<template>
  <div class="artwork-gallery">
    <div class="main-image">
      <img :src="getImageUrl(currentImageUrl)" :alt="artwork.title" @load="imageLoaded = true"
        @error="imageError = true" :class="{ loaded: imageLoaded, error: imageError }" crossorigin="anonymous" />
      <div v-if="!imageLoaded && !imageError" class="image-placeholder">
        <LoadingSpinner text="图片加载中..." />
      </div>
      <div v-if="imageError" class="image-error">
        <span>图片加载失败</span>
      </div>
      <!-- 页面切换时的遮罩层 -->
      <div v-if="loading" class="image-overlay">
        <LoadingSpinner text="切换中..." />
      </div>
    </div>

    <!-- 多页作品缩略图 -->
    <div v-if="artwork.page_count > 1" class="thumbnails">
      <button v-for="(page, index) in artwork.meta_pages" :key="index" @click="$emit('pageChange', index)"
        class="thumbnail" :class="{ active: currentPage === index }" ref="thumbnailRefs">
        <!-- 懒加载的缩略图 -->
        <img v-if="visibleThumbnails.has(index)" 
             :src="getImageUrl(page.image_urls.square_medium)" 
             :alt="`第 ${index + 1} 页`" 
             crossorigin="anonymous" />
        <!-- 占位符 -->
        <div v-else class="thumbnail-placeholder">
          <div class="placeholder-content">
            <span>{{ index + 1 }}</span>
          </div>
        </div>
      </button>
    </div>
  </div>
</template>

<script setup lang="ts">
import { ref, computed, watch, onMounted, onUnmounted } from 'vue';
import { getImageProxyUrl } from '@/services/api';
import type { Artwork } from '@/types';
import LoadingSpinner from '@/components/common/LoadingSpinner.vue';

interface Props {
  artwork: Artwork;
  currentPage: number;
  loading?: boolean;
}

const props = withDefaults(defineProps<Props>(), {
  loading: false
});

const emit = defineEmits<{
  pageChange: [page: number];
}>();

// 图片加载状态
const imageLoaded = ref(false);
const imageError = ref(false);

// 懒加载相关
const thumbnailRefs = ref<HTMLElement[]>([]);
const visibleThumbnails = ref<Set<number>>(new Set());
let intersectionObserver: IntersectionObserver | null = null;

// 计算当前图片URL
const currentImageUrl = computed(() => {
  if (!props.artwork) return '';

  if (props.artwork.page_count === 1) {
    return props.artwork.image_urls.large;
  } else if (props.artwork.meta_pages && props.artwork.meta_pages[props.currentPage]) {
    return props.artwork.meta_pages[props.currentPage].image_urls.large;
  }

  return props.artwork.image_urls.large;
});

// 使用统一的图片代理函数
const getImageUrl = getImageProxyUrl;

// 初始化懒加载
const initLazyLoading = () => {
  // 清理之前的观察器
  if (intersectionObserver) {
    intersectionObserver.disconnect();
  }

  // 创建新的 Intersection Observer
  intersectionObserver = new IntersectionObserver((entries) => {
    entries.forEach((entry) => {
      if (entry.isIntersecting) {
        const index = parseInt(entry.target.getAttribute('data-index') || '0');
        visibleThumbnails.value.add(index);
      }
    });
  }, {
    root: null,
    rootMargin: '50px', // 提前50px开始加载
    threshold: 0.1
  });

  // 观察所有缩略图
  thumbnailRefs.value.forEach((el, index) => {
    if (el) {
      el.setAttribute('data-index', index.toString());
      intersectionObserver?.observe(el);
    }
  });
};

// 监听页面变化，重置图片加载状态
watch(() => props.currentPage, () => {
  imageLoaded.value = false;
  imageError.value = false;
});

// 监听作品变化，重置图片加载状态和懒加载
watch(() => props.artwork.id, () => {
  imageLoaded.value = false;
  imageError.value = false;
  // 重置懒加载状态
  visibleThumbnails.value.clear();
  
  // 重新初始化懒加载
  setTimeout(() => {
    initLazyLoading();
  }, 100);
});

// 监听当前页面变化，确保当前页面的缩略图可见
watch(() => props.currentPage, (newPage) => {
  // 确保当前页面的缩略图可见
  visibleThumbnails.value.add(newPage);
});

// 监听缩略图引用变化
watch(thumbnailRefs, () => {
  if (thumbnailRefs.value.length > 0) {
    initLazyLoading();
  }
}, { deep: true });

onMounted(() => {
  // 确保当前页面的缩略图可见
  visibleThumbnails.value.add(props.currentPage);
  
  // 初始化懒加载
  setTimeout(() => {
    initLazyLoading();
  }, 100);
});

onUnmounted(() => {
  // 清理观察器
  if (intersectionObserver) {
    intersectionObserver.disconnect();
    intersectionObserver = null;
  }
});
</script>

<style scoped>
.artwork-gallery {
  background: var(--color-bg-primary);
  border-radius: var(--radius-xl);
  overflow: hidden;
  box-shadow: var(--shadow-md);
}

.main-image {
  position: relative;
  aspect-ratio: 1;
  background: var(--color-bg-tertiary);
  overflow: hidden;
}

.main-image img {
  width: 100%;
  height: 100%;
  object-fit: contain;
  opacity: 0;
  transition: opacity 0.3s;
}

.main-image img.loaded {
  opacity: 1;
}

.main-image img.error {
  opacity: 0.5;
}

.image-placeholder,
.image-error {
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--color-bg-tertiary);
}

.image-error {
  color: var(--color-text-secondary);
  font-size: 0.875rem;
}

.image-overlay {
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  background: rgba(255, 255, 255, 0.9);
  backdrop-filter: blur(2px);
  z-index: 10;
}

.thumbnails {
  display: flex;
  gap: 0.5rem;
  padding: 1rem;
  overflow-x: auto;
}

.thumbnail {
  flex-shrink: 0;
  width: 60px;
  height: 60px;
  border: 2px solid transparent;
  border-radius: var(--radius-md);
  overflow: hidden;
  cursor: pointer;
  transition: border-color var(--transition-normal);
  background: none;
  padding: 0;
}

.thumbnail.active {
  border-color: var(--color-primary);
}

.thumbnail img {
  width: 100%;
  height: 100%;
  object-fit: cover;
}

.thumbnail-placeholder {
  width: 100%;
  height: 100%;
  background: var(--color-bg-tertiary);
  display: flex;
  align-items: center;
  justify-content: center;
}

.placeholder-content {
  color: var(--color-text-tertiary);
  font-size: 0.75rem;
  font-weight: 500;
}

@media (max-width: 768px) {
  .thumbnails {
    padding: 0.5rem;
  }

  .thumbnail {
    width: 50px;
    height: 50px;
  }
}
</style>