<template>
  <div class="my-carousel" @mouseenter="stop" @mouseleave="start">
    <ul class="carousel-body">
      <li v-for="(item, i) in findBannerList" :key="item.id" class="carousel-item" :class="{ fade: index === i }">
        <RouterLink to="/">
          <img :src="item.imgUrl" alt="图片" />
        </RouterLink>
      </li>
    </ul>
    <a @click="clickFn(-1)" href="javascript:;" class="carousel-btn prev"><i class="iconfont icon-angle-left"></i></a>
    <a @click="clickFn(1)" href="javascript:;" class="carousel-btn next"><i class="iconfont icon-angle-right"></i></a>
    <div class="carousel-indicator">
      <span @click="active(i)" v-for="(item, i) in findBannerList" :key="i" :class="{ active: index === i }"></span>
    </div>
  </div>
</template>

<script>
import { onUnmounted, ref, watch } from 'vue'
export default {
  name: 'Carousel',
  props: {
    findBannerList: {
      type: Array,
      default: () => []
    },
    autoplay: {
      type: Boolean,
      default: true
    },
    duration: {
      type: Number,
      default: 3
    }
  },
  setup(props) {
    const index = ref(0)
    // 定义一个常量存储定时器
    const timer = ref(null)
    // 定时器方法，实现自动轮播效果
    const autoplayFn = () => {
      // 防抖，防止多次触发定时器
      clearInterval(timer.value)
      timer.value = setInterval(() => {
        index.value += 1
        if (index.value >= props.findBannerList.length) {
          index.value = 0
        }
      }, props.duration * 1000)
    }
    // 侦听器，根据接口返回的数据与传递的相关属性参数 autoplay 开启轮播
    // 监听返回的数据的长度，当长度大于1的时候并且 autoplay 的为 true 的时候开启轮播
    watch(
      () => props.findBannerList,
      () => {
        if (props.findBannerList.length > 1 && props.autoplay) {
          autoplayFn()
        }
      }
    )
    // 鼠标移入轮播图，停止自动播放
    const stop = () => {
      if (timer.value) clearInterval(timer.value)
    }
    // 鼠标移出轮播图，开启定时器
    const start = () => {
      if (props.findBannerList.length > 1 && props.autoplay) {
        autoplayFn()
      }
    }
    // 点击轮播图上的左右按钮，切换轮播图，通过传递进来的参数，决定轮播图往左往右
    const clickFn = e => {
      index.value += e
      if (index.value >= props.findBannerList.length) {
        index.value = 0
      }
      if (index.value < 0) {
        index.value = props.findBannerList.length - 1
      }
    }
    // 点击指示器（轮播图底下的小点）切换轮播图
    const active = e => {
      index.value = e
    }
    // 组件销毁的时候情书定时器，避免性能损耗
    onUnmounted(() => {
      if (timer.value) clearInterval(timer.value)
    })
    return { index, stop, start, clickFn, active }
  }
}
</script>
<style scoped lang="less">
.my-carousel {
  width: 100%;
  height: 100%;
  min-width: 300px;
  min-height: 150px;
  position: relative;
  .carousel {
    &-body {
      width: 100%;
      height: 100%;
    }
    &-item {
      width: 100%;
      height: 100%;
      position: absolute;
      left: 0;
      top: 0;
      opacity: 0;
      transition: opacity 0.5s linear;
      &.fade {
        opacity: 1;
        z-index: 1;
      }
      img {
        width: 100%;
        height: 100%;
      }
    }
    &-indicator {
      position: absolute;
      left: 0;
      bottom: 20px;
      z-index: 2;
      width: 100%;
      text-align: center;
      span {
        display: inline-block;
        width: 12px;
        height: 12px;
        background: rgba(0, 0, 0, 0.2);
        border-radius: 50%;
        cursor: pointer;
        ~ span {
          margin-left: 12px;
        }
        &.active {
          background: #fff;
        }
      }
    }
    &-btn {
      width: 44px;
      height: 44px;
      background: rgba(0, 0, 0, 0.2);
      color: #fff;
      border-radius: 50%;
      position: absolute;
      top: 228px;
      z-index: 2;
      text-align: center;
      line-height: 44px;
      opacity: 0;
      transition: all 0.5s;
      &.prev {
        left: 20px;
      }
      &.next {
        right: 20px;
      }
    }
  }
  &:hover {
    .carousel-btn {
      opacity: 1;
    }
  }
}
</style>

import MyCarousel from './my-carousel.vue'
export default {
  install(app) {
    app.component(MyCarousel.name, MyCarousel)
  }
}

import { createApp } from 'vue'
import App from './App.vue'
import MyUI from './components/library'

// 插件的使用，在main.js使用app.use(插件)
createApp(App).use(MyUI).mount('#app')

<template>
  <div class="home-banner">
    <MyCarousel :findBannerList="findBannerList" :autoplay="true" :duration="3" />
  </div>
</template>