huskies/frontend/src/hooks/useChatHistory.test.ts

import { act, renderHook } from "@testing-library/react";
import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
import type { Message } from "../types";
import { useChatHistory } from "./useChatHistory";

const PROJECT = "/tmp/test-project";
const STORAGE_KEY = `storykit-chat-history:${PROJECT}`;

const sampleMessages: Message[] = [
	{ role: "user", content: "Hello" },
	{ role: "assistant", content: "Hi there!" },
];

describe("useChatHistory", () => {
	beforeEach(() => {
		localStorage.clear();
	});

	afterEach(() => {
		localStorage.clear();
	});

	it("AC1: restores messages from localStorage on mount", () => {
		localStorage.setItem(STORAGE_KEY, JSON.stringify(sampleMessages));

		const { result } = renderHook(() => useChatHistory(PROJECT));

		expect(result.current.messages).toEqual(sampleMessages);
	});

	it("AC1: returns empty array when localStorage has no data", () => {
		const { result } = renderHook(() => useChatHistory(PROJECT));

		expect(result.current.messages).toEqual([]);
	});

	it("AC1: returns empty array when localStorage contains invalid JSON", () => {
		localStorage.setItem(STORAGE_KEY, "not-json{{{");

		const { result } = renderHook(() => useChatHistory(PROJECT));

		expect(result.current.messages).toEqual([]);
	});

	it("AC1: returns empty array when localStorage contains a non-array", () => {
		localStorage.setItem(STORAGE_KEY, JSON.stringify({ not: "array" }));

		const { result } = renderHook(() => useChatHistory(PROJECT));

		expect(result.current.messages).toEqual([]);
	});

	it("AC2: saves messages to localStorage when setMessages is called with an array", () => {
		const { result } = renderHook(() => useChatHistory(PROJECT));

		act(() => {
			result.current.setMessages(sampleMessages);
		});

		const stored = JSON.parse(localStorage.getItem(STORAGE_KEY) ?? "[]");
		expect(stored).toEqual(sampleMessages);
	});

	it("AC2: saves messages to localStorage when setMessages is called with updater function", () => {
		const { result } = renderHook(() => useChatHistory(PROJECT));

		act(() => {
			result.current.setMessages(() => sampleMessages);
		});

		const stored = JSON.parse(localStorage.getItem(STORAGE_KEY) ?? "[]");
		expect(stored).toEqual(sampleMessages);
	});

	it("AC3: clearMessages removes messages from state and localStorage", () => {
		localStorage.setItem(STORAGE_KEY, JSON.stringify(sampleMessages));

		const { result } = renderHook(() => useChatHistory(PROJECT));

		expect(result.current.messages).toEqual(sampleMessages);

		act(() => {
			result.current.clearMessages();
		});

		expect(result.current.messages).toEqual([]);
		expect(localStorage.getItem(STORAGE_KEY)).toBeNull();
	});

	it("AC4: handles localStorage quota errors gracefully", () => {
		const warnSpy = vi.spyOn(console, "warn").mockImplementation(() => {});
		const setItemSpy = vi
			.spyOn(Storage.prototype, "setItem")
			.mockImplementation(() => {
				throw new DOMException("QuotaExceededError");
			});

		const { result } = renderHook(() => useChatHistory(PROJECT));

		// Should not throw
		act(() => {
			result.current.setMessages(sampleMessages);
		});

		// State should still update even though storage failed
		expect(result.current.messages).toEqual(sampleMessages);
		expect(warnSpy).toHaveBeenCalledWith(
			"Failed to persist chat history to localStorage:",
			expect.any(DOMException),
		);

		warnSpy.mockRestore();
		setItemSpy.mockRestore();
	});

	it("AC5: scopes storage key to project path", () => {
		const projectA = "/projects/a";
		const projectB = "/projects/b";
		const keyA = `storykit-chat-history:${projectA}`;
		const keyB = `storykit-chat-history:${projectB}`;

		const messagesA: Message[] = [{ role: "user", content: "From project A" }];
		const messagesB: Message[] = [{ role: "user", content: "From project B" }];

		localStorage.setItem(keyA, JSON.stringify(messagesA));
		localStorage.setItem(keyB, JSON.stringify(messagesB));

		const { result: resultA } = renderHook(() => useChatHistory(projectA));
		const { result: resultB } = renderHook(() => useChatHistory(projectB));

		expect(resultA.current.messages).toEqual(messagesA);
		expect(resultB.current.messages).toEqual(messagesB);
	});

	it("AC2: removes localStorage key when messages are set to empty array", () => {
		localStorage.setItem(STORAGE_KEY, JSON.stringify(sampleMessages));

		const { result } = renderHook(() => useChatHistory(PROJECT));

		act(() => {
			result.current.setMessages([]);
		});

		expect(localStorage.getItem(STORAGE_KEY)).toBeNull();
	});
});