ensure that items are not enqueued twice

sokra · sokra · commit 04045644683e · 2018-01-11T13:37:29.000+01:00
Use nice SetIterator trick
diff --git a/lib/util/Queue.js b/lib/util/Queue.js
@@ -2,50 +2,22 @@
 
 module.exports = class Queue {
 	constructor(items) {
-		this.first = null;
-		this.last = null;
-		this.recycle = [];
-		this.length = 0;
-		if(items) {
-			for(const item of items) {
-				this.enqueue(item);
-			}
-		}
+		this.set = new Set(items);
+		this.iterator = this.set[Symbol.iterator]();
+	}
+
+	get length() {
+		return this.set.size;
 	}
 
 	enqueue(item) {
-		const first = this.first;
-		let node;
-		if(this.recycle.length > 0) {
-			node = this.recycle.pop();
-			node.item = item;
-			node.next = null;
-		} else {
-			node = {
-				item,
-				next: null
-			};
-		}
-		if(first === null) {
-			this.last = node;
-		} else {
-			first.next = node;
-		}
-		this.first = node;
-		this.length++;
+		this.set.add(item);
 	}
 
 	dequeue() {
-		const last = this.last;
-		if(last === null)
-			return undefined;
-		const next = last.next;
-		if(next === null) {
-			this.first = null;
-		}
-		this.last = next;
-		this.length--;
-		this.recycle.push(last);
-		return last.item;
+		const result = this.iterator.next();
+		if(result.done) return undefined;
+		this.set.delete(result.value);
+		return result.value;
 	}
 };
