co-mono/packages/agent/test/agent.test.ts

import { type AssistantMessage, type AssistantMessageEvent, EventStream, getModel } from "@mariozechner/pi-ai";
import { describe, expect, it } from "vitest";
import { Agent } from "../src/index.js";

// Mock stream that mimics AssistantMessageEventStream
class MockAssistantStream extends EventStream<AssistantMessageEvent, AssistantMessage> {
	constructor() {
		super(
			(event) => event.type === "done" || event.type === "error",
			(event) => {
				if (event.type === "done") return event.message;
				if (event.type === "error") return event.error;
				throw new Error("Unexpected event type");
			},
		);
	}
}

function createAssistantMessage(text: string): AssistantMessage {
	return {
		role: "assistant",
		content: [{ type: "text", text }],
		api: "openai-responses",
		provider: "openai",
		model: "mock",
		usage: {
			input: 0,
			output: 0,
			cacheRead: 0,
			cacheWrite: 0,
			totalTokens: 0,
			cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0, total: 0 },
		},
		stopReason: "stop",
		timestamp: Date.now(),
	};
}

describe("Agent", () => {
	it("should create an agent instance with default state", () => {
		const agent = new Agent();

		expect(agent.state).toBeDefined();
		expect(agent.state.systemPrompt).toBe("");
		expect(agent.state.model).toBeDefined();
		expect(agent.state.thinkingLevel).toBe("off");
		expect(agent.state.tools).toEqual([]);
		expect(agent.state.messages).toEqual([]);
		expect(agent.state.isStreaming).toBe(false);
		expect(agent.state.streamMessage).toBe(null);
		expect(agent.state.pendingToolCalls).toEqual(new Set());
		expect(agent.state.error).toBeUndefined();
	});

	it("should create an agent instance with custom initial state", () => {
		const customModel = getModel("openai", "gpt-4o-mini");
		const agent = new Agent({
			initialState: {
				systemPrompt: "You are a helpful assistant.",
				model: customModel,
				thinkingLevel: "low",
			},
		});

		expect(agent.state.systemPrompt).toBe("You are a helpful assistant.");
		expect(agent.state.model).toBe(customModel);
		expect(agent.state.thinkingLevel).toBe("low");
	});

	it("should subscribe to events", () => {
		const agent = new Agent();

		let eventCount = 0;
		const unsubscribe = agent.subscribe((_event) => {
			eventCount++;
		});

		// No initial event on subscribe
		expect(eventCount).toBe(0);

		// State mutators don't emit events
		agent.setSystemPrompt("Test prompt");
		expect(eventCount).toBe(0);
		expect(agent.state.systemPrompt).toBe("Test prompt");

		// Unsubscribe should work
		unsubscribe();
		agent.setSystemPrompt("Another prompt");
		expect(eventCount).toBe(0); // Should not increase
	});

	it("should update state with mutators", () => {
		const agent = new Agent();

		// Test setSystemPrompt
		agent.setSystemPrompt("Custom prompt");
		expect(agent.state.systemPrompt).toBe("Custom prompt");

		// Test setModel
		const newModel = getModel("google", "gemini-2.5-flash");
		agent.setModel(newModel);
		expect(agent.state.model).toBe(newModel);

		// Test setThinkingLevel
		agent.setThinkingLevel("high");
		expect(agent.state.thinkingLevel).toBe("high");

		// Test setTools
		const tools = [{ name: "test", description: "test tool" } as any];
		agent.setTools(tools);
		expect(agent.state.tools).toBe(tools);

		// Test replaceMessages
		const messages = [{ role: "user" as const, content: "Hello", timestamp: Date.now() }];
		agent.replaceMessages(messages);
		expect(agent.state.messages).toEqual(messages);
		expect(agent.state.messages).not.toBe(messages); // Should be a copy

		// Test appendMessage
		const newMessage = { role: "assistant" as const, content: [{ type: "text" as const, text: "Hi" }] };
		agent.appendMessage(newMessage as any);
		expect(agent.state.messages).toHaveLength(2);
		expect(agent.state.messages[1]).toBe(newMessage);

		// Test clearMessages
		agent.clearMessages();
		expect(agent.state.messages).toEqual([]);
	});

	it("should support steering message queue", async () => {
		const agent = new Agent();

		const message = { role: "user" as const, content: "Steering message", timestamp: Date.now() };
		agent.steer(message);

		// The message is queued but not yet in state.messages
		expect(agent.state.messages).not.toContainEqual(message);
	});

	it("should support follow-up message queue", async () => {
		const agent = new Agent();

		const message = { role: "user" as const, content: "Follow-up message", timestamp: Date.now() };
		agent.followUp(message);

		// The message is queued but not yet in state.messages
		expect(agent.state.messages).not.toContainEqual(message);
	});

	it("should handle abort controller", () => {
		const agent = new Agent();

		// Should not throw even if nothing is running
		expect(() => agent.abort()).not.toThrow();
	});

	it("should throw when prompt() called while streaming", async () => {
		let abortSignal: AbortSignal | undefined;
		const agent = new Agent({
			// Use a stream function that responds to abort
			streamFn: (_model, _context, options) => {
				abortSignal = options?.signal;
				const stream = new MockAssistantStream();
				queueMicrotask(() => {
					stream.push({ type: "start", partial: createAssistantMessage("") });
					// Check abort signal periodically
					const checkAbort = () => {
						if (abortSignal?.aborted) {
							stream.push({ type: "error", reason: "aborted", error: createAssistantMessage("Aborted") });
						} else {
							setTimeout(checkAbort, 5);
						}
					};
					checkAbort();
				});
				return stream;
			},
		});

		// Start first prompt (don't await, it will block until abort)
		const firstPrompt = agent.prompt("First message");

		// Wait a tick for isStreaming to be set
		await new Promise((resolve) => setTimeout(resolve, 10));
		expect(agent.state.isStreaming).toBe(true);

		// Second prompt should reject
		await expect(agent.prompt("Second message")).rejects.toThrow(
			"Agent is already processing a prompt. Use steer() or followUp() to queue messages, or wait for completion.",
		);

		// Cleanup - abort to stop the stream
		agent.abort();
		await firstPrompt.catch(() => {}); // Ignore abort error
	});

	it("should throw when continue() called while streaming", async () => {
		let abortSignal: AbortSignal | undefined;
		const agent = new Agent({
			streamFn: (_model, _context, options) => {
				abortSignal = options?.signal;
				const stream = new MockAssistantStream();
				queueMicrotask(() => {
					stream.push({ type: "start", partial: createAssistantMessage("") });
					const checkAbort = () => {
						if (abortSignal?.aborted) {
							stream.push({ type: "error", reason: "aborted", error: createAssistantMessage("Aborted") });
						} else {
							setTimeout(checkAbort, 5);
						}
					};
					checkAbort();
				});
				return stream;
			},
		});

		// Start first prompt
		const firstPrompt = agent.prompt("First message");
		await new Promise((resolve) => setTimeout(resolve, 10));
		expect(agent.state.isStreaming).toBe(true);

		// continue() should reject
		await expect(agent.continue()).rejects.toThrow(
			"Agent is already processing. Wait for completion before continuing.",
		);

		// Cleanup
		agent.abort();
		await firstPrompt.catch(() => {});
	});
});