/*
 * Copyright 2017 - 2018 Anton Tananaev (anton@traccar.org)
 *
 * Licensed 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.traccar.protocol;

import org.traccar.BaseFrameDecoder;

import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.Channel;
import io.netty.channel.ChannelHandlerContext;

public class Vt200FrameDecoder extends BaseFrameDecoder {

    @Override
    protected Object decode(
            ChannelHandlerContext ctx, Channel channel, ByteBuf buf) throws Exception {

        int endIndex = buf.indexOf(buf.readerIndex(), buf.writerIndex(), (byte) ')') + 1;
        if (endIndex > 0) {

            ByteBuf frame = Unpooled.buffer();

            while (buf.readerIndex() < endIndex) {
                int b = buf.readByte();
                if (b == '=') {
                    frame.writeByte(buf.readByte() ^ '=');
                } else {
                    frame.writeByte(b);
                }
            }

            return frame;

        }

        return null;
    }

}