/*
 * Copyright (c) 2012, 2018 Oracle and/or its affiliates. All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v. 2.0, which is available at
 * http://www.eclipse.org/legal/epl-2.0.
 *
 * This Source Code may also be made available under the following Secondary
 * Licenses when the conditions for such availability set forth in the
 * Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
 * version 2 with the GNU Classpath Exception, which is available at
 * https://www.gnu.org/software/classpath/license.html.
 *
 * SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
 */

package org.glassfish.hk2.api;

import java.io.Serializable;
import java.lang.annotation.Annotation;
import java.lang.reflect.AccessibleObject;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.Arrays;

/**
 * <p>Supports inline instantiation of annotation type instances.</p>
 * 
 * <p>An instance of an annotation type may be obtained by subclassing 
 * <tt>AnnotationLiteral</tt>.</p>
 * 
 * <pre>
 * public abstract class PayByQualifier 
 *       extends AnnotationLiteral&lt;PayBy&gt;
 *       implements PayBy {}
 * </pre>
 * 
 * <p>
 * An extension of AnnotationLiteral must do two things:<OL>
 * <LI>Must have the target annotation as its generic type</LI>
 * <LI>Must implement the target type</LI>
 * </OL>
 * </p>
 * In particular, in-line anonymous extensions of AnnotationLiteral will not
 * work because in-line anonymous extensions of AnnotationLiteral cannot implement
 * the target annotation
 * 
 * @author jwells
 * 
 * @param <T> the annotation type
 */
public abstract class AnnotationLiteral<T extends Annotation> implements Annotation, Serializable {
    /**
     * For serialization
     */
    private static final long serialVersionUID = -3645430766814376616L;
    
    private transient Class<T> annotationType;
    private transient Method[] members;

    protected AnnotationLiteral() {
        Class<?> thisClass = this.getClass();
        
        boolean foundAnnotation = false;
        for (Class<?> iClass : thisClass.getInterfaces()) {
            if (iClass.isAnnotation()) {
                foundAnnotation = true;
                break;
            }
            
        }
        
        if (!foundAnnotation) {
            throw new IllegalStateException("The subclass " + thisClass.getName() + " of AnnotationLiteral must implement an Annotation");
        }
    }
    
    private Method[] getMembers() 
    {
      if (members==null) {
        members = AccessController.doPrivileged(new PrivilegedAction<Method[]>() {

          @Override
          public Method[] run() {
            return annotationType().getDeclaredMethods();
          }
               
        });
          
        if ( members.length>0 && !annotationType().isAssignableFrom(this.getClass()) ) {
          throw new RuntimeException(getClass() + " does not implement the annotation type with members " + annotationType().getName());
        }
      }
      return members;
    }
        
    private static Class<?> getAnnotationLiteralSubclass(Class<?> clazz)
    {
       Class<?> superclass = clazz.getSuperclass();
       if (superclass.equals(AnnotationLiteral.class))
       {
          return clazz;
       }
       else if (superclass.equals(Object.class))
       {
          return null;
       }
       else
       {
          return (getAnnotationLiteralSubclass(superclass));
       }
    }
    
    @SuppressWarnings("unchecked")
    private static <T> Class<T> getTypeParameter(Class<?> annotationLiteralSuperclass)
    {
       Type type = annotationLiteralSuperclass.getGenericSuperclass();
       if (type instanceof ParameterizedType)
       {
          ParameterizedType parameterizedType = (ParameterizedType) type;
          if (parameterizedType.getActualTypeArguments().length == 1)
          {
             return (Class<T>) parameterizedType
                   .getActualTypeArguments()[0];
          }
       }
       return null;
    }

    public Class<? extends Annotation> annotationType()
    {
       if (annotationType==null) 
       {
          Class<?> annotationLiteralSubclass = getAnnotationLiteralSubclass(this.getClass());
          if (annotationLiteralSubclass == null)
          {
             throw new RuntimeException(getClass() + "is not a subclass of AnnotationLiteral");
          }
          annotationType = getTypeParameter(annotationLiteralSubclass);
          if (annotationType == null)
          {
             throw new RuntimeException(getClass() + " does not specify the type parameter T of AnnotationLiteral<T>");
          }
       }
       return annotationType;
    }
    
    @Override
    public boolean equals(Object other)
    {
       if (other instanceof Annotation)
       {
          Annotation that = (Annotation) other;
          if (this.annotationType().equals(that.annotationType()))
          {
             for (Method member : getMembers())
             {
                Object thisValue = invoke(member, this);
                Object thatValue = invoke(member, that);
                if (thisValue instanceof byte[] && thatValue instanceof byte[])
                {
                   if ( !Arrays.equals((byte[])thisValue, (byte[])thatValue) ) return false;
                }
                else if (thisValue instanceof short[] && thatValue instanceof short[])
                {
                   if ( !Arrays.equals((short[])thisValue, (short[])thatValue) ) return false;
                }
                else if (thisValue instanceof int[] && thatValue instanceof int[])
                {
                   if ( !Arrays.equals((int[])thisValue, (int[])thatValue) ) return false;
                }
                else if (thisValue instanceof long[] && thatValue instanceof long[])
                {
                   if ( !Arrays.equals((long[])thisValue, (long[])thatValue) ) return false;
                }
                else if (thisValue instanceof float[] && thatValue instanceof float[])
                {
                   if ( !Arrays.equals((float[])thisValue, (float[])thatValue) ) return false;
                }
                else if (thisValue instanceof double[] && thatValue instanceof double[])
                {
                   if ( !Arrays.equals((double[])thisValue, (double[])thatValue) ) return false;
                }
                else if (thisValue instanceof char[] && thatValue instanceof char[])
                {
                   if ( !Arrays.equals((char[])thisValue, (char[])thatValue) ) return false;
                }
                else if (thisValue instanceof boolean[] && thatValue instanceof boolean[])
                {
                   if ( !Arrays.equals((boolean[])thisValue, (boolean[])thatValue) ) return false;
                }
                else if (thisValue instanceof Object[] && thatValue instanceof Object[])
                {
                   if ( !Arrays.equals((Object[])thisValue, (Object[])thatValue) ) return false;
                }
                else 
                {
                    if (!thisValue.equals(thatValue)) return false;
                }
             }
             return true;
          }
       }
       return false;
    }
    
    @Override
    public int hashCode()
    {
        
       int hashCode = 0;
       for (Method member: getMembers())
       {
          int memberNameHashCode = 127 * member.getName().hashCode();
          Object value = invoke(member, this);
          int memberValueHashCode;
          if (value instanceof boolean[])
          {
             memberValueHashCode = Arrays.hashCode((boolean[]) value);
          }
          else if (value instanceof short[])
          {
             memberValueHashCode = Arrays.hashCode((short[]) value);
          }
          else if (value instanceof int[])
          {
             memberValueHashCode = Arrays.hashCode((int[]) value);
          }
          else if (value instanceof long[])
          {
             memberValueHashCode = Arrays.hashCode((long[]) value);
          }
          else if (value instanceof float[])
          {
             memberValueHashCode = Arrays.hashCode((float[]) value);
          }
          else if (value instanceof double[])
          {
             memberValueHashCode = Arrays.hashCode((double[]) value);
          }
          else if (value instanceof byte[])
          {
             memberValueHashCode = Arrays.hashCode((byte[]) value);
          }
          else if (value instanceof char[])
          {
             memberValueHashCode = Arrays.hashCode((char[]) value);
          }
          else if (value instanceof Object[])
          {
             memberValueHashCode = Arrays.hashCode((Object[]) value);
          }
          else 
          {
             memberValueHashCode = value.hashCode();
          }
          hashCode += memberNameHashCode ^ memberValueHashCode;
       }       
       return hashCode;
    }
    
    private static void setAccessible(final AccessibleObject ao) {
        AccessController.doPrivileged(new PrivilegedAction<Object>() {

            @Override
            public Object run() {
                ao.setAccessible(true);
                return null;
            }
            
        });
        
    }
    
    private static Object invoke(Method method, Object instance)
    {
       try
       {
          if (!method.isAccessible()) {
              setAccessible(method);
          }
          return method.invoke(instance);
       }
       catch (IllegalArgumentException e)
       {
          throw new RuntimeException("Error checking value of member method " + method.getName() + " on " + method.getDeclaringClass(), e);
       }
       catch (IllegalAccessException e)
       {
          throw new RuntimeException("Error checking value of member method " + method.getName() + " on " + method.getDeclaringClass(), e);
       }
       catch (InvocationTargetException e)
       {
          throw new RuntimeException("Error checking value of member method " + method.getName() + " on " + method.getDeclaringClass(), e);
       }
    }
    
    

}
