/*

  * 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.apache.commons.classscan.builtin;

 import java.io.IOException;

 import java.io.InputStream;

 import java.net.URL;

 import java.util.Map;

 import java.util.ServiceConfigurationError;

 import org.apache.commons.classscan.ClassPathElement;

 import org.apache.commons.classscan.MetaClassLoader;

 import org.apache.commons.classscan.MetaClassPathElement;

 import org.apache.commons.classscan.spi.ClassDigesterFactory;

 import org.apache.commons.classscan.spi.ClassPathElementFactory;

 import org.apache.commons.classscan.spi.ClassPathFactory;

 import org.apache.commons.classscan.spi.model.SpiClassDigester;

 import org.apache.commons.classscan.spi.model.SpiClassPath;

 import org.apache.commons.classscan.spi.model.SpiClassPathElement;

 import org.apache.commons.classscan.spi.model.SpiMetaClass;

 import org.apache.commons.classscan.spi.model.SpiMetaClassPathElement;

 import org.apache.commons.classscan.spi.model.SpiMetaRegistry;

 import org.apache.commons.classscan.util.FactoryCache;

 import org.apache.commons.classscan.util.ReapingHashMap;

 import org.apache.commons.classscan.util.ServiceVisitor;

 import org.slf4j.Logger;

 import org.slf4j.LoggerFactory;

 /**

  * The factory for MetaClassLoaders. Wherever possible, an existing

  * MetaClassLoader is returned for a ClassLoader. The implementation should not

  * prevent the garbage collection of a ClassLoader.

  */

 public class DefaultMetaRegistry implements SpiMetaRegistry {

     private static final Logger logger = LoggerFactory.getLogger(DefaultMetaRegistry.class);

     private final Map<ClassLoader, MetaClassLoader> metaClassLoaders;

         private final FactoryCache<ClassPathFactory> classPathFactories;

         private final FactoryCache<ClassPathElementFactory> classPathElementFactories;

         private SpiClassDigester classDigester;

         public DefaultMetaRegistry() {

             metaClassLoaders = new ReapingHashMap<ClassLoader, MetaClassLoader>();

                 ClassLoader classLoader = getClass().getClassLoader();

                 classPathFactories = new FactoryCache<ClassPathFactory>(ClassPathFactory.class, classLoader);

                 classPathElementFactories = new FactoryCache<ClassPathElementFactory>(ClassPathElementFactory.class, classLoader);

                 findClassDigester(classLoader);

         }

         private void findClassDigester(ClassLoader classLoader) {

                 new ServiceVisitor<ClassDigesterFactory>() {

                         @Override

                         protected boolean visit(ClassDigesterFactory factory) {

                                 try {

                                         classDigester= factory.createDigester(DefaultMetaRegistry.this);

                                         return false;

                                 }

                                 catch(Throwable error) {

                                         logger.warn("Ignoring configuration error", error);

                                         return true;

                                 }

                         }

                 }.visitProviders(ClassDigesterFactory.class, classLoader);

                 if(classDigester==null) {

                         throw new ServiceConfigurationError("Could not load a ClassDigester");

                 }

         }

         @Override

         public MetaClassLoader getMetaClassLoader(ClassLoader classLoader) {

             synchronized(metaClassLoaders) {

             MetaClassLoader mcl = metaClassLoaders.get(classLoader);

             if (mcl == null) {

                 mcl = createMetaClassLoader(classLoader);

                 metaClassLoaders.put(classLoader, mcl);

             }

             return mcl;

             }

     }

         public MetaClassLoader createMetaClassLoader(ClassLoader classLoader) {

                 SpiClassPath cp= getClassPath(classLoader);

                 return cp.createMetaClassLoader(this, classLoader);

         }

     @Override

         public SpiClassPath getClassPath(ClassLoader classLoader) {

             for(ClassPathFactory factory : classPathFactories) {

                     SpiClassPath cp= factory.getClassPath(this, classLoader);

                     if(cp!=null) {

                             return cp;

                     }

             }

             throw new IllegalArgumentException("No ClassPathFactory found for ClassLoader "+classLoader);

     }

         @Override

         public SpiClassPathElement createClassPathElement(URL url) throws IOException {

             for(ClassPathElementFactory factory : classPathElementFactories) {

                     SpiClassPathElement cp= factory.getClassPathElement(this, url);

                     if(cp!=null) {

                             return cp;

                     }

             }

             return null;

         }

         @Override

         public SpiMetaClassPathElement createMetaClassPathElement(ClassPathElement pathElement) {

                 return new DefaultMetaClassPathElement(this, pathElement);

         }

         @Override

         public SpiMetaClass createMetaClass(MetaClassPathElement location, String className, InputStream byteStream) throws IOException {

                 try {

                         SpiMetaClass smc = classDigester.createMetaClass(location, className, byteStream);

                 if (!className.equals(smc.getName())) {

                     throw new IllegalArgumentException("Expecting classname " + className + " but found " + smc.getName());

                 }

                 return smc;

                 }

                 finally {

                         byteStream.close();

                 }

         }

 }