import { useEffect, useRef, useCallback } from 'preact/hooks';


export const useLoadMore = (onReachBottom, options: {
  threshold?: number;
  debounceDelay?: number;

  isEnabled?: boolean;
  finished?: boolean;

  containerRef?: any;
} = {}) => {
  const {
    threshold = 100,
    debounceDelay = 100,

    isEnabled = true,
    finished,

    containerRef: externalContainerRef, // 外部传入的容器ref
  } = options;

  const internalContainerRef = useRef(null);
  const containerRef = externalContainerRef || internalContainerRef;

  // 防抖函数
  const debounce = useCallback((func, delay) => {
    let timeoutId;
    return (...args) => {
      clearTimeout(timeoutId);
      timeoutId = setTimeout(() => func.apply(this, args), delay);
    };
  }, []);

  // 触底判断
  const checkIsBottom = useCallback((element) => {
    if (!element) return false;

    const { scrollTop, scrollHeight, clientHeight } = element;
    const scrollBottom = scrollHeight - scrollTop - clientHeight;
    return scrollBottom <= threshold;
  }, [threshold]);

  // 滚动处理
  const handleScroll = useCallback(
    debounce(() => {
      if (!isEnabled || finished) return; // finished时不再触发


      const container = containerRef.current;
      if (!container) return;

      if (checkIsBottom(container)) {
        onReachBottom();
      }
    }, debounceDelay),
    [finished, debounceDelay, isEnabled, checkIsBottom, onReachBottom],
  );

  // 事件监听
  useEffect(() => {
    const container = containerRef.current;
    if (!container) return;
    if (!isEnabled) {
      container.removeEventListener('scroll', handleScroll);
      return;
    }

    container.addEventListener('scroll', handleScroll);

    return () => {
      container.removeEventListener('scroll', handleScroll);
    };
  }, [handleScroll, isEnabled, containerRef]);


  return {
    containerRef,
  };
};