"use client";

import { useEffect } from "react";
import type { Dispatch, MutableRefObject, SetStateAction } from "react";
import { isEditableTarget } from "@/features/entries/components/entries-panel.utils";

type UseInfiniteVisibleCountParams = {
    enabled: boolean;
    hasMore: boolean;
    totalCount: number;
    pageSize: number;
    sentinelRef: MutableRefObject<HTMLDivElement | null>;
    setVisibleCount: Dispatch<SetStateAction<number>>;
};

export default function useInfiniteVisibleCount({
    enabled,
    hasMore,
    totalCount,
    pageSize,
    sentinelRef,
    setVisibleCount
}: UseInfiniteVisibleCountParams) {
    useEffect(() => {
        if (!enabled || !hasMore) return;

        let touchY: number | null = null;
        let lastLoadAt = 0;
        let lastScrollY = window.scrollY;

        function shouldLoadMore() {
            const sentinel = sentinelRef.current;
            if (!sentinel) return false;
            const rect = sentinel.getBoundingClientRect();
            return rect.top <= window.innerHeight + 48;
        }

        function tryLoadMore() {
            if (!shouldLoadMore()) return;
            const now = Date.now();
            if (now - lastLoadAt < 150) return;
            lastLoadAt = now;
            setVisibleCount(prev => {
                if (prev >= totalCount) return prev;
                return Math.min(prev + pageSize, totalCount);
            });
        }

        function onWheel(event: WheelEvent) {
            if (event.deltaY <= 0) return;
            tryLoadMore();
        }

        function onScroll() {
            const nextY = window.scrollY;
            if (nextY <= lastScrollY) {
                lastScrollY = nextY;
                return;
            }
            lastScrollY = nextY;
            tryLoadMore();
        }

        function onKeyDown(event: KeyboardEvent) {
            if (isEditableTarget(event.target)) return;
            if (event.key === "ArrowDown" || event.key === "PageDown" || event.key === "End" || (event.key === " " && !event.shiftKey)) {
                tryLoadMore();
            }
        }

        function onTouchStart(event: TouchEvent) {
            touchY = event.touches[0]?.clientY ?? null;
        }

        function onTouchMove(event: TouchEvent) {
            const nextY = event.touches[0]?.clientY;
            if (touchY == null || nextY == null) return;
            const delta = touchY - nextY;
            touchY = nextY;
            if (delta > 10) tryLoadMore();
        }

        window.addEventListener("wheel", onWheel, { passive: true });
        window.addEventListener("scroll", onScroll, { passive: true });
        window.addEventListener("keydown", onKeyDown);
        window.addEventListener("touchstart", onTouchStart, { passive: true });
        window.addEventListener("touchmove", onTouchMove, { passive: true });

        return () => {
            window.removeEventListener("wheel", onWheel);
            window.removeEventListener("scroll", onScroll);
            window.removeEventListener("keydown", onKeyDown);
            window.removeEventListener("touchstart", onTouchStart);
            window.removeEventListener("touchmove", onTouchMove);
        };
    }, [enabled, hasMore, pageSize, sentinelRef, setVisibleCount, totalCount]);
}