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.remote.internal;
  
  import static java.util.stream.Collectors.toList;
  
  import com.google.common.collect.ImmutableMap;
  import java.lang.reflect.Array;
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.HashMap;
  import java.util.List;
  import java.util.Map;
  import java.util.function.Function;
  import org.openqa.selenium.WrapsElement;
  import org.openqa.selenium.remote.Dialect;
  import org.openqa.selenium.remote.RemoteWebElement;
  
  /**
   * Converts {@link RemoteWebElement} objects, which may be {@link WrapsElement wrapped}, into their
   * JSON representation as defined by the WebDriver wire protocol. This class will recursively
   * convert Lists and Maps to catch nested references.
   *
   * @see <a
   *     href="https://github.com/SeleniumHQ/selenium/wiki/JsonWireProtocol#webelement-json-object">
   *     WebDriver JSON Wire Protocol</a>
   */
  public class WebElementToJsonConverter implements Function<Object, Object> {
    @Override
    public Object apply(Object arg) {
      if (arg == null || arg instanceof String || arg instanceof Boolean || arg instanceof Number) {
        return arg;
      }
  
      while (arg instanceof WrapsElement) {
        arg = ((WrapsElement) arg).getWrappedElement();
      }
  
      if (arg instanceof RemoteWebElement) {
        return ImmutableMap.of(Dialect.W3C.getEncodedElementKey(), ((RemoteWebElement) arg).getId());
      }
  
      if (arg.getClass().isArray()) {
        arg = arrayToList(arg);
      }
  
      if (arg instanceof Collection<?>) {
        Collection<?> args = (Collection<?>) arg;
        return args.stream().map(this).collect(toList());
      }
  
      if (arg instanceof Map<?, ?>) {
        Map<?, ?> args = (Map<?, ?>) arg;
        Map<String, Object> converted = new HashMap<>(args.size());
        for (Map.Entry<?, ?> entry : args.entrySet()) {
          Object key = entry.getKey();
          if (!(key instanceof String)) {
            throw new IllegalArgumentException(
                "All keys in Map script arguments must be strings: " + key.getClass().getName());
          }
          converted.put((String) key, apply(entry.getValue()));
        }
        return converted;
      }
  
      throw new IllegalArgumentException(
          "Argument is of an illegal type: " + arg.getClass().getName());
    }
  
    private static List<Object> arrayToList(Object array) {
      List<Object> list = new ArrayList<>();
      for (int i = 0; i < Array.getLength(array); i++) {
        list.add(Array.get(array, i));
      }
      return list;
    }
  }
  