import * as echarts from 'echarts';

/**
 * 为 ECharts 实例添加自动滚动功能（精确固定窗口项数 + 用户操作暂停）
 * @param chartInstance ECharts 实例
 * @param totalItems x轴总项数
 * @param windowSize 显示窗口项数，默认 6
 * @param interval 滚动间隔，默认 1500ms
 * @returns 停止函数
 */
export function enableEchartsAutoScroll(
  chartInstance: echarts.ECharts,
  totalItems: number,
  windowSize: number = 6,
  interval: number = 1500
): () => void {
  let index = 0;
  let isUserInteracting = false;
  let lastInteractionTime = Date.now();
  let currentWindowSize = windowSize;

  // 主动初始化窗口大小（如果设置了 dataZoom）
  const option = chartInstance.getOption();
  const zoom = option?.dataZoom?.[0];
  if (zoom && zoom.start != null && zoom.end != null) {
    const startIndex = Math.round((zoom.start / 100) * totalItems);
    const endIndex = Math.round((zoom.end / 100) * totalItems);
    currentWindowSize = endIndex - startIndex;
  }

  // 监听用户操作
  const dataZoomHandler = (params: any) => {
    const zoom = params.batch ? params.batch[0] : params;
    const startIndex = Math.round((zoom.start / 100) * totalItems);
    const endIndex = Math.round((zoom.end / 100) * totalItems);
    currentWindowSize = endIndex - startIndex;

    isUserInteracting = true;
    lastInteractionTime = Date.now();
  };

  chartInstance.on('dataZoom', dataZoomHandler);

  // 自动滚动定时器
  const timer = setInterval(() => {
    const now = Date.now();
    if (isUserInteracting && now - lastInteractionTime < 1000) return;

    isUserInteracting = false;

    if (index + currentWindowSize > totalItems) {
      index = 0;
    }

    const startPercent = (index / totalItems) * 100;
    const endPercent = ((index + currentWindowSize) / totalItems) * 100;

    chartInstance.setOption({
      dataZoom: [
        {
          start: startPercent,
          end: endPercent
        }
      ]
    });

    index++;
  }, interval);

  // 返回停止方法
  return () => {
    clearInterval(timer);
    chartInstance.off('dataZoom', dataZoomHandler);
  };
}