/**
 * Unit tests for the CommandCode executor early-error peek.
 *
 * The upstream emits AI SDK v5 NDJSON over an HTTP 200 stream, so a terminal
 * `{"type":"error"}` event is invisible to the normal `response.ok` success
 * check. `peekForUpstreamError` reads the first events before committing the
 * response: an error event → non-ok Response (fallback can kick in); otherwise
 * the buffered bytes are re-emitted and streaming proceeds as before.
 */
import { describe, it, expect } from "vitest";
import { peekForUpstreamError } from "../../open-sse/executors/commandcode.js";

const encoder = new TextEncoder();

function ndjsonResponse(lines) {
	const body = new ReadableStream({
		start(controller) {
			for (const line of lines) controller.enqueue(encoder.encode(line + "\n"));
			controller.close();
		},
	});
	return new Response(body, {
		status: 200,
		headers: { "content-type": "text/event-stream" },
	});
}

describe("commandcode executor — early-error peek", () => {
	it("returns 502 when the first meaningful event is an error", async () => {
		const res = await peekForUpstreamError(
			ndjsonResponse([
				'{"type":"error","error":{"type":"server_error","message":"Network connection lost."}}',
			]),
			"model",
		);
		expect(res.status).toBe(502);
		const body = await res.json();
		expect(body.error.message).toBe("Network connection lost.");
		expect(body.error.type).toBe("server_error");
	});

	it("detects an error event even when metadata events arrive first", async () => {
		const res = await peekForUpstreamError(
			ndjsonResponse([
				'{"type":"start"}',
				'{"type":"start-step"}',
				'{"type":"error","error":{"type":"server_error","message":"Network connection lost."}}',
			]),
			"model",
		);
		expect(res.status).toBe(502);
		const body = await res.json();
		expect(body.error.message).toContain("Network connection lost");
	});

	it("commits and streams normally when the first meaningful event is content", async () => {
		const res = await peekForUpstreamError(
			ndjsonResponse([
				'{"type":"start"}',
				'{"type":"text-delta","text":"hi there"}',
				'{"type":"finish"}',
			]),
			"model",
		);
		expect(res.status).toBe(200);
		const text = await res.text();
		expect(text).toContain('"content":"hi there"');
		expect(text).not.toContain("[CommandCode error:");
	});

	it("commits when the stream ends without any event", async () => {
		const res = await peekForUpstreamError(ndjsonResponse([]), "model");
		expect(res.status).toBe(200);
		await res.body.cancel();
	});

	it("commits (does not hang) when no event arrives before the peek timeout", async () => {
		const stalled = new Response(new ReadableStream({ start() {} }), {
			status: 200,
			headers: { "content-type": "text/event-stream" },
		});
		const res = await peekForUpstreamError(stalled, "model", { timeoutMs: 50 });
		expect(res.status).toBe(200);
		await res.body.cancel();
	});

	it("does not hang when the request signal aborts during the peek", async () => {
		const controller = new AbortController();
		const stalled = new Response(new ReadableStream({ start() {} }), {
			status: 200,
			headers: { "content-type": "text/event-stream" },
		});
		setTimeout(() => controller.abort(new Error("client gone")), 10);
		const res = await peekForUpstreamError(stalled, "model", {
			signal: controller.signal,
			timeoutMs: 2000,
		});
		expect(res.status).toBe(200);
		await res.body.cancel();
	});

	it("re-emits raw bytes so a multi-byte char split across the peek boundary survives", async () => {
		// chunk1 ends mid-é (0xC3); the peek commits on the first complete line
		// (text-delta "hi") while the decoder still holds 0xC3. Re-emission must
		// use RAW bytes — re-encoding decoded text would replace 0xC3 with U+FFFD.
		const first = Buffer.from(
			'{"type":"text-delta","text":"hi"}\n{"type":"text-delta","text":"caf',
		);
		const chunk1 = new Uint8Array([...first, 0xc3]);
		const rest = new Uint8Array([0xa9, 0x22, 0x7d, 0x0a]); // é"}\n
		const body = new ReadableStream({
			start(c) {
				c.enqueue(chunk1);
				c.enqueue(rest);
				c.close();
			},
		});
		const res = await peekForUpstreamError(
			new Response(body, { status: 200 }),
			"m",
		);
		const text = await res.text();
		expect(text).toContain("café");
		expect(text).not.toContain("\uFFFD");
	});
});