add filesystem caching with cacache

classes/caching/file_system_cache.js

@@ -1,26 +1,72 @@
-import FPersist from 'fpersist';
+import cacache from 'cacache';
+import { Readable } from 'stream';
 import { KeyTimeout } from './key_timeout.js';
 
+function getBodyAndMetaKeys(key) {
+  return [`${key}body`, `${key}meta`];
+}
+
 export class FileSystemCache {
   constructor(options = {}) {
     this.ttl = options.ttl;
     this.keyTimeout = new KeyTimeout();
-
-    const cacheDirectory = options.cacheDirectory || '.cache';
-    this.cache = new FPersist(cacheDirectory);
+    this.cacheDirectory = options.cacheDirectory || '.cache';
   }
 
-  get(key) {
-    return this.cache.getItem(key);
+  async get(key) {
+    const [, metaKey] = getBodyAndMetaKeys(key);
+
+    const metaInfo = await cacache.get.info(this.cacheDirectory, metaKey);
+
+    if (!metaInfo) {
+      return undefined;
+    }
+
+    const metaBuffer = await cacache.get.byDigest(this.cacheDirectory, metaInfo.integrity);
+    const metaData = JSON.parse(metaBuffer);
+    const { bodyStreamIntegrity, bodyStreamLength } = metaData;
+    delete metaData.bodyStreamIntegrity;
+    delete metaData.bodyStreamLength;
+
+    const bodyStream = bodyStreamLength > 0
+      ? cacache.get.stream.byDigest(this.cacheDirectory, bodyStreamIntegrity)
+      : Readable.from(Buffer.alloc(0));
+
+    return {
+      bodyStream,
+      metaData,
+    };
   }
 
   remove(key) {
+    const [bodyKey, metaKey] = getBodyAndMetaKeys(key);
+
     this.keyTimeout.clearTimeout(key);
-    return this.cache.deleteItem(key);
+
+    return Promise.all([
+      cacache.rm.entry(this.cacheDirectory, bodyKey),
+      cacache.rm.entry(this.cacheDirectory, metaKey),
+    ]);
   }
 
-  async set(key, value) {
-    await this.cache.setItem(key, value);
+  async set(key, bodyStream, metaData, bodyStreamLength) {
+    const [bodyKey, metaKey] = getBodyAndMetaKeys(key);
+    const metaCopy = { ...metaData, bodyStreamLength };
+
+    this.keyTimeout.clearTimeout(key);
+
+    if (bodyStreamLength > 0) {
+      metaCopy.bodyStreamIntegrity = await new Promise((fulfill, reject) => {
+        bodyStream.pipe(cacache.put.stream(this.cacheDirectory, bodyKey))
+          .on('integrity', (i) => fulfill(i))
+          .on('error', (e) => {
+            reject(e);
+          });
+      });
+    }
+
+    const metaBuffer = Buffer.from(JSON.stringify(metaCopy));
+    await cacache.put(this.cacheDirectory, metaKey, metaBuffer);
 
     if (typeof this.ttl === 'number') {
       this.keyTimeout.updateTimeout(key, this.ttl, () => this.remove(key));