scrollTo.ts

import getScrollTop from './getScrollTop'
import setScrollTop from './setScrollTop'

const requestAnimFrame = (function () {
  // @ts-expect-error ts-migrate(2339)
  return window.requestAnimationFrame || window?.webkitRequestAnimationFrame || window?.mozRequestAnimationFrame
    || function (callback) {
      window.setTimeout(callback, 1000 / 60)
    }
})()

/**
 * @param to - 滚动到的位置
 * @param duration - 滚动的时间
 * @description 在${duration}时间内，滚动条平滑滚动到${to}指定位置
*/

export default function scrollTo(to: number, duration: number): void {
  if (duration < 0) {
    setScrollTop(to)
    return
  }

  const diff = to - getScrollTop()
  if (diff === 0)
    return

  const step = diff / duration * 10
  requestAnimFrame(
    () => {
      if (Math.abs(step) > Math.abs(diff)) {
        setScrollTop(getScrollTop() + diff)
        return
      }
      setScrollTop(getScrollTop() + step)
      if ((diff > 0 && getScrollTop() >= to) || (diff < 0 && getScrollTop() <= to))
        return

      scrollTo(to, duration - 16)
    })
}