/*
 * SRT - Secure, Reliable, Transport
 * Copyright (c) 2018 Haivision Systems Inc.
 * 
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 * 
 */

/*****************************************************************************
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#ifndef INC_SRT_HANDSHAKE_H
#define INC_SRT_HANDSHAKE_H

#include <vector>

#include "crypto.h"
#include "utilities.h"

namespace srt
{

typedef Bits<31, 16> HS_CMDSPEC_CMD;
typedef Bits<15, 0> HS_CMDSPEC_SIZE;

// NOTE: Some of these flags represent CAPABILITIES, that is,
// as long as these flags are defined, they must be always set
// (unless they are deprecated).
enum SrtOptions
{
    SRT_OPT_TSBPDSND  = BIT(0), /* Timestamp-based Packet delivery real-time data sender */
    SRT_OPT_TSBPDRCV  = BIT(1), /* Timestamp-based Packet delivery real-time data receiver */
    SRT_OPT_HAICRYPT  = BIT(2), /* CAPABILITY: HaiCrypt AES-128/192/256-CTR */
    SRT_OPT_TLPKTDROP = BIT(3), /* Drop real-time data packets too late to be processed in time */
    SRT_OPT_NAKREPORT = BIT(4), /* Periodic NAK report */
    SRT_OPT_REXMITFLG = BIT(5), // CAPABILITY: One bit in payload packet msgno is "retransmitted" flag
                                // (this flag can be reused for something else, when pre-1.2.0 versions are all abandoned)
    SRT_OPT_STREAM    = BIT(6), // STREAM MODE (not MESSAGE mode)
    SRT_OPT_FILTERCAP = BIT(7), // CAPABILITY: Packet filter supported
};

inline int SrtVersionCapabilities()
{
    // NOTE: SRT_OPT_REXMITFLG is not included here because
    // SRT is prepared to handle also peers that don't have this
    // capability, so a listener responding to a peer that doesn't
    // support it should NOT set this flag.
    //
    // This state will remain until this backward compatibility is
    // decided to be broken, in which case this flag will be always
    // set, and clients that do not support this capability will be
    // rejected.
    return SRT_OPT_HAICRYPT | SRT_OPT_FILTERCAP;
}


std::string SrtFlagString(int32_t flags);

const int SRT_CMD_REJECT = 0, // REJECT is only a symbol for return type
      SRT_CMD_HSREQ = 1,
      SRT_CMD_HSRSP = 2,
      SRT_CMD_KMREQ = 3,
      SRT_CMD_KMRSP = 4,
      SRT_CMD_SID = 5,
      SRT_CMD_CONGESTION = 6,
      SRT_CMD_FILTER = 7,
      SRT_CMD_GROUP = 8,
      SRT_CMD_NONE = -1; // for cases when {no pong for ping is required} | {no extension block found}

enum SrtDataStruct
{
    SRT_HS_VERSION = 0,
    SRT_HS_FLAGS,
    SRT_HS_LATENCY,

    // Keep it always last
    SRT_HS_E_SIZE
};

// For HSv5 the lo and hi part is used for particular side's latency
typedef Bits<31, 16> SRT_HS_LATENCY_RCV;
typedef Bits<15, 0> SRT_HS_LATENCY_SND;
// For HSv4 only the lower part is used.
typedef Bits<15, 0> SRT_HS_LATENCY_LEG;


struct SrtHandshakeExtension
{
    int16_t type;
    std::vector<uint32_t> contents;

    SrtHandshakeExtension(int16_t cmd): type(cmd) {}
};

// Implemented in core.cpp, so far
void SrtExtractHandshakeExtensions(const char* bufbegin, size_t size,
        std::vector<SrtHandshakeExtension>& w_output);


struct SrtHSRequest: public SrtHandshakeExtension
{
    typedef Bits<31, 16> SRT_HSTYPE_ENCFLAGS;
    typedef Bits<15, 0> SRT_HSTYPE_HSFLAGS;

    // For translating PBKEYLEN into crypto flags
    // This value is 16, 24, 32; after cutting off
    // the leftmost 3 bits, it is 2, 3, 4.
    typedef Bits<5, 3> SRT_PBKEYLEN_BITS;

    // This value fits ins SRT_HSTYPE_HSFLAGS.
    //  ....                                HAIVISIOn
    static const int32_t SRT_MAGIC_CODE = 0x4A17;

    static int32_t wrapFlags(bool withmagic, int crypto_keylen)
    {
        int32_t base = withmagic ? SRT_MAGIC_CODE : 0;
        return base | SRT_HSTYPE_ENCFLAGS::wrap( SRT_PBKEYLEN_BITS::unwrap(crypto_keylen) );
    }

    // Group handshake extension layout

    //  0                   1                   2                   3
    //  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    //  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    //  |                           Group ID                            |
    //  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    //  | Group Type  | Group's Flags |       Group's Weight            |
    //  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    typedef Bits<31, 24> HS_GROUP_TYPE;
    typedef Bits<23, 16> HS_GROUP_FLAGS;
    typedef Bits<15, 0> HS_GROUP_WEIGHT;

private:
    friend class CHandShake;

    static const size_t SRT_HS_SIZE = 4*sizeof(uint32_t); // 4 existing fields
    static const size_t SRT_EXT_HS_SIZE = 2*sizeof(uint32_t) + SRT_HS_SIZE; // SRT magic and SRT HS type, used only in UDT HS ext

    typedef Bits<15, 0> SRT_TSBPD_DELAY;

    uint32_t m_iSrtVersion;
    uint32_t m_iSrtFlags;
    uint32_t m_iSrtTsbpd;
    uint32_t m_iSrtReserved;

public:

    SrtHSRequest(): SrtHandshakeExtension(SRT_CMD_HSREQ), m_iSrtVersion(), m_iSrtFlags(), m_iSrtTsbpd(), m_iSrtReserved() {}

    void setVersion(uint32_t v) { m_iSrtVersion = v; }
    uint32_t version() const { return m_iSrtVersion; }

    void setFlag(SrtOptions opt) { m_iSrtFlags |= uint32_t(opt); }
    void clearFlag(SrtOptions opt) { m_iSrtFlags &= ~opt; }
    uint32_t flags() const { return m_iSrtFlags; }

    void setTsbPdDelay(uint16_t delay) { m_iSrtTsbpd |= SRT_TSBPD_DELAY::wrap(delay); }
    // Unknown what the 1-16 bits have to be used for.
    uint16_t tsbPdDelay() const
    {
        return SRT_TSBPD_DELAY::unwrap(m_iSrtTsbpd);
    }

    size_t size() const { return SRT_EXT_HS_SIZE; }

    bool serialize(char* p, size_t size) const;
    bool deserialize(const char* mem, size_t size);
};

struct SrtKMRequest: public SrtHandshakeExtension
{
    uint32_t m_iKmState;
    char m_aKey[1]; // dynamic size
};


////////////////////////////////////////////////////////////////////////////////

enum UDTRequestType
{
    URQ_INDUCTION_TYPES = 0, // XXX used to check in one place. Consdr rm.

    URQ_INDUCTION = 1, // First part for client-server connection
    URQ_WAVEAHAND = 0, // First part for rendezvous connection

    URQ_CONCLUSION = -1, // Second part of handshake negotiation
    URQ_AGREEMENT = -2, // Extra (last) step for rendezvous only
    URQ_DONE = -3,      // Special value used only in state-switching, to state that nothing should be sent in response

    // Note: the client-server connection uses:
    // --> INDUCTION (empty)
    // <-- INDUCTION (cookie)
    // --> CONCLUSION (cookie)
    // <-- CONCLUSION (ok)

    // The rendezvous HSv4 (legacy):
    // --> WAVEAHAND (effective only if peer is also connecting)
    // <-- CONCLUSION (empty) (consider yourself connected upon reception)
    // --> AGREEMENT (sent as a response for conclusion, requires no response)

    // The rendezvous HSv5 (using SRT extensions):
    // --> WAVEAHAND (with cookie)
    // --- (selecting INITIATOR/RESPONDER by cookie contest - comparing one another's cookie)
    // <-- CONCLUSION (without extensions, if RESPONDER, with extensions, if INITIATOR)
    // --> CONCLUSION (with response extensions, if RESPONDER)
    // <-- AGREEMENT (sent exclusively by INITIATOR upon reception of CONCLUSIOn with response extensions)

    // This marks the beginning of values that are error codes.
    URQ_FAILURE_TYPES = 1000,

    // NOTE: codes above 1000 are reserved for failure codes for
    // rejection reason, as per `SRT_REJECT_REASON` enum. The
    // actual rejection code is the value of the request type
    // minus URQ_FAILURE_TYPES.

    // This is in order to return standard error codes for server
    // data retrieval failures.
    URQ_SERVER_FAILURE_TYPES = URQ_FAILURE_TYPES + SRT_REJC_PREDEFINED,

    // This is for a completely user-defined reject reasons.
    URQ_USER_FAILURE_TYPES = URQ_FAILURE_TYPES + SRT_REJC_USERDEFINED
};

inline UDTRequestType URQFailure(int reason)
{
    return UDTRequestType(URQ_FAILURE_TYPES + int(reason));
}

inline int RejectReasonForURQ(UDTRequestType req)
{
    if (req < URQ_FAILURE_TYPES)
        return SRT_REJ_UNKNOWN;

    int reason = req - URQ_FAILURE_TYPES;
    if (reason < SRT_REJC_PREDEFINED && reason >= SRT_REJ_E_SIZE)
        return SRT_REJ_UNKNOWN;

    return reason;
}

// DEPRECATED values. Use URQFailure(SRT_REJECT_REASON).
const UDTRequestType URQ_ERROR_REJECT SRT_ATR_DEPRECATED = (UDTRequestType)1002; // == 1000 + SRT_REJ_PEER
const UDTRequestType URQ_ERROR_INVALID SRT_ATR_DEPRECATED = (UDTRequestType)1004; // == 1000 + SRT_REJ_ROGUE

// XXX Change all uses of that field to UDTRequestType when possible
#if ENABLE_LOGGING
std::string RequestTypeStr(UDTRequestType);
#else
inline std::string RequestTypeStr(UDTRequestType) { return ""; }
#endif


class CHandShake
{
public:
    CHandShake();

    int store_to(char* buf, size_t& size);
    int load_from(const char* buf, size_t size);

public:
    // This is the size of SERIALIZED handshake.
    // Might be defined as simply sizeof(CHandShake), but the
    // enum values would have to be forced as int32_t, which is only
    // available in C++11. Theoretically they are all 32-bit, but
    // such a statement is not reliable and not portable.
    static const size_t m_iContentSize = 48;	// Size of hand shake data

    // Extension flags

    static const int32_t HS_EXT_HSREQ = BIT(0);
    static const int32_t HS_EXT_KMREQ = BIT(1);
    static const int32_t HS_EXT_CONFIG  = BIT(2);

    static std::string ExtensionFlagStr(int32_t fl);

    // Applicable only when m_iVersion == HS_VERSION_SRT1
    int32_t flags() { return m_iType; }

public:
    int32_t m_iVersion;          // UDT version (HS_VERSION_* symbols)
    int32_t m_iType;             // UDT4: socket type (only UDT_DGRAM is valid); SRT1: extension flags
    int32_t m_iISN;              // random initial sequence number
    int32_t m_iMSS;              // maximum segment size
    int32_t m_iFlightFlagSize;   // flow control window size
    UDTRequestType m_iReqType;   // handshake stage
    int32_t m_iID;               // SRT socket ID of HS sender
    int32_t m_iCookie;		// cookie
    uint32_t m_piPeerIP[4];	// The IP address that the peer's UDP port is bound to

    bool m_extension;

    bool valid();
    std::string show();

    // The rendezvous state machine used in HSv5 only (in HSv4 everything is happening the old way).
    //
    // The WAVING state is the very initial state of the rendezvous connection and restored after the
    // connection is closed.
    // The ATTENTION and FINE are two alternative states that are transited to from WAVING. The possible
    // situations are:
    // - "serial arrangement": one party transits to ATTENTION and the other party transits to FINE
    // - "parallel arrangement" both parties transit to ATTENTION
    //
    // Parallel arrangement is a "virtually impossible" case, in which both parties must send the first
    // URQ_WAVEAHAND message in a perfect time synchronization, when they are started at exactly the same
    // time, on machines with exactly the same performance and all things preceding the message sending
    // have taken perfectly identical amount of time. This isn't anyhow possible otherwise because if
    // the clients have started at different times, the one who started first sends a message and the
    // system of the receiver buffers this message even before the client binds the port for enough long
    // time so that it outlasts also the possible second, repeated waveahand.
    enum RendezvousState
    {
        RDV_INVALID,    //< This socket wasn't prepared for rendezvous process. Reject any events.
        RDV_WAVING,     //< Initial state for rendezvous. No contact seen from the peer.
        RDV_ATTENTION,  //< When received URQ_WAVEAHAND. [WAVING]:URQ_WAVEAHAND  --> [ATTENTION].
        RDV_FINE,       //< When received URQ_CONCLUSION. [WAVING]:URQ_CONCLUSION --> [FINE].
        RDV_INITIATED,  //< When received URQ_CONCLUSION+HSREQ extension in ATTENTION state. 
        RDV_CONNECTED   //< Final connected state. [ATTENTION]:URQ_CONCLUSION --> [CONNECTED] <-- [FINE]:URQ_AGREEMENT.
    };

#if ENABLE_LOGGING
    static std::string RdvStateStr(RendezvousState s);
#else
    static std::string RdvStateStr(RendezvousState) { return ""; }
#endif

};

} // namespace srt

#endif