Refactor player and room to support adding effects.

Vessel.ts

@@ -0,0 +1,65 @@
+import type { Conditions, Effect, Item, VesselProperties } from "./types.ts";
+
+export default class Vessel<T extends VesselProperties> {
+	protected _conditions: Conditions<T>;
+	protected _properties: T;
+	protected _activeEffects: string[];
+
+	constructor(
+		properties: T,
+		conditions: Conditions<T>,
+		activeEffects: string[] = []
+	) {
+		this._conditions = conditions;
+		this._properties = properties;
+		this._activeEffects = activeEffects;
+	}
+
+	get activeEffects(): string[] {
+		return this._activeEffects;
+	}
+
+	description(items: Item[]): string | null {
+		if (items.length === 0) return null;
+
+		const vowels = ["a", "e", "i", "o", "u"];
+		const description = items
+			.map(({ name }, i) => {
+				let anItem = `${vowels.includes(name[0]) ? "an" : "a"} ${name}`;
+
+				// if we have more than one item, and this is the last item...
+				if (i > 1 && i + 1 === items.length) {
+					anItem = `and ${anItem}`;
+				}
+
+				return anItem;
+			})
+			.join(", ");
+
+		return description;
+	}
+
+	// Player effects should be applied first, then scene effects should be applied.
+	// This will mean that scene effects will take precedence over player effects.
+	applyEffects(
+		activePlayerEffects: string[],
+		activeSceneEffects: string[]
+	): T {
+		const activeEffects = [...activePlayerEffects, ...activeSceneEffects];
+		const map = this._conditions.effects.reduce(
+			(map: { [name: string]: Effect<T> }, effect: Effect<T>) => {
+				map[effect.name] = effect;
+				return map;
+			},
+			{}
+		);
+		const effects = activeEffects.map((e) => map[e]);
+		const appliedProperties = { ...this._properties };
+
+		for (const effect of effects) {
+			Object.assign(appliedProperties, effect.properties);
+		}
+
+		return appliedProperties;
+	}
+}