썸네일 로딩 로직 최적화

src/lib/components/atoms/buttons/FileThumbnailButton.svelte

@@ -1,7 +1,6 @@
 <script lang="ts">
-  import { browser } from "$app/environment";
+  import { getFileThumbnail } from "$lib/modules/file";
   import type { SummarizedFileInfo } from "$lib/modules/filesystem";
-  import { requestFileThumbnailDownload } from "$lib/services/file";
 
   interface Props {
     info: SummarizedFileInfo;
@@ -10,25 +9,16 @@
 
   let { info, onclick }: Props = $props();
 
-  let showThumbnail = $derived(
-    browser && (info.contentType.startsWith("image/") || info.contentType.startsWith("video/")),
-  );
-  let thumbnailPromise = $derived(
-    showThumbnail ? requestFileThumbnailDownload(info.id, info.dataKey?.key) : null,
-  );
+  let thumbnail = $derived(getFileThumbnail(info));
 </script>
 
 <button
   onclick={onclick && (() => setTimeout(() => onclick(info), 100))}
   class="aspect-square overflow-hidden rounded transition active:scale-95 active:brightness-90"
 >
-  {#await thumbnailPromise}
+  {#if $thumbnail}
+    <img src={$thumbnail} alt={info.name} class="h-full w-full object-cover" />
+  {:else}
     <div class="h-full w-full bg-gray-100"></div>
-  {:then thumbnail}
-    {#if thumbnail}
-      <img src={thumbnail} alt={info.name} class="h-full w-full object-cover" />
-    {:else}
-      <div class="h-full w-full bg-gray-100"></div>
-    {/if}
-  {/await}
+  {/if}
 </button>

src/lib/components/organisms/Category/File.svelte

@@ -1,9 +1,8 @@
 <script lang="ts">
-  import { browser } from "$app/environment";
   import { ActionEntryButton } from "$lib/components/atoms";
   import { DirectoryEntryLabel } from "$lib/components/molecules";
+  import { getFileThumbnail } from "$lib/modules/file";
   import type { CategoryFileInfo } from "$lib/modules/filesystem";
-  import { requestFileThumbnailDownload } from "$lib/services/file";
   import type { SelectedFile } from "./service";
 
   import IconClose from "~icons/material-symbols/close";
@@ -16,12 +15,7 @@
 
   let { info, onclick, onRemoveClick }: Props = $props();
 
-  let showThumbnail = $derived(
-    browser && (info.contentType.startsWith("image/") || info.contentType.startsWith("video/")),
-  );
-  let thumbnailPromise = $derived(
-    showThumbnail ? requestFileThumbnailDownload(info.id, info.dataKey?.key) : null,
-  );
+  let thumbnail = $derived(getFileThumbnail(info));
 </script>
 
 <ActionEntryButton
@@ -30,9 +24,5 @@
   actionButtonIcon={onRemoveClick && IconClose}
   onActionButtonClick={() => onRemoveClick?.(info)}
 >
-  {#await thumbnailPromise}
-    <DirectoryEntryLabel type="file" name={info.name} />
-  {:then thumbnail}
-    <DirectoryEntryLabel type="file" thumbnail={thumbnail ?? undefined} name={info.name} />
-  {/await}
+  <DirectoryEntryLabel type="file" thumbnail={$thumbnail} name={info.name} />
 </ActionEntryButton>

src/lib/modules/file/cache.ts

@@ -1,15 +1,12 @@
-import { LRUCache } from "lru-cache";
 import {
   getFileCacheIndex as getFileCacheIndexFromIndexedDB,
   storeFileCacheIndex,
   deleteFileCacheIndex,
   type FileCacheIndex,
 } from "$lib/indexedDB";
-import { readFile, writeFile, deleteFile, deleteDirectory } from "$lib/modules/opfs";
-import { getThumbnailUrl } from "$lib/modules/thumbnail";
+import { readFile, writeFile, deleteFile } from "$lib/modules/opfs";
 
 const fileCacheIndex = new Map<number, FileCacheIndex>();
-const loadedThumbnails = new LRUCache<number, string>({ max: 100 });
 
 export const prepareFileCache = async () => {
   for (const cache of await getFileCacheIndexFromIndexedDB()) {
@@ -51,30 +48,3 @@ export const deleteFileCache = async (fileId: number) => {
   await deleteFile(`/cache/${fileId}`);
   await deleteFileCacheIndex(fileId);
 };
-
-export const getFileThumbnailCache = async (fileId: number) => {
-  const thumbnail = loadedThumbnails.get(fileId);
-  if (thumbnail) return thumbnail;
-
-  const thumbnailBuffer = await readFile(`/thumbnail/file/${fileId}`);
-  if (!thumbnailBuffer) return null;
-
-  const thumbnailUrl = getThumbnailUrl(thumbnailBuffer);
-  loadedThumbnails.set(fileId, thumbnailUrl);
-  return thumbnailUrl;
-};
-
-export const storeFileThumbnailCache = async (fileId: number, thumbnailBuffer: ArrayBuffer) => {
-  await writeFile(`/thumbnail/file/${fileId}`, thumbnailBuffer);
-  loadedThumbnails.set(fileId, getThumbnailUrl(thumbnailBuffer));
-};
-
-export const deleteFileThumbnailCache = async (fileId: number) => {
-  loadedThumbnails.delete(fileId);
-  await deleteFile(`/thumbnail/file/${fileId}`);
-};
-
-export const deleteAllFileThumbnailCaches = async () => {
-  loadedThumbnails.clear();
-  await deleteDirectory("/thumbnail/file");
-};

src/lib/modules/file/index.ts

@@ -1,3 +1,4 @@
 export * from "./cache";
 export * from "./download.svelte";
+export * from "./thumbnail";
 export * from "./upload.svelte";

src/lib/modules/file/thumbnail.ts

@@ -0,0 +1,90 @@
+import { LRUCache } from "lru-cache";
+import { writable, type Writable } from "svelte/store";
+import { browser } from "$app/environment";
+import { decryptData } from "$lib/modules/crypto";
+import type { SummarizedFileInfo } from "$lib/modules/filesystem";
+import { readFile, writeFile, deleteFile, deleteDirectory } from "$lib/modules/opfs";
+import { getThumbnailUrl } from "$lib/modules/thumbnail";
+import { isTRPCClientError, trpc } from "$trpc/client";
+
+const loadedThumbnails = new LRUCache<number, Writable<string>>({ max: 100 });
+const loadingThumbnails = new Map<number, Writable<string | undefined>>();
+
+const fetchFromOpfs = async (fileId: number) => {
+  const thumbnailBuffer = await readFile(`/thumbnail/file/${fileId}`);
+  if (thumbnailBuffer) {
+    return getThumbnailUrl(thumbnailBuffer);
+  }
+};
+
+const fetchFromServer = async (fileId: number, dataKey: CryptoKey) => {
+  try {
+    const [thumbnailEncrypted, { contentIv: thumbnailEncryptedIv }] = await Promise.all([
+      fetch(`/api/file/${fileId}/thumbnail/download`),
+      trpc().file.thumbnail.query({ id: fileId }),
+    ]);
+    const thumbnailBuffer = await decryptData(
+      await thumbnailEncrypted.arrayBuffer(),
+      thumbnailEncryptedIv,
+      dataKey,
+    );
+
+    void writeFile(`/thumbnail/file/${fileId}`, thumbnailBuffer);
+    return getThumbnailUrl(thumbnailBuffer);
+  } catch (e) {
+    if (isTRPCClientError(e) && e.data?.code === "NOT_FOUND") {
+      return null;
+    }
+    throw e;
+  }
+};
+
+export const getFileThumbnail = (file: SummarizedFileInfo) => {
+  if (
+    !browser ||
+    !(file.contentType.startsWith("image/") || file.contentType.startsWith("video/"))
+  ) {
+    return undefined;
+  }
+
+  const thumbnail = loadedThumbnails.get(file.id);
+  if (thumbnail) return thumbnail;
+
+  let loadingThumbnail = loadingThumbnails.get(file.id);
+  if (loadingThumbnail) return loadingThumbnail;
+
+  loadingThumbnail = writable(undefined);
+  loadingThumbnails.set(file.id, loadingThumbnail);
+
+  fetchFromOpfs(file.id)
+    .then((thumbnail) => thumbnail ?? (file.dataKey && fetchFromServer(file.id, file.dataKey.key)))
+    .then((thumbnail) => {
+      if (thumbnail) {
+        loadingThumbnail.set(thumbnail);
+        loadedThumbnails.set(file.id, loadingThumbnail as Writable<string>);
+      }
+      loadingThumbnails.delete(file.id);
+    });
+  return loadingThumbnail;
+};
+
+export const storeFileThumbnailCache = async (fileId: number, thumbnailBuffer: ArrayBuffer) => {
+  await writeFile(`/thumbnail/file/${fileId}`, thumbnailBuffer);
+
+  const oldThumbnail = loadedThumbnails.get(fileId);
+  if (oldThumbnail) {
+    oldThumbnail.set(getThumbnailUrl(thumbnailBuffer));
+  } else {
+    loadedThumbnails.set(fileId, writable(getThumbnailUrl(thumbnailBuffer)));
+  }
+};
+
+export const deleteFileThumbnailCache = async (fileId: number) => {
+  loadedThumbnails.delete(fileId);
+  await deleteFile(`/thumbnail/file/${fileId}`);
+};
+
+export const deleteAllFileThumbnailCaches = async () => {
+  loadedThumbnails.clear();
+  await deleteDirectory(`/thumbnail/file`);
+};

src/lib/services/file.ts

@@ -1,15 +1,11 @@
 import { getAllFileInfos } from "$lib/indexedDB/filesystem";
-import { decryptData } from "$lib/modules/crypto";
 import {
   getFileCache,
   storeFileCache,
   deleteFileCache,
-  getFileThumbnailCache,
-  storeFileThumbnailCache,
-  deleteFileThumbnailCache,
   downloadFile,
+  deleteFileThumbnailCache,
 } from "$lib/modules/file";
-import { getThumbnailUrl } from "$lib/modules/thumbnail";
 import type { FileThumbnailUploadRequest } from "$lib/server/schemas";
 import { trpc } from "$trpc/client";
 
@@ -44,29 +40,6 @@ export const requestFileThumbnailUpload = async (
   return await fetch(`/api/file/${fileId}/thumbnail/upload`, { method: "POST", body: form });
 };
 
-export const requestFileThumbnailDownload = async (fileId: number, dataKey?: CryptoKey) => {
-  const cache = await getFileThumbnailCache(fileId);
-  if (cache || !dataKey) return cache;
-
-  let thumbnailInfo;
-  try {
-    thumbnailInfo = await trpc().file.thumbnail.query({ id: fileId });
-  } catch {
-    // TODO: Error Handling
-    return null;
-  }
-  const { contentIv: thumbnailEncryptedIv } = thumbnailInfo;
-
-  const res = await fetch(`/api/file/${fileId}/thumbnail/download`);
-  if (!res.ok) return null;
-
-  const thumbnailEncrypted = await res.arrayBuffer();
-  const thumbnailBuffer = await decryptData(thumbnailEncrypted, thumbnailEncryptedIv, dataKey);
-
-  storeFileThumbnailCache(fileId, thumbnailBuffer); // Intended
-  return getThumbnailUrl(thumbnailBuffer);
-};
-
 export const requestDeletedFilesCleanup = async () => {
   let liveFiles;
   try {