import { useQuery } from '@tanstack/react-query';
import api from '@/lib/api-client';

/**
 * Mirrors the BacklinksResult shape from the backend (R3.2).
 */
export interface PageSummary {
  id: string;
  title: string | null;
  slugId: string | null;
  icon: string | null;
  spaceSlug: string | null;
  spaceName: string | null;
}

export interface BacklinkEntry {
  source: PageSummary;
  linkType: 'wikilink' | 'mention' | 'database_embed';
  contextExcerpt: string | null;
}

export interface BacklinksResult {
  wikilinks: BacklinkEntry[];
  mentions: BacklinkEntry[];
  database_embeds: BacklinkEntry[];
  total: number;
}

async function fetchBacklinks(pageId: string): Promise<BacklinksResult> {
  const res = await api.get<BacklinksResult>(
    `/acadenice/pages/${pageId}/backlinks`,
  );
  return res.data;
}

/**
 * React Query hook that fetches backlinks for a given page.
 *
 * Cache policy:
 *   - staleTime: 30s — backlinks are eventually consistent (indexed async).
 *   - gcTime: 5 min — keep in memory while navigating between pages.
 *
 * The hook is a no-op when pageId is empty/undefined.
 */
export function useBacklinks(pageId: string | undefined) {
  return useQuery({
    queryKey: ['acadenice', 'backlinks', pageId],
    queryFn: () => fetchBacklinks(pageId!),
    enabled: !!pageId,
    staleTime: 30_000,
    gcTime: 5 * 60_000,
  });
}