/*
 * Copyright (C) 2005-2007 Alfresco Software Limited.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.

 * This program 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 General Public License for more details.

 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.

 * As a special exception to the terms and conditions of version 2.0 of 
 * the GPL, you may redistribute this Program in connection with Free/Libre 
 * and Open Source Software ("FLOSS") applications as described in Alfresco's 
 * FLOSS exception.  You should have recieved a copy of the text describing 
 * the FLOSS exception, and it is also available here: 
 * http://www.alfresco.com/legal/licensing"
 */
package org.alfresco.jcr.util;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;

import javax.jcr.AccessDeniedException;
import javax.jcr.RepositoryException;
import javax.jcr.lock.LockException;
import javax.jcr.nodetype.ConstraintViolationException;
import javax.jcr.nodetype.NoSuchNodeTypeException;

import org.alfresco.error.AlfrescoRuntimeException;
import org.alfresco.jcr.session.SessionImpl;
import org.alfresco.repo.node.integrity.IntegrityException;
import org.alfresco.service.cmr.dictionary.InvalidTypeException;
import org.alfresco.service.cmr.lock.NodeLockedException;
import org.alfresco.service.cmr.security.AuthenticationService;


/**
 * Factory for creating a JCR Session Context Proxy
 * 
 * The Session Context Proxy is responsible for ensuring that the appropriate Alfresco
 * Repository context is setup when a method is executed within a JCR session.  For
 * example, the appropriate authenticated user is validated.
 * 
 * @author David Caruana
 *
 */
public class JCRProxyFactory
{
    
    /**
     * Create a Session Context Proxy
     * 
     * @param target  target object to wrap
     * @param proxyInterface  the proxy interface to export
     * @param context  the session context
     * @return  the proxied target
     */
    public static Object create(Object target, Class proxyInterface, SessionImpl context)
    {
        InvocationHandler handler = new SessionContextInvocationHandler(target, context);
        return Proxy.newProxyInstance(proxyInterface.getClassLoader(), new Class[]{proxyInterface}, handler);
    }


    /**
     * Session Context Invocation Handler
     * 
     * @author David Caruana
     */
    private static class SessionContextInvocationHandler implements InvocationHandler
    {
        private Object target;
        private SessionImpl session;
        private AuthenticationService authenticationService;

        /**
         * Constuct.
         * 
         * @param instance  the object instance holding the method
         * @param delegateMethod  the method to invoke
         */
        private SessionContextInvocationHandler(Object target, SessionImpl context)
        {
            this.target = target;
            this.session = context;
            this.authenticationService = session.getRepositoryImpl().getServiceRegistry().getAuthenticationService();
        }
        
        /* (non-Javadoc)
         * @see java.lang.reflect.InvocationHandler#invoke(java.lang.Object, java.lang.reflect.Method, java.lang.Object[])
         */
        public Object invoke(Object proxy, Method method, Object[] args) throws Throwable
        {
            // Handle Object level methods
            if (method.getName().equals("toString"))
            {
                return toString();
            }
            else if (method.getName().equals("hashCode"))
            {
                return hashCode();
            }
            else if (method.getName().equals("equals"))
            {
                if (Proxy.isProxyClass(args[0].getClass()))
                {
                    return equals(Proxy.getInvocationHandler(args[0]));
                }
                return false;
            }

            try
            {
                // establish authentication context 
                String username = authenticationService.getCurrentUserName();

                try
                {
                    // setup authentication context, if one does not exist (for example, in remote case)
                    if (!method.getName().equals("logout"))
                    {
                        if (username == null)
                        {
                            authenticationService.validate(session.getTicket());
                        }
                    }

                    // invoke underlying service
                    return method.invoke(target, args);
                }
                catch (InvocationTargetException e)
                {
                    Throwable cause = e.getCause();
                    throw cause;
                }
                finally
                {
                    // cleanup authentication context (only if one didn't exist before)
                    if (username == null)
                    {
                        authenticationService.clearCurrentSecurityContext();
                    }
                }
            }
            catch(Throwable cause)
            {
                // Map Alfresco exceptions to JCR exceptions
                if (cause instanceof IntegrityException)
                {
                    throw new ConstraintViolationException(cause);
                }
                else if (cause instanceof NodeLockedException)
                {
                    throw new LockException(cause);
                }
                else if (cause instanceof InvalidTypeException)
                {
                    throw new NoSuchNodeTypeException(cause);
                }
                else if (cause instanceof org.alfresco.repo.security.permissions.AccessDeniedException)
                {
                    throw new AccessDeniedException(cause);
                }
                else if (cause instanceof AlfrescoRuntimeException)
                {
                    throw new RepositoryException(cause);
                }
                throw cause;
            }
        }
    
        @Override
        public boolean equals(Object obj)
        {
            if (obj == this)
            {
                return true;
            }
            else if (obj == null || !(obj instanceof SessionContextInvocationHandler))
            {
                return false;
            }
            SessionContextInvocationHandler other = (SessionContextInvocationHandler)obj;
            return target.equals(other.target);
        }
    
        @Override
        public int hashCode()
        {
            return target.hashCode();
        }
    
        @Override
        public String toString()
        {
            return target.toString();
        }
    }

}