파일 페이지에서의 네트워크 호출 최적화

src/lib/modules/file/download.svelte.ts

@@ -0,0 +1,97 @@
+import axios from "axios";
+import { limitFunction } from "p-limit";
+import { decryptData } from "$lib/modules/crypto";
+
+export interface FileDownloadState {
+  id: number;
+  status:
+    | "download-pending"
+    | "downloading"
+    | "decryption-pending"
+    | "decrypting"
+    | "decrypted"
+    | "canceled"
+    | "error";
+  progress?: number;
+  rate?: number;
+  estimated?: number;
+  result?: ArrayBuffer;
+}
+
+export type LiveFileDownloadState = FileDownloadState & {
+  status: "download-pending" | "downloading" | "decryption-pending" | "decrypting";
+};
+
+let downloadingFiles: FileDownloadState[] = $state([]);
+
+export const isFileDownloading = (
+  status: FileDownloadState["status"],
+): status is LiveFileDownloadState["status"] =>
+  ["download-pending", "downloading", "decryption-pending", "decrypting"].includes(status);
+
+export const getFileDownloadState = (fileId: number) => {
+  return downloadingFiles.find((file) => file.id === fileId && isFileDownloading(file.status));
+};
+
+export const getDownloadingFiles = () => {
+  return downloadingFiles.filter((file): file is LiveFileDownloadState =>
+    isFileDownloading(file.status),
+  );
+};
+
+export const clearDownloadedFiles = () => {
+  downloadingFiles = downloadingFiles.filter((file) => isFileDownloading(file.status));
+};
+
+const requestFileDownload = limitFunction(
+  async (state: FileDownloadState, id: number) => {
+    state.status = "download-pending";
+
+    const res = await axios.get(`/api/file/${id}/download`, {
+      responseType: "arraybuffer",
+      onDownloadProgress: ({ progress, rate, estimated }) => {
+        state.progress = progress;
+        state.rate = rate;
+        state.estimated = estimated;
+      },
+    });
+    const fileEncrypted: ArrayBuffer = res.data;
+
+    state.status = "decryption-pending";
+    return fileEncrypted;
+  },
+  { concurrency: 1 },
+);
+
+const decryptFile = limitFunction(
+  async (
+    state: FileDownloadState,
+    fileEncrypted: ArrayBuffer,
+    fileEncryptedIv: string,
+    dataKey: CryptoKey,
+  ) => {
+    state.status = "decrypting";
+
+    const fileBuffer = await decryptData(fileEncrypted, fileEncryptedIv, dataKey);
+
+    state.status = "decrypted";
+    state.result = fileBuffer;
+    return fileBuffer;
+  },
+  { concurrency: 4 },
+);
+
+export const downloadFile = async (id: number, fileEncryptedIv: string, dataKey: CryptoKey) => {
+  downloadingFiles.push({
+    id,
+    status: "download-pending",
+  });
+  const state = downloadingFiles.at(-1)!;
+
+  try {
+    return await decryptFile(state, await requestFileDownload(state, id), fileEncryptedIv, dataKey);
+  } catch (e) {
+    state.status = "error";
+    throw e;
+  }
+};