/*
 * Copyright  2000-2004 The Apache Software Foundation
 *
 *  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.bcel.util;

import java.io.IOException;
import java.io.InputStream;
import java.lang.ref.SoftReference;
import java.util.HashMap;
import java.util.Map;

import org.apache.bcel.classfile.ClassParser;
import org.apache.bcel.classfile.JavaClass;

/**
 * This repository is used in situations where a Class is created outside the
 * realm of a ClassLoader. Classes are loaded from the file systems using the
 * paths specified in the given class path. By default, this is the value
 * returned by ClassPath.getClassPath(). <br>
 * It is designed to be used as a singleton, however it can also be used with
 * custom classpaths.
 * 
 * /** Abstract definition of a class repository. Instances may be used to load
 * classes from different sources and may be used in the
 * Repository.setRepository method.
 * 
 * @see org.apache.bcel.Repository
 * 
 * @version $Id: SyntheticRepository.java 386056 2006-03-15 11:31:56Z tcurdt $
 * @author <A HREF="mailto:m.dahm@gmx.de">M. Dahm</A>
 * @author David Dixon-Peugh
 */
public class SyntheticRepository implements Repository {

	/**
	 * 
	 */
	private static final long serialVersionUID = 1L;
	private static Map<ClassPath, SyntheticRepository> _instances = new HashMap<ClassPath, SyntheticRepository>(); // CLASSPATH
																													// X
																													// REPOSITORY
	private ClassPath _path = null;
	private Map<String, SoftReference<JavaClass>> _loadedClasses = new HashMap<String, SoftReference<JavaClass>>(); // CLASSNAME
																													// X
																													// JAVACLASS

	private SyntheticRepository(ClassPath path) {
		_path = path;
	}

	public static SyntheticRepository getInstance() {
		return getInstance(ClassPath.SYSTEM_CLASS_PATH);
	}

	public static SyntheticRepository getInstance(ClassPath classPath) {
		SyntheticRepository rep = _instances.get(classPath);
		if (rep == null) {
			rep = new SyntheticRepository(classPath);
			_instances.put(classPath, rep);
		}
		return rep;
	}

	/**
	 * Store a new JavaClass instance into this Repository.
	 */
	@Override
	public void storeClass(JavaClass clazz) {
		_loadedClasses.put(clazz.getClassName(), new SoftReference<JavaClass>(
				clazz));
		clazz.setRepository(this);
	}

	/**
	 * Remove class from repository
	 */
	@Override
	public void removeClass(JavaClass clazz) {
		_loadedClasses.remove(clazz.getClassName());
	}

	/**
	 * Find an already defined (cached) JavaClass object by name.
	 */
	@Override
	public JavaClass findClass(String className) {
		SoftReference<?> ref = _loadedClasses.get(className);
		if (ref == null) {
			return null;
		}
		return (JavaClass) ref.get();
	}

	/**
	 * Find a JavaClass object by name. If it is already in this Repository, the
	 * Repository version is returned. Otherwise, the Repository's classpath is
	 * searched for the class (and it is added to the Repository if found).
	 * 
	 * @param className
	 *            the name of the class
	 * @return the JavaClass object
	 * @throws ClassNotFoundException
	 *             if the class is not in the Repository, and could not be found
	 *             on the classpath
	 */
	@Override
	public JavaClass loadClass(String className) throws ClassNotFoundException {
		if (className == null || className.equals("")) {
			throw new IllegalArgumentException("Invalid class name "
					+ className);
		}
		className = className.replace('/', '.'); // Just in case, canonical form
		JavaClass clazz = findClass(className);
		if (clazz != null) {
			return clazz;
		}
		try {
			return loadClass(_path.getInputStream(className), className);
		} catch (IOException e) {
			throw new ClassNotFoundException(
					"Exception while looking for class " + className + ": "
							+ e.toString());
		}
	}

	/**
	 * Find the JavaClass object for a runtime Class object. If a class with the
	 * same name is already in this Repository, the Repository version is
	 * returned. Otherwise, getResourceAsStream() is called on the Class object
	 * to find the class's representation. If the representation is found, it is
	 * added to the Repository.
	 * 
	 * @see Class
	 * @param clazz
	 *            the runtime Class object
	 * @return JavaClass object for given runtime class
	 * @throws ClassNotFoundException
	 *             if the class is not in the Repository, and its representation
	 *             could not be found
	 */
	@Override
	public JavaClass loadClass(Class<?> clazz) throws ClassNotFoundException {
		String className = clazz.getName();
		JavaClass repositoryClass = findClass(className);
		if (repositoryClass != null) {
			return repositoryClass;
		}
		String name = className;
		int i = name.lastIndexOf('.');
		if (i > 0) {
			name = name.substring(i + 1);
		}
		return loadClass(clazz.getResourceAsStream(name + ".class"), className);
	}

	private JavaClass loadClass(InputStream is, String className)
			throws ClassNotFoundException {
		try {
			if (is != null) {
				ClassParser parser = new ClassParser(is, className);
				JavaClass clazz = parser.parse();
				storeClass(clazz);
				return clazz;
			}
		} catch (IOException e) {
			throw new ClassNotFoundException(
					"Exception while looking for class " + className + ": "
							+ e.toString());
		}
		throw new ClassNotFoundException("SyntheticRepository could not load "
				+ className);
	}

	/**
	 * ClassPath associated with the Repository.
	 */
	@Override
	public ClassPath getClassPath() {
		return _path;
	}

	/**
	 * Clear all entries from cache.
	 */
	@Override
	public void clear() {
		_loadedClasses.clear();
	}
}
