#ifndef PACKETPP_TCP_LAYER
#define PACKETPP_TCP_LAYER

#include "Layer.h"
#include "TLVData.h"
#include <string.h>

/// @file

/**
 * \namespace pcpp
 * \brief The main namespace for the PcapPlusPlus lib
 */
namespace pcpp
{

	/**
	 * @struct tcphdr
	 * Represents an TCP protocol header
	 */
#pragma pack(push,1)
	struct tcphdr
	{
		/** Source TCP port */
		uint16_t portSrc;
		/** Destination TCP port */
		uint16_t portDst;
		/** Sequence number */
		uint32_t sequenceNumber;
		/** Acknowledgment number */
		uint32_t ackNumber;
#if (BYTE_ORDER == LITTLE_ENDIAN)
		uint16_t reserved:4,
		/** Specifies the size of the TCP header in 32-bit words */
		dataOffset:4,
		/** FIN flag */
		finFlag:1,
		/** SYN flag */
		synFlag:1,
		/** RST flag */
		rstFlag:1,
		/** PSH flag */
		pshFlag:1,
		/** ACK flag */
		ackFlag:1,
		/** URG flag */
		urgFlag:1,
		/** ECE flag */
		eceFlag:1,
		/** CWR flag */
		cwrFlag:1;
#elif (BYTE_ORDER == BIG_ENDIAN)
		/** Specifies the size of the TCP header in 32-bit words */
		uint16_t dataOffset:4,
		reserved:4,
		/** CWR flag */
		cwrFlag:1,
		/** ECE flag */
		eceFlag:1,
		/** URG flag */
		urgFlag:1,
		/** ACK flag */
		ackFlag:1,
		/** PSH flag */
		pshFlag:1,
		/** RST flag */
		rstFlag:1,
		/** SYN flag */
		synFlag:1,
		/** FIN flag */
		finFlag:1;
#else
#error	"Endian is not LE nor BE..."
#endif
		/** The size of the receive window, which specifies the number of window size units (by default, bytes) */
		uint16_t	windowSize;
		/** The 16-bit checksum field is used for error-checking of the header and data */
		uint16_t	headerChecksum;
		/** If the URG flag (@ref tcphdr#urgFlag) is set, then this 16-bit field is an offset from the sequence number indicating the last urgent data byte */
		uint16_t	urgentPointer;
	};
#pragma pack(pop)


	/**
	 * TCP options types
	 */
	enum TcpOptionType
	{
		/** Padding */
		PCPP_TCPOPT_NOP =       1,
		/** End of options */
		PCPP_TCPOPT_EOL =       0,
		/** Segment size negotiating */
		TCPOPT_MSS =          	2,
		/** Window scaling */
		PCPP_TCPOPT_WINDOW =    3,
		/** SACK Permitted */
		TCPOPT_SACK_PERM =      4,
		/** SACK Block */
		PCPP_TCPOPT_SACK =      5,
		/** Echo (obsoleted by option ::PCPP_TCPOPT_TIMESTAMP) */
		TCPOPT_ECHO =           6,
		/** Echo Reply (obsoleted by option ::PCPP_TCPOPT_TIMESTAMP) */
		TCPOPT_ECHOREPLY =      7,
		/** TCP Timestamps */
		PCPP_TCPOPT_TIMESTAMP = 8,
		/** CC (obsolete) */
		TCPOPT_CC =             11,
		/** CC.NEW (obsolete) */
		TCPOPT_CCNEW =          12,
		/** CC.ECHO(obsolete) */
		TCPOPT_CCECHO =         13,
		/** MD5 Signature Option */
		TCPOPT_MD5 =            19,
		/** Multipath TCP */
		TCPOPT_MPTCP =          0x1e,
		/** SCPS Capabilities */
		TCPOPT_SCPS =           20,
		/** SCPS SNACK */
		TCPOPT_SNACK =          21,
		/** SCPS Record Boundary */
		TCPOPT_RECBOUND =       22,
		/** SCPS Corruption Experienced */
		TCPOPT_CORREXP =        23,
		/** Quick-Start Response */
		TCPOPT_QS =             27,
		/** User Timeout Option (also, other known unauthorized use) */
		TCPOPT_USER_TO =        28,
		/** RFC3692-style Experiment 1 (also improperly used for shipping products) */
		TCPOPT_EXP_FD =         0xfd,
		/** RFC3692-style Experiment 2 (also improperly used for shipping products) */
		TCPOPT_EXP_FE =         0xfe,
		/** Riverbed probe option, non IANA registered option number */
		TCPOPT_RVBD_PROBE =     76,
		/** Riverbed transparency option, non IANA registered option number */
		TCPOPT_RVBD_TRPY =      78,
		/** Unknown option */
		TCPOPT_Unknown =        255
	};


	// TCP option lengths

	/** pcpp::PCPP_TCPOPT_NOP length */
#define PCPP_TCPOLEN_NOP            1
	/** pcpp::PCPP_TCPOPT_EOL length */
#define PCPP_TCPOLEN_EOL            1
	/** pcpp::TCPOPT_MSS length */
#define PCPP_TCPOLEN_MSS            4
	/** pcpp::PCPP_TCPOPT_WINDOW length */
#define PCPP_TCPOLEN_WINDOW         3
	/** pcpp::TCPOPT_SACK_PERM length */
#define PCPP_TCPOLEN_SACK_PERM      2
	/** pcpp::PCPP_TCPOPT_SACK length */
#define PCPP_TCPOLEN_SACK_MIN       2
	/** pcpp::TCPOPT_ECHO length */
#define PCPP_TCPOLEN_ECHO           6
	/** pcpp::TCPOPT_ECHOREPLY length */
#define PCPP_TCPOLEN_ECHOREPLY      6
	/** pcpp::PCPP_TCPOPT_TIMESTAMP length */
#define PCPP_TCPOLEN_TIMESTAMP     10
	/** pcpp::TCPOPT_CC length */
#define PCPP_TCPOLEN_CC             6
	/** pcpp::TCPOPT_CCNEW length */
#define PCPP_TCPOLEN_CCNEW          6
	/** pcpp::TCPOPT_CCECHO length */
#define PCPP_TCPOLEN_CCECHO         6
	/** pcpp::TCPOPT_MD5 length */
#define PCPP_TCPOLEN_MD5           18
	/** pcpp::TCPOPT_MPTCP length */
#define PCPP_TCPOLEN_MPTCP_MIN      8
	/** pcpp::TCPOPT_SCPS length */
#define PCPP_TCPOLEN_SCPS           4
	/** pcpp::TCPOPT_SNACK length */
#define PCPP_TCPOLEN_SNACK          6
	/** pcpp::TCPOPT_RECBOUND length */
#define PCPP_TCPOLEN_RECBOUND       2
	/** pcpp::TCPOPT_CORREXP length */
#define PCPP_TCPOLEN_CORREXP        2
	/** pcpp::TCPOPT_QS length */
#define PCPP_TCPOLEN_QS             8
	/** pcpp::TCPOPT_USER_TO length */
#define PCPP_TCPOLEN_USER_TO        4
	/** pcpp::TCPOPT_RVBD_PROBE length */
#define PCPP_TCPOLEN_RVBD_PROBE_MIN 3
	/** pcpp::TCPOPT_RVBD_TRPY length */
#define PCPP_TCPOLEN_RVBD_TRPY_MIN 16
	/** pcpp::TCPOPT_EXP_FD and pcpp::TCPOPT_EXP_FE length */
#define PCPP_TCPOLEN_EXP_MIN        2


	/**
	 * @class TcpOption
	 * A wrapper class for TCP options. This class does not create or modify TCP option records, but rather
	 * serves as a wrapper and provides useful methods for retrieving data from them
	 */
	class TcpOption : public TLVRecord<uint8_t, uint8_t>
	{
	public:

		/**
		 * A c'tor for this class that gets a pointer to the option raw data (byte array)
		 * @param[in] optionRawData A pointer to the TCP option raw data
		 */
		explicit TcpOption(uint8_t* optionRawData) : TLVRecord(optionRawData) { }

		/**
		 * A d'tor for this class, currently does nothing
		 */
		~TcpOption() { }

		/**
		 * @return TCP option type casted as pcpp::TcpOptionType enum. If the data is null a value
		 * of ::TCPOPT_Unknown is returned
		 */
		TcpOptionType getTcpOptionType() const
		{
			if (m_Data == nullptr)
				return TCPOPT_Unknown;

			return (TcpOptionType)m_Data->recordType;
		}

		// implement abstract methods

		size_t getTotalSize() const
		{
			if (m_Data == nullptr)
				return 0;

			if (m_Data->recordType == (uint8_t)PCPP_TCPOPT_NOP || m_Data->recordType == (uint8_t)PCPP_TCPOPT_EOL)
				return sizeof(uint8_t);

			return (size_t)m_Data->recordLen;
		}

		size_t getDataSize() const
		{
			if (m_Data == nullptr)
				return 0;

			if (m_Data->recordType == (uint8_t)PCPP_TCPOPT_NOP || m_Data->recordType == (uint8_t)PCPP_TCPOPT_EOL)
				return 0;

			return (size_t)m_Data->recordLen - (2*sizeof(uint8_t));
		}
	};


	/**
	 * @class TcpOptionBuilder
	 * A class for building TCP option records. This builder receives the TCP option parameters in its c'tor,
	 * builds the TCP option raw buffer and provides a build() method to get a TcpOption object out of it
	 */
	class TcpOptionBuilder : public TLVRecordBuilder
	{

	public:

		/**
		 * An enum to describe NOP and EOL TCP options. Used in one of this class's c'tors
		 */
		enum NopEolOptionTypes
		{
			/** NOP TCP option */
			NOP,
			/** EOL TCP option */
			EOL
		};

		/**
		 * A c'tor for building TCP options which their value is a byte array. The TcpOption object can be later
		 * retrieved by calling build()
		 * @param[in] optionType TCP option type
		 * @param[in] optionValue A buffer containing the option value. This buffer is read-only and isn't modified in any way.
		 * @param[in] optionValueLen Option value length in bytes
		 */
		TcpOptionBuilder(TcpOptionType optionType, const uint8_t* optionValue, uint8_t optionValueLen) :
			TLVRecordBuilder((uint8_t)optionType, optionValue, optionValueLen) {}

		/**
		 * A c'tor for building TCP options which have a 1-byte value. The TcpOption object can be later retrieved
		 * by calling build()
		 * @param[in] optionType TCP option type
		 * @param[in] optionValue A 1-byte option value
		 */
		TcpOptionBuilder(TcpOptionType optionType, uint8_t optionValue) :
			TLVRecordBuilder((uint8_t)optionType, optionValue) {}

		/**
		 * A c'tor for building TCP options which have a 2-byte value. The TcpOption object can be later retrieved
		 * by calling build()
		 * @param[in] optionType TCP option type
		 * @param[in] optionValue A 2-byte option value
		 */
		TcpOptionBuilder(TcpOptionType optionType, uint16_t optionValue) :
			TLVRecordBuilder((uint8_t)optionType, optionValue) {}

		/**
		 * A c'tor for building TCP options which have a 4-byte value. The TcpOption object can be later retrieved
		 * by calling build()
		 * @param[in] optionType TCP option type
		 * @param[in] optionValue A 4-byte option value
		 */
		TcpOptionBuilder(TcpOptionType optionType, uint32_t optionValue) :
			TLVRecordBuilder((uint8_t)optionType, optionValue) {}

		/**
		 * A c'tor for building TCP NOP and EOL options. These option types are special in that they contain only 1 byte
		 * which is the TCP option type (NOP or EOL). The TcpOption object can be later retrieved
		 * by calling build()
		 * @param[in] optionType An enum value indicating which option type to build (NOP or EOL)
		 */
		explicit TcpOptionBuilder(NopEolOptionTypes optionType);

		/**
		 * Build the TcpOption object out of the parameters defined in the c'tor
		 * @return The TcpOption object
		 */
		TcpOption build() const;
	};


	/**
	 * @class TcpLayer
	 * Represents a TCP (Transmission Control Protocol) protocol layer
	 */
	class TcpLayer : public Layer
	{
	public:
		/**
		 * A constructor that creates the layer from an existing packet raw data
		 * @param[in] data A pointer to the raw data (will be casted to @ref tcphdr)
		 * @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
		 */
		TcpLayer(uint8_t* data, size_t dataLen, Layer* prevLayer, Packet* packet);

		/**
		 * A constructor that allocates a new TCP header with zero TCP options
		 */
		TcpLayer();

		/**
		 * A constructor that allocates a new TCP header with source port and destination port and zero TCP options
		 * @param[in] portSrc Source port
		 * @param[in] portDst Destination port
		 */
		TcpLayer(uint16_t portSrc, uint16_t portDst);

		~TcpLayer() {}

		/**
		 * A copy constructor that copy the entire header from the other TcpLayer (including TCP options)
		 */
		TcpLayer(const TcpLayer& other);

		/**
		 * An assignment operator that first delete all data from current layer and then copy the entire header from the other TcpLayer (including TCP options)
		 */
		TcpLayer& operator=(const TcpLayer& other);

		/**
		 * Get a pointer to the TCP header. Notice this points directly to the data, so every change will change the actual packet data
		 * @return A pointer to the @ref tcphdr
		 */
		tcphdr* getTcpHeader() const { return (tcphdr*)m_Data; }

		/**
		 * @return TCP source port
		 */
		uint16_t getSrcPort() const;

		/**
		 * @return TCP destination port
		 */
		uint16_t getDstPort() const;

		/**
		 * Get a TCP option by type
		 * @param[in] option TCP option type to retrieve
		 * @return An TcpOption object that contains the first option that matches this type, or logical NULL
		 * (TcpOption#isNull() == true) if no such option found
		 */
		TcpOption getTcpOption(TcpOptionType option) const;

		/**
		 * @return The first TCP option in the packet. If the current layer contains no options the returned value will contain
		 * a logical NULL (TcpOption#isNull() == true)
		 */
		TcpOption getFirstTcpOption() const;

		/**
		 * Get the TCP option that comes after a given option. If the given option was the last one, the
		 * returned value will contain a logical NULL (TcpOption#isNull() == true)
		 * @param[in] tcpOption A TCP option object that exists in the current layer
		 * @return A TcpOption object that contains the TCP option data that comes next, or logical NULL if the given
		 * TCP option: (1) was the last one; or (2) contains a logical NULL; or (3) doesn't belong to this packet
		 */
		TcpOption getNextTcpOption(TcpOption& tcpOption) const;

		/**
		 * @return The number of TCP options in this layer
		 */
		size_t getTcpOptionCount() const;

		/**
		 * Add a new TCP option at the end of the layer (after the last TCP option)
		 * @param[in] optionBuilder A TcpOptionBuilder object that contains the TCP option data to be added
		 * @return A TcpOption object that contains the newly added TCP option data or logical NULL
		 * (TcpOption#isNull() == true) if addition failed. In case of a failure a corresponding error message will be
		 * printed to log
		 */
		TcpOption addTcpOption(const TcpOptionBuilder& optionBuilder);

		/**
		 * Add a new TCP option after an existing one
		 * @param[in] optionBuilder A TcpOptionBuilder object that contains the requested TCP option data to be added
		 * @param[in] prevOptionType The TCP option which the newly added option should come after. This is an optional parameter which
		 * gets a default value of ::TCPOPT_Unknown if omitted, which means the new option will be added as the first option in the layer
		 * @return A TcpOption object containing the newly added TCP option data or logical NULL
		 * (TcpOption#isNull() == true) if addition failed. In case of a failure a corresponding error message will be
		 * printed to log
		 */
		TcpOption addTcpOptionAfter(const TcpOptionBuilder& optionBuilder, TcpOptionType prevOptionType = TCPOPT_Unknown);

		/**
		 * Remove an existing TCP option from the layer. TCP option is found by type
		 * @param[in] optionType The TCP option type to remove
		 * @return True if TCP option was removed or false if type wasn't found or if removal failed (in each case a proper error
		 * will be written to log)
		 */
		bool removeTcpOption(TcpOptionType optionType);

		/**
		 * Remove all TCP options in this layer
		 * @return True if all TCP options were successfully removed or false if removal failed for some reason
		 * (a proper error will be written to log)
		 */
		bool removeAllTcpOptions();


		/**
		 * Calculate the checksum from header and data and possibly write the result to @ref tcphdr#headerChecksum
		 * @param[in] writeResultToPacket If set to true then checksum result will be written to @ref tcphdr#headerChecksum
		 * @return The checksum result
		 */
		uint16_t calculateChecksum(bool writeResultToPacket);

		/**
		 * The static method makes validation of input data
		 * @param[in] data The pointer to the beginning of byte stream of TCP packet
		 * @param[in] dataLen The length of byte stream
		 * @return True if the data is valid and can represent a TCP packet
		 */
		static inline bool isDataValid(const uint8_t* data, size_t dataLen);

		// implement abstract methods

		/**
		 * Currently identifies the following next layers: HttpRequestLayer, HttpResponseLayer. Otherwise sets PayloadLayer
		 */
		void parseNextLayer();

		/**
		 * @return Size of @ref tcphdr + all TCP options
		 */
		size_t getHeaderLen() const { return getTcpHeader()->dataOffset*4 ;}

		/**
		 * Calculate @ref tcphdr#headerChecksum field
		 */
		void computeCalculateFields();

		std::string toString() const;

		OsiModelLayer getOsiModelLayer() const { return OsiModelTransportLayer; }

	private:

		TLVRecordReader<TcpOption> m_OptionReader;
		int m_NumOfTrailingBytes;

		void initLayer();
		uint8_t* getOptionsBasePtr() const { return m_Data + sizeof(tcphdr); }
		TcpOption addTcpOptionAt(const TcpOptionBuilder& optionBuilder, int offset);
		void adjustTcpOptionTrailer(size_t totalOptSize);
		void copyLayerData(const TcpLayer& other);
	};


	// implementation of inline methods

	bool TcpLayer::isDataValid(const uint8_t* data, size_t dataLen)
	{
		const tcphdr* hdr = reinterpret_cast<const tcphdr*>(data);
		return dataLen >= sizeof(tcphdr)
			&& hdr->dataOffset >= 5 /* the minimum TCP header size */
			&& dataLen >= hdr->dataOffset * sizeof(uint32_t);
	}

} // namespace pcpp

#endif /* PACKETPP_TCP_LAYER */