/**
 * Global Date Formatting Utility
 * Formats dates to relative time strings (today, yesterday, etc.)
 * Usage: formatRelativeDate('2025-01-15') or formatRelativeDate(new Date())
 */

export function formatRelativeDate(dateString: string | Date): string {
  if (!dateString) {
    return 'Today';
  }
  
  const date = typeof dateString === 'string' ? new Date(dateString) : dateString;
  
  // Check if date is valid
  if (isNaN(date.getTime())) {
    return 'Today';
  }
  
  const now = new Date();
  
  // Set time to midnight for both dates to compare days only
  const today = new Date(now.getFullYear(), now.getMonth(), now.getDate());
  const dateOnly = new Date(date.getFullYear(), date.getMonth(), date.getDate());
  
  const diffTime = today.getTime() - dateOnly.getTime();
  const diffDays = Math.floor(diffTime / (1000 * 60 * 60 * 24));

  if (diffDays === 0) {
    return 'Today';
  } else if (diffDays === 1) {
    return 'Yesterday';
  } else if (diffDays < 30) {
    return `${diffDays} days ago`;
  } else if (diffDays < 365) {
    const months = Math.floor(diffDays / 30);
    const remainingDays = diffDays % 30;
    if (remainingDays === 0) {
      return `${months} month${months > 1 ? 's' : ''} ago`;
    } else {
      return `${months} month${months > 1 ? 's' : ''} ${remainingDays} day${remainingDays > 1 ? 's' : ''} ago`;
    }
  } else {
    const years = Math.floor(diffDays / 365);
    const remainingMonths = Math.floor((diffDays % 365) / 30);
    if (remainingMonths === 0) {
      return `${years} year${years > 1 ? 's' : ''} ago`;
    } else {
      return `${years} year${years > 1 ? 's' : ''} ${remainingMonths} month${remainingMonths > 1 ? 's' : ''} ago`;
    }
  }
}

/**
 * Format date to a standard display format
 * @param dateString - ISO date string or Date object
 * @param options - Intl.DateTimeFormat options
 * @returns Formatted date string (e.g., "Jan 7, 2026")
 */
export function formatDate(
  dateString: string | Date | null | undefined,
  options: Intl.DateTimeFormatOptions = { month: 'short', day: 'numeric', year: 'numeric' }
): string {
  if (!dateString) return '-';
  
  const date = typeof dateString === 'string' ? new Date(dateString) : dateString;
  
  if (isNaN(date.getTime())) return '-';
  
  return date.toLocaleDateString('en-US', options);
}

/**
 * Format date and time to a standard display format
 * @param dateString - ISO date string or Date object
 * @returns Formatted date and time string (e.g., "Jan 7, 2026, 3:30 PM")
 */
export function formatDateTime(
  dateString: string | Date | null | undefined
): string {
  if (!dateString) return '-';
  
  const date = typeof dateString === 'string' ? new Date(dateString) : dateString;
  
  if (isNaN(date.getTime())) return '-';
  
  return date.toLocaleDateString('en-US', {
    month: 'short',
    day: 'numeric',
    year: 'numeric',
    hour: 'numeric',
    minute: '2-digit',
    hour12: true
  });
}