//
//  ========================================================================
//  Copyright (c) 1995-2016 Mort Bay Consulting Pty. Ltd.
//  ------------------------------------------------------------------------
//  All rights reserved. This program and the accompanying materials
//  are made available under the terms of the Eclipse Public License v1.0
//  and Apache License v2.0 which accompanies this distribution.
//
//      The Eclipse Public License is available at
//      http://www.eclipse.org/legal/epl-v10.html
//
//      The Apache License v2.0 is available at
//      http://www.opensource.org/licenses/apache2.0.php
//
//  You may elect to redistribute this code under either of these licenses.
//  ========================================================================
//

package org.eclipse.jetty.osgi.boot.internal.webapp;

import java.io.File;
import java.io.IOException;
import java.lang.reflect.Field;
import java.net.URL;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Enumeration;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
import java.util.StringTokenizer;
import java.util.jar.JarFile;

import javax.servlet.http.HttpServlet;

import org.eclipse.jetty.osgi.boot.utils.BundleClassLoaderHelperFactory;
import org.eclipse.jetty.util.log.Log;
import org.eclipse.jetty.util.log.Logger;
import org.eclipse.jetty.util.resource.Resource;
import org.eclipse.jetty.webapp.WebAppClassLoader;
import org.eclipse.jetty.webapp.WebAppContext;
import org.osgi.framework.Bundle;
import org.osgi.framework.BundleReference;

/**
 * OSGiWebappClassLoader
 * 
 * 
 * Extends the webapp classloader to also use the classloader of the Bundle defining the webapp.
 */
public class OSGiWebappClassLoader extends WebAppClassLoader implements BundleReference
{

    private static final Logger __logger = Log.getLogger(OSGiWebappClassLoader.class.getName());

    /**
     * when a logging framework is setup in the osgi classloaders, it can access
     * this and register the classes that must not be found in the jar.
     */
    public static final Set<String> JAR_WITH_SUCH_CLASS_MUST_BE_EXCLUDED = new HashSet<String>();

    public static void addClassThatIdentifiesAJarThatMustBeRejected(Class<?> zclass)
    {
        JAR_WITH_SUCH_CLASS_MUST_BE_EXCLUDED.add(zclass.getName().replace('.', '/') + ".class");
    }

    public static void addClassThatIdentifiesAJarThatMustBeRejected(String zclassName)
    {
        JAR_WITH_SUCH_CLASS_MUST_BE_EXCLUDED.add(zclassName.replace('.', '/') + ".class");
    }

    static
    {
        addClassThatIdentifiesAJarThatMustBeRejected(HttpServlet.class);
    }

    private ClassLoader _osgiBundleClassLoader;

    private Bundle _contributor;

    private boolean _lookInOsgiFirst = true;

    /* ------------------------------------------------------------ */
    /**
     * @param parent The parent classloader.
     * @param context The WebAppContext
     * @param contributor The bundle that defines this web-application.
     * @throws IOException if unable to cerate the OSGiWebappClassLoader
     */
    public OSGiWebappClassLoader(ClassLoader parent, WebAppContext context, Bundle contributor)
    throws IOException
    {
        super(parent, context);
        _contributor = contributor;
        _osgiBundleClassLoader = BundleClassLoaderHelperFactory.getFactory().getHelper().getBundleClassLoader(contributor);
    }
    
    
    
    @Override
    public Class<?> loadClass(String name) throws ClassNotFoundException
    {
        return super.loadClass(name);
    }

    /* ------------------------------------------------------------ */
    /**
     * Returns the <code>Bundle</code> that defined this web-application.
     * 
     * @return The <code>Bundle</code> object associated with this
     *         <code>BundleReference</code>.
     */
    public Bundle getBundle()
    {
        return _contributor;
    }

    /* ------------------------------------------------------------ */
    @Override
    public Enumeration<URL> getResources(String name) throws IOException
    {
        Enumeration<URL> osgiUrls = _osgiBundleClassLoader.getResources(name);
        Enumeration<URL> urls = super.getResources(name);
        if (_lookInOsgiFirst)
        {
            return Collections.enumeration(toList(osgiUrls, urls));
        }
        else
        {
            return Collections.enumeration(toList(urls, osgiUrls));
        }
    }
    
    
    
    /* ------------------------------------------------------------ */
    @Override
    public URL getResource(String name)
    {
        if (_lookInOsgiFirst)
        {
            URL url = _osgiBundleClassLoader.getResource(name);
            return url != null ? url : super.getResource(name);
        }
        else
        {
            URL url = super.getResource(name);
            return url != null ? url : _osgiBundleClassLoader.getResource(name);
        }
    }
    
    
    
    /* ------------------------------------------------------------ */
    private List<URL> toList(Enumeration<URL> e, Enumeration<URL> e2)
    {
        List<URL> list = new ArrayList<URL>();
        while (e != null && e.hasMoreElements())
            list.add(e.nextElement());
        while (e2 != null && e2.hasMoreElements())
            list.add(e2.nextElement());
        return list;
    }

    
    /* ------------------------------------------------------------ */
    protected Class<?> findClass(String name) throws ClassNotFoundException
    {
        try
        {
            return _lookInOsgiFirst ? _osgiBundleClassLoader.loadClass(name) : super.findClass(name);
        }
        catch (ClassNotFoundException cne)
        {
            try
            {
                return _lookInOsgiFirst ? super.findClass(name) : _osgiBundleClassLoader.loadClass(name);
            }
            catch (ClassNotFoundException cne2)
            {
                throw cne;
            }
        }
    }
    
    
    
    /* ------------------------------------------------------------ */
    /**
     * Parse the classpath ourselves to be able to filter things. This is a
     * derivative work of the super class
     */
    @Override
    public void addClassPath(String classPath) throws IOException
    {

        StringTokenizer tokenizer = new StringTokenizer(classPath, ",;");
        while (tokenizer.hasMoreTokens())
        {
            String path = tokenizer.nextToken();
            Resource resource = getContext().newResource(path);

            // Resolve file path if possible
            File file = resource.getFile();
            if (file != null && isAcceptableLibrary(file, JAR_WITH_SUCH_CLASS_MUST_BE_EXCLUDED))
            {
                super.addClassPath(path);
            }
            else
            {
                __logger.info("Did not add " + path + " to the classloader of the webapp " + getContext());
            }
        }

    }

    
    /* ------------------------------------------------------------ */
    /**
     * @param lib
     * @return true if the lib should be included in the webapp classloader.
     */
    private boolean isAcceptableLibrary(File file, Set<String> pathToClassFiles)
    {
        try
        {
            if (file.isDirectory())
            {
                for (String criteria : pathToClassFiles)
                {
                    if (new File(file, criteria).exists()) { return false; }
                }
            }
            else
            {
                JarFile jar = null;
                try
                {
                    jar = new JarFile(file);
                    for (String criteria : pathToClassFiles)
                    {
                        if (jar.getEntry(criteria) != null) { return false; }
                    }
                }
                finally
                {
                    if (jar != null) try
                    {
                        jar.close();
                    }
                    catch (IOException ioe)
                    {
                    }
                }
            }
        }
        catch (IOException e)
        {
            // nevermind. just trying our best
            __logger.ignore(e);
        }
        return true;
    }

    private static Field _contextField;

    
    /* ------------------------------------------------------------ */
    /**
     * In the case of the generation of a webapp via a jetty context file we
     * need a proper classloader to setup the app before we have the
     * WebappContext So we place a fake one there to start with. We replace it
     * with the actual webapp context with this method. We also apply the
     * extraclasspath there at the same time.
     * @param webappContext the web app context
     */
    public void setWebappContext(WebAppContext webappContext)
    {
        try
        {
            if (_contextField == null)
            {
                _contextField = WebAppClassLoader.class.getDeclaredField("_context");
                _contextField.setAccessible(true);
            }
            _contextField.set(this, webappContext);
            if (webappContext.getExtraClasspath() != null)
            {
                addClassPath(webappContext.getExtraClasspath());
            }
        }
        catch (Throwable t)
        {
            // humf that will hurt if it does not work.
            __logger.warn("Unable to set webappcontext", t);
        }
    }
}
