/**
 * 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`;
    }
  }
}