// src/views/Community/components/DynamicNewsCard/VirtualizedFourRowGrid.js
// 四列纵向滚动虚拟化网格组件（每行4列，纵向滚动 + 无限滚动）

import React, { useRef, useMemo, useEffect } from 'react';
import { useVirtualizer } from '@tanstack/react-virtual';
import { Box, Grid, Spinner, Text, VStack, Center } from '@chakra-ui/react';
import { useColorModeValue } from '@chakra-ui/react';
import DynamicNewsEventCard from '../EventCard/DynamicNewsEventCard';

/**
 * 四列纵向滚动虚拟化网格组件（支持无限滚动）
 * @param {Object} props
 * @param {Array} props.events - 事件列表（累积显示）
 * @param {Object} props.selectedEvent - 当前选中的事件
 * @param {Function} props.onEventSelect - 事件选择回调
 * @param {Object} props.eventFollowStatus - 事件关注状态
 * @param {Function} props.onToggleFollow - 关注切换回调
 * @param {Function} props.getTimelineBoxStyle - 时间轴样式获取函数
 * @param {string} props.borderColor - 边框颜色
 * @param {Function} props.loadNextPage - 加载下一页（无限滚动）
 * @param {boolean} props.hasMore - 是否还有更多数据
 * @param {boolean} props.loading - 加载状态
 */
const VirtualizedFourRowGrid = ({
  events,
  selectedEvent,
  onEventSelect,
  eventFollowStatus,
  onToggleFollow,
  getTimelineBoxStyle,
  borderColor,
  loadNextPage,
  hasMore,
  loading,
}) => {
  const parentRef = useRef(null);
  const isLoadingMore = useRef(false);  // 防止重复加载

  // 滚动条颜色（主题适配）
  const scrollbarTrackBg = useColorModeValue('#f1f1f1', '#2D3748');
  const scrollbarThumbBg = useColorModeValue('#888', '#4A5568');
  const scrollbarThumbHoverBg = useColorModeValue('#555', '#718096');

  // 将事件按4个一组分成行（每行4列）
  const rows = useMemo(() => {
    const r = [];
    for (let i = 0; i < events.length; i += 4) {
      r.push(events.slice(i, i + 4));
    }
    return r;
  }, [events]);

  // 配置虚拟滚动器（纵向滚动 + 动态高度测量）
  const rowVirtualizer = useVirtualizer({
    count: rows.length,
    getScrollElement: () => parentRef.current,
    estimateSize: () => 250, // 提供初始估算值，库会自动测量实际高度
    overscan: 2,             // 预加载2行（上下各1行）
  });

  // 无限滚动逻辑 - 监听滚动事件，到达底部时加载下一页
  useEffect(() => {
    const scrollElement = parentRef.current;
    if (!scrollElement || !loadNextPage) return;

    const handleScroll = async () => {
      // 防止重复触发
      if (isLoadingMore.current || !hasMore || loading) return;

      const { scrollTop, scrollHeight, clientHeight } = scrollElement;
      const scrollPercentage = (scrollTop + clientHeight) / scrollHeight;

      // 滚动到 80% 时开始加载下一页
      if (scrollPercentage > 0.8) {
        console.log('%c📜 [无限滚动] 到达底部，加载下一页', 'color: #8B5CF6; font-weight: bold;');
        isLoadingMore.current = true;
        await loadNextPage();
        isLoadingMore.current = false;
      }
    };

    scrollElement.addEventListener('scroll', handleScroll);
    return () => scrollElement.removeEventListener('scroll', handleScroll);
  }, [loadNextPage, hasMore, loading]);

  // 底部加载指示器
  const renderLoadingIndicator = () => {
    if (!hasMore) {
      return (
        <Center py={6}>
          <Text color="gray.500" fontSize="sm">
            已加载全部内容
          </Text>
        </Center>
      );
    }
    if (loading) {
      return (
        <Center py={6}>
          <VStack spacing={2}>
            <Spinner size="md" color="blue.500" thickness="3px" />
            <Text color="gray.500" fontSize="sm">
              加载中...
            </Text>
          </VStack>
        </Center>
      );
    }
    return null;
  };

  return (
    <Box
      ref={parentRef}
      overflowY="auto"
      overflowX="hidden"
      maxH="600px"
      w="100%"
      position="relative"
      css={{
        // 滚动条样式
        '&::-webkit-scrollbar': {
          width: '8px',
        },
        '&::-webkit-scrollbar-track': {
          background: scrollbarTrackBg,
          borderRadius: '10px',
        },
        '&::-webkit-scrollbar-thumb': {
          background: scrollbarThumbBg,
          borderRadius: '10px',
        },
        '&::-webkit-scrollbar-thumb:hover': {
          background: scrollbarThumbHoverBg,
        },
        scrollBehavior: 'smooth',
        WebkitOverflowScrolling: 'touch',
      }}
    >
      {/* 虚拟滚动容器 + 底部加载指示器 */}
      <Box position="relative" w="100%">
        {/* 虚拟滚动内容 */}
        <Box
          position="relative"
          w="100%"
          h={`${rowVirtualizer.getTotalSize()}px`}
        >
          {rowVirtualizer.getVirtualItems().map((virtualRow) => {
            const rowEvents = rows[virtualRow.index];

            return (
              <Box
                key={virtualRow.key}
                data-index={virtualRow.index}
                ref={rowVirtualizer.measureElement}
                position="absolute"
                top={0}
                left={0}
                w="100%"
                transform={`translateY(${virtualRow.start}px)`}
              >
                {/* 每行使用 Grid 横向排列4个卡片 */}
                <Grid
                  templateColumns="repeat(4, 1fr)"
                  gap={4}
                  w="100%"
                >
                  {rowEvents.map((event, colIndex) => (
                    <Box key={event.id}>
                      <DynamicNewsEventCard
                        event={event}
                        index={virtualRow.index * 4 + colIndex}
                        isFollowing={eventFollowStatus[event.id]?.isFollowing || false}
                        followerCount={eventFollowStatus[event.id]?.followerCount || event.follower_count || 0}
                        isSelected={selectedEvent?.id === event.id}
                        onEventClick={(clickedEvent) => {
                          onEventSelect(clickedEvent);
                        }}
                        onTitleClick={(e) => {
                          e.preventDefault();
                          e.stopPropagation();
                          onEventSelect(event);
                        }}
                        onToggleFollow={() => onToggleFollow?.(event.id)}
                        timelineStyle={getTimelineBoxStyle()}
                        borderColor={borderColor}
                      />
                    </Box>
                  ))}
                </Grid>
              </Box>
            );
          })}
        </Box>

        {/* 底部加载指示器 - 绝对定位在虚拟内容底部 */}
        <Box
          position="absolute"
          top={`${rowVirtualizer.getTotalSize()}px`}
          left={0}
          right={0}
          w="100%"
        >
          {renderLoadingIndicator()}
        </Box>
      </Box>
    </Box>
  );
};

export default VirtualizedFourRowGrid;