/**
 * Convert a title into a URL-safe slug.
 * Lowercases, strips accents, replaces non-alphanumerics with hyphens,
 * collapses repeated hyphens, and trims leading/trailing hyphens.
 */
export function slugify(title: string): string {
  return title
    .toLowerCase()
    .normalize('NFKD')
    .replace(/[\u0300-\u036f]/g, '')
    .replace(/[^a-z0-9]+/g, '-')
    .replace(/-+/g, '-')
    .replace(/^-|-$/g, '');
}

/**
 * Generate a slug from a title that does not collide with any of the
 * provided existing slugs. Appends -2, -3, ... when needed.
 */
export function uniqueSlug(title: string, existingSlugs: string[]): string {
  const base = slugify(title) || 'event';
  const taken = new Set(existingSlugs);
  if (!taken.has(base)) return base;
  let n = 2;
  while (taken.has(`${base}-${n}`)) n++;
  return `${base}-${n}`;
}