import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest';
import http from 'node:http';
import { mkdtempSync, rmSync, readFileSync, writeFileSync } from 'node:fs';
import { tmpdir } from 'node:os';
import { join } from 'node:path';
import {
  VirtualLlmRegistrar,
  type RegistrarPublishedProvider,
} from '../src/providers/registrar.js';
import type { LlmProvider, CompletionOptions, CompletionResult } from '../src/providers/types.js';

/**
 * The registrar talks HTTP. Spin a tiny in-process server in each test so
 * we can assert what it sends without mocking node:http itself.
 */
interface FakeServer {
  url: string;
  close: () => Promise<void>;
  /** Calls observed in arrival order. */
  calls: Array<{ method: string; path: string; body: string; headers: Record<string, string | string[] | undefined> }>;
  /**
   * Optional handler. If set, runs per-request and decides response. If not,
   * defaults to 201 + JSON `{ providerSessionId: 'sess-FAKE' }` for register
   * and 200 + `{}` for everything else.
   */
  handler?: (req: http.IncomingMessage, res: http.ServerResponse, body: string) => void;
}

async function startFakeServer(): Promise<FakeServer> {
  const calls: FakeServer['calls'] = [];
  let server!: http.Server;
  const ready = new Promise<FakeServer>((resolve, reject) => {
    server = http.createServer((req, res) => {
      const chunks: Buffer[] = [];
      req.on('data', (c: Buffer) => chunks.push(c));
      req.on('end', () => {
        const body = Buffer.concat(chunks).toString('utf-8');
        calls.push({
          method: req.method ?? '',
          path: req.url ?? '',
          body,
          headers: req.headers,
        });
        if (fake.handler !== undefined) {
          fake.handler(req, res, body);
          return;
        }
        if (req.url === '/api/v1/llms/_provider-register') {
          res.writeHead(201, { 'content-type': 'application/json' });
          res.end(JSON.stringify({ providerSessionId: 'sess-FAKE', llms: [] }));
          return;
        }
        res.writeHead(200, { 'content-type': 'application/json' });
        res.end('{}');
      });
    });
    server.listen(0, '127.0.0.1', () => {
      const addr = server.address();
      if (addr === null || typeof addr === 'string') {
        reject(new Error('listen failed'));
        return;
      }
      const fakeReady: FakeServer = {
        url: `http://127.0.0.1:${String(addr.port)}`,
        close: () => new Promise<void>((r) => { server.close(() => r()); }),
        calls,
      };
      Object.assign(fake, fakeReady);
      resolve(fake);
    });
  });
  const fake: FakeServer = {} as FakeServer;
  return ready;
}

function makeProvider(name: string, content = 'hi from local'): LlmProvider {
  return {
    name,
    async complete(_opts: CompletionOptions): Promise<CompletionResult> {
      return {
        content,
        toolCalls: [],
        usage: { promptTokens: 1, completionTokens: 1, totalTokens: 2 },
        finishReason: 'stop',
      };
    },
    async listModels() { return []; },
    async isAvailable() { return true; },
  };
}

let tempDir: string;

beforeEach(() => {
  tempDir = mkdtempSync(join(tmpdir(), 'mcpctl-registrar-test-'));
});

afterEach(() => {
  rmSync(tempDir, { recursive: true, force: true });
});

function silentLog(): { info: ReturnType<typeof vi.fn>; warn: ReturnType<typeof vi.fn>; error: ReturnType<typeof vi.fn> } {
  return { info: vi.fn(), warn: vi.fn(), error: vi.fn() };
}

describe('VirtualLlmRegistrar', () => {
  it('start() with no published providers is a silent no-op', async () => {
    const log = silentLog();
    const registrar = new VirtualLlmRegistrar({
      mcpdUrl: 'http://unreachable.example',
      token: 'tok',
      publishedProviders: [],
      sessionFilePath: join(tempDir, 'provider-session'),
      log,
    });
    await registrar.start();
    expect(log.info).toHaveBeenCalledWith(expect.stringContaining('nothing to publish'));
    registrar.stop();
  });

  it('register POSTs to /_provider-register and persists the returned sessionId', async () => {
    const fake = await startFakeServer();
    try {
      const sessionFilePath = join(tempDir, 'provider-session');
      const published: RegistrarPublishedProvider[] = [
        { provider: makeProvider('vllm-local'), type: 'openai', model: 'qwen', tier: 'fast' },
      ];
      const registrar = new VirtualLlmRegistrar({
        mcpdUrl: fake.url,
        token: 'tok-abc',
        publishedProviders: published,
        sessionFilePath,
        log: silentLog(),
        // Make heartbeat huge so it doesn't fire mid-test.
        heartbeatIntervalMs: 60_000,
      });
      await registrar.start();
      // Allow the SSE open to enter flight (we never feed it a response,
      // but the request fires synchronously after register).
      await new Promise((r) => setTimeout(r, 20));

      const registerCall = fake.calls.find((c) => c.path === '/api/v1/llms/_provider-register');
      expect(registerCall).toBeDefined();
      expect(registerCall!.method).toBe('POST');
      const body = JSON.parse(registerCall!.body) as { providers: Array<{ name: string; type: string; model: string; tier: string }> };
      expect(body.providers).toEqual([{
        name: 'vllm-local',
        type: 'openai',
        model: 'qwen',
        tier: 'fast',
      }]);
      expect(registerCall!.headers['authorization']).toBe('Bearer tok-abc');

      // Sticky session id persisted.
      expect(readFileSync(sessionFilePath, 'utf-8').trim()).toBe('sess-FAKE');
      expect(registrar.getSessionId()).toBe('sess-FAKE');

      registrar.stop();
    } finally {
      await fake.close();
    }
  });

  it('reuses an existing sticky session id from disk on next start', async () => {
    const fake = await startFakeServer();
    try {
      const sessionFilePath = join(tempDir, 'provider-session');
      writeFileSync(sessionFilePath, 'sess-existing\n', 'utf-8');

      const registrar = new VirtualLlmRegistrar({
        mcpdUrl: fake.url,
        token: 't',
        publishedProviders: [
          { provider: makeProvider('vllm-local'), type: 'openai', model: 'm' },
        ],
        sessionFilePath,
        log: silentLog(),
        heartbeatIntervalMs: 60_000,
      });
      await registrar.start();
      await new Promise((r) => setTimeout(r, 20));

      const registerCall = fake.calls.find((c) => c.path === '/api/v1/llms/_provider-register');
      const body = JSON.parse(registerCall!.body) as { providerSessionId?: string };
      expect(body.providerSessionId).toBe('sess-existing');

      registrar.stop();
    } finally {
      await fake.close();
    }
  });

  it('heartbeat ticker POSTs the session id at the configured interval', async () => {
    const fake = await startFakeServer();
    try {
      const registrar = new VirtualLlmRegistrar({
        mcpdUrl: fake.url,
        token: 't',
        publishedProviders: [
          { provider: makeProvider('vllm-local'), type: 'openai', model: 'm' },
        ],
        sessionFilePath: join(tempDir, 'provider-session'),
        log: silentLog(),
        heartbeatIntervalMs: 30, // tight so the test doesn't drag
      });
      await registrar.start();
      // Wait long enough for at least 2 heartbeats to fire.
      await new Promise((r) => setTimeout(r, 100));
      registrar.stop();

      const heartbeats = fake.calls.filter((c) => c.path === '/api/v1/llms/_provider-heartbeat');
      expect(heartbeats.length).toBeGreaterThanOrEqual(2);
      for (const h of heartbeats) {
        const body = JSON.parse(h.body) as { providerSessionId: string };
        expect(body.providerSessionId).toBe('sess-FAKE');
      }
    } finally {
      await fake.close();
    }
  });

  it('throws when mcpd returns non-201 from /_provider-register', async () => {
    const fake = await startFakeServer();
    fake.handler = (_req, res, _body) => {
      res.writeHead(409, { 'content-type': 'application/json' });
      res.end(JSON.stringify({ error: 'Cannot publish over public LLM: vllm-local' }));
    };
    try {
      const registrar = new VirtualLlmRegistrar({
        mcpdUrl: fake.url,
        token: 't',
        publishedProviders: [
          { provider: makeProvider('vllm-local'), type: 'openai', model: 'm' },
        ],
        sessionFilePath: join(tempDir, 'provider-session'),
        log: silentLog(),
        heartbeatIntervalMs: 60_000,
      });
      await expect(registrar.start()).rejects.toThrow(/HTTP 409/);
    } finally {
      await fake.close();
    }
  });
});