package org.apache.cassandra.triggers;
/*
 *
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.
 *
 */


import java.io.File;
import java.io.FilenameFilter;
import java.io.IOError;
import java.io.IOException;
import java.net.URL;
import java.net.URLClassLoader;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.google.common.io.Files;

Custom class loader will load the classes from the class path, CCL will load
the classes from the the URL first, if it cannot find the required class it
will let the parent class loader do the its job.
Note: If the CCL is GC'ed then the associated classes will be unloaded.
/**
 * Custom class loader will load the classes from the class path, CCL will load
 * the classes from the the URL first, if it cannot find the required class it
 * will let the parent class loader do the its job.
 *
 * Note: If the CCL is GC'ed then the associated classes will be unloaded.
 */
public class CustomClassLoader extends URLClassLoader
{
    private static final Logger logger = LoggerFactory.getLogger(CustomClassLoader.class);
    private final Map<String, Class<?>> cache = new ConcurrentHashMap<String, Class<?>>();
    private final ClassLoader parent;

    public CustomClassLoader(ClassLoader parent)
    {
        super(new URL[] {}, parent);
        assert parent != null;
        this.parent = getParent();
    }

    public CustomClassLoader(ClassLoader parent, File classPathDir)
    {
        super(new URL[] {}, parent);
        assert parent != null;
        this.parent = getParent();
        addClassPath(classPathDir);
    }

    public void addClassPath(File dir)
    {
        if (dir == null || !dir.exists())
            return;
        FilenameFilter filter = new FilenameFilter()
        {
            public boolean accept(File dir, String name)
            {
                return name.endsWith(".jar");
            }
        };
        for (File inputJar : dir.listFiles(filter))
        {
            File lib = new File(System.getProperty("java.io.tmpdir"), "lib");
            if (!lib.exists())
            {
                lib.mkdir();
                lib.deleteOnExit();
            }
            try
            {
                File out = File.createTempFile("cassandra-", ".jar", lib);
                out.deleteOnExit();
                logger.info("Loading new jar {}", inputJar.getAbsolutePath());
                Files.copy(inputJar, out);
                addURL(out.toURI().toURL());
            }
            catch (IOException ex)
            {
                throw new IOError(ex);
            }
        }
    }

    @Override
    public Class<?> loadClass(String name) throws ClassNotFoundException
    {
        Class<?> clazz = cache.get(name);
        if (clazz == null)
            return loadClassInternal(name);
        return clazz;
    }

    public synchronized Class<?> loadClassInternal(String name) throws ClassNotFoundException
    {
        try
        {
            return parent.loadClass(name);
        }
        catch (ClassNotFoundException ex)
        {
            logger.trace("Class not found using parent class loader,", ex);
            // Don't throw the exception here, try triggers directory.
        }
        Class<?> clazz = this.findClass(name);
        cache.put(name, clazz);
        return clazz;
    }
}