/*
    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 org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.apache.wiki.api.core.Context;
import org.apache.wiki.api.core.ContextEnum;
import org.apache.wiki.api.core.Engine;
import org.apache.wiki.api.spi.Wiki;
import org.apache.wiki.util.ClassUtil;
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;

import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.util.Vector;

/**
 *  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 Engine m_engine;
    private final XmlRpcServer m_xmlrpcServer = new XmlRpcServer();

    private static final Logger LOG = LogManager.getLogger( RPCServlet.class );

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

    /**
     *  Initializes the servlet.
     */
    @Override
    public void init( final ServletConfig config ) throws ServletException {
        m_engine = Wiki.engine().find( 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( final 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.
     */
    @Override
    public void doPost( final HttpServletRequest request, final HttpServletResponse response ) throws ServletException {
        LOG.debug("Received POST to RPCServlet");

        try {
            final Context ctx = Wiki.context().create( m_engine, request, ContextEnum.PAGE_NONE.getRequestContext() );
            final XmlRpcContext xmlrpcContext = new WikiXmlRpcContext( m_xmlrpcServer.getHandlerMapping(), ctx );
            final 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 );

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

            // LOG.debug("Result = "+new String(result) );
        } catch( final 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.
     */
    @Override
    public void doGet( final HttpServletRequest request, final HttpServletResponse response ) throws ServletException {
        LOG.debug("Received HTTP GET to RPCServlet");

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

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

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

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

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

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

            final Invoker invoker = new Invoker( rpchandler );
            return invoker.execute( method, params );
        }
    }

    private static class WikiXmlRpcContext implements XmlRpcContext {

        private final XmlRpcHandlerMapping m_mapping;
        private final Context m_context;

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

        @Override
        public XmlRpcHandlerMapping getHandlerMapping()
        {
            return m_mapping;
        }

        @Override
        public String getPassword() {
            return null;
        }

        @Override
        public String getUserName() {
            return null;
        }

        public Context getWikiContext()
        {
            return m_context;
        }
    }

}