add day 79 (finally object reactive data)

day79/src/lib/lruCache.ts

@@ -0,0 +1,31 @@
+// ruthlessly stolen from @trunarla on twitter
+export class LRUCache {
+	#cache: Map<string, string | Record<string, string | Record<string, string | boolean>>>;
+	#capacity: number;
+
+	constructor(capacity: number) {
+		this.#capacity = capacity;
+		this.#cache = new Map<string, string | Record<string, string | Record<string, string | boolean>>>();
+	}
+
+	set(key: string, value: string | Record<string, string | Record<string, string | boolean>>) {
+		// If we're at capacity, we need to delete the least-recently-used item:
+		if (this.#cache.size >= this.#capacity) {
+			// Manually invoke the keys iterator to get the least-recently-used key:
+			const keyToDelete = this.#cache.keys().next().value;
+			this.#cache.delete(keyToDelete);
+		}
+		this.#cache.delete(key);
+		this.#cache.set(key, value);
+	}
+
+	get(key: string): Record<string, string | Record<string, string | boolean>> | string | undefined {
+		if (this.#cache.has(key)) {
+			const value = this.#cache.get(key);
+			if (!value) return;
+			this.#cache.delete(key);
+			this.#cache.set(key, value);
+			return value;
+		}
+	}
+}