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.config;
  
  import static java.util.Comparator.naturalOrder;
  
  import com.google.common.collect.ImmutableList;
  import com.google.common.collect.ImmutableMap;
  import com.google.common.collect.ImmutableSortedSet;
  import java.util.AbstractMap;
  import java.util.List;
  import java.util.Locale;
  import java.util.Map;
  import java.util.Optional;
  import java.util.Set;
  import org.openqa.selenium.internal.Require;
  
  public class ConcatenatingConfig implements Config {
  
    private final String prefix;
    private final char separator;
    private final Map<String, String> values;
  
    public ConcatenatingConfig(String prefix, char separator, Map<?, ?> values) {
      this.prefix = prefix == null || "".equals(prefix) ? "" : (prefix + separator);
      this.separator = separator;
  
      this.values =
          Require.nonNull("Config values", values).entrySet().stream()
              .peek(entry -> Require.nonNull("Key", entry.getKey()))
              .peek(entry -> Require.nonNull("Value", entry.getValue()))
              .map(
                  entry ->
                      new AbstractMap.SimpleImmutableEntry<>(
                          String.valueOf(entry.getKey()), String.valueOf(entry.getValue())))
              .collect(ImmutableMap.toImmutableMap(Map.Entry::getKey, Map.Entry::getValue));
    }
  
    @Override
    public Optional<List<String>> getAll(String section, String option) {
      Require.nonNull("Section name", section);
      Require.nonNull("Option name", option);
  
      String key = prefix + section + separator + option;
  
      return values.entrySet().stream()
          .filter(entry -> key.equalsIgnoreCase(entry.getKey()))
          .map(Map.Entry::getValue)
          .findFirst()
          .map(ImmutableList::of);
    }
  
    @Override
    public Set<String> getSectionNames() {
      String actualPrefix = prefix.toLowerCase(Locale.ENGLISH);
  
      return values.keySet().stream()
          .filter(key -> key.toLowerCase(Locale.ENGLISH).startsWith(actualPrefix))
          .filter(key -> key.length() > (actualPrefix.length() + 1))
          .map(key -> key.substring(actualPrefix.length()))
          .filter(key -> key.indexOf(separator) > -1)
          .map(key -> key.substring(0, key.indexOf(separator)))
          .map(key -> key.toLowerCase(Locale.ENGLISH))
          .collect(ImmutableSortedSet.toImmutableSortedSet(naturalOrder()));
    }
  
    @Override
    public Set<String> getOptions(String section) {
      Require.nonNull("Section name to get options for", section);
  
      String actualPrefix = String.format("%s%s_", prefix, section).toLowerCase(Locale.ENGLISH);
  
      return values.keySet().stream()
          .filter(key -> key.toLowerCase(Locale.ENGLISH).startsWith(actualPrefix))
          .filter(key -> key.length() > actualPrefix.length() + 1)
          .map(key -> key.substring(actualPrefix.length()))
          .map(key -> key.toLowerCase(Locale.ENGLISH))
          .collect(ImmutableSortedSet.toImmutableSortedSet(naturalOrder()));
    }
  }
  