import type { PageCommentsView } from '@dorfteich/shared';
import { useQuery, useQueryClient, type UseQueryResult } from '@tanstack/react-query';

import { apiGet } from '../lib/api';

/**
 * Page comments data (issue #92). One query per page, shared between the
 * panel and the toggle button's unread badge. "Unread" is a purely local
 * notion: newer than the last time this browser opened the panel
 * (localStorage — no server round-trip, per the issue's design).
 */

export const commentsQueryKey = (pageId: string): [string, string] => ['comments', pageId];

export function useComments(pageId: string | undefined): UseQueryResult<PageCommentsView> {
  return useQuery({
    queryKey: commentsQueryKey(pageId ?? ''),
    queryFn: () => apiGet<PageCommentsView>(`/pages/${pageId}/comments`),
    enabled: Boolean(pageId),
  });
}

export function useInvalidateComments(pageId: string): () => Promise<void> {
  const queryClient = useQueryClient();
  return () => queryClient.invalidateQueries({ queryKey: commentsQueryKey(pageId) });
}

const seenKey = (pageId: string): string => `dorfteich.comments.seen.${pageId}`;

export function markCommentsSeen(pageId: string): void {
  try {
    localStorage.setItem(seenKey(pageId), new Date().toISOString());
  } catch {
    // Storage full/blocked: the badge simply stays — never break the page.
  }
}

/** Comments newer than the last visit, not authored by the viewer. */
export function unreadCount(
  view: PageCommentsView | undefined,
  pageId: string,
  viewerId: string | undefined,
): number {
  if (!view) return 0;
  let since = 0;
  try {
    const stored = localStorage.getItem(seenKey(pageId));
    since = stored ? new Date(stored).getTime() : 0;
  } catch {
    since = 0;
  }
  let count = 0;
  for (const thread of view.threads) {
    for (const comment of [thread.root, ...thread.replies]) {
      if (new Date(comment.createdAt).getTime() > since && comment.author?.id !== viewerId) {
        count += 1;
      }
    }
  }
  return count;
}