/*
 * 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.juneau.internal;

import static org.apache.juneau.common.utils.Utils.*;

import java.lang.annotation.*;
import java.lang.reflect.*;
import java.util.*;
import java.util.stream.*;

import org.apache.juneau.common.utils.*;

/**
 * Annotation utilities.
 *
 * <h5 class='section'>See Also:</h5><ul>
 * </ul>
 */
public class AnnotationUtils {

   /**
    * Checks if two annotations are equal using the criteria for equality presented in the {@link Annotation#equals(Object)} API docs.
    *
    * @param a1 the first Annotation to compare, {@code null} returns {@code false} unless both are {@code null}
    * @param a2 the second Annotation to compare, {@code null} returns {@code false} unless both are {@code null}
    * @return {@code true} if the two annotations are {@code equal} or both {@code null}
    */
   public static boolean equals(Annotation a1, Annotation a2) {
      if (a1 == a2)
         return true;
      if (a1 == null || a2 == null)
         return false;

      Class<? extends Annotation> t1 = a1.annotationType();
      Class<? extends Annotation> t2 = a2.annotationType();

      if (! t1.equals(t2))
         return false;

      boolean b= getAnnotationMethods(t1)
         .anyMatch(x -> ! memberEquals(x.getReturnType(), Utils.safeSupplier(()->x.invoke(a1)), Utils.safeSupplier(()->x.invoke(a2))));
      if (b)
         return false;

      return true;
   }

   /**
    * Generate a hash code for the given annotation using the algorithm presented in the {@link Annotation#hashCode()} API docs.
    *
    * @param a the Annotation for a hash code calculation is desired, not {@code null}
    * @return the calculated hash code
    * @throws RuntimeException if an {@code Exception} is encountered during annotation member access
    * @throws IllegalStateException if an annotation method invocation returns {@code null}
    */
   public static int hashCode(Annotation a) {
      return getAnnotationMethods(a.annotationType())
         .mapToInt(x -> hashMember(x.getName(), Utils.safeSupplier(()->x.invoke(a))))
         .sum();
   }

   private static Stream<Method> getAnnotationMethods(Class<? extends Annotation> type) {
      return alist(type.getDeclaredMethods())
         .stream()
         .filter(x -> x.getParameterCount() == 0 && x.getDeclaringClass().isAnnotation())
      ;
   }

   private static int hashMember(String name, Object value) {
      int part1 = name.hashCode() * 127;
      if (value == null)
         return part1;
      if (isArray(value))
         return part1 ^ arrayMemberHash(value.getClass().getComponentType(), value);
      if (value instanceof Annotation)
         return part1 ^ hashCode((Annotation) value);
      return part1 ^ value.hashCode();
   }

   private static boolean memberEquals(Class<?> type, Object o1, Object o2) {
      if (o1 == o2)
         return true;
      if (o1 == null || o2 == null)
         return false;
      if (type.isArray())
         return arrayMemberEquals(type.getComponentType(), o1, o2);
      if (type.isAnnotation())
         return equals((Annotation) o1, (Annotation) o2);
      return o1.equals(o2);
   }

   private static boolean arrayMemberEquals(Class<?> componentType, Object o1, Object o2) {
      if (componentType.isAnnotation())
         return annotationArrayMemberEquals((Annotation[]) o1, (Annotation[]) o2);
      if (componentType.equals(Byte.TYPE))
         return Arrays.equals((byte[]) o1, (byte[]) o2);
      if (componentType.equals(Short.TYPE))
         return Arrays.equals((short[]) o1, (short[]) o2);
      if (componentType.equals(Integer.TYPE))
         return Arrays.equals((int[]) o1, (int[]) o2);
      if (componentType.equals(Character.TYPE))
         return Arrays.equals((char[]) o1, (char[]) o2);
      if (componentType.equals(Long.TYPE))
         return Arrays.equals((long[]) o1, (long[]) o2);
      if (componentType.equals(Float.TYPE))
         return Arrays.equals((float[]) o1, (float[]) o2);
      if (componentType.equals(Double.TYPE))
         return Arrays.equals((double[]) o1, (double[]) o2);
      if (componentType.equals(Boolean.TYPE))
         return Arrays.equals((boolean[]) o1, (boolean[]) o2);
      return Arrays.equals((Object[]) o1, (Object[]) o2);
   }

   private static boolean annotationArrayMemberEquals(Annotation[] a1, Annotation[] a2) {
      if (a1.length != a2.length)
         return false;
      for (int i = 0; i < a1.length; i++)
         if (! equals(a1[i], a2[i]))
            return false;
      return true;
   }

   private static int arrayMemberHash(Class<?> componentType, Object o) {
      if (componentType.equals(Byte.TYPE))
         return Arrays.hashCode((byte[]) o);
      if (componentType.equals(Short.TYPE))
         return Arrays.hashCode((short[]) o);
      if (componentType.equals(Integer.TYPE))
         return Arrays.hashCode((int[]) o);
      if (componentType.equals(Character.TYPE))
         return Arrays.hashCode((char[]) o);
      if (componentType.equals(Long.TYPE))
         return Arrays.hashCode((long[]) o);
      if (componentType.equals(Float.TYPE))
         return Arrays.hashCode((float[]) o);
      if (componentType.equals(Double.TYPE))
         return Arrays.hashCode((double[]) o);
      if (componentType.equals(Boolean.TYPE))
         return Arrays.hashCode((boolean[]) o);
      return Arrays.hashCode((Object[]) o);
   }
}