code: // Licensed to the Software Freedom Conservancy (SFC) under one
  // or more contributor license agreements.  See the NOTICE file
  // distributed with this work for additional information
  // regarding copyright ownership.  The SFC licenses this file
  // to you under the Apache License, Version 2.0 (the
  // "License"); you may not use this file except in compliance
  // with the License.  You may obtain a copy of the License at
  //
  //   http://www.apache.org/licenses/LICENSE-2.0
  //
  // Unless required by applicable law or agreed to in writing,
  // software distributed under the License is distributed on an
  // "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
  // KIND, either express or implied.  See the License for the
  // specific language governing permissions and limitations
  // under the License.
  
  package org.openqa.selenium.grid;
  
  import java.util.Arrays;
  import java.util.Collections;
  import java.util.List;
  import java.util.Optional;
  import java.util.function.BiFunction;
  import java.util.function.Consumer;
  import java.util.function.Function;
  import java.util.function.Supplier;
  import org.openqa.selenium.grid.config.CompoundConfig;
  import org.openqa.selenium.grid.config.Config;
  import org.openqa.selenium.grid.config.MemoizedConfig;
  import org.openqa.selenium.grid.server.BaseServerOptions;
  import org.openqa.selenium.grid.server.Server;
  import org.openqa.selenium.internal.Require;
  import org.openqa.selenium.netty.server.NettyServer;
  import org.openqa.selenium.remote.http.HttpHandler;
  import org.openqa.selenium.remote.http.Message;
  import org.openqa.selenium.remote.http.Routable;
  import org.openqa.selenium.remote.http.Route;
  
  public abstract class TemplateGridServerCommand extends TemplateGridCommand {
  
    public Server<?> asServer(Config initialConfig) {
      Require.nonNull("Config", initialConfig);
  
      Config config = new MemoizedConfig(new CompoundConfig(initialConfig, getDefaultConfig()));
  
      Handlers handler = createHandlers(config);
  
      return new NettyServer(
          new BaseServerOptions(config), handler.httpHandler, handler.websocketHandler);
    }
  
    private static final String GRAPHQL = "/graphql";
  
    protected static Routable graphqlRoute(String prefix, Supplier<HttpHandler> handler) {
      Routable optionsRoute = buildRoute(GRAPHQL, prefix, path -> Route.options(path).to(handler));
      Routable postRoute = buildRoute(GRAPHQL, prefix, path -> Route.post(path).to(handler));
      return Route.combine(optionsRoute, postRoute);
    }
  
    protected static Routable hubRoute(String prefix, Route route) {
      return buildRoute("/wd/hub", prefix, path -> Route.prefix(path).to(route));
    }
  
    private static Routable buildRoute(String url, String prefix, Function<String, Route> mapper) {
      List<String> subPaths =
          prefix.isEmpty() ? Collections.singletonList(url) : Arrays.asList(prefix + url, url);
      return subPaths.stream().map(mapper).reduce(Route::combine).get();
    }
  
    protected static Routable baseRoute(String prefix, Route route) {
      return Route.prefix(prefix).to(route);
    }
  
    protected abstract Handlers createHandlers(Config config);
  
    public static class Handlers {
      public final HttpHandler httpHandler;
      public final BiFunction<String, Consumer<Message>, Optional<Consumer<Message>>>
          websocketHandler;
  
      public Handlers(
          HttpHandler http,
          BiFunction<String, Consumer<Message>, Optional<Consumer<Message>>> websocketHandler) {
        this.httpHandler = Require.nonNull("HTTP handler", http);
        this.websocketHandler =
            websocketHandler == null ? (str, sink) -> Optional.empty() : websocketHandler;
      }
    }
  }
  