Server authority

server/game/lru.ts

@@ -0,0 +1,35 @@
+// a Map that forgets the least recently used entries past max_size
+export class LruMap<K, V> {
+	#map = new Map<K, V>();
+	readonly max_size: number;
+
+	constructor(max_size: number) {
+		this.max_size = max_size;
+	}
+
+	get(key: K): V | undefined {
+		const value = this.#map.get(key);
+		if (value !== undefined) {
+			// maps keep insertion order, so re-inserting moves it to the back
+			this.#map.delete(key);
+			this.#map.set(key, value);
+		}
+		return value;
+	}
+
+	set(key: K, value: V) {
+		this.#map.delete(key);
+		this.#map.set(key, value);
+		if (this.#map.size > this.max_size) {
+			this.#map.delete(this.#map.keys().next().value!);
+		}
+	}
+
+	delete(key: K) {
+		this.#map.delete(key);
+	}
+
+	get size() {
+		return this.#map.size;
+	}
+}