import { expect, tap } from '@push.rocks/tapbundle';
import * as net from 'net';
import * as crypto from 'crypto';
import { RemoteIngressHub, RemoteIngressEdge } from '../ts/index.js';

// ---------------------------------------------------------------------------
// Helpers
// ---------------------------------------------------------------------------

/** Find N free ports by binding to port 0 and collecting OS-assigned ports. */
async function findFreePorts(count: number): Promise<number[]> {
  const servers: net.Server[] = [];
  const ports: number[] = [];
  for (let i = 0; i < count; i++) {
    const server = net.createServer();
    await new Promise<void>((resolve) => server.listen(0, '127.0.0.1', resolve));
    ports.push((server.address() as net.AddressInfo).port);
    servers.push(server);
  }
  await Promise.all(servers.map((s) => new Promise<void>((resolve) => s.close(() => resolve()))));
  return ports;
}

type TrackingServer = net.Server & { destroyAll: () => void };

/** Start a TCP echo server that tracks connections for force-close. */
function startEchoServer(port: number, host: string): Promise<TrackingServer> {
  return new Promise((resolve, reject) => {
    const connections = new Set<net.Socket>();
    const server = net.createServer((socket) => {
      connections.add(socket);
      socket.on('close', () => connections.delete(socket));

      // Skip PROXY protocol v1 header line before echoing
      let proxyHeaderParsed = false;
      let pendingBuf = Buffer.alloc(0);
      socket.on('data', (data: Buffer) => {
        if (!proxyHeaderParsed) {
          pendingBuf = Buffer.concat([pendingBuf, data]);
          const idx = pendingBuf.indexOf('\r\n');
          if (idx !== -1) {
            proxyHeaderParsed = true;
            const remainder = pendingBuf.subarray(idx + 2);
            if (remainder.length > 0) {
              socket.write(remainder);
            }
          }
          return;
        }
        socket.write(data);
      });
      socket.on('error', () => {});
    }) as TrackingServer;

    server.destroyAll = () => {
      for (const conn of connections) conn.destroy();
      connections.clear();
    };

    server.on('error', reject);
    server.listen(port, host, () => resolve(server));
  });
}

/**
 * Start a server that sends a large response immediately on first data received.
 * Does NOT wait for end (the tunnel protocol has no half-close).
 * On receiving first data chunk after PROXY header, sends responseSize bytes then closes.
 */
function startLargeResponseServer(port: number, host: string, responseSize: number): Promise<TrackingServer> {
  return new Promise((resolve, reject) => {
    const connections = new Set<net.Socket>();
    const server = net.createServer((socket) => {
      connections.add(socket);
      socket.on('close', () => connections.delete(socket));

      let proxyHeaderParsed = false;
      let pendingBuf = Buffer.alloc(0);
      let responseSent = false;

      socket.on('data', (data: Buffer) => {
        if (!proxyHeaderParsed) {
          pendingBuf = Buffer.concat([pendingBuf, data]);
          const idx = pendingBuf.indexOf('\r\n');
          if (idx !== -1) {
            proxyHeaderParsed = true;
            const remainder = pendingBuf.subarray(idx + 2);
            if (remainder.length > 0 && !responseSent) {
              responseSent = true;
              sendLargeResponse(socket, responseSize);
            }
          }
          return;
        }
        if (!responseSent) {
          responseSent = true;
          sendLargeResponse(socket, responseSize);
        }
      });
      socket.on('error', () => {});
    }) as TrackingServer;

    server.destroyAll = () => {
      for (const conn of connections) conn.destroy();
      connections.clear();
    };

    server.on('error', reject);
    server.listen(port, host, () => resolve(server));
  });
}

function sendLargeResponse(socket: net.Socket, totalBytes: number) {
  const chunkSize = 32 * 1024;
  let sent = 0;
  const writeChunk = () => {
    while (sent < totalBytes) {
      const toWrite = Math.min(chunkSize, totalBytes - sent);
      // Use a deterministic pattern for verification
      const chunk = Buffer.alloc(toWrite, (sent % 256) & 0xff);
      const canContinue = socket.write(chunk);
      sent += toWrite;
      if (!canContinue) {
        socket.once('drain', writeChunk);
        return;
      }
    }
    socket.end();
  };
  writeChunk();
}

/** Force-close a server: destroy all connections, then close. */
async function forceCloseServer(server: TrackingServer): Promise<void> {
  server.destroyAll();
  await new Promise<void>((resolve) => server.close(() => resolve()));
}

interface TestTunnel {
  hub: RemoteIngressHub;
  edge: RemoteIngressEdge;
  edgePort: number;
  cleanup: () => Promise<void>;
}

/**
 * Start a full hub + edge tunnel.
 * Edge binds to 127.0.0.1, upstream server binds to 127.0.0.2.
 * Hub targetHost = 127.0.0.2 so hub -> upstream doesn't loop back to edge.
 */
async function startTunnel(edgePort: number, hubPort: number): Promise<TestTunnel> {
  const hub = new RemoteIngressHub();
  const edge = new RemoteIngressEdge();

  await hub.start({
    tunnelPort: hubPort,
    targetHost: '127.0.0.2',
  });

  await hub.updateAllowedEdges([
    { id: 'test-edge', secret: 'test-secret', listenPorts: [edgePort] },
  ]);

  const connectedPromise = new Promise<void>((resolve, reject) => {
    const timeout = setTimeout(() => reject(new Error('Edge did not connect within 10s')), 10000);
    edge.once('tunnelConnected', () => {
      clearTimeout(timeout);
      resolve();
    });
  });

  await edge.start({
    hubHost: '127.0.0.1',
    hubPort,
    edgeId: 'test-edge',
    secret: 'test-secret',
    bindAddress: '127.0.0.1',
  });

  await connectedPromise;
  await new Promise((resolve) => setTimeout(resolve, 500));

  return {
    hub,
    edge,
    edgePort,
    cleanup: async () => {
      await edge.stop();
      await hub.stop();
    },
  };
}

/**
 * Send data through the tunnel and collect the echoed response.
 */
function sendAndReceive(port: number, data: Buffer, timeoutMs = 30000): Promise<Buffer> {
  return new Promise((resolve, reject) => {
    const chunks: Buffer[] = [];
    let totalReceived = 0;
    const expectedLength = data.length;
    let settled = false;

    const client = net.createConnection({ host: '127.0.0.1', port }, () => {
      client.write(data);
      client.end();
    });

    const timer = setTimeout(() => {
      if (!settled) {
        settled = true;
        client.destroy();
        reject(new Error(`Timeout after ${timeoutMs}ms — received ${totalReceived}/${expectedLength} bytes`));
      }
    }, timeoutMs);

    client.on('data', (chunk: Buffer) => {
      chunks.push(chunk);
      totalReceived += chunk.length;
      if (totalReceived >= expectedLength && !settled) {
        settled = true;
        clearTimeout(timer);
        client.destroy();
        resolve(Buffer.concat(chunks));
      }
    });

    client.on('end', () => {
      if (!settled) {
        settled = true;
        clearTimeout(timer);
        resolve(Buffer.concat(chunks));
      }
    });

    client.on('error', (err) => {
      if (!settled) {
        settled = true;
        clearTimeout(timer);
        reject(err);
      }
    });
  });
}

/**
 * Connect to the tunnel, send a small request, and collect a large response.
 * Does NOT call end() — the tunnel has no half-close.
 * Instead, collects until expectedResponseSize bytes arrive.
 */
function sendAndReceiveLarge(
  port: number,
  data: Buffer,
  expectedResponseSize: number,
  timeoutMs = 60000,
): Promise<Buffer> {
  return new Promise((resolve, reject) => {
    const chunks: Buffer[] = [];
    let totalReceived = 0;
    let settled = false;

    const client = net.createConnection({ host: '127.0.0.1', port }, () => {
      client.write(data);
      // Do NOT call client.end() — the server will respond immediately
      // and the tunnel CLOSE will happen when the download finishes
    });

    const timer = setTimeout(() => {
      if (!settled) {
        settled = true;
        client.destroy();
        reject(new Error(`Timeout after ${timeoutMs}ms — received ${totalReceived}/${expectedResponseSize} bytes`));
      }
    }, timeoutMs);

    client.on('data', (chunk: Buffer) => {
      chunks.push(chunk);
      totalReceived += chunk.length;
      if (totalReceived >= expectedResponseSize && !settled) {
        settled = true;
        clearTimeout(timer);
        client.destroy();
        resolve(Buffer.concat(chunks));
      }
    });

    client.on('end', () => {
      if (!settled) {
        settled = true;
        clearTimeout(timer);
        resolve(Buffer.concat(chunks));
      }
    });

    client.on('error', (err) => {
      if (!settled) {
        settled = true;
        clearTimeout(timer);
        reject(err);
      }
    });
  });
}

function sha256(buf: Buffer): string {
  return crypto.createHash('sha256').update(buf).digest('hex');
}

// ---------------------------------------------------------------------------
// Tests
// ---------------------------------------------------------------------------

let tunnel: TestTunnel;
let echoServer: TrackingServer;
let hubPort: number;
let edgePort: number;

tap.test('setup: start echo server and tunnel', async () => {
  [hubPort, edgePort] = await findFreePorts(2);

  echoServer = await startEchoServer(edgePort, '127.0.0.2');
  tunnel = await startTunnel(edgePort, hubPort);

  expect(tunnel.hub.running).toBeTrue();
});

tap.test('single stream: 32MB transfer exceeding initial 4MB window', async () => {
  const size = 32 * 1024 * 1024;
  const data = crypto.randomBytes(size);
  const expectedHash = sha256(data);

  const received = await sendAndReceive(edgePort, data, 60000);

  expect(received.length).toEqual(size);
  expect(sha256(received)).toEqual(expectedHash);
});

tap.test('200 concurrent streams with 64KB each', async () => {
  const streamCount = 200;
  const payloadSize = 64 * 1024;

  const promises = Array.from({ length: streamCount }, () => {
    const data = crypto.randomBytes(payloadSize);
    const hash = sha256(data);
    return sendAndReceive(edgePort, data, 30000).then((received) => ({
      sent: hash,
      received: sha256(received),
      sizeOk: received.length === payloadSize,
    }));
  });

  const results = await Promise.all(promises);
  const failures = results.filter((r) => !r.sizeOk || r.sent !== r.received);

  expect(failures.length).toEqual(0);
});

tap.test('512 concurrent streams at minimum window boundary (16KB each)', async () => {
  const streamCount = 512;
  const payloadSize = 16 * 1024;

  const promises = Array.from({ length: streamCount }, () => {
    const data = crypto.randomBytes(payloadSize);
    const hash = sha256(data);
    return sendAndReceive(edgePort, data, 60000).then((received) => ({
      sent: hash,
      received: sha256(received),
      sizeOk: received.length === payloadSize,
    }));
  });

  const results = await Promise.all(promises);
  const failures = results.filter((r) => !r.sizeOk || r.sent !== r.received);

  expect(failures.length).toEqual(0);
});

tap.test('asymmetric transfer: 4KB request -> 4MB response', async () => {
  // Swap to large-response server
  await forceCloseServer(echoServer);
  const responseSize = 4 * 1024 * 1024; // 4 MB
  const largeServer = await startLargeResponseServer(edgePort, '127.0.0.2', responseSize);

  try {
    const requestData = crypto.randomBytes(4 * 1024); // 4 KB
    const received = await sendAndReceiveLarge(edgePort, requestData, responseSize, 60000);
    expect(received.length).toEqual(responseSize);
  } finally {
    // Always restore echo server even on failure
    await forceCloseServer(largeServer);
    echoServer = await startEchoServer(edgePort, '127.0.0.2');
  }
});

tap.test('100 streams x 1MB each (100MB total exceeding 32MB budget)', async () => {
  const streamCount = 100;
  const payloadSize = 1 * 1024 * 1024;

  const promises = Array.from({ length: streamCount }, () => {
    const data = crypto.randomBytes(payloadSize);
    const hash = sha256(data);
    return sendAndReceive(edgePort, data, 120000).then((received) => ({
      sent: hash,
      received: sha256(received),
      sizeOk: received.length === payloadSize,
    }));
  });

  const results = await Promise.all(promises);
  const failures = results.filter((r) => !r.sizeOk || r.sent !== r.received);

  expect(failures.length).toEqual(0);
});

tap.test('active stream counter tracks concurrent connections', async () => {
  const N = 50;

  // Open N connections and keep them alive (send data but don't close)
  const sockets: net.Socket[] = [];
  const connectPromises = Array.from({ length: N }, () => {
    return new Promise<net.Socket>((resolve, reject) => {
      const sock = net.createConnection({ host: '127.0.0.1', port: edgePort }, () => {
        resolve(sock);
      });
      sock.on('error', () => {});
      setTimeout(() => reject(new Error('connect timeout')), 5000);
    });
  });

  const connected = await Promise.all(connectPromises);
  sockets.push(...connected);

  // Brief delay for stream registration to propagate
  await new Promise((resolve) => setTimeout(resolve, 500));

  // Verify the edge reports >= N active streams.
  // This counter is the input to compute_window_for_stream_count(),
  // so its accuracy determines whether adaptive window sizing is correct.
  const status = await tunnel.edge.getStatus();
  expect(status.activeStreams).toBeGreaterThanOrEqual(N);

  // Clean up: destroy all sockets (the tunnel's 300s stream timeout will handle cleanup)
  for (const sock of sockets) {
    sock.destroy();
  }
});

tap.test('50 streams x 2MB each (forces multiple window refills per stream)', async () => {
  // At 50 concurrent streams: adaptive window = 32MB/50 = 655KB per stream
  // Each stream sends 2MB → needs ~3 WINDOW_UPDATE refill cycles per stream
  const streamCount = 50;
  const payloadSize = 2 * 1024 * 1024;

  const promises = Array.from({ length: streamCount }, () => {
    const data = crypto.randomBytes(payloadSize);
    const hash = sha256(data);
    return sendAndReceive(edgePort, data, 120000).then((received) => ({
      sent: hash,
      received: sha256(received),
      sizeOk: received.length === payloadSize,
    }));
  });

  const results = await Promise.all(promises);
  const failures = results.filter((r) => !r.sizeOk || r.sent !== r.received);

  expect(failures.length).toEqual(0);
});

tap.test('teardown: stop tunnel and echo server', async () => {
  await tunnel.cleanup();
  await forceCloseServer(echoServer);
});

export default tap.start();