import { useState, useMemo } from 'react';
import { useQuery } from '@tanstack/react-query';
import api from '@/lib/api';
import type { Calendar, SharedCalendarMembership } from '@/types';

interface UseCalendarsOptions {
  pollingEnabled?: boolean;
}

export function useCalendars({ pollingEnabled = false }: UseCalendarsOptions = {}) {
  const ownedQuery = useQuery({
    queryKey: ['calendars'],
    queryFn: async () => {
      const { data } = await api.get<Calendar[]>('/calendars');
      return data;
    },
  });

  // AS-4: Gate shared-calendar polling on whether user participates in sharing.
  // Saves ~12 API calls/min for personal-only users.
  // Uses useState (not useRef) so changes trigger a re-render and the
  // refetchInterval picks up the new value immediately.
  const [hasSharing, setHasSharing] = useState(false);
  const ownsShared = (ownedQuery.data ?? []).some((c) => c.is_shared);
  if (ownsShared && !hasSharing) setHasSharing(true);

  const sharedQuery = useQuery({
    queryKey: ['calendars', 'shared'],
    queryFn: async () => {
      const { data } = await api.get<SharedCalendarMembership[]>('/shared-calendars');
      return data;
    },
    refetchInterval: pollingEnabled && hasSharing ? 5_000 : false,
    staleTime: 3_000,
  });

  // Also latch if user is a member of others' shared calendars
  if ((sharedQuery.data ?? []).length > 0 && !hasSharing) setHasSharing(true);

  const allCalendarIds = useMemo(() => {
    const owned = (ownedQuery.data ?? []).map((c) => c.id);
    const shared = (sharedQuery.data ?? []).map((m) => m.calendar_id);
    return new Set([...owned, ...shared]);
  }, [ownedQuery.data, sharedQuery.data]);

  return {
    data: ownedQuery.data ?? [],
    sharedData: sharedQuery.data ?? [],
    allCalendarIds,
    isLoading: ownedQuery.isLoading,
    isLoadingShared: sharedQuery.isLoading,
  };
}