/*
    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.
 */
package org.apache.wiki.xmlrpc;

import java.io.IOException;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.util.Vector;

import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.log4j.Logger;
import org.apache.wiki.WikiContext;
import org.apache.wiki.WikiEngine;
import org.apache.xmlrpc.ContextXmlRpcHandler;
import org.apache.xmlrpc.Invoker;
import org.apache.xmlrpc.XmlRpcContext;
import org.apache.xmlrpc.XmlRpcHandlerMapping;
import org.apache.xmlrpc.XmlRpcServer;

/**
 *  Handles all incoming servlet requests for XML-RPC calls.
 *  <P>
 *  Uses two initialization parameters:
 *  <UL>
 *  <LI><B>handler</B> : the class which is used to handle the RPC calls.
 *  <LI><B>prefix</B> : The command prefix for that particular handler.
 *  </UL>
 *
 *  @since 1.6.6
 */
public class RPCServlet extends HttpServlet
{
    private static final long serialVersionUID = 3976735878410416180L;

    /** This is what is appended to each command, if the handler has
        not been specified.  */
    // FIXME: Should this be $default?
    public static final String XMLRPC_PREFIX = "wiki";

    private WikiEngine       m_engine;
    private XmlRpcServer     m_xmlrpcServer = new XmlRpcServer();

    static Logger log = Logger.getLogger( RPCServlet.class );

    public void initHandler( String prefix, String handlerName )
        throws ClassNotFoundException,
               InstantiationException,
               IllegalAccessException
    {
        /*
        Class handlerClass = Class.forName( handlerName );
        WikiRPCHandler rpchandler = (WikiRPCHandler) handlerClass.newInstance();
        rpchandler.initialize( m_engine );
        m_xmlrpcServer.addHandler( prefix, rpchandler );
        */
        Class< ? > handlerClass = Class.forName( handlerName );
        m_xmlrpcServer.addHandler( prefix, new LocalHandler(handlerClass) );
    }

    /**
     *  Initializes the servlet.
     */
    public void init( ServletConfig config )
        throws ServletException
    {
        m_engine = WikiEngine.getInstance( config );

        String handlerName = config.getInitParameter( "handler" );
        String prefix      = config.getInitParameter( "prefix" );

        if( handlerName == null ) handlerName = "org.apache.wiki.xmlrpc.RPCHandler";
        if( prefix == null )      prefix = XMLRPC_PREFIX;

        try
        {
            initHandler( prefix, handlerName );

            //
            // FIXME: The metaweblog API should be possible to turn off.
            //
            initHandler( "metaWeblog",
                         "org.apache.wiki.xmlrpc.MetaWeblogHandler" );
        }
        catch( Exception e )
        {
            log.fatal("Unable to start RPC interface: ", e);
            throw new ServletException( "No RPC interface", e );
        }
    }

    /**
     *  Handle HTTP POST.  This is an XML-RPC call, and we'll just forward
     *  the query to an XmlRpcServer.
     */
    public void doPost( HttpServletRequest request, HttpServletResponse response )
        throws ServletException
    {
        log.debug("Received POST to RPCServlet");

        try
        {
            WikiContext ctx = m_engine.createContext( request, WikiContext.NONE );

            XmlRpcContext xmlrpcContext = new WikiXmlRpcContext( m_xmlrpcServer.getHandlerMapping(),
                                                                 ctx );

            byte[] result = m_xmlrpcServer.execute( request.getInputStream(), xmlrpcContext );

            //
            //  I think it's safe to write the output as UTF-8:
            //  The XML-RPC standard never creates other than USASCII
            //  (which is UTF-8 compatible), and our special UTF-8
            //  hack just creates UTF-8.  So in all cases our butt
            //  should be covered.
            //
            response.setContentType( "text/xml; charset=utf-8" );
            response.setContentLength( result.length );

            OutputStream out = response.getOutputStream();
            out.write( result );
            out.flush();

            // log.debug("Result = "+new String(result) );
        }
        catch( IOException e )
        {
            throw new ServletException("Failed to build RPC result", e);
        }
    }

    /**
     *  Handles HTTP GET.  However, we do not respond to GET requests,
     *  other than to show an explanatory text.
     */
    public void doGet( HttpServletRequest request, HttpServletResponse response )
        throws ServletException
    {
        log.debug("Received HTTP GET to RPCServlet");

        try
        {
            String msg = "We do not support HTTP GET here.  Sorry.";
            response.setContentType( "text/plain" );
            response.setContentLength( msg.length() );

            PrintWriter writer = new PrintWriter( new OutputStreamWriter( response.getOutputStream() ) );

            writer.println( msg );
            writer.flush();
        }
        catch( IOException e )
        {
            throw new ServletException("Failed to build RPC result", e);
        }
    }

    private static class LocalHandler
        implements ContextXmlRpcHandler
    {
        private Class< ? > m_clazz;

        public LocalHandler( Class< ? > clazz )
        {
            m_clazz = clazz;
        }

        public Object execute(String method, Vector params, XmlRpcContext context) throws Exception
        {
            WikiRPCHandler rpchandler = (WikiRPCHandler) m_clazz.newInstance();
            rpchandler.initialize( ((WikiXmlRpcContext)context).getWikiContext() );

            Invoker invoker = new Invoker( rpchandler );

            return invoker.execute( method, params );
        }
    }

    private static class WikiXmlRpcContext
        implements XmlRpcContext
    {
        private XmlRpcHandlerMapping m_mapping;
        private WikiContext m_context;

        public WikiXmlRpcContext( XmlRpcHandlerMapping map, WikiContext ctx )
        {
            m_mapping = map;
            m_context = ctx;
        }

        public XmlRpcHandlerMapping getHandlerMapping()
        {
            return m_mapping;
        }

        public String getPassword()
        {
            // TODO Auto-generated method stub
            return null;
        }

        public String getUserName()
        {
            // TODO Auto-generated method stub
            return null;
        }

        public WikiContext getWikiContext()
        {
            return m_context;
        }
    }
}