photo-live/apps/viewer/src/components/PhotoFeed.vue

<script setup lang="ts">
import { computed, onBeforeUnmount, reactive, ref, watch } from 'vue';
import { useI18n } from 'vue-i18n';
import type { PublicPhoto } from '../api/client';
import type { PhotoSequence } from '../feed/sequence';
import { layoutWaterfall } from '../feed/layout';

// 观众瀑布流（Task 7；Task 8 起数据层上提）：双列绝对定位（短列优先，条目高按
// browse 宽高比例预留）+ IntersectionObserver 懒加载 + 哨兵无限滚动 + 新照片提示条。
// 数据生命周期（分页/去重/轮询/深链 solo）在 ActivityPage 创建的 PhotoSequence
// composable（feed/sequence.ts）——feed 与大图查看器共享同一序列，切换大图时
// 保持浏览顺序、越过末尾自动扩展。
//
// 关键决策（沿用 Task 7）：
//   · 懒加载 = 仅当单元格接近视口才绑定 <img src>；shownIds 集合跨刷新保留——
//     刷新只换签名 URL，同 id 单元格不必重新判定；IO 不可用（旧环境/jsdom）时
//     退化为立即加载，功能不缺失。
//   · 图片 onerror 重试一次：经 sequence.refreshPhotoUrls 换新签名 URL 再换绑；
//     再失败（或照片已下线）则收起该图（占位底色仍在，布局因高度预留不跳动）。
//   · 单元格点击 emit('open', photoId) → ActivityPage 打开大图（Task 8）。

const props = defineProps<{
  sequence: PhotoSequence;
}>();

const emit = defineEmits<{
  open: [photoId: string];
}>();

const { t } = useI18n();

const photos = computed(() => props.sequence.photos);
const initialLoading = computed(() => props.sequence.initialLoading);
const initialErrorKey = computed(() => props.sequence.initialErrorKey);
const loadingMore = computed(() => props.sequence.loadingMore);
const moreFailed = computed(() => props.sequence.moreFailed);
const hasMore = computed(() => props.sequence.hasMore);
const hasNew = computed(() => props.sequence.hasNew);

// 懒加载/重试视图状态（按 photoId，跨刷新保留，见顶部决策注）。
const shownIds = reactive(new Set<string>());
const retriedIds = reactive(new Set<string>());
const failedIds = reactive(new Set<string>());

// —— 布局：容器宽 → 纯函数双列放置（ResizeObserver 跟踪容器宽度变化） ——

const trackEl = ref<HTMLElement | null>(null);
const sentinelEl = ref<HTMLElement | null>(null);
const containerWidth = ref(0);

const layout = computed(() => layoutWaterfall(photos.value, containerWidth.value));

let resizeObserver: ResizeObserver | null = null;

function measureContainer(): void {
  if (trackEl.value !== null) containerWidth.value = trackEl.value.clientWidth;
}

watch(
  trackEl,
  (el) => {
    resizeObserver?.disconnect();
    resizeObserver = null;
    if (el === null) return;
    measureContainer();
    if (typeof ResizeObserver !== 'undefined') {
      resizeObserver = new ResizeObserver(measureContainer);
      resizeObserver.observe(el);
    }
  },
  { flush: 'post' },
);

// —— 懒加载/哨兵 IntersectionObserver ——

const cellElements = new Map<Element, string>();
let lazyObserver: IntersectionObserver | null = null;
let sentinelObserver: IntersectionObserver | null = null;

function ensureLazyObserver(): IntersectionObserver | null {
  if (lazyObserver !== null) return lazyObserver;
  if (typeof IntersectionObserver === 'undefined') return null;
  lazyObserver = new IntersectionObserver(
    (entries) => {
      for (const entry of entries) {
        if (!entry.isIntersecting) continue;
        const photoId = cellElements.get(entry.target);
        if (photoId !== undefined) shownIds.add(photoId);
        lazyObserver?.unobserve(entry.target);
      }
    },
    { rootMargin: '400px 0px' },
  );
  return lazyObserver;
}

/** v-for 函数 ref：登记 el → photoId 并纳入懒观察；IO 不可用退化立即显示。
 * 按下标取 photos（卸载时 ref 收到 null 先行返回——函数 ref 在整表替换后
 * 会对旧 vnode 重算，此时闭包里的数组访问必须可空）。 */
function registerCell(el: unknown, index: number): void {
  if (!(el instanceof HTMLElement)) return;
  const photo = photos.value[index];
  if (photo === undefined) return;
  cellElements.set(el, photo.photoId);
  if (shownIds.has(photo.photoId)) return;
  const observer = ensureLazyObserver();
  if (observer === null) {
    shownIds.add(photo.photoId);
    return;
  }
  observer.observe(el);
}

/** 移除已脱离文档的单元格映射（整表替换后 DOM 销毁的 el 不再可达）。 */
function pruneCellElements(): void {
  for (const [el] of cellElements) {
    if (!el.isConnected) cellElements.delete(el);
  }
}

watch(
  photos,
  () => pruneCellElements(),
);

watch(
  sentinelEl,
  (el) => {
    sentinelObserver?.disconnect();
    sentinelObserver = null;
    if (el === null) return;
    // IO 不可用（jsdom/旧环境）时不观察：无限滚动退化为已加载内容（不崩溃）。
    if (typeof IntersectionObserver === 'undefined') return;
    sentinelObserver = new IntersectionObserver(
      (entries) => {
        if (entries.some((entry) => entry.isIntersecting)) void props.sequence.loadMore();
      },
      { rootMargin: '600px 0px' },
    );
    sentinelObserver.observe(el);
  },
  { flush: 'post' },
);

/** 缩略图加载失败：重试一次（单图端点换新签名 URL）；再失败/已下线则收起图片。 */
async function onImgError(photo: PublicPhoto): Promise<void> {
  if (failedIds.has(photo.photoId)) return;
  if (retriedIds.has(photo.photoId)) {
    failedIds.add(photo.photoId);
    return;
  }
  retriedIds.add(photo.photoId);
  const result = await props.sequence.refreshPhotoUrls(photo.photoId);
  if (result !== 'replaced') failedIds.add(photo.photoId);
}

onBeforeUnmount(() => {
  lazyObserver?.disconnect();
  sentinelObserver?.disconnect();
  resizeObserver?.disconnect();
});
</script>

<template>
  <div class="photo-feed">
    <button v-if="hasNew" type="button" class="new-photo-bar" @click="props.sequence.refreshFromHint()">
      {{ t('album.newPhotos') }}
    </button>

    <p v-if="initialLoading" class="status">{{ t('album.loading') }}</p>

    <div v-else-if="initialErrorKey !== null" class="error" role="alert">
      <p>{{ t(initialErrorKey) }}</p>
      <button type="button" @click="props.sequence.resetAndLoad">{{ t('album.retry') }}</button>
    </div>

    <div v-else-if="photos.length === 0" class="feed">
      <p class="empty-notice">{{ t('album.emptyNotice') }}</p>
    </div>

    <template v-else>
      <div ref="trackEl" class="waterfall" :style="{ height: `${layout.height}px` }">
        <div
          v-for="placement in layout.placements"
          :key="photos[placement.index].photoId"
          :ref="(el) => registerCell(el, placement.index)"
          class="cell"
          :style="{
            left: `${placement.left}px`,
            top: `${placement.top}px`,
            width: `${layout.columnWidth}px`,
            height: `${placement.height}px`,
          }"
          @click="emit('open', photos[placement.index].photoId)"
        >
          <img
            v-if="shownIds.has(photos[placement.index].photoId) && !failedIds.has(photos[placement.index].photoId)"
            class="cell-img"
            :src="photos[placement.index].thumb.url"
            :alt="`${t('route.photoLabel')} ${placement.index + 1}`"
            loading="lazy"
            decoding="async"
            @error="onImgError(photos[placement.index])"
          >
        </div>
      </div>

      <p v-if="loadingMore" class="status more-status">{{ t('album.loadingMore') }}</p>
      <div v-else-if="moreFailed" class="more-failed">
        <button type="button" @click="props.sequence.loadMore">{{ t('album.retry') }}</button>
      </div>
      <p v-else-if="!hasMore" class="end-note">{{ t('album.end') }}</p>

      <div v-if="hasMore" ref="sentinelEl" class="sentinel" aria-hidden="true" />
    </template>
  </div>
</template>

<style scoped>
/* 极简基线样式：视觉打磨留待 P4a。 */
.photo-feed {
  position: relative;
}
.new-photo-bar {
  position: sticky;
  top: 0;
  z-index: 1;
  display: block;
  width: 100%;
  margin-bottom: 12px;
  border: 1px solid #1d4ed8;
  border-radius: 8px;
  background: #eff6ff;
  color: #1d4ed8;
  padding: 8px 12px;
  font-size: 0.875rem;
  cursor: pointer;
}
.status {
  color: #6b7280;
}
.more-status {
  text-align: center;
  padding: 8px 0;
}
.error {
  color: #b91c1c;
}
.error button,
.more-failed button {
  margin-top: 8px;
  border: 1px solid #d1d5db;
  border-radius: 6px;
  background: #fff;
  padding: 4px 12px;
  cursor: pointer;
}
.more-failed {
  text-align: center;
}
.feed {
  border: 1px dashed #e5e7eb;
  border-radius: 8px;
  padding: 48px 16px;
  text-align: center;
}
.empty-notice {
  margin: 0;
  color: #9ca3af;
}
.waterfall {
  position: relative;
}
.cell {
  position: absolute;
  border-radius: 6px;
  overflow: hidden;
  background: linear-gradient(160deg, #f3f4f6, #e5e7eb);
  cursor: pointer;
}
.cell-img {
  display: block;
  width: 100%;
  height: 100%;
  object-fit: cover;
}
.end-note {
  text-align: center;
  color: #9ca3af;
  font-size: 0.875rem;
  padding: 12px 0;
  margin: 0;
}
.sentinel {
  height: 1px;
}
</style>