<template>
 <div class="newsList">
  <div v-for="(items, index) in newsList">
   <div class="date">{{showDay(index)}}</div>
   <div class="list" >
    <ul>
     <li class="list-item" v-for="item in items">
      <span class="text">{{item.title}}</span>
      <img :src="attachImageUrl(item.images[0])" class="image"/>
     </li>
    </ul>
   </div>
  </div>
  <div class="infinite-scroll" v-show="loading">
   <svg class="loader-circular" viewBox="25 25 50 50">
    <circle class="loader-path" cx="50" cy="50" r="20" fill="none" stroke="rgb(53, 157, 218)" stroke-width="5"></circle>
   </svg>
   <span class="infinite-scroll-text">{{tips}}</span>
  </div>
 </div>
</template>
<script>
 import axios from 'axios';
 export default {
  data () {
   return {
    newsList: [],
    date: [],
    todayDate: '',
    REQUIRE: true,
    loading: false,
    tips: '努力加載中...'
   }
  },
  created () {
   // 獲取今日新聞
   axios.get('http://zhihuapi.herokuapp.com/api/4/news/latest')
    .then( (res) => {
    this.newsList.push(res.data['stories'])
    this.date.push(res.data['date']);
    this.todayDate = res.data['date']
   })
  },
  mounted () {
   // 添加滾動(dòng)事件，檢測滾動(dòng)到頁面底部
   window.addEventListener('scroll', this.scrollBottom)
  },
  methods: {
   scrollBottom() {
    // 滾動(dòng)到頁面底部時(shí)，請求前一天的文章內(nèi)容
    if (((window.screen.height + document.body.scrollTop) > (document.body.clientHeight)) && this.REQUIRE) {
     // 請求的數(shù)據(jù)未加載完成時(shí)，滾動(dòng)到底部不再請求前一天的數(shù)據(jù)
     this.REQUIRE = false;
     this.loading = true;
     this.tips = '努力加載中...';
     axios.get('http://zhihuapi.herokuapp.com/api/4/news/before/' + this.todayDate).then((res) => {
      this.newsList.push(res.data['stories']);
     this.date.push(res.data['date']);
     this.todayDate = res.data['date'];
     // 請求的數(shù)據(jù)加載完成后，再次滾動(dòng)到底部時(shí)，允許請求前一天數(shù)據(jù)
     this.$nextTick(() => {
      this.REQUIRE = true;
      this.loading = false;
     });
    }).catch(() => {
      this.tips = '連接失敗，請稍后重試';
     // 請求失敗時(shí)，將 REQUIRE 置為 true，滾動(dòng)到底部時(shí)，再次請求
     this.REQUIRE = true;
    });
    }
   },
   showDay (index) {
    if (index === 0) {
     return '今日新聞'
    } else {
     return this.getToday(index)
    }
   },
   getToday (index) {
    let year = this.date[index].slice(0, 4);
    let month = this.date[index].slice(4, 6);
    let day = this.date[index].slice(6);
    let today = new Date(year + '/' + month + '/' + day);
    let week = ['日', '一', '二', '三', '四', '五', '六'];
    return month + '月' + day + '日' + ' 星期' + week[today.getDay()];
   },
   attachImageUrl (srcUrl) {
    if (srcUrl !== undefined) {
     return 'http://read.html5.qq.com/image?src=forum&q=5&r=0&imgflag=7&imageUrl=' + srcUrl.slice(0, 4) + srcUrl.slice(5);
    }
   }
  }
 }
</script>