perf: Use cache for all remote resources

backend/src/utils/download.js

@@ -1,12 +1,14 @@
 import { HTTP } from '@/vendor/open-api';
+import { hex_md5 } from '@/vendor/md5';
+import resourceCache from '@/utils/resource-cache';
 
-const cache = new Map();
+const tasks = new Map();
 
 export default async function download(url, ua) {
     ua = ua || 'Quantumult%20X/1.0.29 (iPhone14,5; iOS 15.4.1)';
-    const id = ua + url;
-    if (cache.has(id)) {
-        return cache.get(id);
+    const id = hex_md5(ua + url);
+    if (tasks.has(id)) {
+        return tasks.get(id);
     }
 
     const http = HTTP({
@@ -16,18 +18,27 @@ export default async function download(url, ua) {
     });
 
     const result = new Promise((resolve, reject) => {
-        http.get(url)
-            .then((resp) => {
-                const body = resp.body;
-                if (body.replace(/\s/g, '').length === 0)
-                    reject(new Error('订阅内容为空！'));
-                else resolve(body);
-            })
-            .catch(() => {
-                reject(new Error(`无法下载 URL：${url}`));
-            });
+        // try to find in app cache
+        const cached = resourceCache.get(id);
+        if (cached) {
+            resolve(cached);
+        } else {
+            http.get(url)
+                .then((resp) => {
+                    const body = resp.body;
+                    if (body.replace(/\s/g, '').length === 0)
+                        reject(new Error('远程资源内容为空！'));
+                    else {
+                        resourceCache.set(id, body);
+                        resolve(body);
+                    }
+                })
+                .catch(() => {
+                    reject(new Error(`无法下载 URL：${url}`));
+                });
+        }
     });
 
-    cache.set(id, result);
+    tasks.set(id, result);
     return result;
 }

backend/src/utils/resource-cache.js

@@ -0,0 +1,47 @@
+import $ from '@/core/app';
+import { CACHE_EXPIRATION_TIME_MS, RESOURCE_CACHE_KEY } from '@/constants';
+
+class ResourceCache {
+    constructor(expires) {
+        this.expires = expires;
+        if (!$.read(RESOURCE_CACHE_KEY)) {
+            $.write('{}', RESOURCE_CACHE_KEY);
+        }
+        this.resourceCache = JSON.parse($.read(RESOURCE_CACHE_KEY));
+        this._cleanup();
+    }
+
+    _cleanup() {
+        // clear obsolete cached resource
+        let clear = false;
+        Object.entries(this.resourceCache).forEach((entry) => {
+            const [id, updated] = entry;
+            if (new Date().getTime() - updated > this.expires) {
+                $.delete(`#${id}`);
+                delete this.resourceCache[id];
+                clear = true;
+            }
+        });
+        if (clear) this._persist();
+    }
+
+    _persist() {
+        $.write(JSON.stringify(this.resourceCache), RESOURCE_CACHE_KEY);
+    }
+
+    get(id) {
+        const updated = this.resourceCache[id];
+        if (updated && new Date().getTime() - updated <= this.expires) {
+            return $.read(`#${id}`);
+        }
+        return null;
+    }
+
+    set(id, value) {
+        this.resourceCache[id] = new Date().getTime();
+        this._persist();
+        $.write(value, `#${id}`);
+    }
+}
+
+export default new ResourceCache(CACHE_EXPIRATION_TIME_MS);