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/*
 * Copyright (c) 2014, Parallel Universe Software Co. All rights reserved.
 * 
 * This program and the accompanying materials are licensed under the terms 
 * of the Eclipse Public License v1.0, available at
 * http://www.eclipse.org/legal/epl-v10.html
 */
package co.paralleluniverse.common;

import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.util.Enumeration;

/**
 *
 * @author pron
 */
public abstract class FlexibleClassLoader extends ClassLoader {
    private final boolean childFirst;
    private final ThreadLocal inGetResourceAsStream = new ThreadLocal();

    public FlexibleClassLoader(ClassLoader parent, boolean childFirst) {
        super(parent);
        this.childFirst = childFirst;
    }

    public FlexibleClassLoader(boolean childFirst) {
        this.childFirst = childFirst;
    }

    @Override
    public URL getResource(String name) {
        if (!childFirst)
            return super.getResource(name);
        URL url = findResource(name);
        if (url == null)
            url = super.getResource(name);
        return url;
    }

    @Override
    public InputStream getResourceAsStream(String name) {
        inGetResourceAsStream.set(Boolean.TRUE);
        try {
            InputStream is = null;
            if (!childFirst)
                is = super.getResourceAsStream(name);
            if (is == null)
                is = findResourceAsStream(name);
            if (is == null && childFirst)
                is = super.getResourceAsStream(name);
            return is;
        } finally {
            inGetResourceAsStream.remove();
        }
    }

    @Override
    protected Class loadClass(String name, boolean resolve) throws ClassNotFoundException {
        if (!childFirst)
            return super.loadClass(name, resolve);
        Class c;
        try {
            c = findClass(name);
            if (resolve)
                resolveClass(c);
            return c;
        } catch (ClassNotFoundException e) {
        }
        return super.loadClass(name, resolve);
    }

    @Override
    public Enumeration getResources(String name) throws IOException {
        Enumeration[] tmp = new Enumeration[2];
        tmp[childFirst ? 1 : 0] = super.getResources(name);
        tmp[childFirst ? 0 : 1] = findResources1(name);
        return new sun.misc.CompoundEnumeration<>(tmp);
    }

    @Override
    protected Class findClass(String name) throws ClassNotFoundException {
        final byte[] buf = readResource(name.replace('.', '/') + ".class");
        if (buf == null)
            throw new ClassNotFoundException(name);
        return defineClass(name, buf, 0, buf.length);
    }

    @Override
    protected URL findResource(String name) {
        if (inGetResourceAsStream.get() == Boolean.TRUE)
            return null;
        return findResource1(name);
    }
    
    protected abstract URL findResource1(String name);
    
    protected abstract Enumeration findResources1(String name);

    protected abstract InputStream findResourceAsStream(String name);
    
    protected abstract byte[] readResource(String name);
}