import { formatDistanceToNow, parseISO, addYears, differenceInDays } from 'date-fns';

// Deterministic avatar color from name hash
export const avatarColors = [
  'bg-rose-500/20 text-rose-400',
  'bg-blue-500/20 text-blue-400',
  'bg-purple-500/20 text-purple-400',
  'bg-pink-500/20 text-pink-400',
  'bg-teal-500/20 text-teal-400',
  'bg-orange-500/20 text-orange-400',
  'bg-green-500/20 text-green-400',
  'bg-amber-500/20 text-amber-400',
];

export function getInitials(name: string): string {
  const parts = name.trim().split(/\s+/);
  if (parts.length >= 2) return (parts[0][0] + parts[parts.length - 1][0]).toUpperCase();
  return name.slice(0, 2).toUpperCase();
}

export function getAvatarColor(name: string): string {
  let hash = 0;
  for (let i = 0; i < name.length; i++) {
    hash = ((hash << 5) - hash + name.charCodeAt(i)) | 0;
  }
  return avatarColors[Math.abs(hash) % avatarColors.length];
}

export function formatUpdatedAt(updatedAt: string): string {
  try {
    return `Updated ${formatDistanceToNow(parseISO(updatedAt), { addSuffix: true })}`;
  } catch {
    return '';
  }
}

export function getNextBirthday(birthday: string): Date {
  const today = new Date();
  const parsed = parseISO(birthday);
  const thisYear = new Date(today.getFullYear(), parsed.getMonth(), parsed.getDate());
  if (thisYear < today) {
    return addYears(thisYear, 1);
  }
  return thisYear;
}

export function getDaysUntilBirthday(birthday: string): number {
  const next = getNextBirthday(birthday);
  return differenceInDays(next, new Date());
}

export function splitName(name: string): { firstName: string; lastName: string } {
  const idx = name.indexOf(' ');
  if (idx === -1) return { firstName: name, lastName: '' };
  return { firstName: name.slice(0, idx), lastName: name.slice(idx + 1) };
}