Added new cache object

src/cache.ts

@@ -0,0 +1,73 @@
+/**
+ * Map of data which tracks whether it is a complete collection & offers optional expiry of cached values
+ */
+export class Cache<K, T> extends Map<K, T> {
+
+	/** Whether cache is complete */
+	complete = false;
+
+	/**
+	 * Create new cache
+	 *
+	 * @param {keyof T} key Default property to use as primary key
+	 * @param {number} ttl Default expiry in milliseconds
+	 */
+	constructor(public readonly key: keyof T, public ttl?: number) {
+		super();
+	}
+
+	private getKey(value: T): K {
+		return <K>value[this.key];
+	}
+
+	/**
+	 * Get all cached items
+	 *
+	 * @return {T[]} Array of items
+	 */
+	all() {
+		return Array.from(this.values());
+	}
+
+	/**
+	 * Add a new item to the cache. Like set, but finds key automatically
+	 *
+	 * @param {T} value Item to add to cache
+	 * @param {number | undefined} ttl Override default expiry
+	 * @return {this}
+	 */
+	add(value: T, ttl = this.ttl): this {
+		const key = this.getKey(value);
+		this.set(key, value, ttl);
+		return this;
+	}
+
+	/**
+	 * Add several rows to the cache
+	 *
+	 * @param {T[]} rows Several items that will be cached using the default key
+	 * @param complete Mark cache as complete & reliable, defaults to true
+	 * @return {this}
+	 */
+	addAll(rows: T[], complete = true): this {
+		rows.forEach(r => this.add(r));
+		this.complete = complete;
+		return this;
+	}
+
+	/**
+	 * Add an item to the cache manually specifying the key
+	 * @param {K} key Key item will be cached under
+	 * @param {T} value Item to cache
+	 * @param {number | undefined} ttl Override default expiry
+	 * @return {this}
+	 */
+	set(key: K, value: T, ttl = this.ttl): this {
+		super.set(key, value);
+		if(ttl) setTimeout(() => {
+			this.complete = false;
+			super.delete(key)
+		}, ttl);
+		return this;
+	}
+}