/*
 * Copyright 2014 Attila Szegedi, Daniel Dekany, Jonathan Revusky
 * 
 * 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 freemarker.template;

import java.lang.ref.ReferenceQueue;
import java.util.WeakHashMap;

import freemarker.ext.beans.BeansWrapper;
import freemarker.ext.beans.BeansWrapperBuilder;
import freemarker.ext.beans.BeansWrapperConfiguration;
import freemarker.ext.beans._BeansAPI;

/**
 * Gets/creates a {@link DefaultObjectWrapper} singleton instance that's already configured as specified in the
 * properties of this object; this is recommended over using the {@link DefaultObjectWrapper} constructors. The returned
 * instance can't be further configured (it's write protected).
 * 
 * <p>See {@link BeansWrapperBuilder} for more info, as that works identically. 
 * 
 * @since 2.3.21
 */
public class DefaultObjectWrapperBuilder extends DefaultObjectWrapperConfiguration {

    private final static WeakHashMap/*<ClassLoader, Map<BeansWrapperSettings, WeakReference<DefaultObjectWrapper>>*/
            INSTANCE_CACHE = new WeakHashMap();
    private final static ReferenceQueue INSTANCE_CACHE_REF_QUEUE = new ReferenceQueue();
    
    /**
     * Creates a builder that creates a {@link DefaultObjectWrapper} with the given {@code incompatibleImprovements};
     * using at least 2.3.22 is highly recommended. See {@link DefaultObjectWrapper#DefaultObjectWrapper(Version)} for
     * more information about the impact of {@code incompatibleImprovements} values.
     */
    public DefaultObjectWrapperBuilder(Version incompatibleImprovements) {
        super(incompatibleImprovements);
    }

    /** For unit testing only */
    static void clearInstanceCache() {
        synchronized (INSTANCE_CACHE) {
            INSTANCE_CACHE.clear();
        }
    }
    
    /**
     * Returns a {@link DefaultObjectWrapper} instance that matches the settings of this builder. This will be possibly
     * a singleton that is also in use elsewhere. 
     */
    public DefaultObjectWrapper build() {
        return (DefaultObjectWrapper) _BeansAPI.getBeansWrapperSubclassSingleton(
                this, INSTANCE_CACHE, INSTANCE_CACHE_REF_QUEUE, DefaultObjectWrapperFactory.INSTANCE);
    }
    
    private static class DefaultObjectWrapperFactory
        implements _BeansAPI._BeansWrapperSubclassFactory {
    
        private static final DefaultObjectWrapperFactory INSTANCE = new DefaultObjectWrapperFactory(); 
        
        public BeansWrapper create(BeansWrapperConfiguration bwConf) {
            return new DefaultObjectWrapper(bwConf, true);
        }
    }

}