<click-scroll>
  <template slot="content">
    <div>
      我是实际要展示的内容啊啊啊啊啊……
    </div>
  </template>
</click-scroll>

<template>
 <div class="hui-hui" :id="domId.compID">
  <!--向左滑动-->
  <div class="hui-drag-left"
     :class="{'hui-drag-action': drag.isLeft}"
     v-if="drag.isShow"
     @click="onClickLeft">
  </div>

  <!--展示的内容-->
  <div :id="domId.containerID"
     class="hui-container"
     v-show="hasContent"
     ref='container'
     @mousedown="onMouseDown">
   <slot name="content"></slot>
  </div>
  <div v-show="!hasContent" class="hui-no-data">暂无数据</div>

  <!--向右滑动-->
  <div class="hui-drag-right"
     :class="{'hui-drag-action': drag.isRight}"
     v-if="drag.isShow"
     @click="onClickRight">
  </div>
 </div>
</template>

<script>
import store from '@/store'
export default {
 name: 'cards-container',
 data () {
  return {
   hasContent: false,
   domId: {
    compID: `hui-comp-${+new Date()}`,
    containerID: `hui-container-${+new Date()}`
   },
   drag: {
    isShow: false,
    isLeft: false,
    isRight: false
   }
  }
 },
 methods: {
  judgeHasContent () {
   this.hasContent = this.$slots.hasOwnProperty('content')
  },

  judgeDragIsShow () {
   const compWidth = this.getCompWidth()
   const contextMaxWidth = this.getContextMaxWidth()

   if (compWidth >= contextMaxWidth) {
    this.drag.isShow = false
   } else {
    this.drag.isShow = true
   }
   return this.drag.isShow
  },
  judgeIsLeft () {
   const containerDom = this.getContainerDom()
   const contentWidth = this.getContextMaxWidth()

   if (!containerDom && !contentWidth) this.drag.isLeft = false
   if (containerDom.offsetWidth + containerDom.scrollLeft >= contentWidth) {
    this.drag.isLeft = false
   } else {
    this.drag.isLeft = true
   }
  },
  judgeIsRight () {
   const containerDom = this.getContainerDom()

   if (!containerDom) this.drag.isRight = false
   if (containerDom.scrollLeft === 0) {
    this.drag.isRight = false
   } else {
    this.drag.isRight = true
   }
  },

  getCompDom () {
   return document.getElementById(this.domId.compID) || null
  },
  getCompWidth () {
   const compDom = this.getCompDom()
   if (!compDom) {
    return 0
   } else {
    return compDom.offsetWidth
   }
  },
  getContainerDom () {
   return document.getElementById(this.domId.containerID) || null
  },
  getContextMaxWidth () {
   if (!this.$refs.hasOwnProperty('container')) {
    return 0
   } else {
    const widthArr = []
    for(let e of this.$refs['container'].childNodes) {
     widthArr.push(e.offsetWidth)
    }
    return Math.max(...widthArr)
   }
  },

  onMouseDown (e) { // 手动滑动
   const containerDom = this.getContainerDom()
   if (!containerDom) return

   let scrollLeft = containerDom.scrollLeft
   const containerLeft = containerDom.offsetLeft
   let ev = e || window.event
   let offsetLeft = ev.clientX - containerLeft

   document.onmousemove = (e) => {
    let ev = e || window.event
    let nowOffsetLeft = ev.clientX - containerLeft
    containerDom.scrollLeft = scrollLeft + (offsetLeft - nowOffsetLeft)

    this.judgeIsLeft()
    this.judgeIsRight()
   }

   document.onmouseup = () => {
    document.onmousemove = null
    document.onmouseup = null
   }
  },

  onClickLeft () { // 向左滑动
   if (!this.hasContent && !this.drag.isLeft) return

   const containerDom = this.getContainerDom()
   if (!containerDom) return

   const scrollWidth = containerDom.offsetWidth
   containerDom.scrollLeft += scrollWidth

   this.judgeIsLeft()
   this.judgeIsRight()
  },

  onClickRight () { // 向右滑动
   if (!this.hasContent && !this.drag.isRight) return

   const containerDom = this.getContainerDom()
   if (!containerDom) return

   const scrollWidth = containerDom.offsetWidth
   containerDom.scrollLeft -= scrollWidth

   this.judgeIsLeft()
   this.judgeIsRight()
  }
 },
 updated () {
  this.$nextTick(() => {
   this.judgeHasContent()
   const isShow = this.judgeDragIsShow()
   if (isShow) {
    this.judgeIsLeft()
    this.judgeIsRight()
   }
  })
 },
 mounted () {
  this.judgeHasContent()
  const isShow = this.judgeDragIsShow()
  if (isShow) {
   this.judgeIsLeft()
   this.judgeIsRight()
  }
 }
}
</script>