优化缩略图

web/public/artwork-cache-sw.js

@@ -1,8 +1,22 @@
 const ARTWORK_CACHE_PREFIX = 'mebox-artwork-'
-const ARTWORK_CACHE = `${ARTWORK_CACHE_PREFIX}v2`
+const ARTWORK_CACHE = `${ARTWORK_CACHE_PREFIX}v3`
 const MIN_CACHEABLE_ARTWORK_BYTES = 128
 const STRIP_QUERY_KEYS = ['token', 'profile_id', 'profile_pin_token']
 
+// 浏览器侧作品缓存的容量上限。
+//
+// 没有上限时 Cache Storage 会一直增长，浏览器在存储压力下会整体清空该
+// origin 的缓存，失效时机完全不可控。条数上限每次写入都检查（只是读一遍
+// 键，开销小）；字节上限最多每两分钟统计一次，因为需要逐个读取已存响应的
+// Content-Length。两者都淘汰到上限的 80%，避免刚清完又立刻触发。
+const MAX_CACHE_ENTRIES = 500
+const MAX_CACHE_BYTES = 64 * 1024 * 1024
+const TRIM_TARGET_RATIO = 0.8
+const BYTE_TRIM_INTERVAL_MS = 2 * 60 * 1000
+
+let lastByteTrimAt = 0
+let trimInFlight = null
+
 function isArtworkRequest(url) {
   if (url.origin !== self.location.origin) return false
   if (url.pathname === '/api/img') return true
@@ -54,10 +68,69 @@ async function cacheArtwork(request) {
   if (cacheResponse) {
     await cache.put(cacheKey, cacheResponse)
     await deleteOldArtworkVariants(cache, cacheKey)
+    await trimArtworkCache(cache)
   }
   return response
 }
 
+// trimArtworkCache 把缓存裁剪回容量上限之内，按写入顺序淘汰（最旧的先删）。
+// 同一时刻只允许一次裁剪在跑。
+async function trimArtworkCache(cache) {
+  if (trimInFlight) return trimInFlight
+  trimInFlight = runArtworkTrim(cache).catch(() => undefined)
+  try {
+    await trimInFlight
+  } finally {
+    trimInFlight = null
+  }
+}
+
+async function runArtworkTrim(cache) {
+  const keys = await cache.keys()
+  if (keys.length > MAX_CACHE_ENTRIES) {
+    const keep = Math.floor(MAX_CACHE_ENTRIES * TRIM_TARGET_RATIO)
+    await deleteOldestArtwork(cache, keys, keys.length - keep)
+    return
+  }
+
+  const now = Date.now()
+  if (now - lastByteTrimAt < BYTE_TRIM_INTERVAL_MS) return
+  lastByteTrimAt = now
+
+  const sizes = []
+  let total = 0
+  for (const key of keys) {
+    const response = await cache.match(key)
+    const size = cacheableResponseSize(response)
+    sizes.push(size)
+    total += size
+  }
+  if (total <= MAX_CACHE_BYTES) return
+
+  const target = Math.floor(MAX_CACHE_BYTES * TRIM_TARGET_RATIO)
+  let remaining = total
+  const evicted = []
+  for (let i = 0; i < keys.length && remaining > target; i += 1) {
+    remaining -= sizes[i]
+    evicted.push(keys[i])
+  }
+  await Promise.all(evicted.map((key) => cache.delete(key)))
+}
+
+// cacheableResponseSize 用 Content-Length 估算体积。MeBox 的图片响应由
+// ServeContent 生成，始终带该头；缺失时按 0 计（只是少算，不会误删）。
+function cacheableResponseSize(response) {
+  if (!response) return 0
+  const size = Number(response.headers.get('Content-Length') || '0')
+  return Number.isFinite(size) && size > 0 ? size : 0
+}
+
+// deleteOldestArtwork 按 cache.keys() 的顺序（写入顺序）删除最旧的若干条。
+async function deleteOldestArtwork(cache, keys, count) {
+  const victims = keys.slice(0, Math.max(0, count))
+  await Promise.all(victims.map((key) => cache.delete(key)))
+}
+
 async function cloneCacheableArtworkResponse(response) {
   if (!response.ok) return null
   const contentType = response.headers.get('Content-Type') || ''