initiative/packages/domain/src/__tests__/set-temp-hp.test.ts

import { describe, expect, it } from "vitest";
import { setTempHp } from "../set-temp-hp.js";
import type { Combatant, Encounter } from "../types.js";
import { combatantId, isDomainError } from "../types.js";
import { expectDomainError } from "./test-helpers.js";

function makeCombatant(
	name: string,
	opts?: { maxHp: number; currentHp: number; tempHp?: number },
): Combatant {
	return {
		id: combatantId(name),
		name,
		...(opts
			? {
					maxHp: opts.maxHp,
					currentHp: opts.currentHp,
					tempHp: opts.tempHp,
				}
			: {}),
	};
}

function enc(combatants: Combatant[]): Encounter {
	return { combatants, activeIndex: 0, roundNumber: 1 };
}

function successResult(
	encounter: Encounter,
	id: string,
	tempHp: number | undefined,
) {
	const result = setTempHp(encounter, combatantId(id), tempHp);
	if (isDomainError(result)) {
		throw new Error(`Expected success, got error: ${result.message}`);
	}
	return result;
}

describe("setTempHp", () => {
	describe("acceptance scenarios", () => {
		it("sets temp HP on a combatant with HP tracking enabled", () => {
			const e = enc([makeCombatant("A", { maxHp: 20, currentHp: 15 })]);
			const { encounter } = successResult(e, "A", 8);
			expect(encounter.combatants[0].tempHp).toBe(8);
		});

		it("keeps higher value when existing temp HP is greater", () => {
			const e = enc([
				makeCombatant("A", { maxHp: 20, currentHp: 10, tempHp: 5 }),
			]);
			const { encounter } = successResult(e, "A", 3);
			expect(encounter.combatants[0].tempHp).toBe(5);
		});

		it("replaces when new value is higher", () => {
			const e = enc([
				makeCombatant("A", { maxHp: 20, currentHp: 10, tempHp: 3 }),
			]);
			const { encounter } = successResult(e, "A", 7);
			expect(encounter.combatants[0].tempHp).toBe(7);
		});

		it("clears temp HP when set to undefined", () => {
			const e = enc([
				makeCombatant("A", { maxHp: 20, currentHp: 10, tempHp: 5 }),
			]);
			const { encounter } = successResult(e, "A", undefined);
			expect(encounter.combatants[0].tempHp).toBeUndefined();
		});
	});

	describe("invariants", () => {
		it("is pure — same input produces same output", () => {
			const e = enc([makeCombatant("A", { maxHp: 20, currentHp: 15 })]);
			const r1 = setTempHp(e, combatantId("A"), 5);
			const r2 = setTempHp(e, combatantId("A"), 5);
			expect(r1).toEqual(r2);
		});

		it("does not mutate input encounter", () => {
			const e = enc([makeCombatant("A", { maxHp: 20, currentHp: 15 })]);
			const original = JSON.parse(JSON.stringify(e));
			setTempHp(e, combatantId("A"), 5);
			expect(e).toEqual(original);
		});

		it("emits TempHpSet event with correct shape", () => {
			const e = enc([
				makeCombatant("A", { maxHp: 20, currentHp: 15, tempHp: 3 }),
			]);
			const { events } = successResult(e, "A", 7);
			expect(events).toEqual([
				{
					type: "TempHpSet",
					combatantId: combatantId("A"),
					previousTempHp: 3,
					newTempHp: 7,
				},
			]);
		});

		it("preserves activeIndex and roundNumber", () => {
			const e = {
				combatants: [
					makeCombatant("A", { maxHp: 20, currentHp: 10 }),
					makeCombatant("B"),
				],
				activeIndex: 1,
				roundNumber: 5,
			};
			const { encounter } = successResult(e, "A", 5);
			expect(encounter.activeIndex).toBe(1);
			expect(encounter.roundNumber).toBe(5);
		});
	});

	describe("error cases", () => {
		it("returns error for nonexistent combatant", () => {
			const e = enc([makeCombatant("A", { maxHp: 20, currentHp: 10 })]);
			const result = setTempHp(e, combatantId("Z"), 5);
			expectDomainError(result, "combatant-not-found");
		});

		it("returns error when HP tracking is not enabled", () => {
			const e = enc([makeCombatant("A")]);
			const result = setTempHp(e, combatantId("A"), 5);
			expectDomainError(result, "no-hp-tracking");
		});

		it("rejects temp HP of 0", () => {
			const e = enc([makeCombatant("A", { maxHp: 20, currentHp: 10 })]);
			const result = setTempHp(e, combatantId("A"), 0);
			expectDomainError(result, "invalid-temp-hp");
		});

		it("rejects negative temp HP", () => {
			const e = enc([makeCombatant("A", { maxHp: 20, currentHp: 10 })]);
			const result = setTempHp(e, combatantId("A"), -3);
			expectDomainError(result, "invalid-temp-hp");
		});

		it("rejects non-integer temp HP", () => {
			const e = enc([makeCombatant("A", { maxHp: 20, currentHp: 10 })]);
			const result = setTempHp(e, combatantId("A"), 2.5);
			expectDomainError(result, "invalid-temp-hp");
		});
	});

	describe("edge cases", () => {
		it("does not affect other combatants", () => {
			const e = enc([
				makeCombatant("A", { maxHp: 20, currentHp: 15 }),
				makeCombatant("B", { maxHp: 30, currentHp: 25, tempHp: 4 }),
			]);
			const { encounter } = successResult(e, "A", 5);
			expect(encounter.combatants[1].tempHp).toBe(4);
		});

		it("does not affect currentHp or maxHp", () => {
			const e = enc([makeCombatant("A", { maxHp: 20, currentHp: 15 })]);
			const { encounter } = successResult(e, "A", 8);
			expect(encounter.combatants[0].maxHp).toBe(20);
			expect(encounter.combatants[0].currentHp).toBe(15);
		});

		it("event reflects no change when existing value equals new value", () => {
			const e = enc([
				makeCombatant("A", { maxHp: 20, currentHp: 10, tempHp: 5 }),
			]);
			const { events } = successResult(e, "A", 5);
			expect(events).toEqual([
				{
					type: "TempHpSet",
					combatantId: combatantId("A"),
					previousTempHp: 5,
					newTempHp: 5,
				},
			]);
		});
	});
});