api/api-keys: watch for file changes instead of polling

api/src/misc/file-watcher.js

@@ -0,0 +1,43 @@
+import { EventEmitter } from 'node:events';
+import * as fs from 'node:fs/promises';
+
+export class FileWatcher extends EventEmitter {
+    #path;
+    #hasWatcher = false;
+    #lastChange = new Date().getTime();
+
+    constructor({ path, ...rest }) {
+        super(rest);
+        this.#path = path;
+    }
+
+    async #setupWatcher() {
+        if (this.#hasWatcher)
+            return;
+
+        this.#hasWatcher = true;
+        const watcher = fs.watch(this.#path);
+        for await (const _ of watcher) {
+            if (new Date() - this.#lastChange > 50) {
+                this.emit('file-updated');
+                this.#lastChange = new Date().getTime();
+            }
+        }
+    }
+
+    read() {
+        this.#setupWatcher();
+        return fs.readFile(this.#path, 'utf8');
+    }
+
+    static fromFileProtocol(url_) {
+        const url = new URL(url_);
+        if (url.protocol !== 'file:') {
+            return;
+        }
+
+        const pathname = url.pathname === '/' ? '' : url.pathname;
+        const file_path = decodeURIComponent(url.host + pathname);
+        return new this({ path: file_path });
+    }
+}