const net = require('net');

// Create a server that demonstrates half-close
const server = net.createServer({ allowHalfOpen: true }, (socket) => {
  console.log('Server: Client connected');
  
  // Set encoding for the socket
  socket.setEncoding('utf8');
  
  // Track if we've received the FIN from client
  let receivedFin = false;
  
  // Handle data from client
  socket.on('data', (data) => {
    console.log(`Server received: ${data.trim()}`);
    
    // After receiving data, send a response but don't end the connection
    if (!receivedFin) {
      console.log('Server: Sending response but keeping write side open');
      socket.write('SERVER: Received your message. Send more or end your side.\n');
    }
  });
  
  // Handle client ending their write side (sending FIN)
  socket.on('end', () => {
    receivedFin = true;
    console.log('Server: Client ended their write side (FIN received)');
    
    // We can still write to the client
    console.log('Server: Sending final response');
    socket.write('SERVER: Got your FIN. This is the final response.\n');
    
    // Now we can fully close the connection
    setTimeout(() => {
      console.log('Server: Fully closing the connection');
      socket.end();
    }, 1000);
  });
  
  // Handle errors
  socket.on('error', (err) => {
    console.error('Server socket error:', err.message);
  });
  
  // Handle connection close
  socket.on('close', (hadError) => {
    console.log(`Server: Connection closed ${hadError ? 'with error' : 'normally'}`);
  });
  
  // Initial welcome message
  socket.write('Welcome to the half-close demo server!\n');
  socket.write('Send some data, then call end() on your side.\n');
});

// Start the server
const PORT = 3006;
const HOST = 'localhost';

server.listen(PORT, HOST, () => {
  console.log(`Server running at ${HOST}:${PORT}`);
  
  // Create a client to test half-close
  const client = new net.Socket({ allowHalfOpen: true });
  
  // Set encoding for the client
  client.setEncoding('utf8');
  
  // Track if we've received the FIN from server
  let receivedFin = false;
  
  // Connect to the server
  client.connect(PORT, HOST, () => {
    console.log('Client: Connected to server');
    
    // Send initial data
    console.log('Client: Sending initial data');
    client.write('CLIENT: Hello from client\n');
    
    // After a delay, send more data then half-close
    setTimeout(() => {
      console.log('Client: Sending more data then half-closing');
      client.write('CLIENT: This is my last message\n');
      
      // Half-close the connection (send FIN, but can still receive)
      console.log('Client: Half-closing (ending write side)');
      client.end('CLIENT: Ending my write side\n');
      
      // We can still read from the server
      console.log('Client: Write side closed, but can still receive data');
    }, 1000);
  });
  
  // Handle data from server
  let receivedData = '';
  client.on('data', (data) => {
    receivedData += data;
    console.log('Client received data chunk');
    
    // Check if we've received the final response
    if (data.includes('final response')) {
      console.log('Client: Received final response from server');
      console.log('Full response:');
      console.log(receivedData);
    }
  });
  
  // Handle server ending their write side
  client.on('end', () => {
    receivedFin = true;
    console.log('Client: Server ended their write side (FIN received)');
    
    // Fully close the connection after a short delay
    setTimeout(() => {
      console.log('Client: Fully closing the connection');
      client.destroy();
    }, 1000);
  });
  
  // Handle connection close
  client.on('close', (hadError) => {
    console.log(`Client: Connection closed ${hadError ? 'with error' : 'normally'}`);
    
    // Close the server
    server.close();
  });
  
  // Handle errors
  client.on('error', (err) => {
    console.error('Client error:', err.message);
    server.close();
  });
});

// Handle server errors
server.on('error', (err) => {
  console.error('Server error:', err.message);
});

// Close server after 30 seconds if not already closed
setTimeout(() => {
  if (server.listening) {
    console.log('Closing server due to timeout');
    server.close();
  }
}, 30000);