const PRIORITIES = new Set(['LOW', 'NORMAL', 'HIGH', 'CRITICAL']);

export function createTicket({ id, summary, priority = 'NORMAL', requestedAt }) {
  if (!id || !summary?.trim() || !requestedAt || !PRIORITIES.has(priority)) {
    throw new Error('invalid ticket input');
  }
  return { id, summary: summary.trim(), priority, requestedAt, status: 'OPEN', assignee: null, resolvedAt: null };
}

export function assignTicket(ticket, assignee) {
  if (!assignee?.trim() || !['OPEN', 'ASSIGNED'].includes(ticket.status)) {
    throw new Error('ticket cannot be assigned');
  }
  return { ...ticket, assignee: assignee.trim(), status: 'ASSIGNED' };
}

export function resolveTicket(ticket, resolvedAt) {
  if (ticket.status !== 'ASSIGNED' || !resolvedAt) throw new Error('ticket cannot be resolved');
  return { ...ticket, status: 'RESOLVED', resolvedAt };
}

export function isSlaBreached(ticket, now) {
  const targetHours = ticket.priority === 'CRITICAL' ? 1 : ticket.priority === 'HIGH' ? 4 : 24;
  const elapsed = new Date(now).getTime() - new Date(ticket.requestedAt).getTime();
  return ticket.status !== 'RESOLVED' && elapsed > targetHours * 60 * 60 * 1000;
}