import { describe, it, expect } from "vitest";
import { maybeRejectEarlyStreamError } from "../../open-sse/utils/streamErrorPeek.js";

const encoder = new TextEncoder();
const sseResp = (lines) =>
	new Response(
		new ReadableStream({
			start(c) {
				for (const l of lines) c.enqueue(encoder.encode(l));
				c.close();
			},
		}),
		{ status: 200, headers: { "content-type": "text/event-stream" } },
	);

describe("maybeRejectEarlyStreamError", () => {
	it("returns 502 when a pattern matches early stream text", async () => {
		const res = await maybeRejectEarlyStreamError(
			sseResp([
				'{"type":"start"}\n{"type":"error","error":{"type":"server_error","message":"Network connection lost."}}\n',
			]),
			["server_error"],
		);
		expect(res.status).toBe(502);
		const body = await res.json();
		expect(body.error.message).toContain("server_error");
	});

	it("passes the stream through unchanged when nothing matches", async () => {
		const res = await maybeRejectEarlyStreamError(
			sseResp([
				'data: {"choices":[{"delta":{"content":"hello"},"finish_reason":null}]}\n\ndata: [DONE]\n\n',
			]),
			["server_error"],
		);
		expect(res.status).toBe(200);
		const text = await res.text();
		expect(text).toContain("hello");
		expect(text).toContain("[DONE]");
	});

	it("commits on timeout without hanging", async () => {
		const stalled = new Response(new ReadableStream({ start() {} }), {
			status: 200,
		});
		const res = await maybeRejectEarlyStreamError(stalled, ["x"], {
			timeoutMs: 50,
		});
		expect(res.status).toBe(200);
		await res.body.cancel();
	});

	it("commits on abort without hanging", async () => {
		const ctrl = new AbortController();
		const stalled = new Response(new ReadableStream({ start() {} }), {
			status: 200,
		});
		setTimeout(() => ctrl.abort(new Error("gone")), 10);
		const res = await maybeRejectEarlyStreamError(stalled, ["x"], {
			signal: ctrl.signal,
			timeoutMs: 2000,
		});
		expect(res.status).toBe(200);
		await res.body.cancel();
	});

	it("commits (passthrough) when patterns are empty", async () => {
		const res = await maybeRejectEarlyStreamError(
			sseResp(["data: hi\n\n"]),
			[],
		);
		expect(res.status).toBe(200);
		expect(await res.text()).toBe("data: hi\n\n");
	});

	it("multi-byte UTF-8 split across peek boundary round-trips losslessly", async () => {
		// "café" split mid-é: the peek consumes bytes up to and including 0xC3
		// (the first half of é); the re-emitted stream must contain the RAW bytes
		// (never a re-encoded decoded string — TextDecoder flush would replace the
		// lone 0xC3 with U+FFFD and corrupt the output).
		const bytes = [
			0x64, 0x61, 0x74, 0x61, 0x3a, 0x20, 0x22, 0x63, 0x61, 0x66, 0xc3,
		];
		const rest = new Uint8Array([0xa9, 0x22, 0x0a, 0x0a]);
		const body = new ReadableStream({
			start(c) {
				c.enqueue(new Uint8Array(bytes));
				c.enqueue(rest);
				c.close();
			},
		});
		const res = await maybeRejectEarlyStreamError(
			new Response(body, { status: 200 }),
			["nomatch"],
			{ maxBytes: 11 },
		);
		expect(await res.text()).toBe('data: "café"\n\n');
	});
});