RocketChat/Rocket.Chat

import type { IRoom } from '@rocket.chat/core-typings';
import { useMergedRefs } from '@rocket.chat/fuselage-hooks';
import type { RefObject } from 'react';
import { useCallback } from 'react';

import { isAtBottom } from '../../../../../app/ui/client/views/app/lib/scrolling';
import { withThrottling } from '../../../../../lib/utils/highOrderFunctions';
import { RoomManager } from '../../../../lib/RoomManager';

export function useRestoreScrollPosition(roomId: IRoom['_id']) {
    const ref = useCallback(
        (node: HTMLElement | null) => {
            if (!node) {
                return;
            }
            const store = RoomManager.getStore(roomId);

            if (store?.scroll && !store.atBottom) {
                node.scrollTo({
                    left: 30,
                    top: store.scroll,
                });
            } else {
                node.scrollTo({
                    top: node.scrollHeight,
                });
            }
        },
        [roomId],
    );

    const refCallback = useCallback(
        (node: HTMLElement | null) => {
            if (!node) {
                return;
            }

            const store = RoomManager.getStore(roomId);

            const handleWrapperScroll = withThrottling({ wait: 100 })(() => {
                store?.update({ scroll: node.scrollTop, atBottom: isAtBottom(node, 50) });
            });

            node.addEventListener('scroll', handleWrapperScroll, {
                passive: true,
            });
        },
        [roomId],
    );

    return {
        innerRef: useMergedRefs(refCallback, ref) as unknown as RefObject<HTMLElement>,
    };
}