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/*
 * Copyright 2003-2007 the original author or authors.
 *
 * 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 groovy.lang;

import groovy.lang.MetaClassRegistry.MetaClassCreationHandle;
import org.codehaus.groovy.reflection.ClassInfo;

/**
 * A handle for the MetaClassRegistry that changes all classes loaded into the Grails VM
 * to use ExpandoMetaClass instances
 *
 * 
The handle should be registered with the Groovy runtime before Groovy loads, for example
 * in your main method.
 *
 * GroovySystem.metaClassRegistry.metaClassCreationHandle = new ExpandoMetaClassCreationHandle()
 *
 * @see groovy.lang.MetaClassRegistry
 * @see groovy.lang.MetaClassRegistry.MetaClassCreationHandle
 * @see org.codehaus.groovy.runtime.metaclass.MetaClassRegistryImpl#setMetaClassCreationHandle(groovy.lang.MetaClassRegistry.MetaClassCreationHandle)
 *
 * @author Graeme Rocher
 * @since 1.5
 */
public class ExpandoMetaClassCreationHandle extends MetaClassCreationHandle {

    public static final ExpandoMetaClassCreationHandle instance = new ExpandoMetaClassCreationHandle();

    /* (non-Javadoc)
     * @see groovy.lang.MetaClassRegistry.MetaClassCreationHandle#create(java.lang.Class, groovy.lang.MetaClassRegistry)
     */
    protected MetaClass createNormalMetaClass(Class theClass, MetaClassRegistry registry) {
        if(theClass != ExpandoMetaClass.class) {
            return new ExpandoMetaClass(theClass, true, true);
        }
        else {
            return super.createNormalMetaClass(theClass, registry);
        }
    }

    /**
     * Registers a modified ExpandoMetaClass with the creation handle
     *
     * @param emc The EMC
     */
    public void registerModifiedMetaClass(ExpandoMetaClass emc) {
        final Class klazz = emc.getJavaClass();
        GroovySystem.getMetaClassRegistry().setMetaClass(klazz,emc);
    }

    public boolean hasModifiedMetaClass(ExpandoMetaClass emc) {
        return emc.getClassInfo().getModifiedExpando() != null;
    }

    /**
     * Enables the ExpandoMetaClassCreationHandle with the registry
     *
     * ExpandoMetaClassCreationHandle.enable();
     *
     */
    public static void enable() {
        final MetaClassRegistry metaClassRegistry = GroovySystem.getMetaClassRegistry();
        synchronized (metaClassRegistry) {
            if (metaClassRegistry.getMetaClassCreationHandler() != instance) {
                ClassInfo.clearModifiedExpandos();
                metaClassRegistry.setMetaClassCreationHandle(instance);
            }
        }
    }

    public static void disable() {
        final MetaClassRegistry metaClassRegistry = GroovySystem.getMetaClassRegistry();
        synchronized (metaClassRegistry) {
            if (metaClassRegistry.getMetaClassCreationHandler() == instance) {
                ClassInfo.clearModifiedExpandos();
                metaClassRegistry.setMetaClassCreationHandle(new MetaClassCreationHandle());
            }
        }
    }
}