<template>
 <div class="mu-load-more"
  @touchstart="touchStart($event)" @touchmove="touchMove($event)" @touchend="touchEnd($event)">
 <div class="mu-refresh-control" v-if="!isNaN(top) && top !== 0" :style="{ transform: 'translate3d(0, ' + top + 'px, 0)' }">
  <svg-icon icon-class="gengxin" class="mu-refresh-svg-icon" v-if="state === 0 || state === 1" :style="{ transform: 'rotate(' + (top * 2) + 'deg)' }"></svg-icon>
 </div>
 <div class="mu-refresh-control son" v-if="state === 2" :style="{ 'margin-top': marginTop + 'px' }">
  <svg-icon icon-class="jianchagengxin" class="mu-refresh-svg-icon refresh" v-if="state === 2"></svg-icon>
 </div>
 <slot></slot>
 </div>
</template>

<script>
export default {
 props: {
  offset: {
   type: Number,
   default: 40
  },
  enableInfinite: {
   type: Boolean,
   default: true
  },
  enableRefresh: {
   type: Boolean,
   default: true
  },
  onRefresh: {
   type: Function,
   default: undefined,
   required: false
  },
  onInfinite: {
   type: Function,
   default: undefined,
   require: false
  }
 },
 data() {
  return {
   top: 0,
   state: 0,
   // 開始滑動時，y軸位置
   startY: 0,
   startScroll: 0,
   touching: false,
   infiniteLoading: false,
   refreshShow: true,
   infiniteState: true,
   showLoad: false,
   marginTop: 0
  }
 },
 created(){
  if(this.enableRefresh === false) {
   this.refreshShow = false
  }
  window.addEventListener('scroll', this.onScroll)
 },
 destroyed () {
  window.removeEventListener('scroll', this.onScroll)
 },
 methods: {
  // 觸摸開始（手指放在觸摸屏上） 
  touchStart(e) {
   if(window.pageYOffset > 0) return
   if(!this.enableRefresh) return
   this.startY = e.targetTouches[0].pageY
   this.startScroll = this.$el.scrollTop || 0
   //開啟滑動記錄
   this.touching = true
  },
  // 拖動（手指在觸摸屏上移動）
  touchMove(e) {
   // 這里控制是否可以上下拉  代表正在滑動 
   if (!this.enableRefresh || this.$el.scrollTop > 0 || !this.touching) {
    return
   }
   // 獲取拉取的間隔差  當(dāng)前移動的y點   初始的y點    初始頂部距離
   let diff = e.targetTouches[0].pageY - this.startY - this.startScroll
   //如果是往上滑的話，就取消事件
   if (diff > 0) e.preventDefault()
   // 對狀態(tài)進(jìn)行處理，看是否處于刷新中
   this.top = Math.pow(diff, 0.8) + (this.state === 2 ? this.offset : 0)

   if (this.state === 2) { // in refreshing
    return
   }
   if (this.top >= this.offset) {
    this.state = 1
   } else {
    this.state = 0
   }
  },
  // 觸摸結(jié)束（手指從觸摸屏上移開）
  touchEnd() {
   if (!this.enableRefresh) return
   this.touching = false
   if (this.state === 2) {
    this.state = 2
    this.top = 0
    return
   }
   if (this.top >= this.offset) {
    this.refresh()
   } else {
    this.state = 0
    this.top = 0
   }
  },
  refresh() {
   this.marginTop = this.top
   this.state = 2
   this.top = 0
   this.onRefresh(this.refreshDone)
  },
  refreshDone() {
   this.state = 0
   this.top = 0
   this.marginTop = 0
  },
  infinite() {
   this.infiniteLoading = true
   this.onInfinite(this.infiniteDone)
  },
  infiniteDone(length) {
   const self = this 
   if(length === 0) {
    self.infiniteState = false
   }
   this.showLoad = false
   self.infiniteLoading = false 
  },
  onScroll() {
   if (this.onInfinite) {
    let scrollTop = this.getScrollTop()
    let scrollHeight = this.getScrollHeight()
    let windowHeight = this.getWindowHeight()
    if (scrollTop + windowHeight === scrollHeight) {
     this.showLoad = true
     this.infinite()
    }
   }
  },
  // 滾動條在Y軸上的滾動距離
  getScrollTop() {
   var scrollTop = 0, bodyScrollTop = 0, documentScrollTop = 0
   if (document.body) {
    bodyScrollTop = document.body.scrollTop
   }
   if (document.documentElement) {
    documentScrollTop = document.documentElement.scrollTop
   }
   scrollTop = (bodyScrollTop - documentScrollTop > 0) ? bodyScrollTop : documentScrollTop
   return scrollTop
  },
  // 文檔的總高度
  getScrollHeight() {
   var scrollHeight = 0, bodyScrollHeight = 0, documentScrollHeight = 0
   if (document.body) {
    bodyScrollHeight = document.body.scrollHeight;
   }
   if (document.documentElement) {
    documentScrollHeight = document.documentElement.scrollHeight;
   }
   scrollHeight = (bodyScrollHeight - documentScrollHeight > 0) ? bodyScrollHeight : documentScrollHeight
   return scrollHeight
  },
  // 瀏覽器視口的高度
  getWindowHeight() {
   var windowHeight = 0
   if (document.compatMode === 'CSS1Compat') {
    windowHeight = document.documentElement.clientHeight
   } else {
    windowHeight = document.body.clientHeight
   }
   return windowHeight
  }
 }
}
</script>

<style lang="scss" scoped>
.mu-load-more {
 position: relative;
 overflow: hidden;
}
.mu-refresh-control {
 display: flex;
 margin: 0 auto;
 width: 80px;
 height: 80px;
 color: #2196f3;
 align-items: center;
 justify-content: center;
 background-color: #FFF;
 border-radius: 50%;
 -webkit-box-shadow: 0 3px 1px -2px rgba(0,0,0,.2), 0 2px 2px 0 rgba(0,0,0,.14), 0 1px 5px 0 rgba(0,0,0,.12);
 box-shadow: 0 3px 1px -2px rgba(0,0,0,.2), 0 2px 2px 0 rgba(0,0,0,.14), 0 1px 5px 0 rgba(0,0,0,.12);
 position: absolute;
 left: 50%;
 margin-left: -38px;
 margin-top: 24px;
 z-index: 90;
}
.mu-refresh-svg-icon {
 display: inline-block;
 width: 20px;
 height: 20px;
 fill: currentColor;
}
.refresh {
 -webkit-transform: rotate(360deg);
 animation: rotation 1s linear infinite;
 -moz-animation: rotation 1s linear infinite;
 -webkit-animation: rotation 1s linear infinite;
 -o-animation: rotation 1s linear infinite;
}
@-webkit-keyframes rotation {
 from {
  transform: rotate(0deg);
 }
 to {
  transform: rotate(360deg);
 }
}
.son {
 position: absolute;
 animation: lightAni 1s linear 1;
}
@keyframes lightAni {
 0% {
  transform: translateY(0);
 }
 50% {
  transform: translateY(-50px);
 }
 100% {
  transform: translateY(-100px);
 }
}
</style>

<scrollRefresh :on-refresh="refresh" :on-infinite="load">
 <!-- 頁面內(nèi)容 -->
</scrollRefresh>

<script>
// 引入組件
import scrollRefresh from '@/components/scrollRefresh'
export default {
 components: {
   scrollRefresh
  }
}
</script>