story-kit: create 174_story_matrix_chatbot_interface_for_story_kit

frontend/src/hooks/useChatHistory.test.ts

@@ -5,12 +5,20 @@ import { useChatHistory } from "./useChatHistory";
 
 const PROJECT = "/tmp/test-project";
 const STORAGE_KEY = `storykit-chat-history:${PROJECT}`;
+const LIMIT_KEY = `storykit-chat-history-limit:${PROJECT}`;
 
 const sampleMessages: Message[] = [
 	{ role: "user", content: "Hello" },
 	{ role: "assistant", content: "Hi there!" },
 ];
 
+function makeMessages(count: number): Message[] {
+	return Array.from({ length: count }, (_, i) => ({
+		role: "user" as const,
+		content: `Message ${i + 1}`,
+	}));
+}
+
 describe("useChatHistory", () => {
 	beforeEach(() => {
 		localStorage.clear();
@@ -143,4 +151,125 @@ describe("useChatHistory", () => {
 
 		expect(localStorage.getItem(STORAGE_KEY)).toBeNull();
 	});
+
+	// --- Story 179: Chat history pruning tests ---
+
+	it("S179: default limit of 200 is applied when saving to localStorage", () => {
+		const { result } = renderHook(() => useChatHistory(PROJECT));
+
+		expect(result.current.maxMessages).toBe(200);
+	});
+
+	it("S179: messages are pruned from the front when exceeding the limit", () => {
+		// Set a small limit to make testing practical
+		localStorage.setItem(LIMIT_KEY, "3");
+
+		const { result } = renderHook(() => useChatHistory(PROJECT));
+		const fiveMessages = makeMessages(5);
+
+		act(() => {
+			result.current.setMessages(fiveMessages);
+		});
+
+		// localStorage should contain only the last 3 messages
+		const stored: Message[] = JSON.parse(
+			localStorage.getItem(STORAGE_KEY) ?? "[]",
+		);
+		expect(stored).toEqual(fiveMessages.slice(-3));
+		expect(stored).toHaveLength(3);
+		expect(stored[0].content).toBe("Message 3");
+	});
+
+	it("S179: messages under the limit are not pruned", () => {
+		localStorage.setItem(LIMIT_KEY, "10");
+
+		const { result } = renderHook(() => useChatHistory(PROJECT));
+		const threeMessages = makeMessages(3);
+
+		act(() => {
+			result.current.setMessages(threeMessages);
+		});
+
+		const stored: Message[] = JSON.parse(
+			localStorage.getItem(STORAGE_KEY) ?? "[]",
+		);
+		expect(stored).toEqual(threeMessages);
+		expect(stored).toHaveLength(3);
+	});
+
+	it("S179: limit is configurable via localStorage key", () => {
+		localStorage.setItem(LIMIT_KEY, "5");
+
+		const { result } = renderHook(() => useChatHistory(PROJECT));
+
+		expect(result.current.maxMessages).toBe(5);
+	});
+
+	it("S179: setMaxMessages updates the limit and persists it", () => {
+		const { result } = renderHook(() => useChatHistory(PROJECT));
+
+		act(() => {
+			result.current.setMaxMessages(50);
+		});
+
+		expect(result.current.maxMessages).toBe(50);
+		expect(localStorage.getItem(LIMIT_KEY)).toBe("50");
+	});
+
+	it("S179: a limit of 0 means unlimited (no pruning)", () => {
+		localStorage.setItem(LIMIT_KEY, "0");
+
+		const { result } = renderHook(() => useChatHistory(PROJECT));
+		const manyMessages = makeMessages(500);
+
+		act(() => {
+			result.current.setMessages(manyMessages);
+		});
+
+		const stored: Message[] = JSON.parse(
+			localStorage.getItem(STORAGE_KEY) ?? "[]",
+		);
+		expect(stored).toHaveLength(500);
+		expect(stored).toEqual(manyMessages);
+	});
+
+	it("S179: changing the limit re-prunes messages on next save", () => {
+		const { result } = renderHook(() => useChatHistory(PROJECT));
+		const tenMessages = makeMessages(10);
+
+		act(() => {
+			result.current.setMessages(tenMessages);
+		});
+
+		// All 10 saved (default limit 200 > 10)
+		let stored: Message[] = JSON.parse(
+			localStorage.getItem(STORAGE_KEY) ?? "[]",
+		);
+		expect(stored).toHaveLength(10);
+
+		// Now lower the limit — the effect re-runs and prunes
+		act(() => {
+			result.current.setMaxMessages(3);
+		});
+
+		stored = JSON.parse(localStorage.getItem(STORAGE_KEY) ?? "[]");
+		expect(stored).toHaveLength(3);
+		expect(stored[0].content).toBe("Message 8");
+	});
+
+	it("S179: invalid limit in localStorage falls back to default", () => {
+		localStorage.setItem(LIMIT_KEY, "not-a-number");
+
+		const { result } = renderHook(() => useChatHistory(PROJECT));
+
+		expect(result.current.maxMessages).toBe(200);
+	});
+
+	it("S179: negative limit in localStorage falls back to default", () => {
+		localStorage.setItem(LIMIT_KEY, "-5");
+
+		const { result } = renderHook(() => useChatHistory(PROJECT));
+
+		expect(result.current.maxMessages).toBe(200);
+	});
 });