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

import { describe, expect, it } from "vitest";
import type { HpRange, HpVariant } from "../hp-range.js";
import { setHpVariant } from "../set-hp-variant.js";
import type { Combatant, Encounter } from "../types.js";
import { combatantId, isDomainError } from "../types.js";
import { expectDomainError } from "./test-helpers.js";

// A 3d6 + 6 creature: 9 / 16 / 24.
const RANGE: HpRange = { min: 9, average: 16, max: 24 };

function makeCombatant(opts?: Partial<Combatant>): Combatant {
	return {
		id: combatantId("c-1"),
		name: "Ogre",
		maxHp: 16,
		currentHp: 16,
		...opts,
	};
}

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

function apply(
	encounter: Encounter,
	variant: HpVariant | undefined,
	range: HpRange = RANGE,
) {
	const result = setHpVariant(encounter, combatantId("c-1"), variant, range);
	if (isDomainError(result)) {
		throw new Error(`Expected success, got error: ${result.message}`);
	}
	return result;
}

describe("setHpVariant", () => {
	describe("acceptance scenarios", () => {
		it("average → max raises maxHp and currentHp to the maximum roll", () => {
			const { encounter } = apply(enc([makeCombatant()]), "max");
			const c = encounter.combatants[0];
			expect(c.maxHp).toBe(24);
			expect(c.currentHp).toBe(24);
			expect(c.hpVariant).toBe("max");
		});

		it("average → min lowers maxHp and currentHp to the minimum roll", () => {
			const { encounter } = apply(enc([makeCombatant()]), "min");
			const c = encounter.combatants[0];
			expect(c.maxHp).toBe(9);
			expect(c.currentHp).toBe(9);
			expect(c.hpVariant).toBe("min");
		});

		it("max → average restores the printed average", () => {
			const start = enc([
				makeCombatant({ maxHp: 24, currentHp: 24, hpVariant: "max" }),
			]);
			const { encounter } = apply(start, undefined);
			const c = encounter.combatants[0];
			expect(c.maxHp).toBe(16);
			expect(c.currentHp).toBe(16);
			expect(c.hpVariant).toBeUndefined();
		});

		it("min → max spans the full range in one step", () => {
			const start = enc([
				makeCombatant({ maxHp: 9, currentHp: 9, hpVariant: "min" }),
			]);
			const { encounter } = apply(start, "max");
			expect(encounter.combatants[0].maxHp).toBe(24);
		});
	});

	describe("damage already taken", () => {
		it("keeps the amount of damage taken when raising max HP", () => {
			// 5 damage taken: 11/16 → 19/24
			const start = enc([makeCombatant({ maxHp: 16, currentHp: 11 })]);
			const { encounter } = apply(start, "max");
			const c = encounter.combatants[0];
			expect(c.maxHp).toBe(24);
			expect(c.currentHp).toBe(19);
		});

		it("floors currentHp at 0 when lowering max HP past the damage taken", () => {
			const start = enc([makeCombatant({ maxHp: 16, currentHp: 3 })]);
			const { encounter } = apply(start, "min");
			const c = encounter.combatants[0];
			expect(c.maxHp).toBe(9);
			expect(c.currentHp).toBe(0);
		});

		it("clamps currentHp to the new maxHp", () => {
			const start = enc([makeCombatant({ maxHp: 100, currentHp: 100 })]);
			const { encounter } = apply(start, "min");
			const c = encounter.combatants[0];
			expect(c.maxHp).toBe(93);
			expect(c.currentHp).toBe(93);
		});
	});

	describe("edge cases", () => {
		it("preserves a manual max HP edit as an offset", () => {
			// User bumped the ogre to 20 HP; max is 8 above average.
			const start = enc([makeCombatant({ maxHp: 20, currentHp: 20 })]);
			const { encounter } = apply(start, "max");
			expect(encounter.combatants[0].maxHp).toBe(28);
		});

		it("never lets maxHp drop below 1", () => {
			const start = enc([makeCombatant({ maxHp: 2, currentHp: 2 })]);
			const { encounter } = apply(start, "min");
			expect(encounter.combatants[0].maxHp).toBe(1);
		});

		it("leaves a combatant without HP untouched but records the variant", () => {
			const start = enc([
				makeCombatant({ maxHp: undefined, currentHp: undefined }),
			]);
			const { encounter } = apply(start, "max");
			const c = encounter.combatants[0];
			expect(c.maxHp).toBeUndefined();
			expect(c.currentHp).toBeUndefined();
			expect(c.hpVariant).toBe("max");
		});

		it("is a no-op when the variant is already active", () => {
			const start = enc([
				makeCombatant({ maxHp: 24, currentHp: 20, hpVariant: "max" }),
			]);
			const { encounter, events } = apply(start, "max");
			expect(encounter.combatants[0].currentHp).toBe(20);
			expect(events).toEqual([]);
		});

		it("returns a domain error for an unknown combatant", () => {
			const result = setHpVariant(
				enc([makeCombatant()]),
				combatantId("c-99"),
				"max",
				RANGE,
			);
			expectDomainError(result, "combatant-not-found");
		});
	});

	it("emits an HpVariantSet event carrying the HP change", () => {
		const { events } = apply(enc([makeCombatant()]), "max");
		expect(events).toEqual([
			{
				type: "HpVariantSet",
				combatantId: combatantId("c-1"),
				variant: "max",
				previousMaxHp: 16,
				newMaxHp: 24,
			},
		]);
	});
});