWeek(date) {
  const days = ['So', 'Mo', 'Di', 'Mi', 'Do', 'Fr', 'Sa'];
  return days[date.getDay()];
}

/**
 * Get month name in German
 */
function getMonthName(month) {
  const months = [
    'Januar', 'Februar', 'März', 'April', 'Mai', 'Juni',
    'Juli', 'August', 'September', 'Oktober', 'November', 'Dezember'
  ];
  return months[month];
}