#pragma once

#include "Layer.h"

/// @file

/// @namespace pcpp

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

namespace pcpp

{

  /// @struct gre_basic_header

  /// Represents GRE basic protocol header (common for GREv0 and GREv1)

#pragma pack(push, 1)

  struct gre_basic_header

  {

#if (BYTE_ORDER == LITTLE_ENDIAN)

    /// Number of additional encapsulations which are permitted. 0 is the default value

    uint8_t recursionControl : 3,

        /// Strict source routing bit (GRE v0 only)

        strictSourceRouteBit : 1,

        /// Set if sequence number exists

        sequenceNumBit : 1,

        /// Set if key exists

        keyBit : 1,

        /// Set if routing exists (GRE v0 only)

        routingBit : 1,

        /// Set if checksum exists (GRE v0 only)

        checksumBit : 1;

#else

    /// Set if checksum exists (GRE v0 only)

    uint8_t checksumBit : 1,

        /// Set if routing exists (GRE v0 only)

        routingBit : 1,

        /// Set if key exists

        keyBit : 1,

        /// Set if sequence number exists

        sequenceNumBit : 1,

        /// Strict source routing bit (GRE v0 only)

        strictSourceRouteBit : 1,

        /// Number of additional encapsulations which are permitted. 0 is the default value

        recursionControl : 3;

#endif

#if (BYTE_ORDER == LITTLE_ENDIAN)

    /// GRE version - can be 0 or 1

    uint8_t version : 3,

        /// Reserved

        flags : 4,

        /// Set if acknowledgment number is set (GRE v1 only)

        ackSequenceNumBit : 1;

#else

    /// Set if acknowledgment number is set (GRE v1 only)

    uint8_t ackSequenceNumBit : 1,

        /// Reserved

        flags : 4,

        /// GRE version - can be 0 or 1

        version : 3;

#endif

    /// Protocol type of the next layer

    uint16_t protocol;

  };

#pragma pack(pop)

  static_assert(sizeof(gre_basic_header) == 4, "gre_basic_header size is not 4 bytes");

  /// @struct gre1_header

  /// Represents GREv1 protocol header

#pragma pack(push, 1)

  struct gre1_header : gre_basic_header

  {

    /// Size of the payload not including the GRE header

    uint16_t payloadLength;

    /// Contains the Peer's Call ID for the session to which this packet belongs

    uint16_t callID;

  };

#pragma pack(pop)

  static_assert(sizeof(gre1_header) == 8, "gre1_header size is not 8 bytes");

  /// @struct ppp_pptp_header

  /// Represents PPP layer that comes after GREv1 as part of PPTP protocol

#pragma pack(push, 1)

  struct ppp_pptp_header

  {

    /// Broadcast address

    uint8_t address;

    /// Control byte

    uint8_t control;

    /// Protocol type of the next layer (see PPP_* macros at PPPoELayer.h)

    uint16_t protocol;

  };

#pragma pack(pop)

  static_assert(sizeof(ppp_pptp_header) == 4, "ppp_pptp_header size is not 4 bytes");

  /// @class GreLayer

  /// Abstract base class for GRE layers (GREv0Layer and GREv1Layer). Cannot be instantiated and contains common logic

  /// for derived classes

  class GreLayer : public Layer

  {

  public:

    ~GreLayer() override = default;

    /// A static method that determines the GRE version of GRE layer raw data by looking at the

    /// gre_basic_header#version field

    /// @param[in] greData GRE layer raw data

    /// @param[in] greDataLen Size of raw data

    /// @return ::GREv0 or ::GREv1 values if raw data is GREv0 or GREv1 (accordingly) or ::UnknownProtocol otherwise

    static ProtocolType getGREVersion(uint8_t* greData, size_t greDataLen);

    /// Get sequence number value if field exists in layer

    /// @param[out] seqNumber The returned sequence number value if exists in layer. Else remain unchanged

    /// @return True if sequence number field exists in layer. In this case seqNumber will be filled with the value.

    /// Or false if sequence number field doesn't exist in layer

    bool getSequenceNumber(uint32_t& seqNumber) const;

    /// Set sequence number value. If field already exists (gre_basic_header#sequenceNumBit is set) then only the

    /// new value is set. If field doesn't exist it will be added to the layer, gre_basic_header#sequenceNumBit will

    /// be set and the new value will be set

    /// @param[in] seqNumber The sequence number value to set

    /// @return True if managed to set the value successfully, or false otherwise (if couldn't extend the layer)

    bool setSequenceNumber(uint32_t seqNumber);

    /// Unset sequence number and remove it from the layer

    /// @return True if managed to unset successfully or false (and error log) if sequence number wasn't set in the

    /// first place or if didn't manage to remove it from the layer

    bool unsetSequenceNumber();

    // implement abstract methods

    /// Currently identifies the following next layers:

    ///   IPv4Layer, IPv6Layer, VlanLayer, MplsLayer, PPP_PPTPLayer, EthLayer, EthDot3Layer

    /// Otherwise sets PayloadLayer

    void parseNextLayer() override;

    /// @return Size of GRE header (may change if optional fields are added or removed)

    size_t getHeaderLen() const override;

    OsiModelLayer getOsiModelLayer() const override

    {

      return OsiModelNetworkLayer;

    }

  protected:

    GreLayer(uint8_t* data, size_t dataLen, Layer* prevLayer, Packet* packet, ProtocolType protocol)

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

    {}

    GreLayer()

    {}

    enum GreField

    {

      GreChecksumOrRouting = 0,

      GreKey = 1,

      GreSeq = 2,

      GreAck = 3

    };

    uint8_t* getFieldValue(GreField field, bool returnOffsetEvenIfFieldMissing) const;

    void computeCalculateFieldsInner();

  };

  /// @class GREv0Layer

  /// Represents a GRE version 0 protocol. Limitation: currently this layer doesn't support GRE routing information

  /// parsing and editing. So if a GREv0 packet includes routing information it won't be parse correctly. I didn't add

  /// it because of lack of time, but if you need it please tell me and I'll add it

  class GREv0Layer : public GreLayer

  {

  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

    GREv0Layer(uint8_t* data, size_t dataLen, Layer* prevLayer, Packet* packet)

        : GreLayer(data, dataLen, prevLayer, packet, GREv0)

    {}

    /// A constructor that creates a new GREv0 header and allocates the data

    GREv0Layer();

    ~GREv0Layer() override = default;

    /// Get a pointer to the basic GRE header containing only non-optional fields. Notice this points directly to

    /// the data, so every change will change the actual packet data. Also please notice that changing the set bits

    /// (gre_basic_header#strictSourceRouteBit, gre_basic_header#sequenceNumBit, gre_basic_header#keyBit,

    /// gre_basic_header#routingBit, gre_basic_header#checksumBit, gre_basic_header#ackSequenceNumBit) without using

    /// the proper set or unset methods (such as setChecksum(), unsetChecksum(), etc.) may result to wrong

    /// calculation of header length and really weird bugs. Please avoid doing so

    /// @return A pointer to the gre_basic_header

    gre_basic_header* getGreHeader() const

    {

      return reinterpret_cast<gre_basic_header*>(m_Data);

    }

    /// Get checksum value if field exists in layer

    /// @param[out] checksum The returned checksum value if exists in layer. Else remain unchanged

    /// @return True if checksum field exists in layer. In this case checksum parameter will be filled with the

    /// value. Or false if checksum field doesn't exist in layer

    bool getChecksum(uint16_t& checksum);

    /// Set checksum value. If checksum or offset fields already exist (gre_basic_header#checksumBit or

    /// gre_basic_header#routingBit are set) then only the new value is set. If both fields don't exist a new 4-byte

    /// value will be added to the layer, gre_basic_header#checksumBit will be set (gre_basic_header#routingBit will

    /// remain unset), the new checksum value will be set and offset value will be set to 0. The reason both fields

    /// are added is that GREv0 protocol states both of them or none of them should exist on packet (even if only

    /// one of the bits are set)

    /// @param[in] checksum The checksum value to set

    /// @return True if managed to set the value/s successfully, or false otherwise (if couldn't extend the layer)

    bool setChecksum(uint16_t checksum);

    /// Unset checksum and possibly remove it from the layer. It will be removed from the layer only if

    /// gre_basic_header#routingBit is not set as well. Otherwise checksum field will remain on packet with value of

    /// 0

    /// @return True if managed to unset successfully or false (and error log) if checksum wasn't set in the first

    /// place or if didn't manage to remove it from the layer

    bool unsetChecksum();

    /// Get offset value if field exists in layer. Notice there is no setOffset() method as GRE routing information

    /// isn't supported yet (see comment on class description)

    /// @param[out] offset The returned offset value if exists in layer. Else remain unchanged

    /// @return True if offset field exists in layer. In this case offset parameter will be filled with the value.

    /// Or false if offset field doesn't exist in layer

    bool getOffset(uint16_t& offset) const;

    /// Get key value if field exists in layer

    /// @param[out] key The returned key value if exists in layer. Else remain unchanged

    /// @return True if key field exists in layer. In this case key parameter will be filled with the value.

    /// Or false if key field doesn't exist in layer

    bool getKey(uint32_t& key) const;

    /// Set key value. If field already exists (gre_basic_header#keyBit is set) then only the new value is set.

    /// If field doesn't exist it will be added to the layer, gre_basic_header#keyBit will be set

    /// and the new value will be set

    /// @param[in] key The key value to set

    /// @return True if managed to set the value successfully, or false otherwise (if couldn't extend the layer)

    bool setKey(uint32_t key);

    /// Unset key and remove it from the layer

    /// @return True if managed to unset successfully or false (and error log) if key wasn't set in the first

    /// place or if didn't manage to remove it from the layer

    bool unsetKey();

    /// A static method that validates the input data

    /// @param[in] data The pointer to the beginning of a byte stream of an GREv0 layer

    /// @param[in] dataLen The length of the byte stream

    /// @return True if the data is valid and can represent an GREv0 layer

    static inline bool isDataValid(const uint8_t* data, size_t dataLen)

    {

      return data && dataLen >= sizeof(gre_basic_header);

    }

    // implement abstract methods

    /// Calculate the following fields:

    /// - gre_basic_header#protocol

    /// - GRE checksum field (if exists in packet)

    void computeCalculateFields() override;

    std::string toString() const override;

  };

  /// @class GREv1Layer

  /// Represents a GRE version 1 protocol

  class GREv1Layer : public GreLayer

  {

  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

    GREv1Layer(uint8_t* data, size_t dataLen, Layer* prevLayer, Packet* packet)

        : GreLayer(data, dataLen, prevLayer, packet, GREv1)

    {}

    /// A constructor that creates a new GREv1 header and allocates the data

    /// @param[in] callID The call ID to set

    explicit GREv1Layer(uint16_t callID);

    ~GREv1Layer() override = default;

    /// Get a pointer to the basic GREv1 header containing all non-optional fields. Notice this points directly to

    /// the data, so every change will change the actual packet data. Also please notice that changing the set bits

    /// (gre_basic_header#strictSourceRouteBit, gre_basic_header#sequenceNumBit, gre_basic_header#keyBit,

    /// gre_basic_header#routingBit, gre_basic_header#checksumBit, gre_basic_header#ackSequenceNumBit) without using

    /// the proper set or unset methods (such as setAcknowledgmentNum(), unsetSequenceNumber(), etc.) may result to

    /// wrong calculation of header length or illegal GREv1 packet and to some really weird bugs. Please avoid doing

    /// so

    /// @return A pointer to the gre1_header

    gre1_header* getGreHeader() const

    {

      return reinterpret_cast<gre1_header*>(m_Data);

    }

    /// Get acknowledgment (ack) number value if field exists in layer

    /// @param[out] ackNum The returned ack number value if exists in layer. Else remain unchanged

    /// @return True if ack number field exists in layer. In this case ackNum will be filled with the value.

    /// Or false if ack number field doesn't exist in layer

    bool getAcknowledgmentNum(uint32_t& ackNum) const;

    /// Set acknowledgment (ack) number value. If field already exists (gre_basic_header#ackSequenceNumBit is set)

    /// then only the new value is set. If field doesn't exist it will be added to the layer,

    /// gre_basic_header#ackSequenceNumBit will be set and the new value will be set

    /// @param[in] ackNum The ack number value to set

    /// @return True if managed to set the value successfully, or false otherwise (if couldn't extend the layer)

    bool setAcknowledgmentNum(uint32_t ackNum);

    /// Unset acknowledgment (ack) number and remove it from the layer

    /// @return True if managed to unset successfully or false (and error log) if ack number wasn't set in the first

    /// place or if didn't manage to remove it from the layer

    bool unsetAcknowledgmentNum();

    /// A static method that validates the input data

    /// @param[in] data The pointer to the beginning of a byte stream of an GREv1 layer

    /// @param[in] dataLen The length of the byte stream

    /// @return True if the data is valid and can represent an GREv1 layer

    static inline bool isDataValid(const uint8_t* data, size_t dataLen)

    {

      return data && dataLen >= sizeof(gre1_header);

    }

    // implement abstract methods

    /// Calculate the following fields:

    /// - gre1_header#payloadLength

    /// - gre_basic_header#protocol

    void computeCalculateFields() override;

    std::string toString() const override;

  };

  /// @class PPP_PPTPLayer

  /// Represent a PPP (point-to-point) protocol header that comes after GREv1 header, as part of PPTP - Point-to-Point

  /// Tunneling Protocol

  class PPP_PPTPLayer : 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 ppp_pptp_header)

    /// @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

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

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

    {}

    /// A constructor that allocates a new PPP-PPTP header

    /// @param[in] address Address field

    /// @param[in] control Control field

    PPP_PPTPLayer(uint8_t address, uint8_t control);

    ~PPP_PPTPLayer() override = default;

    /// Get a pointer to the PPP-PPTP header. Notice this points directly to the data, so every change will change

    /// the actual packet data

    /// @return A pointer to the @ref ppp_pptp_header

    ppp_pptp_header* getPPP_PPTPHeader() const

    {

      return reinterpret_cast<ppp_pptp_header*>(m_Data);

    }

    /// A static method that validates the input data

    /// @param[in] data The pointer to the beginning of a byte stream of a PPP-PPTP packet

    /// @param[in] dataLen The length of the byte stream

    /// @return True if the data is valid and can represent a PPP-PPTP packet

    static inline bool isDataValid(const uint8_t* data, size_t dataLen);

    // implement abstract methods

    /// Currently identifies the following next layers: IPv4Layer, IPv6Layer. Otherwise sets PayloadLayer

    void parseNextLayer() override;

    /// @return The size of @ref ppp_pptp_header

    size_t getHeaderLen() const override

    {

      return sizeof(ppp_pptp_header);

    }

    /// Calculate the following fields:

    /// - ppp_pptp_header#protocol

    void computeCalculateFields() override;

    std::string toString() const override

    {

      return "PPP for PPTP Layer";

    }

    OsiModelLayer getOsiModelLayer() const override

    {

      return OsiModelSesionLayer;

    }

  };

  bool PPP_PPTPLayer::isDataValid(const uint8_t* data, size_t dataLen)

  {

    return data && dataLen >= sizeof(ppp_pptp_header);

  }

}  // namespace pcpp