Merge pull request #44 from ente-io/add-caching-support

disk caching support

main/preload.ts

@@ -12,6 +12,7 @@ import { logError } from './utils/logging';
 import { ElectronFile } from './types';
 import { getEncryptionKey, setEncryptionKey } from './utils/safeStorage';
 import { clearElectronStore } from './utils/electronStore';
+import { openLocalCache } from './utils/cache';
 
 // Patch the global WebSocket constructor to use the correct DevServer url
 const fixHotReloadNext12 = () => {
@@ -193,4 +194,5 @@ windowObject['ElectronAPIs'] = {
     getEncryptionKey,
     setEncryptionKey,
     clearElectronStore,
+    openLocalCache,
 };

main/utils/cache.ts

@@ -0,0 +1,50 @@
+import { ipcRenderer } from 'electron/renderer';
+import path from 'path';
+import { readFile, writeFile, existsSync, mkdir } from 'promise-fs';
+import crypto from 'crypto';
+
+const CACHE_DIR = 'ente';
+
+const getCacheDir = async () => {
+    const systemCacheDir = await ipcRenderer.invoke('get-path', 'cache');
+    return path.join(systemCacheDir, CACHE_DIR);
+};
+
+export async function openLocalCache(cacheName: string) {
+    const cacheDir = await getCacheDir();
+    const cacheBucketDir = path.join(cacheDir, cacheName);
+    if (!existsSync(cacheBucketDir)) {
+        await mkdir(cacheBucketDir, { recursive: true });
+    }
+    return new DiskCache(cacheBucketDir);
+}
+
+class DiskCache {
+    constructor(private cacheBucketDir: string) {}
+
+    async put(cacheKey: string, response: Response): Promise<void> {
+        const cachePath = getAssetCachePath(this.cacheBucketDir, cacheKey);
+        await writeFile(
+            cachePath,
+            new Uint8Array(await response.arrayBuffer())
+        );
+    }
+
+    async match(cacheKey: string): Promise<Response> {
+        const cachePath = getAssetCachePath(this.cacheBucketDir, cacheKey);
+        if (existsSync(cachePath)) {
+            return new Response(await readFile(cachePath));
+        } else {
+            return undefined;
+        }
+    }
+}
+
+function getAssetCachePath(cacheDir: string, cacheKey: string) {
+    // hashing the key to prevent illegal filenames
+    const cacheKeyHash = crypto
+        .createHash('sha256')
+        .update(cacheKey)
+        .digest('hex');
+    return path.join(cacheDir, cacheKeyHash);
+}

main/utils/ipcComms.ts

@@ -5,6 +5,7 @@ import {
     Tray,
     Notification,
     safeStorage,
+    app,
 } from 'electron';
 import { createWindow } from './createWindow';
 import { buildContextMenu } from './menuUtil';
@@ -82,4 +83,8 @@ export default function setupIpcComs(
     ipcMain.handle('safeStorage-decrypt', (_, message) => {
         return safeStorage.decryptString(message);
     });
+
+    ipcMain.handle('get-path', (_, message) => {
+        return app.getPath(message);
+    });
 }