001/*
002 *  Licensed to the Apache Software Foundation (ASF) under one
003 *  or more contributor license agreements.  See the NOTICE file
004 *  distributed with this work for additional information
005 *  regarding copyright ownership.  The ASF licenses this file
006 *  to you under the Apache License, Version 2.0 (the
007 *  "License"); you may not use this file except in compliance
008 *  with the License.  You may obtain a copy of the License at
009 *
010 *    http://www.apache.org/licenses/LICENSE-2.0
011 *
012 *  Unless required by applicable law or agreed to in writing,
013 *  software distributed under the License is distributed on an
014 *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
015 *  KIND, either express or implied.  See the License for the
016 *  specific language governing permissions and limitations
017 *  under the License.
018 *
019 */
020package org.apache.mina.example.tapedeck;
021
022import java.nio.charset.Charset;
023import java.util.LinkedList;
024
025import org.apache.mina.core.buffer.IoBuffer;
026import org.apache.mina.core.filterchain.IoFilter.NextFilter;
027import org.apache.mina.core.session.IoSession;
028import org.apache.mina.filter.codec.ProtocolDecoder;
029import org.apache.mina.filter.codec.ProtocolDecoderOutput;
030import org.apache.mina.filter.codec.textline.LineDelimiter;
031import org.apache.mina.filter.codec.textline.TextLineDecoder;
032
033/**
034 * MINA {@link ProtocolDecoder} which decodes bytes into {@link Command}
035 * objects.
036 *
037 * @author <a href="http://mina.apache.org">Apache MINA Project</a>
038 */
039public class CommandDecoder extends TextLineDecoder {
040    
041    public CommandDecoder() {
042        super(Charset.forName("UTF8"), LineDelimiter.WINDOWS);
043    }
044    
045    private Object parseCommand(String line) throws CommandSyntaxException {
046        String[] temp = line.split(" +", 2);
047        String cmd = temp[0].toLowerCase();
048        String arg = temp.length > 1 ? temp[1] : null;
049        
050        if (LoadCommand.NAME.equals(cmd)) {
051            if (arg == null) {
052                throw new CommandSyntaxException("No tape number specified");
053            }
054            try {
055                return new LoadCommand(Integer.parseInt(arg));
056            } catch (NumberFormatException nfe) {
057                throw new CommandSyntaxException("Illegal tape number: " + arg);
058            }
059        } else if (PlayCommand.NAME.equals(cmd)) {
060            return new PlayCommand();
061        } else if (PauseCommand.NAME.equals(cmd)) {
062            return new PauseCommand();
063        } else if (StopCommand.NAME.equals(cmd)) {
064            return new StopCommand();
065        } else if (ListCommand.NAME.equals(cmd)) {
066            return new ListCommand();
067        } else if (EjectCommand.NAME.equals(cmd)) {
068            return new EjectCommand();
069        } else if (QuitCommand.NAME.equals(cmd)) {
070            return new QuitCommand();
071        } else if (InfoCommand.NAME.equals(cmd)) {
072            return new InfoCommand();
073        } else if (UserCommand.NAME.equals(cmd)) {
074            if (arg == null) {
075                throw new CommandSyntaxException("No username specified");
076            }
077            return new UserCommand(arg);
078        } else if (PasswordCommand.NAME.equals(cmd)) {
079            if (arg == null) {
080                throw new CommandSyntaxException("No password specified");
081            }
082            return new PasswordCommand(arg);
083        }
084        
085        throw new CommandSyntaxException("Unknown command: " + cmd);
086    }
087
088    @Override
089    public void decode(IoSession session, IoBuffer in, final ProtocolDecoderOutput out) 
090            throws Exception {
091        
092        final LinkedList<String> lines = new LinkedList<String>();
093        super.decode(session, in, new ProtocolDecoderOutput() {
094            public void write(Object message) {
095                lines.add((String) message);
096            }
097            public void flush(NextFilter nextFilter, IoSession session) {}
098        });
099        
100        for (String s: lines) {
101            out.write(parseCommand(s));
102        }
103    }
104
105}