/*
 * JBoss, Home of Professional Open Source
 * Copyright 2005, JBoss Inc., and individual contributors as indicated
 * by the @authors tag. See the copyright.txt in the distribution for a
 * full listing of individual contributors.
 *
 * This is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * This software is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this software; if not, write to the Free
 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
 */
package org.jbpm.util;

import java.io.IOException;
import java.io.InputStream;
import java.util.Properties;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.jbpm.JbpmConfiguration;
import org.jbpm.JbpmException;
import org.jbpm.graph.def.ProcessDefinition;
import org.jbpm.instantiation.ProcessClassLoader;

/**
 * provides centralized classloader lookup.
 */
public class ClassLoaderUtil {
    private static Log log = LogFactory.getLog(ClassLoaderUtil.class);

    public static Class loadClass(String className) {
        try {
            return getClassLoader().loadClass(className);
        } catch (ClassNotFoundException e) {
            throw new JbpmException("class not found '" + className + "'", e);
        }
    }

    public static ClassLoader getClassLoader() {
        if (JbpmConfiguration.Configs.hasObject("jbpm.classloader")) {
            String jbpmClassloader = JbpmConfiguration.Configs.getString("jbpm.classloader");
            String jbpmClassloaderClassname = JbpmConfiguration.Configs.getString("jbpm.classloader.classname");
            
            if (jbpmClassloader.equals("jbpm")) {
                return ClassLoaderUtil.class.getClassLoader();
            } else if (jbpmClassloader.equals("context")) {
                return Thread.currentThread().getContextClassLoader();
            } else if (jbpmClassloader.equals("custom")) {
                try {
                    if (jbpmClassloaderClassname == null) {
                        throw new JbpmException(
                                "'jbpm.classloader' property set to 'custom' but 'jbpm.classloader.classname' is empty!");
                    }
                    return (ClassLoader) Thread.currentThread().getContextClassLoader().loadClass(
                            jbpmClassloaderClassname).newInstance();
                } catch (InstantiationException e) {
                    throw new JbpmException("Error instantiating custom classloader " + jbpmClassloaderClassname, e);
                } catch (IllegalAccessException e) {
                    throw new JbpmException("Error accessing custom classloader " + jbpmClassloaderClassname, e);
                } catch (ClassNotFoundException e) {
                    throw new JbpmException("Custom classloader " + jbpmClassloaderClassname + " not found ", e);
                }
            } else {
                throw new JbpmException("'jbpm.classloader' property set to '" + jbpmClassloader
                        + "' but only the values 'jbpm'/'context'/'custom' are supported!");
            }
        } else {
            return ClassLoaderUtil.class.getClassLoader();
        }
    }

    public static InputStream getStream(String resource) {
        return getClassLoader().getResourceAsStream(resource);
    }

    public static Properties getProperties(String resource) {
        Properties properties = new Properties();
        try {
            properties.load(getStream(resource));
        } catch (IOException e) {
            throw new JbpmException("couldn't load properties file '" + resource + "'", e);
        }
        return properties;
    }

    /**
     * searches the given resource, first on the root of the classpath and if
     * not not found there, in the given directory. public static InputStream
     * getStream(String resource, String directory) { InputStream is =
     * getClassLoader().getResourceAsStream(resource); if (is==null) { is =
     * getClassLoader().getResourceAsStream(directory+"/"+resource); } return
     * is; }
     * 
     * public static Properties getProperties(String resource, String directory) {
     * Properties properties = new Properties(); try {
     * properties.load(getStream(resource, directory)); } catch (IOException e) {
     * throw new JbpmException("couldn't load properties file '"+resource+"'",
     * e); } return properties; }
     */

    public static ClassLoader getProcessClassLoader(ProcessDefinition processDefinition) {
        return new ProcessClassLoader(getClassLoader(), processDefinition);
    }

}