text: 'use strict';
  
  function getSocketServerImplementation(options) {
    let ServerImplementation;
    let serverImplFound = true;
    switch (typeof options.transportMode.server) {
      case 'string':
        // could be 'sockjs', in the future 'ws', or a path that should be required
        if (options.transportMode.server === 'sockjs') {
          ServerImplementation = require('../servers/SockJSServer');
        } else if (options.transportMode.server === 'ws') {
          ServerImplementation = require('../servers/WebsocketServer');
        } else {
          try {
            // eslint-disable-next-line import/no-dynamic-require
            ServerImplementation = require(options.transportMode.server);
          } catch (e) {
            serverImplFound = false;
          }
        }
        break;
      case 'function':
        // potentially do more checks here to confirm that the user implemented this properlly
        // since errors could be difficult to understand
        ServerImplementation = options.transportMode.server;
        break;
      default:
        serverImplFound = false;
    }
  
    if (!serverImplFound) {
      throw new Error(
        "transportMode.server must be a string denoting a default implementation (e.g. 'sockjs', 'ws'), a full path to " +
          'a JS file which exports a class extending BaseServer (webpack-dev-server/lib/servers/BaseServer) ' +
          'via require.resolve(...), or the class itself which extends BaseServer'
      );
    }
  
    return ServerImplementation;
  }
  
  module.exports = getSocketServerImplementation;
  