/*
    * 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.shardingsphere.agent.plugin.core.util;
  
  import lombok.AccessLevel;
  import lombok.NoArgsConstructor;
  import lombok.SneakyThrows;
  
  import java.lang.reflect.Field;
  import java.util.Optional;
  
  /**
   * Agent reflection utility class.
   */
  @NoArgsConstructor(access = AccessLevel.PRIVATE)
  public final class AgentReflectionUtils {
      
      /**
       * Get field value.
       *
       * @param target target
       * @param fieldName field name
       * @param <T> type of field value
       * @return field value
       * @throws IllegalStateException illegal state exception
       */
      public static <T> T getFieldValue(final Object target, final String fieldName) {
          Optional<Field> field = findField(fieldName, target.getClass());
          if (field.isPresent()) {
              return getFieldValue(target, field.get());
          }
          throw new IllegalStateException(String.format("Can not find field name `%s` in class %s.", fieldName, target.getClass()));
      }
      
      @SuppressWarnings("unchecked")
      @SneakyThrows(IllegalAccessException.class)
      private static <T> T getFieldValue(final Object target, final Field field) {
          boolean accessible = field.isAccessible();
          if (!accessible) {
              field.setAccessible(true);
          }
          T result = (T) field.get(target);
          if (!accessible) {
              field.setAccessible(false);
          }
          return result;
      }
      
      private static Optional<Field> findField(final String fieldName, final Class<?> targetClass) {
          Class<?> currentTargetClass = targetClass;
          while (Object.class != currentTargetClass) {
              try {
                  return Optional.of(currentTargetClass.getDeclaredField(fieldName));
              } catch (final NoSuchFieldException ignored) {
                  currentTargetClass = currentTargetClass.getSuperclass();
              }
          }
          return Optional.empty();
      }
  }