#pragma once

#include "Layer.h"

/// @file

/// @namespace pcpp

/// @brief The main namespace for the PcapPlusPlus lib

namespace pcpp

{

  /// @class PacketTrailerLayer

  /// A class for representing packet trailer (a.k.a footer or padding) which refers to supplemental data placed at

  /// the end of a block of data being stored or transmitted, which may contain information for the handling of the

  /// data block, or just mark its end (taken from Wikipedia: https://en.wikipedia.org/wiki/Trailer_(computing) )

  ///

  /// There are various reasons for adding a packet trailer, one of the most famous is FCS (Frame check sequence)

  /// which refers to the extra error-detecting code added to a frame. Another usage is padding which means adding

  /// data to reach a minimum required packet length.

  ///

  /// Although this layer inherits from the Layer class, it is not a standard layer in the sense that it can't be

  /// constructed by the user. This layer may be only be constructed in the Packet class, in the process of parsing

  /// the packet and creating the layers; if at the end of the parsing process there is data left that is not

  /// allocated to any layer, it's assumed to be the packet trailer and an instance of this class is created. This

  /// means this layer can only exist as the last layer in a packet, if a packet trailer indeed exists.

  ///

  /// No layer can be added by the user after this layer (trying to do that will result with an error).

  ///

  /// This layer can be removed by the user or extended/shortened, as any layer.

  ///

  /// It also contains method to extract the trailer data

  class PacketTrailerLayer : public Layer

  {

  public:

    /// A constructor that creates the layer from an existing packet raw data

    /// @param[in] data A pointer to the raw data

    /// @param[in] dataLen Size of the data in bytes

    /// @param[in] prevLayer A pointer to the previous layer

    /// @param[in] packet A pointer to the Packet instance where layer will be stored in

    PacketTrailerLayer(uint8_t* data, size_t dataLen, Layer* prevLayer, Packet* packet)

        : Layer(data, dataLen, prevLayer, packet, PacketTrailer)

    {}

    ~PacketTrailerLayer() override = default;

    /// Get a pointer to the trailer data

    /// @return A pointer to the trailer data

    uint8_t* getTrailerData() const

    {

      return m_Data;

    }

    /// @return Trailer data as hex string

    std::string getTrailerDataAsHexString() const;

    /// Get the trailer data length

    /// @return The trailer data length in bytes

    size_t getTrailerLen() const

    {

      return m_DataLen;

    }

    // implement abstract methods

    /// Does nothing for this layer (PacketTrailerLayer is always last)

    void parseNextLayer() override

    {}

    /// @return trailer data length in bytes

    size_t getHeaderLen() const override

    {

      return m_DataLen;

    }

    /// Does nothing for this layer

    void computeCalculateFields() override

    {}

    std::string toString() const override;

    OsiModelLayer getOsiModelLayer() const override

    {

      return OsiModelDataLinkLayer;

    }

  };

}  // namespace pcpp