/*
 *  Copyright 2013 Chris Pheby
 *
 *  Licensed 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.jadira.reflection.cloning;

import java.lang.invoke.MethodHandle;
import java.util.Collections;
import java.util.IdentityHashMap;
import java.util.Set;

import org.jadira.reflection.access.unsafe.UnsafeOperations;
import org.jadira.reflection.cloning.api.CloneDriver;
import org.jadira.reflection.cloning.api.CloneImplementor;
import org.jadira.reflection.cloning.api.Cloner;
import org.jadira.reflection.cloning.implementor.PortableCloneStrategy;
import org.jadira.reflection.cloning.implementor.UnsafeCloneStrategy;
import org.objenesis.ObjenesisException;

/**
 * This is a highly reduced version of {@link Cloner}. It can deliver somewhat better throughput
 * than {@link UnsafeCloneStrategy} using the Server JVM, and around twice the throughput of the
 * {@link PortableCloneStrategy}. Unlike BasicCloner, this cloner does not offer any configuration
 * options. Due to lack of configuration and special functions, this cloner is unsuitable for many
 * datatypes.
 * 
 * Note that MinimalCloner can be slower for certain kinds of data structure. For example, when
 * cloning a linked list, MinimalCloner must visit all the references of the entire data structure,
 * whereas other Cloners can use a CloneImplementor to perform efficient cloning of this structure
 * iteratively.
 * 
 * In general, you are recommended to use MinimalCloner judiciously. Typically you can use it by
 * designating a data type as @Cloneable(implementor=MinimalCloner.class) so that the type known to
 * benefit from this cloner makes use of it.
 */
public class MinimalCloner implements Cloner, CloneDriver, CloneImplementor {

        private static final UnsafeOperations UNSAFE_OPERATIONS = UnsafeOperations.getUnsafeOperations();

        @Override
        public <T> T newInstance(Class<T> c) {
                try {
                        return UNSAFE_OPERATIONS.allocateInstance(c);
                } catch (IllegalStateException e) {
                        throw new ObjenesisException(e.getCause());
                }
        }

        /**
         * Always returns true
         */
        @Override
        public boolean canClone(Class<?> clazz) {
                return true;
        }

        @Override
        public <T> T clone(T obj, CloneDriver context, IdentityHashMap<Object, Object> referencesToReuse, long stackDepth) {

                T copy = UNSAFE_OPERATIONS.deepCopy(obj, referencesToReuse);
                return copy;
        }

        /**
         * This implementation does not delegate to implementors
         */
        @Override
        public CloneImplementor getImplementor(Class<?> clazz) {
                return null;
        }

        /**
         * This implementation cannot invoke clone()
         */
        @Override
        public boolean isUseCloneable() {
                return false;
        }

        /**
         * Transient fields are always cloned
         */
        @Override
        public boolean isCloneTransientFields() {
                return true;
        }

        /**
         * Transient annotated fields are always cloned
         */
        @Override
        public boolean isCloneTransientAnnotatedFields() {
                return true;
        }

        /**
         * Immutable fields are always cloned, but object reference identity in the new structure is
         * preserved
         */
        @Override
        public boolean isCloneImmutable() {
                return true;
        }

        /**
         * No Immutable classes are identified
         */
        @Override
        public Set<Class<?>> getImmutableClasses() {
                return Collections.emptySet();
        }

        /**
         * No Non-Cloneable classes are identified
         */
        @Override
        public Set<Class<?>> getNonCloneableClasses() {
                return Collections.emptySet();
        }

        /**
         * CloneImplementors may not be used
         */
        @Override
        public boolean isUseCloneImplementors() {
                return false;
        }

        @Override
        public <T> T clone(T obj) {
                return clone(obj, this, new IdentityHashMap<Object, Object>(), 0L);
        }

        @Override
        public void initialiseFor(Class<?> classes) {
        }

        /**
         * Cloneable annotation is not supported
         */
        @Override
        public CloneImplementor getAnnotationImplementor(Class<?> clazz) {
                return null;
        }

        /**
         * Cloneable interface is not supported
         */
        @Override
        public MethodHandle getCloneMethod(Class<?> clazz) {
                return null;
        }

        /**
         * Does not clone synthetic fields
         */
        @Override
        public boolean isCloneSyntheticFields() {
                return false;
        }

        @Override
        public void putAnnotationImplementor(Class<?> clazz, CloneImplementor implementor) {
                // No-op
        }

        @Override
        public void putCloneMethod(Class<?> clazz, MethodHandle handle) {
                // No-op
        }

        @Override
        public CloneImplementor getBuiltInImplementor(Class<?> clazz) {
                return null;
        }

        @Override
        public boolean isImmutableInstance(Object instance) {
                return false;
        }

        @Override
        public void putImmutableInstance(Object instance) {
                // no-op
        }

        @Override
        public boolean isTrackReferences() {
                return true;
        }

        @Override
        public boolean isTrackReferencesForFlatClasses() {
                return true;
        }
}