/*
    * 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;
  
  import java.lang.annotation.Annotation;
  import java.lang.reflect.ParameterizedType;
  import java.lang.reflect.Type;
  import java.util.ArrayList;
  import java.util.Collection;
  
  import org.apache.logging.log4j.core.util.ReflectionUtil;
  
  /**
   * Utility class to locate an appropriate {@link ConstraintValidator} implementation for an annotation.
   *
   * @since 2.1
   */
  public final class ConstraintValidators {
  
      private ConstraintValidators() {
      }
  
      /**
       * Finds all relevant {@link ConstraintValidator} objects from an array of annotations. All validators will be
       * {@link ConstraintValidator#initialize(java.lang.annotation.Annotation) initialized} before being returned.
       *
       * @param annotations the annotations to find constraint validators for
       * @return a collection of ConstraintValidators for the given annotations
       */
      public static Collection<ConstraintValidator<?>> findValidators(final Annotation... annotations) {
          final Collection<ConstraintValidator<?>> validators =
              new ArrayList<ConstraintValidator<?>>();
          for (final Annotation annotation : annotations) {
              final Class<? extends Annotation> type = annotation.annotationType();
              if (type.isAnnotationPresent(Constraint.class)) {
                  final ConstraintValidator<?> validator = getValidator(annotation, type);
                  if (validator != null) {
                      validators.add(validator);
                  }
              }
          }
          return validators;
      }
  
      private static <A extends Annotation> ConstraintValidator<A> getValidator(final A annotation,
                                                                                final Class<? extends A> type) {
          final Constraint constraint = type.getAnnotation(Constraint.class);
          final Class<? extends ConstraintValidator<?>> validatorClass = constraint.value();
          if (type.equals(getConstraintValidatorAnnotationType(validatorClass))) {
              @SuppressWarnings("unchecked") // I don't think we could be any more thorough in validation here
              final ConstraintValidator<A> validator = (ConstraintValidator<A>)
                  ReflectionUtil.instantiate(validatorClass);
              validator.initialize(annotation);
              return validator;
          }
          return null;
      }
  
      private static Type getConstraintValidatorAnnotationType(final Class<? extends ConstraintValidator<?>> type) {
          for (final Type parentType : type.getGenericInterfaces()) {
              if (parentType instanceof ParameterizedType) {
                  final ParameterizedType parameterizedType = (ParameterizedType) parentType;
                  if (ConstraintValidator.class.equals(parameterizedType.getRawType())) {
                      return parameterizedType.getActualTypeArguments()[0];
                  }
              }
          }
          return Void.TYPE;
      }
  }