import { logger } from '@sentry/utils';

function debug(...args) {
  logger.log('[https-proxy-agent:parse-proxy-response]', ...args);
}

function parseProxyResponse(socket) {
  return new Promise((resolve, reject) => {
    // we need to buffer any HTTP traffic that happens with the proxy before we get
    // the CONNECT response, so that if the response is anything other than an "200"
    // response code, then we can re-play the "data" events on the socket once the
    // HTTP parser is hooked up...
    let buffersLength = 0;
    const buffers = [];

    function read() {
      const b = socket.read();
      if (b) ondata(b);
      else socket.once('readable', read);
    }

    function cleanup() {
      socket.removeListener('end', onend);
      socket.removeListener('error', onerror);
      socket.removeListener('readable', read);
    }

    function onend() {
      cleanup();
      debug('onend');
      reject(new Error('Proxy connection ended before receiving CONNECT response'));
    }

    function onerror(err) {
      cleanup();
      debug('onerror %o', err);
      reject(err);
    }

    function ondata(b) {
      buffers.push(b);
      buffersLength += b.length;

      const buffered = Buffer.concat(buffers, buffersLength);
      const endOfHeaders = buffered.indexOf('\r\n\r\n');

      if (endOfHeaders === -1) {
        // keep buffering
        debug('have not received end of HTTP headers yet...');
        read();
        return;
      }

      const headerParts = buffered.slice(0, endOfHeaders).toString('ascii').split('\r\n');
      const firstLine = headerParts.shift();
      if (!firstLine) {
        socket.destroy();
        return reject(new Error('No header received from proxy CONNECT response'));
      }
      const firstLineParts = firstLine.split(' ');
      const statusCode = +firstLineParts[1];
      const statusText = firstLineParts.slice(2).join(' ');
      const headers = {};
      for (const header of headerParts) {
        if (!header) continue;
        const firstColon = header.indexOf(':');
        if (firstColon === -1) {
          socket.destroy();
          return reject(new Error(`Invalid header from proxy CONNECT response: "${header}"`));
        }
        const key = header.slice(0, firstColon).toLowerCase();
        const value = header.slice(firstColon + 1).trimStart();
        const current = headers[key];
        if (typeof current === 'string') {
          headers[key] = [current, value];
        } else if (Array.isArray(current)) {
          current.push(value);
        } else {
          headers[key] = value;
        }
      }
      debug('got proxy server response: %o %o', firstLine, headers);
      cleanup();
      resolve({
        connect: {
          statusCode,
          statusText,
          headers,
        },
        buffered,
      });
    }

    socket.on('error', onerror);
    socket.on('end', onend);

    read();
  });
}

export { parseProxyResponse };
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