content: /*
   * Licensed to the Apache Software Foundation (ASF) under one
   * or more contributor license agreements.  See the NOTICE file
   * distributed with this work for additional information
   * regarding copyright ownership.  The ASF 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.apache.cassandra.distributed.shared;
  
  import java.lang.reflect.Field;
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.List;
  import java.util.Map;
  
  public final class WithEnvironment implements AutoCloseable
  {
      private final List<Environment> properties = new ArrayList<>();
  
      public WithEnvironment(String... kvs)
      {
          with(kvs);
      }
  
      public void with(String... kvs)
      {
          assert kvs.length % 2 == 0 : "Input must have an even amount of inputs but given " + kvs.length;
          for (int i = 0; i <= kvs.length - 2; i = i + 2)
          {
              with(kvs[i], kvs[i + 1]);
          }
      }
  
      public void with(String key, String value)
      {
          try
          {
              Map<String, String> writableEnv = getWritableEnv();
              String previous = writableEnv.put(key, value);
              properties.add(new Environment(key, previous));
          } catch (Exception e) {
              throw new IllegalStateException("Failed to set environment variable", e);
          }
      }
  
      private static Map<String, String> getWritableEnv() throws NoSuchFieldException, IllegalAccessException
      {
          Map<String, String> env = System.getenv(); // checkstyle: suppress nearby 'blockSystemPropertyUsage'
          Class<?> cl = env.getClass();
          Field field = cl.getDeclaredField("m");
          field.setAccessible(true);
          return (Map<String, String>) field.get(env);
      }
  
  
      @Override
      public void close()
      {
          Collections.reverse(properties);
          properties.forEach(s -> {
              try
              {
                  Map<String, String> writableEnv = getWritableEnv();
                  if (s.value == null)
                      writableEnv.remove(s.key);
                  else
                      writableEnv.put(s.key, s.value);
              } catch (Exception e) {
                  throw new IllegalStateException("Failed to set environment variable", e);
              }
          });
          properties.clear();
      }
  
      private static final class Environment
      {
          private final String key;
          private final String value;
  
          private Environment(String key, String value)
          {
              this.key = key;
              this.value = value;
          }
      }
  }
  