/*
 * Copyright 2019 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 io.netty.buffer.ByteBuf;
import io.netty.channel.Channel;
import io.netty.channel.ChannelHandlerContext;
import org.traccar.BaseFrameDecoder;

public class ItsFrameDecoder extends BaseFrameDecoder {

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

        int delimiterIndex = buf.indexOf(buf.readerIndex(), buf.writerIndex(), (byte) '*');

        if (buf.writerIndex() > delimiterIndex + 1 && buf.getByte(delimiterIndex + 1) == '*') {
            delimiterIndex += 1;
        }

        ByteBuf frame;
        if (buf.getByte(delimiterIndex - 2) == ',') {
            frame = buf.readRetainedSlice(delimiterIndex - 1 - buf.readerIndex());
            buf.skipBytes(1); // binary checksum
        } else {
            frame = buf.readRetainedSlice(delimiterIndex - buf.readerIndex());
        }

        buf.skipBytes(1); // delimiter

        return frame;
    }

}