파일 캐시 추가

src/lib/modules/cache.ts

@@ -0,0 +1,33 @@
+import { getFileCacheIndex, storeFileCacheIndex, type FileCacheIndex } from "$lib/indexedDB";
+import { readFileFromOpfs, writeFileToOpfs } from "$lib/modules/opfs";
+
+const fileCacheIndex = new Map<number, FileCacheIndex>();
+
+export const prepareFileCache = async () => {
+  for (const cache of await getFileCacheIndex()) {
+    fileCacheIndex.set(cache.fileId, cache);
+  }
+};
+
+export const getFileCache = async (fileId: number) => {
+  const cacheIndex = fileCacheIndex.get(fileId);
+  if (!cacheIndex) return null;
+
+  cacheIndex.lastRetrievedAt = new Date();
+  storeFileCacheIndex(cacheIndex); // Intended
+  return await readFileFromOpfs(`/cache/${fileId}`);
+};
+
+export const storeFileCache = async (fileId: number, fileBuffer: ArrayBuffer) => {
+  const now = new Date();
+  await writeFileToOpfs(`/cache/${fileId}`, fileBuffer);
+
+  const cacheIndex: FileCacheIndex = {
+    fileId,
+    cachedAt: now,
+    lastRetrievedAt: now,
+    size: fileBuffer.byteLength,
+  };
+  fileCacheIndex.set(fileId, cacheIndex);
+  await storeFileCacheIndex(cacheIndex);
+};

src/lib/modules/opfs.ts

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+let rootHandle: FileSystemDirectoryHandle | null = null;
+
+export const prepareOpfs = async () => {
+  rootHandle = await navigator.storage.getDirectory();
+};
+
+const getFileHandle = async (path: string, create = true) => {
+  if (!rootHandle) {
+    throw new Error("OPFS not prepared");
+  } else if (path[0] !== "/") {
+    throw new Error("Path must be absolute");
+  }
+
+  const parts = path.split("/");
+  if (parts.length <= 1) {
+    throw new Error("Invalid path");
+  }
+
+  try {
+    let directoryHandle: FileSystemDirectoryHandle = rootHandle;
+
+    for (const part of parts.slice(0, -1)) {
+      if (!part) continue;
+      directoryHandle = await directoryHandle.getDirectoryHandle(part, { create });
+    }
+
+    return directoryHandle.getFileHandle(parts[parts.length - 1]!, { create });
+  } catch (e) {
+    if (e instanceof DOMException && e.name === "NotFoundError") {
+      return null;
+    }
+    throw e;
+  }
+};
+
+export const readFileFromOpfs = async (path: string) => {
+  const fileHandle = await getFileHandle(path, false);
+  if (!fileHandle) return null;
+
+  const file = await fileHandle.getFile();
+  return await file.arrayBuffer();
+};
+
+export const writeFileToOpfs = async (path: string, data: ArrayBuffer) => {
+  const fileHandle = await getFileHandle(path);
+  const writable = await fileHandle!.createWritable();
+
+  try {
+    await writable.write(data);
+  } finally {
+    await writable.close();
+  }
+};