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// Copyright (c) 2025 Cloudflare, Inc.
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// Licensed under the Apache 2.0 license found in the LICENSE file or at:
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//     https://opensource.org/licenses/Apache-2.0
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const http = require('http');
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const crypto = require('crypto');
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// Handle upgrade requests to switch from HTTP to WebSocket protocol
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function upgradeToWebSocketConnection(req, socket, head) {
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  // Check if it's a WebSocket upgrade request
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  if (req.headers['upgrade'] !== 'websocket') {
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    socket.end('HTTP/1.1 400 Bad Request');
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    return;
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  }
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  // Get the WebSocket key from the client
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  const webSocketKey = req.headers['sec-websocket-key'];
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  const GUID = '258EAFA5-E914-47DA-95CA-C5AB0DC85B11'; // WebSocket protocol GUID
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  // Create the accept key by concatenating the key and GUID, then hashing
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  const acceptKey = crypto
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    .createHash('sha1')
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    .update(webSocketKey + GUID)
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    .digest('base64');
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  // Write WebSocket handshake response headers
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  socket.write(
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    'HTTP/1.1 101 Switching Protocols\r\n' +
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      'Upgrade: websocket\r\n' +
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      'Connection: Upgrade\r\n' +
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      `Sec-WebSocket-Accept: ${acceptKey}\r\n` +
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      '\r\n'
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  );
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  // Socket is now a WebSocket connection
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  handleWebSocketConnection(socket);
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}
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// Function to send a message to the client
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function sendMessage(socket, message) {
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  const payload = Buffer.from(message);
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  const payloadLength = payload.length;
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  // Create frame header
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  let header;
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  if (payloadLength <= 125) {
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    header = Buffer.alloc(2);
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    header[1] = payloadLength;
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  } else if (payloadLength <= 65535) {
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    header = Buffer.alloc(4);
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    header[1] = 126;
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    header.writeUInt16BE(payloadLength, 2);
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  } else {
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    header = Buffer.alloc(10);
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    header[1] = 127;
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    // Write length as 64-bit integer (simplified here)
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    header.writeBigUInt64BE(BigInt(payloadLength), 2);
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  }
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  // Set the first byte: FIN bit (0x80) + opcode 0x01 for text data
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  header[0] = 0x81;
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  // Combine header and payload
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  const frame = Buffer.concat([header, payload]);
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  // Send the frame
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  socket.write(frame);
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}
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// Get the port and host from environment variables
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const port = process.env.BIG_MESSAGE_SERVER_PORT;
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const host = process.env.SIDECAR_HOSTNAME;
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function reportAddress(server) {
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  const address = server.address();
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  console.info(`Listening on ${address.address}:${address.port}`);
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}
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// Create HTTP server to handle the WebSocket handshake
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const server = http.createServer((req, res) => {
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  res.writeHead(200, { 'Content-Type': 'text/plain' });
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  res.end('WebSocket server is running');
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});
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server.on('upgrade', upgradeToWebSocketConnection);
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server.on('error', (event) => {
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  console.log(event);
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  console.log(event.message);
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});
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// Start the server
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server.listen(port, host, () => reportAddress(server));
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// Function to handle WebSocket connections
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function handleWebSocketConnection(socket) {
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  // Send a welcome message
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  sendMessage(socket, new Uint8Array(33 * 1024 * 1024));
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}