import { createServer, type Server } from 'node:http';
import { afterEach, beforeEach, describe, expect, it } from 'vitest';
import { ChatBridgeService } from './chatBridgeService';

/** mock 上游：记录最近一次 /chat/completions 请求，按配置返回非流式或 SSE 流式 */
let upstream: Server;
let upstreamPort = 0;
let lastUpstream: { url: string | null; auth: string | null; extra: string | null; body: Record<string, unknown> | null };
let upstreamMode: 'json' | 'sse' | 'error' = 'json';

const SSE_BODY = [
  `data: ${JSON.stringify({ choices: [{ delta: { content: '你好' }, finish_reason: null }] })}`,
  '',
  `data: ${JSON.stringify({ choices: [{ delta: { content: '世界' }, finish_reason: null }] })}`,
  '',
  `data: ${JSON.stringify({ choices: [{ delta: {}, finish_reason: 'stop' }], usage: { prompt_tokens: 5, completion_tokens: 2, total_tokens: 7 } })}`,
  '',
  'data: [DONE]',
  '',
  '',
].join('\n');

beforeEach(async () => {
  upstreamMode = 'json';
  lastUpstream = { url: null, auth: null, extra: null, body: null };
  upstream = createServer((req, res) => {
    const chunks: Buffer[] = [];
    req.on('data', (chunk: Buffer) => chunks.push(chunk));
    req.on('end', () => {
      lastUpstream = {
        url: req.url ?? null,
        auth: req.headers.authorization ?? null,
        extra: (req.headers['x-extra'] as string) ?? null,
        body: JSON.parse(Buffer.concat(chunks).toString('utf8') || 'null'),
      };
      if (upstreamMode === 'error') {
        res.writeHead(500, { 'content-type': 'application/json' });
        res.end(JSON.stringify({ error: 'boom' }));
        return;
      }
      if (upstreamMode === 'sse') {
        res.writeHead(200, { 'content-type': 'text/event-stream' });
        res.end(SSE_BODY);
        return;
      }
      res.writeHead(200, { 'content-type': 'application/json' });
      res.end(
        JSON.stringify({
          id: 'chatcmpl-1',
          created: 1700000000,
          model: 'qwen',
          choices: [{ finish_reason: 'stop', message: { role: 'assistant', content: '非流式回复' } }],
          usage: { prompt_tokens: 3, completion_tokens: 4, total_tokens: 7 },
        }),
      );
    });
  });
  await new Promise<void>((resolve) => upstream.listen(0, '127.0.0.1', resolve));
  const address = upstream.address();
  upstreamPort = typeof address === 'object' && address ? address.port : 0;
});

afterEach(async () => {
  await new Promise<void>((resolve) => upstream.close(() => resolve()));
});

function makeBridge(): Promise<ChatBridgeService> {
  return Promise.resolve(new ChatBridgeService());
}

describe('ChatBridgeService', () => {
  it('非流式：请求翻译后转发上游，响应翻译回 Responses 形状，头原样透传', async () => {
    const bridge = await makeBridge();
    const info = await bridge.start({
      upstreamBaseUrl: `http://127.0.0.1:${upstreamPort}/v1`,
      headers: { 'X-Extra': 'yes' },
    });
    try {
      const response = await fetch(`${info.url}/responses`, {
        method: 'POST',
        headers: { 'content-type': 'application/json', authorization: 'Bearer sk-live' },
        body: JSON.stringify({
          model: 'qwen',
          instructions: '你是助手',
          input: '你好',
          max_output_tokens: 64,
        }),
      });
      expect(response.status).toBe(200);
      // 上游收到的是 chat 形状
      expect(lastUpstream.url).toBe('/v1/chat/completions');
      expect(lastUpstream.auth).toBe('Bearer sk-live');
      expect(lastUpstream.extra).toBe('yes');
      expect(lastUpstream.body).toMatchObject({
        model: 'qwen',
        max_tokens: 64,
        messages: [
          { role: 'developer', content: '你是助手' },
          { role: 'user', content: '你好' },
        ],
      });
      // 下游拿到的是 responses 形状
      const body = (await response.json()) as Record<string, unknown>;
      expect(body).toMatchObject({
        object: 'response',
        status: 'completed',
        usage: { input_tokens: 3, output_tokens: 4, total_tokens: 7 },
      });
      const output = body.output as Array<Record<string, unknown>>;
      expect((output[0].content as Array<{ text: string }>)[0].text).toBe('非流式回复');
    } finally {
      await bridge.stop();
    }
  });

  it('流式：上游 SSE 逐事件翻译下发，completed 带 usage', async () => {
    upstreamMode = 'sse';
    const bridge = await makeBridge();
    const info = await bridge.start({ upstreamBaseUrl: `http://127.0.0.1:${upstreamPort}/v1` });
    try {
      const response = await fetch(`${info.url}/responses`, {
        method: 'POST',
        headers: { 'content-type': 'application/json' },
        body: JSON.stringify({ model: 'qwen', input: '你好', stream: true }),
      });
      expect(response.status).toBe(200);
      expect(response.headers.get('content-type')).toContain('text/event-stream');
      const text = await response.text();
      const events = text
        .split('\n\n')
        .filter((block) => block.trim())
        .map((block) => {
          const eventMatch = block.match(/^event: (.+)$/mu);
          const dataMatch = block.match(/^data: (.+)$/mu);
          return { event: eventMatch?.[1], data: JSON.parse(dataMatch?.[1] ?? '{}') as Record<string, unknown> };
        });
      const types = events.map((item) => item.event);
      expect(types[0]).toBe('response.created');
      expect(types.at(-1)).toBe('response.completed');
      // 请求侧补了 include_usage
      expect(lastUpstream.body?.stream_options).toEqual({ include_usage: true });
      const deltas = events
        .filter((item) => item.event === 'response.output_text.delta')
        .map((item) => item.data.delta);
      expect(deltas.join('')).toBe('你好世界');
      const completed = events.at(-1)?.data.response as Record<string, unknown>;
      expect(completed.usage).toEqual({ input_tokens: 5, output_tokens: 2, total_tokens: 7 });
    } finally {
      await bridge.stop();
    }
  });

  it('上游非 2xx：状态码与错误体透回', async () => {
    upstreamMode = 'error';
    const bridge = await makeBridge();
    const info = await bridge.start({ upstreamBaseUrl: `http://127.0.0.1:${upstreamPort}/v1` });
    try {
      const response = await fetch(`${info.url}/responses`, {
        method: 'POST',
        headers: { 'content-type': 'application/json' },
        body: JSON.stringify({ model: 'qwen', input: 'x' }),
      });
      expect(response.status).toBe(500);
      const body = (await response.json()) as { error: { message: string } };
      expect(body.error.message).toContain('500');
    } finally {
      await bridge.stop();
    }
  });

  it('只接 POST /v1/responses；stop 后端口释放', async () => {
    const bridge = await makeBridge();
    const info = await bridge.start({ upstreamBaseUrl: `http://127.0.0.1:${upstreamPort}/v1` });
    const wrong = await fetch(`${info.url}/models`);
    expect(wrong.status).toBe(404);
    await bridge.stop();
    await expect(fetch(`${info.url}/responses`, { method: 'POST' })).rejects.toThrow();
  });
});

/**
 * Codex 等不到就会挂断重来，而自部署的多是单槽推理：
 * 桥接不取消上游，被放弃的那次生成就继续占着槽，下一次请求排在它后面 —— 越重试越慢。
 */
describe('Codex 提前挂断时取消上游', () => {
  it('上游请求在挂断后立即中止', async () => {
    let diedAt = 0;
    const neverEnds = createServer((req, res) => {
      req.resume();
      req.on('end', () => {
        res.writeHead(200, { 'content-type': 'text/event-stream' });
        res.write(`data: ${JSON.stringify({ choices: [{ delta: { content: '第一段' }, finish_reason: null }] })}\n\n`);
        const timer = setInterval(() => res.write(': tick\n\n'), 50);
        const stop = (): void => {
          clearInterval(timer);
          if (!diedAt) diedAt = Date.now();
        };
        res.on('close', stop);
        req.on('aborted', stop);
      });
    });
    await new Promise<void>((resolve) => neverEnds.listen(0, '127.0.0.1', resolve));
    const port = (neverEnds.address() as { port: number }).port;
    const bridge = new ChatBridgeService();
    try {
      const info = await bridge.start({ upstreamBaseUrl: `http://127.0.0.1:${port}/v1` });
      const controller = new AbortController();
      const response = await fetch(`${info.url}/responses`, {
        method: 'POST',
        headers: { 'content-type': 'application/json' },
        body: JSON.stringify({ model: 'm', input: '讲个长故事', stream: true }),
        signal: controller.signal,
      });
      // 收到第一个事件再挂断，确保桥接确实已经在上游吞吐数据
      await response.body?.getReader().read();
      const abortAt = Date.now();
      controller.abort();

      const deadline = abortAt + 2_000;
      while (!diedAt && Date.now() < deadline) {
        await new Promise((resolve) => setTimeout(resolve, 25));
      }
      expect(diedAt).toBeGreaterThan(0);
      expect(diedAt - abortAt).toBeLessThan(1_000);
    } finally {
      await bridge.stop();
      await new Promise<void>((resolve) => neverEnds.close(() => resolve()));
    }
  }, 20_000);
});

/**
 * 单槽自部署服务光 prefill 就要几分钟才吐首个字节。桥接要是等上游响应头到手才给 Codex 写东西，
 * Codex 面对的就是一条一个字节都没有的死连接 —— 它会掐了重发，于是越重试越慢。
 * 流式请求一到就先把 SSE 建起来，上游慢不影响客户端侧有字节可收。
 */
describe('上游首字节很慢时先把流建起来', () => {
  it('立刻回 response.created，不等上游', async () => {
    const slowUpstream = createServer((req, res) => {
      req.resume();
      req.on('end', () => {
        setTimeout(() => {
          res.writeHead(200, { 'content-type': 'text/event-stream' });
          res.end(SSE_BODY);
        }, 6_000);
      });
    });
    await new Promise<void>((resolve) => slowUpstream.listen(0, '127.0.0.1', resolve));
    const port = (slowUpstream.address() as { port: number }).port;
    const bridge = new ChatBridgeService();
    const controller = new AbortController();
    try {
      const info = await bridge.start({ upstreamBaseUrl: `http://127.0.0.1:${port}/v1` });
      const startedAt = Date.now();
      const response = await fetch(`${info.url}/responses`, {
        method: 'POST',
        headers: { 'content-type': 'application/json' },
        body: JSON.stringify({ model: 'm', input: '讲个故事', stream: true }),
        signal: controller.signal,
      });
      const reader = response.body?.getReader();
      if (!reader) throw new Error('没有响应体');
      const first = await reader.read();
      const firstAt = Date.now() - startedAt;
      const firstText = new TextDecoder().decode(first.value ?? new Uint8Array());
      expect(firstText).toContain('event: response.created');
      expect(firstAt).toBeLessThan(1_500);

      // 流没断：上游 6 秒后才回，最终回复照样要翻给客户端
      let all = firstText;
      for (;;) {
        const { done, value } = await reader.read();
        if (done) break;
        all += new TextDecoder().decode(value);
      }
      expect(all).toContain('你好');
      expect(all).toContain('event: response.completed');
    } finally {
      controller.abort();
      await bridge.stop();
      await new Promise<void>((resolve) => slowUpstream.close(() => resolve()));
    }
  }, 30_000);
});