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

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";
import { expectDomainError } from "./test-helpers.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);

		expectDomainError(result, "combatant-not-found");
	});

	it("returns error for negative AC", () => {
		const e = enc([makeCombatant("A")]);
		const result = setAc(e, combatantId("A"), -1);

		expectDomainError(result, "invalid-ac");
	});

	it("returns error for non-integer AC", () => {
		const e = enc([makeCombatant("A")]);
		const result = setAc(e, combatantId("A"), 3.5);

		expectDomainError(result, "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);
	});
});