import { afterEach, describe, expect, it, vi } from 'vitest';

import { streamPlainTextCompletion } from './llmClient';

function createSseResponse(body: string) {
  const encoder = new TextEncoder();
  const stream = new ReadableStream<Uint8Array>({
    start(controller) {
      controller.enqueue(encoder.encode(body));
      controller.close();
    },
  });

  return new Response(stream, {
    headers: {
      'Content-Type': 'text/event-stream; charset=utf-8',
    },
  });
}

describe('llmClient streamPlainTextCompletion', () => {
  afterEach(() => {
    vi.unstubAllGlobals();
    vi.restoreAllMocks();
  });

  it('reads OpenAI compatible SSE through the shared stream reader', async () => {
    const onUpdate = vi.fn();
    const fetchMock = vi.fn().mockResolvedValue(
      createSseResponse(
        [
          'data: {"choices":[{"delta":{"content":"溪上"}}]}\r\n\r\n',
          'data: not-json\r\n\r\n',
          'data: {"choices":[{"delta":{"content":"春风"}}]}\r\n\r\n',
          'data: [DONE]\r\n\r\n',
          'data: {"choices":[{"delta":{"content":"不应读取"}}]}\r\n\r\n',
        ].join(''),
      ),
    );
    vi.stubGlobal('fetch', fetchMock);

    const result = await streamPlainTextCompletion('system', 'user', {
      onUpdate,
    });

    expect(result).toBe('溪上春风');
    expect(onUpdate).toHaveBeenNthCalledWith(1, '溪上');
    expect(onUpdate).toHaveBeenNthCalledWith(2, '溪上春风');
    expect(onUpdate).toHaveBeenCalledTimes(2);
  });
});