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 {
        try {
            int totalLength = 0;

            // 编码 TLV-VALUE
            int tmplen = encoder.prependNonNegativeInteger(this.congestionMark);
            if (tmplen <= 0) {
                return -1;
            }
            totalLength += tmplen;

            // 编码 TLV-LENGTH
            tmplen += encoder.prependVarNumber(new VlInt(totalLength));
            if (tmplen <= 0) {
                return -1;
            }
            totalLength += tmplen;

            // 编码 TLV-TYPE
            tmplen += encoder.prependVarNumber(new VlInt(TLV.TlvCongestionMark));
            if (tmplen <= 0) {
                return -1;
            }
            totalLength += tmplen;

            return totalLength;
        } catch (EncoderException e) {
            throw new ComponentException("CongestionMark.wireEncode: " + e.getMessage());
        }
    }

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

            // 读取 CongestionMark
            long value = 0;
            value = TLV.readNonNegativeInteger(block.getValue(), 0, block.getLength().getVlIntValue2Int());

            if (value < 0) {
                return false;
            }
            this.setCongestionLevel(value);

            return true;
        } catch (TLVException | VlIntException e) {
            throw new ComponentException("CongestionMark.wireDecode: " + e.getMessage());
        }
    }
}