#pragma once

#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, 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. nullptr 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. nullptr 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() override

    {}

    /// @return Get the size of the layer

    size_t getHeaderLen() const override

    {

      return m_DataLen;

    }

    /// Does nothing for this layer

    void computeCalculateFields() override

    {}

    /// @return The OSI layer level of Telnet (Application Layer).

    OsiModelLayer getOsiModelLayer() const override

    {

      return OsiModelApplicationLayer;

    }

    /// @return Returns the protocol info as readable string

    std::string toString() const override;

  };

}  // namespace pcpp