CardPool: Override all mutating Map methods, making sure _count stays…

… in sync.

src/CardTypes.ts

@@ -82,20 +82,39 @@ export class Card {
 
 export type DeckBasicLands = { [key in CardColor]: number };
 
+// Implements a MultiSet using a standard Map.
 export class CardPool extends Map<CardID, number> {
 	private _count = 0;
 
 	constructor() {
 		super();
 	}
 
+	// Set the number of copies of a card in the pool.
+	// Note: If count is <= 0, the card entry will be removed entirely.
 	set(cid: CardID, count: number) {
-		if (super.has(cid)) this._count -= super.get(cid)!;
-		super.set(cid, count);
-		this._count += count;
+		if (super.has(cid)) {
+			this._count -= super.get(cid)!;
+			if (count <= 0) super.delete(cid);
+		}
+		if (count > 0) {
+			super.set(cid, count);
+			this._count += count;
+		}
 		return this;
 	}
 
+	clear(): void {
+		super.clear();
+		this._count = 0;
+	}
+
+	delete(key: string): boolean {
+		const oldValue = super.get(key);
+		if (oldValue) this._count -= oldValue;
+		return super.delete(key);
+	}
+
 	// Remove a single copy of a card from the pool.
 	removeCard(cid: CardID) {
 		const oldValue = this.get(cid);
@@ -104,8 +123,9 @@ export class CardPool extends Map<CardID, number> {
 			console.trace();
 			throw `Called removeCard on a non-existing card (${cid}).`;
 		}
-		if (oldValue === 1) this.delete(cid);
-		else super.set(cid, oldValue - 1); // Purposefully bypassing our caching overload and calling super.set directly here.
+		// Purposefully bypassing our caching overload and calling super.set() and super.delete() directly here.
+		if (oldValue === 1) super.delete(cid);
+		else super.set(cid, oldValue - 1);
 		--this._count;
 	}