Implement the 016-combatant-ac feature that adds an optional Armor Class field to combatants with shield icon display and inline editing in the encounter tracker

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

packages/domain/src/__tests__/set-ac.test.ts

@@ -0,0 +1,143 @@
+import { describe, expect, it } from "vitest";
+import { setAc } from "../set-ac.js";
+import type { Combatant, Encounter } from "../types.js";
+import { combatantId, isDomainError } from "../types.js";
+
+function makeCombatant(name: string, ac?: number): Combatant {
+	return ac === undefined
+		? { id: combatantId(name), name }
+		: { id: combatantId(name), name, ac };
+}
+
+function enc(
+	combatants: Combatant[],
+	activeIndex = 0,
+	roundNumber = 1,
+): Encounter {
+	return { combatants, activeIndex, roundNumber };
+}
+
+function successResult(
+	encounter: Encounter,
+	id: string,
+	value: number | undefined,
+) {
+	const result = setAc(encounter, combatantId(id), value);
+	if (isDomainError(result)) {
+		throw new Error(`Expected success, got error: ${result.message}`);
+	}
+	return result;
+}
+
+describe("setAc", () => {
+	it("sets AC to a valid value", () => {
+		const e = enc([makeCombatant("A"), makeCombatant("B")]);
+		const { encounter, events } = successResult(e, "A", 15);
+
+		expect(encounter.combatants[0].ac).toBe(15);
+		expect(events).toEqual([
+			{
+				type: "AcSet",
+				combatantId: combatantId("A"),
+				previousAc: undefined,
+				newAc: 15,
+			},
+		]);
+	});
+
+	it("sets AC to 0", () => {
+		const e = enc([makeCombatant("A")]);
+		const { encounter } = successResult(e, "A", 0);
+
+		expect(encounter.combatants[0].ac).toBe(0);
+	});
+
+	it("clears AC with undefined", () => {
+		const e = enc([makeCombatant("A", 15)]);
+		const { encounter, events } = successResult(e, "A", undefined);
+
+		expect(encounter.combatants[0].ac).toBeUndefined();
+		expect(events[0]).toMatchObject({
+			previousAc: 15,
+			newAc: undefined,
+		});
+	});
+
+	it("returns error for nonexistent combatant", () => {
+		const e = enc([makeCombatant("A")]);
+		const result = setAc(e, combatantId("nonexistent"), 10);
+
+		expect(isDomainError(result)).toBe(true);
+		if (isDomainError(result)) {
+			expect(result.code).toBe("combatant-not-found");
+		}
+	});
+
+	it("returns error for negative AC", () => {
+		const e = enc([makeCombatant("A")]);
+		const result = setAc(e, combatantId("A"), -1);
+
+		expect(isDomainError(result)).toBe(true);
+		if (isDomainError(result)) {
+			expect(result.code).toBe("invalid-ac");
+		}
+	});
+
+	it("returns error for non-integer AC", () => {
+		const e = enc([makeCombatant("A")]);
+		const result = setAc(e, combatantId("A"), 3.5);
+
+		expect(isDomainError(result)).toBe(true);
+		if (isDomainError(result)) {
+			expect(result.code).toBe("invalid-ac");
+		}
+	});
+
+	it("returns error for NaN", () => {
+		const e = enc([makeCombatant("A")]);
+		const result = setAc(e, combatantId("A"), Number.NaN);
+		expect(isDomainError(result)).toBe(true);
+	});
+
+	it("preserves other fields when setting AC", () => {
+		const combatant: Combatant = {
+			id: combatantId("A"),
+			name: "Aria",
+			initiative: 15,
+			maxHp: 20,
+			currentHp: 18,
+		};
+		const e = enc([combatant]);
+		const { encounter } = successResult(e, "A", 16);
+
+		const updated = encounter.combatants[0];
+		expect(updated.ac).toBe(16);
+		expect(updated.name).toBe("Aria");
+		expect(updated.initiative).toBe(15);
+		expect(updated.maxHp).toBe(20);
+		expect(updated.currentHp).toBe(18);
+	});
+
+	it("does not reorder combatants", () => {
+		const e = enc([makeCombatant("A"), makeCombatant("B")]);
+		const { encounter } = successResult(e, "B", 18);
+
+		expect(encounter.combatants[0].id).toBe(combatantId("A"));
+		expect(encounter.combatants[1].id).toBe(combatantId("B"));
+	});
+
+	it("preserves activeIndex and roundNumber", () => {
+		const e = enc([makeCombatant("A"), makeCombatant("B")], 1, 5);
+		const { encounter } = successResult(e, "A", 14);
+
+		expect(encounter.activeIndex).toBe(1);
+		expect(encounter.roundNumber).toBe(5);
+	});
+
+	it("does not mutate input encounter", () => {
+		const e = enc([makeCombatant("A")]);
+		const original = JSON.parse(JSON.stringify(e));
+		setAc(e, combatantId("A"), 10);
+		expect(e).toEqual(original);
+	});
+});