initiative/packages/application/src/__tests__/roll-initiative-use-case.test.ts

import {
	type Creature,
	type CreatureId,
	combatantId,
	createEncounter,
	creatureId,
	isDomainError,
} from "@initiative/domain";
import { describe, expect, it } from "vitest";
import { addCombatantUseCase } from "../add-combatant-use-case.js";
import { rollInitiativeUseCase } from "../roll-initiative-use-case.js";
import { expectError, requireSaved, stubEncounterStore } from "./helpers.js";

const GOBLIN_ID = creatureId("goblin");

function makeCreature(overrides?: Partial<Creature>): Creature {
	return {
		id: GOBLIN_ID,
		name: "Goblin",
		source: "mm",
		sourceDisplayName: "Monster Manual",
		size: "Small",
		type: "humanoid",
		alignment: "neutral evil",
		ac: 15,
		hp: { average: 7, formula: "2d6" },
		speed: "30 ft.",
		abilities: { str: 8, dex: 14, con: 10, int: 10, wis: 8, cha: 8 },
		cr: "1/4",
		initiativeProficiency: 0,
		proficiencyBonus: 2,
		passive: 9,
		...overrides,
	};
}

function encounterWithCreatureLink(name: string, creature: CreatureId) {
	const enc = createEncounter([]);
	if (isDomainError(enc)) throw new Error("Setup failed");
	const id = combatantId(name);
	const store = stubEncounterStore(enc);
	addCombatantUseCase(store, id, name);
	const saved = requireSaved(store.saved);
	const result = createEncounter(
		saved.combatants.map((c) =>
			c.id === id ? { ...c, creatureId: creature } : c,
		),
		saved.activeIndex,
		saved.roundNumber,
	);
	if (isDomainError(result)) throw new Error("Setup failed");
	return result;
}

describe("rollInitiativeUseCase", () => {
	it("returns domain error when combatant not found", () => {
		const enc = createEncounter([]);
		if (isDomainError(enc)) throw new Error("Setup failed");
		const store = stubEncounterStore(enc);

		const result = rollInitiativeUseCase(
			store,
			combatantId("unknown"),
			10,
			() => undefined,
		);

		expectError(result);
		expect(result.code).toBe("combatant-not-found");
		expect(store.saved).toBeNull();
	});

	it("returns domain error when combatant has no creature link", () => {
		const enc = createEncounter([]);
		if (isDomainError(enc)) throw new Error("Setup failed");
		const store1 = stubEncounterStore(enc);
		addCombatantUseCase(store1, combatantId("Fighter"), "Fighter");

		const store = stubEncounterStore(requireSaved(store1.saved));
		const result = rollInitiativeUseCase(
			store,
			combatantId("Fighter"),
			10,
			() => undefined,
		);

		expectError(result);
		expect(result.code).toBe("no-creature-link");
		expect(store.saved).toBeNull();
	});

	it("returns domain error when creature not found in getter", () => {
		const enc = encounterWithCreatureLink("Goblin", GOBLIN_ID);
		const store = stubEncounterStore(enc);

		const result = rollInitiativeUseCase(
			store,
			combatantId("Goblin"),
			10,
			() => undefined,
		);

		expectError(result);
		expect(result.code).toBe("creature-not-found");
		expect(store.saved).toBeNull();
	});

	it("calculates initiative from creature and saves", () => {
		const creature = makeCreature();
		const enc = encounterWithCreatureLink("Goblin", GOBLIN_ID);
		const store = stubEncounterStore(enc);

		// Dex 14 -> modifier +2, CR 1/4 -> PB 2, initiativeProficiency 0
		// So initiative modifier = 2 + 0*2 = 2
		// Roll 10 + modifier 2 = 12
		const result = rollInitiativeUseCase(
			store,
			combatantId("Goblin"),
			10,
			(id) => (id === GOBLIN_ID ? creature : undefined),
		);

		expect(isDomainError(result)).toBe(false);
		expect(requireSaved(store.saved).combatants[0].initiative).toBe(12);
	});

	it("applies initiative proficiency bonus correctly", () => {
		// CR 5 -> PB 3, dex 16 -> mod +3, initiativeProficiency 1
		// modifier = 3 + 1*3 = 6, roll 8 + 6 = 14
		const creature = makeCreature({
			abilities: {
				str: 10,
				dex: 16,
				con: 10,
				int: 10,
				wis: 10,
				cha: 10,
			},
			cr: "5",
			initiativeProficiency: 1,
		});
		const enc = encounterWithCreatureLink("Monster", GOBLIN_ID);
		const store = stubEncounterStore(enc);

		const result = rollInitiativeUseCase(
			store,
			combatantId("Monster"),
			8,
			(id) => (id === GOBLIN_ID ? creature : undefined),
		);

		expect(isDomainError(result)).toBe(false);
		expect(requireSaved(store.saved).combatants[0].initiative).toBe(14);
	});
});