#ifndef PACKETPP_PACKET_TRAILER_LAYER
#define PACKETPP_PACKET_TRAILER_LAYER

/// @file

#include "Layer.h"

namespace pcpp
{
	/**
	 * @class PacketTrailerLayer
	 * A class for representing packet tailer (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) { m_Protocol = PacketTrailer; }

		~PacketTrailerLayer() {}

		/**
		 * 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() {}

		/**
		 * @return trailer data length in bytes
		 */
		size_t getHeaderLen() const { return m_DataLen; }

		/**
		 * Does nothing for this layer
		 */
		void computeCalculateFields() {}

		std::string toString() const;

		OsiModelLayer getOsiModelLayer() const { return OsiModelDataLinkLayer; }
	};

}

#endif // PACKETPP_PACKET_TRAILER_LAYER