<!--
 * @Date: 2024-09-27 19:49:03
 * @LastEditors: hookehuyr hookehuyr@gmail.com
 * @LastEditTime: 2024-09-29 14:58:52
 * @FilePath: /hager/src/components/hagerCarousel.vue
 * @Description: 文件描述
-->
<template>
  <div class="hager-carousel">
    <div class="image-switcher">
      <!-- 缩略图区域 -->
      <div class="thumbnail-container">
        <!-- 上箭头 -->
        <div class="arrow-up" @click="prevImage"><i class="el-icon-arrow-up" style="font-size: 1.35rem;"></i></div>

        <!-- 缩略图列表 -->
        <div class="thumbnails">
          <div
            v-for="(image, index) in visibleThumbnails"
            :key="index"
            :class="['thumbnail', { active: selectedImage === (startIndex + index) }]"
            @click="selectImage(startIndex + index)"
          >
            <img :src="image" alt="thumbnail">
          </div>
        </div>

        <!-- 下箭头 -->
        <div class="arrow-down" @click="nextImage"><i class="el-icon-arrow-down" style="font-size: 1.35rem;"></i></div>
      </div>

      <!-- 右边大图区域 -->
      <div class="main-image" :class="{ 'fade-out': isTransitioning, 'fade-in': !isTransitioning }">
        <img :src="images[selectedImage]" alt="main image">
      </div>
    </div>
  </div>
</template>

<script>
import mixin from "common/mixin";

export default {
  mixins: [mixin.init],
  data() {
    return {
      selectedImage: 0, // 当前选中的图片索引
      startIndex: 0,    // 当前显示的缩略图起始索引
      thumbnailsToShow: 4, // 每次显示4个缩略图
      isTransitioning: false, // 控制大图的切换动画
      images: [
        "https://fuss10.elemecdn.com/e/5d/4a731a90594a4af544c0c25941171jpeg.jpeg",
        "https://fastly.jsdelivr.net/npm/@vant/assets/cat.jpeg",
        "https://fuss10.elemecdn.com/e/5d/4a731a90594a4af544c0c25941171jpeg.jpeg",
        "https://fastly.jsdelivr.net/npm/@vant/assets/cat.jpeg",
        "https://fuss10.elemecdn.com/e/5d/4a731a90594a4af544c0c25941171jpeg.jpeg",
        "https://fastly.jsdelivr.net/npm/@vant/assets/cat.jpeg",
        "https://fuss10.elemecdn.com/e/5d/4a731a90594a4af544c0c25941171jpeg.jpeg",
      ],
    };
  },
  mounted() {},
  computed: {
    // 计算当前显示的缩略图
    visibleThumbnails() {
      return this.images.slice(this.startIndex, this.startIndex + this.thumbnailsToShow);
    },
    endIndex() {
      return this.startIndex + this.thumbnailsToShow - 1;
    }
  },
  methods: {
    // 选择某个图片并更新大图和选中状态
    selectImage(index) {
      this.isTransitioning = true; // 开始大图的淡出动画
      setTimeout(() => {
        this.selectedImage = index; // 切换大图
        this.isTransitioning = false; // 动画结束
        this.ensureVisibleThumbnail(); // 保证选中的缩略图在可视区域
      }, 500); // 动画时间为500ms
    },
    // 控制缩略图上下滚动
    scrollThumbnails(direction) {
      if (direction === 'up' && this.startIndex > 0) {
        this.startIndex--;
      } else if (direction === 'down' && this.endIndex < this.images.length - 1) {
        this.startIndex++;
      }
    },
    // 确保选中的缩略图在可见范围内
    ensureVisibleThumbnail() {
      if (this.selectedImage < this.startIndex) {
        // 如果选中的缩略图在当前显示范围的上方，则向上滚动
        this.startIndex = this.selectedImage;
      } else if (this.selectedImage > this.endIndex) {
        // 如果选中的缩略图在当前显示范围的下方，则向下滚动
        this.startIndex = this.selectedImage - this.thumbnailsToShow + 1;
      }
    },
    // 切换到下一张图片
    nextImage() {
      if (this.selectedImage < this.images.length - 1) {
        this.selectImage(this.selectedImage + 1);
      }
    },
    // 切换到上一张图片
    prevImage() {
      if (this.selectedImage > 0) {
        this.selectImage(this.selectedImage - 1);
      }
    }
  },
};
</script>

<style lang="less" scoped>
.hager-carousel {
  .image-switcher {
    display: flex;
    align-items: center;
  }

  .thumbnail-container {
    display: flex;
    flex-direction: column;
    align-items: center;
    margin-right: 20px;
  }

  .arrow-up,
  .arrow-down {
    cursor: pointer;
    padding: 5px;
    font-size: 18px;
    user-select: none;
  }

  .thumbnails {
    display: flex;
    flex-direction: column;
    align-items: center;
    max-height: 220px; /* 限制缩略图容器的高度 */
    overflow: hidden;
    position: relative; /* 为缩略图滚动效果提供基础 */
  }

  .thumbnail {
    width: 50px;
    height: 50px;
    margin-bottom: 10px;
    cursor: pointer;
    border: 2px solid transparent;
    transition: border 0.3s;
  }

  .thumbnail img {
    width: 100%;
    height: 100%;
    object-fit: cover;
    transition: transform 0.5s ease-in-out; /* 缩略图切换时的动画效果 */
  }

  .thumbnail.active {
    border: 2px solid #00f; /* 选中的缩略图边框样式 */
  }

  .main-image {
    width: 300px;
    height: 300px;
    position: relative;
    transition: opacity 0.5s ease-in-out; /* 大图切换时的淡入淡出效果 */
    opacity: 1;
  }

  .main-image img {
    width: 100%;
    height: 100%;
    object-fit: cover;
    position: absolute;
  }

  .main-image.fade-out {
    opacity: 0; /* 当切换时，将大图的透明度渐变为0 */
  }

  .main-image.fade-in {
    opacity: 1; /* 切换后，图片渐渐显现 */
  }

  .thumbnails-wrapper {
    transition: transform 0.5s ease-in-out; /* 缩略图滑动时的动画效果 */
    display: flex;
    flex-direction: column;
  }
}
</style>