// scrollLoader.vue
// 滚动加载组件

<style scoped>
  .container-main {margin: 0 auto; overflow: auto; overflow-x: hidden; padding: 0;}
  .loading{ width: 100%; height: 40px; position: relative; overflow: hidden; text-align: center; margin: 5px 0 ; color: #999; font-size: 13px;}
  .loading-icon{color: #707070;};
  .loader {
    font-size: 10px;
    margin: 8px auto;
    text-indent: -9999em;
    width: 24px;
    height: 24px;
    border-radius: 50%;
    background: #999;
    background: -moz-linear-gradient(left, #999 10%, rgba(255, 255, 255, 0) 42%);
    background: -webkit-linear-gradient(left, #999 10%, rgba(255, 255, 255, 0) 42%);
    background: -o-linear-gradient(left, #999 10%, rgba(255, 255, 255, 0) 42%);
    background: -ms-linear-gradient(left, #999 10%, rgba(255, 255, 255, 0) 42%);
    background: linear-gradient(to right, #999 10%, rgba(255, 255, 255, 0) 42%);
    position: relative;
    -webkit-animation: load3 1s infinite linear;
    animation: load3 1s infinite linear;
  }
  .loader:before {
    width: 50%;
    height: 50%;
    background: #999;
    border-radius: 100% 0 0 0;
    position: absolute;
    top: 0;
    left: 0;
    content: '';
  }
  .loader:after {
    background: #f5f5f5;
    width: 72%;
    height: 75%;
    border-radius: 68%;
    content: '';
    margin: auto;
    position: absolute;
    top: 0;
    left: 0;
    bottom: 0;
    right: 0;
  }
  @-webkit-keyframes load3 {
  0% {
    -webkit-transform: rotate(0deg);
    transform: rotate(0deg);
  }
  100% {
    -webkit-transform: rotate(360deg);
    transform: rotate(360deg);
  }
  }
  @keyframes load3 {
  0% {
    -webkit-transform: rotate(0deg);
    transform: rotate(0deg);
  }
  100% {
    -webkit-transform: rotate(360deg);
    transform: rotate(360deg);
  }
  }

</style>

<template>
  <div id="scrollLoader-container" class="container-main">
    <div class="loading" v-if="topLoading">
      <div class="loader">加载中...</div>
    </div>

    <div :style="'min-height:' + realMinHeight + 'px; overflow-x:hidden'">
      <slot></slot>
    </div>

    <div class="loading" v-if="bottonLoading">
      <div class="loader">加载中...</div>
    </div>
  </div>
</template>

<script>
  export default {
    name: "scroll-loader",

    props: {
      //给slot传一个最小值，保证一开始能出现滚动条
      'minHeight': {
        type: Number,
        default: 800
      }, 

    },

    created(){
    },
    computed: {
      realMinHeight(){
        return this.minHeight + 30
      }
    },
    data() {
      return {
        topLoading: false,
        bottonLoading: false,

        stopTopLoading: false, //是否停止传播滚动到顶部事件
        stopBottonLoading: false, //是否停止传播滚动到底部事件
      }
    },
    mounted(){
      this.listenScroll();
    },

    methods: {
      listenScroll(){
        var me = this;
        var topDone = (stopTopLoading) => {
          me.topLoading = false;
          if(stopTopLoading) me.stopTopLoading = true;
        };

        var bottonDone = (stopBottonLoading) => {
          me.bottonLoading = false;
          if(stopBottonLoading) me.stopBottonLoading = true;
        };
        setTimeout(function(){
          var scrollContainer = document.getElementById('scrollLoader-container');

          scrollContainer.onscroll = function(){

            if(scrollContainer.scrollTop<=0 && !me.stopTopLoading){
              if(me.topLoading) return;

              me.topLoading = true;
              me.$emit('scroll-to-top', topDone);
            }
            if((scrollContainer.offsetHeight + scrollContainer.scrollTop+1 >= scrollContainer.scrollHeight) && !me.stopBottonLoading){
              if(me.bottonLoading) return;

              me.bottonLoading = true;
              scrollContainer.scrollTop += 40;
              me.$emit('scroll-to-botton', bottonDone);
            }
          }
        }, 50)
      },

    }
  }
</script>