story-kit: accept 145_story_persist_chat_history_to_localstorage_across_rebuilds

frontend/src/hooks/useChatHistory.test.ts

@@ -0,0 +1,146 @@
+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();
+	});
+});

frontend/src/hooks/useChatHistory.ts

@@ -0,0 +1,67 @@
+import { useCallback, useEffect, useRef, useState } from "react";
+import type { Message } from "../types";
+
+const STORAGE_KEY_PREFIX = "storykit-chat-history:";
+
+function storageKey(projectPath: string): string {
+	return `${STORAGE_KEY_PREFIX}${projectPath}`;
+}
+
+function loadMessages(projectPath: string): Message[] {
+	try {
+		const raw = localStorage.getItem(storageKey(projectPath));
+		if (!raw) return [];
+		const parsed: unknown = JSON.parse(raw);
+		if (!Array.isArray(parsed)) return [];
+		return parsed as Message[];
+	} catch {
+		return [];
+	}
+}
+
+function saveMessages(projectPath: string, messages: Message[]): void {
+	try {
+		if (messages.length === 0) {
+			localStorage.removeItem(storageKey(projectPath));
+		} else {
+			localStorage.setItem(storageKey(projectPath), JSON.stringify(messages));
+		}
+	} catch (e) {
+		console.warn("Failed to persist chat history to localStorage:", e);
+	}
+}
+
+export function useChatHistory(projectPath: string) {
+	const [messages, setMessagesState] = useState<Message[]>(() =>
+		loadMessages(projectPath),
+	);
+	const projectPathRef = useRef(projectPath);
+
+	// Keep the ref in sync so the effect closure always has the latest path.
+	projectPathRef.current = projectPath;
+
+	// Persist whenever messages change.
+	useEffect(() => {
+		saveMessages(projectPathRef.current, messages);
+	}, [messages]);
+
+	const setMessages = useCallback(
+		(update: Message[] | ((prev: Message[]) => Message[])) => {
+			setMessagesState(update);
+		},
+		[],
+	);
+
+	const clearMessages = useCallback(() => {
+		setMessagesState([]);
+		// Eagerly remove from storage so clearSession doesn't depend on the
+		// effect firing before the component unmounts or re-renders.
+		try {
+			localStorage.removeItem(storageKey(projectPathRef.current));
+		} catch {
+			// Ignore — quota or security errors.
+		}
+	}, []);
+
+	return { messages, setMessages, clearMessages } as const;
+}