<template>
  <div>
    <button @click="handleClick" :disabled="disabled">
      {{btnText}}
    </button>
    <span>{{tip}}</span>
  </div>
</template>

<script>

  import moment from 'moment'

  export default {
    name: "Spike",
    props: {
      startTime: {
        required: true,
        validator: (val) => {
          return moment.isMoment(val)
        }
      },
      endTime: {
        required: true,
        validator: (val) => {
          return moment.isMoment(val)
        }
      }
    },
    data() {
      return {
        start: false,
        end: false,
        done: false,
        tip: '',
        timeGap: 0,
        btnText:""
      }
    },
      computed: {
      disabled() {
        //当三个异号的时候disable返回真，不可点击，
        // 初始化通过this.updateState确定disable的状态
        return !(this.start && !this.end && !this.done);
      }
    },
    async created() {
      const serverTime=await this.getServerTime();
      this.timeGap=Date.now()-serverTime;//当前时间和服务器时间差
      this.updateState();
      this.timeInterval=setInterval(()=>{
        this.updateState()
      },1000)
    },
    updated(){
      if(this.end||this.done){
        clearInterval(this.timeInterval)
      }
    },
    methods: {
      handleClick() {
        alert("提交成功");
        this.done=true;
        this.btnText="已参加过活动"
      },
      getServerTime() {
        //模拟服务器时间
        return new Promise((resolve, reject) => {
          setTimeout(() => {
            //当前时间慢10秒就是服务器时间
            resolve(new Date(Date.now() -10 * 1000).getTime())//跟本地时间差
          }, 0)
        })
      },
      updateState() {
        const now = moment(new Date(Date.now() - this.timeGap));//当前服务器时间
        const diffStart=this.startTime.diff(now);//开始时间和服务器时间之差
        const diffEnd=this.endTime.diff(now);//结束时间和服务器时间之差
        if(diffStart<0){
          this.start=true;
          this.tip="秒杀已开始";
          this.btnText="参加"
        }else{
          this.tip=`距离秒杀开始还剩${Math.ceil(diffStart/1000)}秒`;
          this.btnText="活动未开始";
        }
        if(diffEnd<=0){
          this.end=true;
          if( !this.btnText==="已参加过活动"||this.btnText==="参加"){
            this.tip="秒杀已结束";
            this.btnText="活动已结束";
          }
        }
      }
    },
    beforeDestroy() {
      clearInterval(this.timeInterval)
    }
  }
</script>

<style scoped>
  button[disabled]{
    cursor: not-allowed;
  }
</style>

<template>
  <div>
    <h1 style="color: red">设计一个秒杀倒计时的组件</h1>
    <Spike :startTime="startTime" :endTime="endTime"></Spike>
  </div>
</template>

<script>
  import Spike from './Spike'
  import moment from 'moment'
  export default {
    name: "index",
    components:{
      Spike
    },
    data(){
      return{
        endTime:moment(new Date(Date.now()+10*1000)),
        startTime:moment(new Date(Date.now()))
      }
    }
  }
</script>

<style scoped>

</style>