/*
    * 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.logging.log4j.core.config.plugins.validation.validators;
  
  import java.util.Collection;
  import java.util.Map;
  
  import org.apache.logging.log4j.Logger;
  import org.apache.logging.log4j.core.config.plugins.validation.ConstraintValidator;
  import org.apache.logging.log4j.core.config.plugins.validation.constraints.Required;
  import org.apache.logging.log4j.status.StatusLogger;
  
  /**
   * Validator that checks an object for emptiness. Emptiness is defined here as:
   * <ul>
   * <li>The value {@code null}</li>
   * <li>An object of type {@link CharSequence} with length 0</li>
   * <li>An empty array</li>
   * <li>An empty {@link Collection}</li>
   * <li>An empty {@link Map}</li>
   * </ul>
   *
   * @since 2.1
   */
  public class RequiredValidator implements ConstraintValidator<Required> {
  
      private static final Logger LOGGER = StatusLogger.getLogger();
  
      private Required annotation;
  
      @Override
      public void initialize(final Required annotation) {
          this.annotation = annotation;
      }
  
      @Override
      public boolean isValid(final Object value) {
          if (value == null) {
              return err();
          }
          if (value instanceof CharSequence) {
              final CharSequence sequence = (CharSequence) value;
              return sequence.length() != 0 || err();
          }
          final Class<?> clazz = value.getClass();
          if (clazz.isArray()) {
              final Object[] array = (Object[]) value;
              return array.length != 0 || err();
          }
          if (Collection.class.isAssignableFrom(clazz)) {
              final Collection<?> collection = (Collection<?>) value;
              return collection.size() != 0 || err();
          }
          if (Map.class.isAssignableFrom(clazz)) {
              final Map<?, ?> map = (Map<?, ?>) value;
              return map.size() != 0 || err();
          }
          LOGGER.debug("Encountered type [{}] which can only be checked for null.", clazz.getName());
          return true;
      }
  
      private boolean err() {
          LOGGER.error(annotation.message());
          return false;
      }
  }