Function startNodeRelay

src/upstreamproxy/relay.ts:245–289

(
  wsUrl: string,
  authHeader: string,
  wsAuthHeader: string,
)

// Exported so tests can exercise the Node path directly — the test runner is
// Bun, so the runtime dispatch in startUpstreamProxyRelay always picks Bun.
export async function startNodeRelay(
  wsUrl: string,
  authHeader: string,
  wsAuthHeader: string,
): Promise<UpstreamProxyRelay> {
  nodeWSCtor = (await import('ws')).default
  const states = new WeakMap<NodeSocket, ConnState>()

  const server = createServer(sock => {
    const st = newConnState()
    states.set(sock, st)
    // Node's sock.write() buffers internally — a false return signals
    // backpressure but the bytes are already queued, so no tail-tracking
    // needed for correctness. Week-1 payloads won't stress the buffer.
    const adapter: ClientSocket = {
      write: payload => {
        sock.write(typeof payload === 'string' ? payload : Buffer.from(payload))
      },
      end: () => sock.end(),
    }
    sock.on('data', data =>
      handleData(adapter, st, data, wsUrl, authHeader, wsAuthHeader),
    )
    sock.on('close', () => cleanupConn(states.get(sock)))
    sock.on('error', err => {
      logForDebugging(`[upstreamproxy] client socket error: ${err.message}`)
      cleanupConn(states.get(sock))
    })
  })

  return new Promise((resolve, reject) => {
    server.once('error', reject)
    server.listen(0, '127.0.0.1', () => {
      const addr = server.address()
      if (addr === null || typeof addr === 'string') {
        reject(new Error('upstreamproxy: server has no TCP address'))
        return
      }
      resolve({
        port: addr.port,
        stop: () => server.close(),
      })
    })
  })
}

/**
 * Shared per-connection data handler. Phase 1 accumulates the CONNECT request;