import React from 'react';

import { notifyManager, useQueryClient } from '@tanstack/react-query';

/**
 * Get the state of the dataProvider connection.
 *
 * Returns true if a query or a mutation is pending.
 *
 * Custom implementation because react-query's useIsFetching and useIsMutating
 * render each time the number of active queries changes, which is too often.
 *
 * @see useIsFetching
 * @see useIsMutating
 */
export const useLoading = (): boolean => {
    const client = useQueryClient();
    const mountedRef = React.useRef(false);
    const isFetchingRef = React.useRef(client.isFetching() > 0);
    const isMutatingRef = React.useRef(client.isMutating() > 0);

    const [isLoading, setIsLoading] = React.useState<boolean>(
        isFetchingRef.current || isMutatingRef.current
    );

    React.useEffect(() => {
        mountedRef.current = true;

        const unsubscribeQueryCache = client.getQueryCache().subscribe(
            notifyManager.batchCalls(() => {
                if (mountedRef.current) {
                    isFetchingRef.current = client.isFetching() > 0;
                    setIsLoading(
                        isFetchingRef.current || isMutatingRef.current
                    );
                }
            })
        );

        const unsubscribeMutationCache = client.getMutationCache().subscribe(
            notifyManager.batchCalls(() => {
                if (mountedRef.current) {
                    isMutatingRef.current = client.isMutating() > 0;
                    setIsLoading(
                        isFetchingRef.current || isMutatingRef.current
                    );
                }
            })
        );

        return () => {
            mountedRef.current = false;
            unsubscribeQueryCache();
            unsubscribeMutationCache();
        };
    }, [client]);

    return isLoading;
};