Implement the 002-add-combatant feature that adds the possibility to add new combatants to an encounter

packages/application/src/add-combatant-use-case.ts

@@ -0,0 +1,24 @@
+import {
+	addCombatant,
+	type CombatantId,
+	type DomainError,
+	type DomainEvent,
+	isDomainError,
+} from "@initiative/domain";
+import type { EncounterStore } from "./ports.js";
+
+export function addCombatantUseCase(
+	store: EncounterStore,
+	id: CombatantId,
+	name: string,
+): DomainEvent[] | DomainError {
+	const encounter = store.get();
+	const result = addCombatant(encounter, id, name);
+
+	if (isDomainError(result)) {
+		return result;
+	}
+
+	store.save(result.encounter);
+	return result.events;
+}