// Pure helpers for the video-SELECTION grounding target (the AI-grounding
// inclusion set), split out of SearchSessionContext so they're unit-testable
// without pulling in the whole client component.

// Drop selected slugs that are no longer among the current (settled) result set,
// so a selection carried across a new/narrower search self-cleans.
export function pruneSelection<T>(
  selected: ReadonlySet<T>,
  present: ReadonlySet<T>,
): Set<T> {
  const next = new Set<T>();
  for (const slug of selected) if (present.has(slug)) next.add(slug);
  return next;
}

// Filter result groups to the selection, preserving result order. Generic over
// any object carrying a `slug` so the search-session's ResultGroup fits without
// a dependency here.
export function selectGroups<G extends { slug: string }>(
  groups: ReadonlyArray<G>,
  selected: ReadonlySet<string>,
): G[] {
  if (selected.size === 0) return [];
  return groups.filter((g) => selected.has(g.slug));
}