import * as React from 'react';
import { useRef } from 'react';
import { useTimeout } from '@fluentui/react-utilities';
/**
 * Optional hook that will enable pagination on the virtualizer so that it 'autoscrolls' to an items exact position
 * Sizes are uniform/static, we round to the nearest item on long scrolls
 * On short scrolls, we will go at minimum to the next/previous item so that arrow pagination works
 * All VirtualizerStaticPaginationProps can be grabbed from Virtualizer hooks externally and passed in
 */ export const useStaticVirtualizerPagination = (virtualizerProps, paginationEnabled = true)=>{
    'use no memo';
    const { itemSize, axis = 'vertical' } = virtualizerProps;
    const [setScrollTimer, clearScrollTimer] = useTimeout();
    const lastScrollPos = useRef(0);
    const lastIndexScrolled = useRef(0);
    const scrollContainer = React.useRef(null);
    const clearListeners = ()=>{
        if (scrollContainer.current) {
            scrollContainer.current.removeEventListener('scroll', onScroll);
            scrollContainer.current = null;
            clearScrollTimer();
        }
    };
    React.useEffect(()=>{
        return ()=>{
            clearListeners();
        };
    // eslint-disable-next-line react-hooks/exhaustive-deps
    }, []);
    /**
   * Handle scroll stop event and paginate to the closest item
   * If the closest item is the same as the previous scroll end
   * we paginate to the next/previous one based on direction
   */ const onScrollEnd = React.useCallback(()=>{
        if (!scrollContainer.current || !paginationEnabled) {
            // No container found
            return;
        }
        const currentScrollPos = Math.round(axis === 'vertical' ? scrollContainer.current.scrollTop : scrollContainer.current.scrollLeft);
        const closestItem = Math.round(currentScrollPos / itemSize);
        let nextItem = 0;
        if (Math.round(closestItem - lastIndexScrolled.current) === 0) {
            // Special case for go to next/previous with minimum amount of scroll needed
            const nextTarget = lastScrollPos.current < currentScrollPos ? 1 : -1;
            const isSecondaryScroll = lastScrollPos.current === currentScrollPos;
            const posMod = isSecondaryScroll ? 0 : nextTarget;
            nextItem = closestItem + posMod;
        } else {
            // Pagination for anything else can just jump to the closest!
            nextItem = closestItem;
        }
        const nextItemPos = nextItem * itemSize;
        if (axis === 'vertical') {
            scrollContainer.current.scrollTo({
                top: nextItemPos,
                behavior: 'smooth'
            });
        } else {
            scrollContainer.current.scrollTo({
                left: nextItemPos,
                behavior: 'smooth'
            });
        }
        lastScrollPos.current = nextItemPos;
        lastIndexScrolled.current = nextItem;
    }, [
        paginationEnabled,
        axis,
        itemSize
    ]);
    /**
   * On scroll timer that will continuously delay callback until scrolling stops
   */ const onScroll = React.useCallback((event)=>{
        clearScrollTimer();
        setScrollTimer(onScrollEnd, 100);
    }, [
        onScrollEnd,
        clearScrollTimer,
        setScrollTimer
    ]);
    /**
   * Pagination ref will ensure we attach listeners to containers on change
   * It is returned from hook and merged into the scroll container externally
   */ const paginationRef = React.useCallback((instance)=>{
        if (!paginationEnabled) {
            clearListeners();
            scrollContainer.current = null;
            return;
        }
        if (scrollContainer.current !== instance) {
            clearListeners();
            scrollContainer.current = instance;
            if (scrollContainer.current) {
                scrollContainer.current.addEventListener('scroll', onScroll);
            }
        }
    }, // eslint-disable-next-line react-hooks/exhaustive-deps
    [
        onScroll,
        onScrollEnd,
        paginationEnabled
    ]);
    return paginationRef;
};