#ifndef PACKETPP_TELNET_LAYER
#define PACKETPP_TELNET_LAYER

#include "Layer.h"

/// @file

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

/**
 * Class for representing the Telnet Layer
 */
class TelnetLayer : public Layer
{
  private:
	// Position iterator for next command
	size_t lastPositionOffset;

	// Checks if position is a data field
	bool isDataField(uint8_t *pos) const;
	// Checks if position is a command field
	bool isCommandField(uint8_t *pos) const;
	// Returns distance to next IAC
	size_t distanceToNextIAC(uint8_t *startPos, size_t maxLength);
	// Returns length of provided field
	size_t getFieldLen(uint8_t *startPos, size_t maxLength);
	// Get position of next data field
	uint8_t *getNextDataField(uint8_t *pos, size_t len);
	// Get position of next command field
	uint8_t *getNextCommandField(uint8_t *pos, size_t len);
	// Get options of provided field
	int16_t getSubCommand(uint8_t *pos, size_t len);
	// Get data of provided field
	uint8_t *getCommandData(uint8_t *pos, size_t &slen);

  public:
	/**
	 * Telnet Command Indicator
	 */
	enum class TelnetCommand : int
	{
		/// Indicator to parser reached end of packet
		TelnetCommandEndOfPacket = -1,

		/// End of file
		EndOfFile = 236,
		/// Suspend current process
		Suspend,
		/// Abort Process
		Abort,
		/// End of Record
		EndOfRecordCommand,
		/// Marks the end of a Telnet option subnegotiation, used with the SB code to specify more specific option
		/// parameters.
		SubnegotiationEnd,
		/// Null command; does nothing.
		NoOperation,
		/// Used to mark the end of a sequence of data that the recipient should scan for urgent Telnet commands.
		DataMark,
		/// Represents the pressing of the “break” or “attention” key on the terminal.
		Break,
		/// Tells the recipient to interrupt, abort, suspend or terminate the process currently in use.
		InterruptProcess,
		/// Instructs the remote host to continue running the current process, but discard all remaining output from it.
		/// This may be needed if a program starts to send unexpectedly large amounts of data to the user.
		AbortOutput,
		/// May be used to check that the remote host is still “alive”. When this character is sent the remote host
		/// returns some type of output to indicate that it is still functioning.
		AreYouThere,
		/// Instructs the recipient to delete the last undeleted character from the data stream. Used to “undo” the
		/// sending of a character.
		EraseCharacter,
		/// Tells the recipient to delete all characters from the data stream back to (but not including) the last end
		/// of line (CR+LF) sequence.
		EraseLine,
		/// Used in Telnet half-duplex mode to signal the other device that it may transmit.
		GoAhead,
		/// Marks the beginning of a Telnet option subnegotiation, used when an option requires the client and server to
		/// exchange parameters.
		Subnegotiation,
		/// Indicates that the device sending this code is willing to perform or continue performing a particular
		/// option.
		WillPerform,
		/// Indicates that the device sending this code is either not willing to perform a particular option, or is now
		/// refusing to continue to perform it.
		WontPerform,
		/// Requests that the other device perform a particular option or confirms the expectation that the other device
		/// will perform that option.
		DoPerform,
		/// Specifies that the other party not perform an option, or confirms a device’s expectation that the other
		/// party not perform an option.
		DontPerform,
		/// Precedes command values 240 through 254 as described above. A pair of IAC bytes in a row represents the data
		/// value 255.
		InterpretAsCommand
	};

	/**
	 * Telnet Options
	 */
	enum class TelnetOption : int
	{
		/// Internal return for no option detected
		TelnetOptionNoOption = -1,

		/// Binary Transmission RFC856 https://www.iana.org/go/rfc856
		TransmitBinary = 0,
		/// Echo RFC857 https://www.iana.org/go/rfc857
		Echo,
		/// Reconnection
		Reconnection,
		/// Suppress Go Ahead RFC858 https://www.iana.org/go/rfc858
		SuppressGoAhead,
		/// Negotiate approximate message size
		ApproxMsgSizeNegotiation,
		/// Status RFC859 https://www.iana.org/go/rfc859
		Status,
		/// Timing Mark RFC860 https://www.iana.org/go/rfc860
		TimingMark,
		/// RCTE, Remote Controlled Transmission and Echo RFC726 https://www.iana.org/go/rfc726
		RemoteControlledTransAndEcho,
		/// Output Line Width
		OutputLineWidth,
		/// Output Page Size
		OutputPageSize,
		/// NAOCRD, Negotiate About Output Carriage-Return Disposition RFC652 https://www.iana.org/go/rfc652
		OutputCarriageReturnDisposition,
		/// NAOHTS, Negotiate About Output Horizontal Tabstops RFC653 https://www.iana.org/go/rfc653
		OutputHorizontalTabStops,
		/// NAOHTD, Negotiate About Output Horizontal Tab Disposition RFC654 https://www.iana.org/go/rfc654
		OutputHorizontalTabDisposition,
		/// NAOFFD, Negotiate About Output Formfeed Disposition RFC655 https://www.iana.org/go/rfc655
		OutputFormfeedDisposition,
		/// NAOVTS, Negotiate About Vertical Tabstops RFC656 https://www.iana.org/go/rfc656
		OutputVerticalTabStops,
		/// NAOVTD, Negotiate About Output Vertcial Tab Disposition RFC657 https://www.iana.org/go/rfc657
		OutputVerticalTabDisposition,
		/// NAOLFD, Negotiate About Output Linefeed Disposition RFC658 https://www.iana.org/go/rfc658
		OutputLinefeedDisposition,
		/// Extended ASCII RFC698 https://www.iana.org/go/rfc698
		ExtendedASCII,
		/// Logout RFC727 https://www.iana.org/go/rfc727
		Logout,
		/// BM, Byte Macro RFC735 https://www.iana.org/go/rfc735
		ByteMacro,
		/// Data Entry Terminal RFC1043 - RFC732 https://www.iana.org/go/rfc1043 https://www.iana.org/go/rfc732
		DataEntryTerminal,
		/// SUPDUP RFC736 - RFC734 https://www.iana.org/go/rfc736 https://www.iana.org/go/rfc734
		SUPDUP,
		/// SUPDUP Output RFC749 https://www.iana.org/go/rfc749
		SUPDUPOutput,
		/// Send Location RFC779 https://www.iana.org/go/rfc779
		SendLocation,
		/// Terminal Type RFC1091 https://www.iana.org/go/rfc1091
		TerminalType,
		/// End of record RFC885 https://www.iana.org/go/rfc885
		EndOfRecordOption,
		/// TUID, TACACS User Identification RFC927 https://www.iana.org/go/rfc927
		TACACSUserIdentification,
		/// OUTMRK, Output Marking RFC933 https://www.iana.org/go/rfc933
		OutputMarking,
		/// TTYLOC, Terminal Location Number RFC946 https://www.iana.org/go/rfc946
		TerminalLocationNumber,
		/// Telnet 3270 Regime RFC1041 https://www.iana.org/go/rfc1041
		Telnet3270Regime,
		/// X.3 PAD RFC1053 https://www.iana.org/go/rfc1053
		X3Pad,
		/// NAWS, Negotiate About Window Size RFC1073 https://www.iana.org/go/rfc1073
		NegotiateAboutWindowSize,
		/// Terminal Speed RFC1079 https://www.iana.org/go/rfc1079
		TerminalSpeed,
		/// Remote Flow Control RFC1372 https://www.iana.org/go/rfc1372
		RemoteFlowControl,
		/// Line Mode RFC1184 https://www.iana.org/go/rfc1184
		Linemode,
		/// X Display Location RFC1096 https://www.iana.org/go/rfc1096
		XDisplayLocation,
		/// Environment Option RFC1408 https://www.iana.org/go/rfc1408
		EnvironmentOption,
		/// Authentication Option RFC2941 https://www.iana.org/go/rfc2941
		AuthenticationOption,
		/// Encryption Option RFC2946 https://www.iana.org/go/rfc2946
		EncryptionOption,
		/// New Environment Option RFC1572 https://www.iana.org/go/rfc1572
		NewEnvironmentOption,
		/// TN3270E RFC2355 https://www.iana.org/go/rfc2355
		TN3270E,
		/// X Server Authentication
		XAuth,
		/// Charset RFC2066 https://www.iana.org/go/rfc2066
		Charset,
		/// RSP, Telnet Remote Serial Port
		TelnetRemoteSerialPort,
		/// Com Port Control Option RFC2217 https://www.iana.org/go/rfc2217
		ComPortControlOption,
		/// Telnet Suppress Local Echo
		TelnetSuppressLocalEcho,
		/// Telnet Start TLS
		TelnetStartTLS,
		/// Kermit RFC2840 https://www.iana.org/go/rfc2840
		Kermit,
		/// Send URL
		SendURL,
		/// Forward X Server
		ForwardX,

		/// Telnet Option Pragma Logon
		TelOptPragmaLogon = 138,
		/// Telnet Option SSPI Logon
		TelOptSSPILogon,
		/// Telnet Option Pragma Heartbeat
		TelOptPragmaHeartbeat,

		/// Extended option list
		ExtendedOptions = 255
	};

	/**
	 * 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
	 */
	TelnetLayer(uint8_t *data, size_t dataLen, Layer *prevLayer, Packet *packet) : Layer(data, dataLen, prevLayer, packet)
	{
		m_Protocol = Telnet;
		lastPositionOffset = SIZE_MAX;
	};

	/**
	 * Get the Telnet data as readable string
	 * @param[in] removeEscapeCharacters Whether non-alphanumerical characters should be removed or not
	 * @return Full payload as readable string, empty if Telnet packet contains control commands/options.
	 */
	std::string getDataAsString(bool removeEscapeCharacters = true);

	/**
	 * Get the total number of detected Telnet commands
	 * @return size_t The number of Telnet commands
	 */
	size_t getTotalNumberOfCommands();

	/**
	 * Returns the number of occurrences of provided command
	 * @param[in] command Telnet command to count
	 * @return size_t Number of occurrences of command
	 */
	size_t getNumberOfCommands(TelnetCommand command);

	/**
	 * Returns the first command of packet
	 * @return TelnetCommand First detected command value, TelnetCommandEndOfPacket if there is no command field
	 */
	TelnetCommand getFirstCommand();

	/**
	 * Returns the next command of packet. Uses an internal iterator. The iterator resets when reached end of packet.
	 * @return TelnetCommand Detected command value, TelnetCommandEndOfPacket if reached the end of packet.
	 */
	TelnetCommand getNextCommand();

	/**
	 * Returns the option of current command. Uses an internal iterator. Iterator can be moved with getNextCommand
	 * @return TelnetOption Option of current command
	 */
	TelnetOption getOption();

	/**
	 * Returns the option of provided command. It will return option of first occurrence of the command
	 * @param[in] command Telnet command to search
	 * @return TelnetOption Option of the command. Returns TelnetOptionNoOption if the provided command not found.
	 */
	TelnetOption getOption(TelnetCommand command);

	/**
	 * Returns the data of current command. Uses an internal iterator. Iterator can be moved with getNextCommand
	 * @param[out] length Length of the data of current command
	 * @return uint8_t* Pointer to the data of current command. NULL if there is no data for this command.
	 */
	uint8_t *getOptionData(size_t &length);

	/**
	 * Returns the data of provided command. It will return data of first occurrence of the command
	 * @param[in] command Telnet command to search
	 * @param[out] length Length of the data of current command
	 * @return uint8_t* Pointer to the data of current command. NULL if there is no data for this command or if can't
	 * find the command.
	 */
	uint8_t *getOptionData(TelnetCommand command, size_t &length);

	/**
	 * Convert the Telnet Command to readable string
	 * @param[in] val Value of the command
	 * @return The Telnet Command as readable string
	 */
	static std::string getTelnetCommandAsString(TelnetCommand val);

	/**
	 * Convert the Telnet option to readable string
	 * @param[in] val Value of the option
	 * @return The Telnet Option as readable string
	 */
	static std::string getTelnetOptionAsString(TelnetOption val);

	/**
	 * A static method that checks whether the port is considered as Telnet
	 * @param[in] port The port number to be checked
	 */
	static bool isTelnetPort(uint16_t port)	{ return port == 23; }

	/**
	 * A static method that takes a byte array and detects whether it is a Telnet message
	 * @param[in] data A byte array
	 * @param[in] dataSize The byte array size (in bytes)
	 * @return True if the data is identified as Telnet message
	 */
	static bool isDataValid(const uint8_t *data, size_t dataSize) { return data && dataSize; }

	// overridden methods

	/// Parses the next layer. Telnet is the always last so does nothing for this layer
	void parseNextLayer() {}

	/**
	 * @return Get the size of the layer
	 */
	size_t getHeaderLen() const	{ return m_DataLen; }

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

	/**
	 * @return The OSI layer level of Telnet (Application Layer).
	 */
	OsiModelLayer getOsiModelLayer() const { return OsiModelApplicationLayer; }

	/**
	 * @return Returns the protocol info as readable string
	 */
	std::string toString() const;
};

} // namespace pcpp

#endif /* PACKETPP_TELNET_LAYER */