First release

src/lib/cache.js

@@ -0,0 +1,66 @@
+class InstaCache {
+	/**
+	 * @property {number} ttl time to keep each resource in milliseconds
+	 */
+	constructor(ttl) {
+		this.ttl = ttl
+		/** @type {Map<string, {data: any, time: number}>} */
+		this.cache = new Map()
+	}
+
+	clean() {
+		for (const key of this.cache.keys()) {
+			const value = this.cache.get(key)
+			if (Date.now() > value.time + this.ttl) this.cache.delete(key)
+		}
+	}
+
+	/**
+	 * @param {string} key
+	 */
+	get(key) {
+		return this.cache.get(key).data
+	}
+
+	/**
+	 * @param {string} key
+	 * @param {any} data
+	 */
+	set(key, data) {
+		this.cache.set(key, {data, time: Date.now()})
+	}
+
+	/**
+	 * @param {string} key
+	 * @param {() => Promise<T>} callback
+	 * @returns {Promise<T>}
+	 * @template T
+	 */
+	getOrFetch(key, callback) {
+		this.clean()
+		if (this.cache.has(key)) return Promise.resolve(this.get(key))
+		else {
+			const pending = callback().then(result => {
+				this.set(key, result)
+				return result
+			})
+			this.set(key, pending)
+			return pending
+		}
+	}
+
+	/**
+	 * @param {string} key
+	 * @param {() => Promise<T>} callback
+	 * @returns {Promise<T>}
+	 * @template T
+	 */
+	getOrFetchPromise(key, callback) {
+		return this.getOrFetch(key, callback).then(result => {
+			this.cache.delete(key)
+			return result
+		})
+	}
+}
+
+module.exports = InstaCache