import { ref, unref, watch, watchEffect, onMounted, onBeforeUnmount } from 'vue'
import TWEEN from '@tweenjs/tween.js'

export default function useSmoothSwipe({
  scrollTargetRef,
  maxTranslateLength,
  viewportWidth = document.documentElement.clientWidth,
  anchorPosList,
  initialAnchorIdx = 0,
} = {}) {

  const isOperating = ref(false)
  const haveSwipedThisTime = ref(false)
  let hasOperatedThisTimeTimeoutId = null

  let translateLength = ref(anchorPosList[initialAnchorIdx])
  let maxTranslateLengthInner = Infinity

  let animationFrameId = null

  let tween = null
  let isTweening = false

  let fingerPosXWhenTouchStart = 0

  let anchorPosListInner = [...anchorPosList].sort((a, b) => {
    return a > b
  })
  let anchorPosListInnerReverse = [...anchorPosListInner].reverse()
  const currentAnchorIdx = ref(initialAnchorIdx)
  const goingToAnchorIdx = ref(null)

  watch(isOperating, (v) => {
    if (v) {
      clearTimeout(hasOperatedThisTimeTimeoutId)
      haveSwipedThisTime.value = false
    } else {
      clearTimeout(hasOperatedThisTimeTimeoutId)
      hasOperatedThisTimeTimeoutId = setTimeout(() => {
        haveSwipedThisTime.value = false
      }, 333)
    }
  })

  // compute maxTranslateLengthInner todo: 不能用if包裹吧？
  if (maxTranslateLength) {
    watchEffect(() => {
      maxTranslateLengthInner = unref(maxTranslateLength) - unref(viewportWidth)
      if (maxTranslateLengthInner < 0) {
        maxTranslateLengthInner = 0
      }
    })
  } else if (scrollTargetRef) {
    watchEffect(() => {
      if (scrollTargetRef.value) {
        maxTranslateLengthInner = scrollTargetRef.value.scrollWidth - unref(viewportWidth)
        if (maxTranslateLengthInner < 0) {
          maxTranslateLengthInner = 0
        }
      } else {
        maxTranslateLengthInner = Infinity
      }
    })
  }

  function onTouchStart(e) {
    isOperating.value = true
    fingerPosXWhenTouchStart = e.changedTouches[0].pageX
  }

  const onTouchMove = (event) => {
    if (isTweening) {
      return
    }

    let currentX = event.changedTouches[0].pageX
    let dX = currentX - fingerPosXWhenTouchStart
    if (dX < -1) { // 左滑，要往右移动
      const destinationIdx = anchorPosListInner.findIndex((item) => {
        return item - translateLength.value > 1
      })
      if ((destinationIdx !== -1) && !isTweening) {
        isTweening = true
        tween = new TWEEN.Tween(translateLength)
        tween.to({
          value: anchorPosListInner[destinationIdx],
        }, 1200)
        tween.easing(TWEEN.Easing.Cubic.InOut)
        tween.start()
        goingToAnchorIdx.value = destinationIdx
        tween.onComplete(() => {
          isTweening = false
          currentAnchorIdx.value = destinationIdx
          goingToAnchorIdx.value = null
        })
      }
    } else if (dX > 1) {
      const destinationIdx = anchorPosListInnerReverse.findIndex((item) => {
        return item - translateLength.value < -1
      })
      if ((destinationIdx !== -1) && !isTweening) {
        isTweening = true
        tween = new TWEEN.Tween(translateLength)
        tween.to({
          value: anchorPosListInnerReverse[destinationIdx],
        }, 1200)
        tween.easing(TWEEN.Easing.Cubic.InOut)
        tween.start()
        goingToAnchorIdx.value = anchorPosList.length - destinationIdx - 1
        tween.onComplete(() => {
          isTweening = false
          currentAnchorIdx.value = anchorPosList.length - destinationIdx - 1
          goingToAnchorIdx.value = null
        })
      }
    }
  }

  function onTouchEnd(e) {
    isOperating.value = false

  }

  function onTouchCancel() {
    isOperating.value = false
  }

  // 在每一帧更新镜头速度、位置
  function animationFrameTask() {
    TWEEN.update()
    animationFrameId = requestAnimationFrame(animationFrameTask)
  }
  onMounted(() => {
    animationFrameId = requestAnimationFrame(animationFrameTask)
  })
  onBeforeUnmount(() => {
    cancelAnimationFrame(animationFrameId)
    tween && tween.stop()
  })

  if (scrollTargetRef) { // todo: 不能用if包裹吧？
    watch(scrollTargetRef, (v) => {
      if (v) {
        v.addEventListener('touchstart', onTouchStart)
        v.addEventListener('touchmove', onTouchMove)
        v.addEventListener('touchend', onTouchEnd)
        v.addEventListener('touchcancel', onTouchCancel)
      }
    }, {
      immediate: true,
    })
  }

  return {
    onTouchStart,
    onTouchMove,
    onTouchEnd,
    onTouchCancel,
    translateLength,
    haveSwipedThisTime,
    currentAnchorIdx,
    goingToAnchorIdx,
  }
}