package component;

import encoding.*;

/*
 * @Author: Wang Feng
 * @Description:表示一个拥塞标记 TLV 组件
 * @Version: 1.0.0
 * @Date: 15:54 2021/3/9
 * @Copyright: MIN-Group；国家重大科技基础设施——未来网络北大实验室；深圳市信息论与未来网络重点实验室
 */
public class CongestionMark implements TlvComponentBase,InitialAble, IEncodingAble {
    // 成员变量 todo: 越界问题
    private long congestionMark;

    // 函数
    public long getCongestionLevel(){
        return this.congestionMark;
    }

    public void setCongestionLevel(long congestionMark){
        this.congestionMark=congestionMark;
        this.doInitial();
    }

    // 接口实现-变量区
    private boolean initial=false;

    // 接口实现-方法区
    @Override
    public void doInitial() {
        initial=true;
    }

    @Override
    public boolean isInitial() {
        return initial;
    }

    /**
     * 将 CongestionMark 线速编码为一个 TLV
     * @param encoder
     * @return
     */
    @Override
    public int wireEncode(Encoder encoder) throws ComponentException {
        int totalLength=0;

        // 编码 TLV-VALUE
        int tmplen= 0;
        try {
            tmplen = encoder.prependNonNegativeInteger(this.congestionMark);
        } catch (EncoderException e) {
            throw new ComponentException("CongestionMark.wireEncode: "+e.getMessage());
        }
        if(tmplen<=0){
            return -1;
        }
        totalLength+=tmplen;

        // 编码 TLV-LENGTH
        try {
            tmplen+=encoder.prependVarNumber(new VlInt(totalLength));
        } catch (EncoderException e) {
            throw new ComponentException("CongestionMark.wireEncode: "+e.getMessage());
        }
        if(tmplen<=0){
            return -1;
        }
        totalLength+=tmplen;

        // 编码 TLV-TYPE
        try {
            tmplen+=encoder.prependVarNumber(new VlInt(TLV.TlvCongestionMark));
        } catch (EncoderException e) {
            throw new ComponentException("CongestionMark.wireEncode: "+e.getMessage());
        }
        if(tmplen<=0){
            return -1;
        }
        totalLength+=tmplen;

        return totalLength;
    }

    /**
     * 从 TLV Block 中解码出一个 CongestionMark
     * @param block
     * @return
     */
    @Override
    public boolean wireDecode(Block block) throws ComponentException {
        // 检查 Type 是否正确
        if(!TLV.expectType(block.getType(),new VlInt(TLV.TlvCongestionMark))){
            return false;
        }

        // 读取 CongestionMark
        long value = 0;
        try {
            value = TLV.readNonNegativeInteger(block.getValue(),0,block.getLength().getVlIntValue2Int());
        } catch (TLVException | VlIntException e) {
            throw new ComponentException("CongestionMark.wireDecode: "+e.getMessage());
        }
        if(value<0){
            return false;
        }
        this.setCongestionLevel(value);

        return true;
    }
}