RocketChat/Rocket.Chat

import type { MutableRefObject } from 'react';
import { useCallback } from 'react';

import { RoomHistoryManager } from '../../../../../app/ui-utils/client';
import { withThrottling } from '../../../../../lib/utils/highOrderFunctions';

export const useGetMore = (rid: string, atBottomRef: MutableRefObject<boolean>) => {
    return {
        innerRef: useCallback(
            (wrapper: HTMLElement | null) => {
                if (!wrapper) {
                    return;
                }

                let lastScrollTopRef = 0;

                wrapper.addEventListener(
                    'scroll',
                    withThrottling({ wait: 100 })((event) => {
                        lastScrollTopRef = event.target.scrollTop;
                        const height = event.target.clientHeight;
                        const isLoading = RoomHistoryManager.isLoading(rid);
                        const hasMore = RoomHistoryManager.hasMore(rid);
                        const hasMoreNext = RoomHistoryManager.hasMoreNext(rid);

                        if ((isLoading === false && hasMore === true) || hasMoreNext === true) {
                            if (hasMore === true && lastScrollTopRef <= height / 3) {
                                RoomHistoryManager.getMore(rid);
                            } else if (hasMoreNext === true && Math.ceil(lastScrollTopRef) >= event.target.scrollHeight - height) {
                                RoomHistoryManager.getMoreNext(rid, atBottomRef);
                                atBottomRef.current = false;
                            }
                        }
                    }),
                );
            },
            [atBottomRef, rid],
        ),
    };
};