/*
 * Copyright (c) 2009 University of Washington
 *
 * SPDX-License-Identifier: GPL-2.0-only
 *
 * Author: Leonard Tracy <lentracy@gmail.com>
 */

#ifndef UAN_MAC_RC_GW_H
#define UAN_MAC_RC_GW_H

#include "uan-mac.h"

#include "ns3/mac8-address.h"
#include "ns3/nstime.h"
#include "ns3/traced-callback.h"

#include <map>
#include <set>

namespace ns3
{

class UanTxMode;

/**
 * @ingroup uan
 *
 * Gateway side of RC-MAC.
 *
 * This MAC protocol assumes a network topology where all traffic
 * is destined for a set of GW nodes which are connected via
 * some out of band (RF?) means.  UanMacRcGw is the protocol
 * which runs on the gateway nodes.
 *
 * This particular implementation
 * assumes that there is only a single gateway.
 *
 * For more information on class operation email
 * lentracy@u.washington.edu
 * (This work is, as of yet, unpublished)
 */
class UanMacRcGw : public UanMac
{
  public:
    UanMacRcGw();           //!< Constructor
    ~UanMacRcGw() override; //!< Dummy destructor, see DoDispose.

    /**
     * Register this type.
     * @return The type ID.
     */
    static TypeId GetTypeId();

    // Inherited methods
    bool Enqueue(Ptr<Packet> pkt, uint16_t protocolNumber, const Address& dest) override;
    void SetForwardUpCb(Callback<void, Ptr<Packet>, uint16_t, const Mac8Address&> cb) override;
    void AttachPhy(Ptr<UanPhy> phy) override;
    void Clear() override;
    int64_t AssignStreams(int64_t stream) override;

    /**
     * TracedCallback signature for
     *
     * @param [in] now, The current simulation time.
     * @param [in] delay Minimum path delay of first RTS.
     * @param [in] numRts Number of pending RTS.
     * @param [in] totalBytes Length of RTS header.
     * @param [in] secs Effective window size for RcCtsGlobal message, or
     *             time to next cycle, both in seconds.
     * @param [in] ctlRate CTL rate in Bps.
     * @param [in] actualX Current retry rate.
     */
    typedef void (*CycleCallback)(Time now,
                                  Time delay,
                                  uint32_t numRts,
                                  uint32_t totalBytes,
                                  double secs,
                                  uint32_t ctlRate,
                                  double actualX);

  private:
    /** Gateway state. */
    enum State
    {
        IDLE,    //!< Initial idle state.
        INCYCLE, //!< Cycling through nodes.
        CTSING   //!< Sending CTS.
    };

    State m_state; //!< Gateway processing state.

    /**
     * @ingroup uan
     * Reservation request.
     */
    struct Request
    {
        uint8_t numFrames; //!< Number of frames.
        uint8_t frameNo;   //!< Current frame number.
        uint8_t retryNo;   //!< Retry number.
        uint16_t length;   //!< Request header length.
        Time rxTime;       //!< Time request received.
    };

    /**
     * @ingroup uan
     * Packet ACK data.
     */
    struct AckData
    {
        uint8_t frameNo;            //!< Frame number being ACK'ed.
        std::set<uint8_t> rxFrames; //!< Received frames.
        uint8_t expFrames;          //!< Expected number of frames.
    };

    /** Forwarding up callback. */
    Callback<void, Ptr<Packet>, uint16_t, const Mac8Address&> m_forwardUpCb;

    Ptr<UanPhy> m_phy; //!< PHY layer attached to this MAC.
    Time m_maxDelta;   //!< Maximum propagation delay between gateway and non-gateway nodes .
    Time m_sifs;       //!< Spacing between frames to account for timing error and processing delay.
    uint32_t m_maxRes; //!< Maximum number of reservations to accept per cycle.
    uint32_t m_numRates;         //!< Number of rates per Phy layer.
    uint32_t m_rtsSize;          //!< Size of UanHeaderCommon and UanHeaderRcRts.
    uint32_t m_ctsSizeN;         //!< Size of UanHeaderRcCts.
    uint32_t m_ctsSizeG;         //!< Size of UanHeaderCommon and UanHeaderRcCtsGlobal.
    uint32_t m_ackSize;          //!< Size of UanHeaderCommon and UanHeaderRcAck.
    uint16_t m_currentRetryRate; //!< Retry rate number for current cycle.
    uint32_t m_currentRateNum;   //!< Rate number corresponding to data rate of current cycle.
    uint32_t m_numNodes;         //!< Number of non-gateway nodes in this gateway's neighborhood.
    uint32_t m_totalRate; //!< Total available channel rate in bps (for a single channel, without
                          //!< splitting reservation channel).
    uint32_t m_rateStep;  //!< Increments available for rate assignment in bps.
    uint32_t m_frameSize; //!< Size of data frames in bytes.

    double m_minRetryRate; //!< Smallest allowed RTS retry rate.
    double m_retryStep;    //!< Retry rate increment.

    /** Propagation delay to each node. */
    std::map<Mac8Address, Time> m_propDelay;

    /** AckData for each node. */
    std::map<Mac8Address, AckData> m_ackData;

    /** Request for each node. */
    std::map<Mac8Address, Request> m_requests;
    /** Queued request times. */
    std::set<std::pair<Time, Mac8Address>> m_sortedRes;

    /** Flag when we've been cleared. */
    bool m_cleared;

    /** A packet was destined for and received at this MAC layer. */
    TracedCallback<Ptr<const Packet>, UanTxMode> m_rxLogger;

    /**
     * A packet was destined for and received at this MAC layer.
     *
     * \pname{Start time}
     * \pname{min propagation delay}
     * \pname{reservations}
     * \pname{frames}
     * \pname{bytes}
     * \pname{window size}
     * \pname{CTS rate}
     * \pname{retry rate}
     */
    TracedCallback<Time, Time, uint32_t, uint32_t, double, uint32_t, double> m_cycleLogger;

    /**
     * PHY receive ok callback.
     *
     * @param pkt The Packet to receive
     * @param sinr The SINR on the channel
     * @param mode The transmission mode
     */
    void ReceivePacket(Ptr<Packet> pkt, double sinr, UanTxMode mode);

    /** Cycle through pending requests. */
    void StartCycle();
    /** End cycle by scheduling pending ACKs. */
    void EndCycle();
    /**
     * Send packet on PHY.
     *
     * @param pkt The Packet.
     * @param rate The UanTxMode number, m_currentRateNum.
     */
    void SendPacket(Ptr<Packet> pkt, uint32_t rate);
    /** Set state to INCYCLE. */
    void CycleStarted();
    /**
     * PHY receive error callback.
     *
     * @param pkt The failed packet.
     * @param sinr The SINR value on the channel.
     */
    void ReceiveError(Ptr<Packet> pkt, double sinr);

    // Stuff for computing exp throughput
    /**
     * Compute alpha parameter.
     *
     * @param totalFrames Total number of frames in m_requests.
     * @param totalBytes Total number of bytes in m_requests.
     * @param n Number of nodes.
     * @param a m_maxRes, or optimal A value.
     * @param deltaK Propagation delay.
     * @return Alpha parameter.
     */
    double ComputeAlpha(uint32_t totalFrames,
                        uint32_t totalBytes,
                        uint32_t n,
                        uint32_t a,
                        double deltaK);
    /**
     * Get the expected propagation delay to each node.
     *
     * @return Vector of expected propagation delays.
     */
    std::vector<double> GetExpPdk();
    /**
     * Throughput for \pname{a} reservations with framesize \pname{ld},
     * given expected delays exppdk.
     *
     * @param a Number of reservations.
     * @param ld Frame size.
     * @param exppdk Expected delays, given by GetExpPdk.
     * @return Expected throughput.
     */
    double ComputeExpS(uint32_t a, uint32_t ld, std::vector<double> exppdk);
    /**
     * Throughput for \pname{a} reservations with framesize \pname{ld}.
     *
     * @param a Number of reservations.
     * @param ld Frame size.
     * @return Expected throughput.
     */
    double ComputeExpS(uint32_t a, uint32_t ld);
    /**
     * Index to the k'th expected delay among n nodes.
     *
     * @param n Number of nodes.
     * @param k Target index.
     * @return The expected index.
     */
    uint32_t CompExpMinIndex(uint32_t n, uint32_t k);
    /**
     * Numeric function.
     *
     * @param a Number of reservations.
     * @param n number of nodes.
     * @param k K'th node.
     * @return Value.
     */
    double ComputePiK(uint32_t a, uint32_t n, uint32_t k);
    /**
     * Numeric function.
     *
     * @param n Number of nodes.
     * @param a Number of reservations.
     * @param ldlh Sum of common header length and frame size.
     * @param deltaK Result of GetExpPdk
     * @return value.
     */
    double ComputeExpBOverA(uint32_t n, uint32_t a, uint32_t ldlh, std::vector<double> deltaK);
    /**
     * Binomial coefficient.
     *
     * @param n Pool size.
     * @param k Selection size.
     * @return Binomial coefficient n choose k.
     */
    uint64_t NchooseK(uint32_t n, uint32_t k);
    /**
     * Compute the optimum maximum number of reservations to accept per cycle.
     *
     * @return Optimum number.
     */
    uint32_t FindOptA();

  protected:
    void DoDispose() override;
};

} // namespace ns3

#endif /* UAN_MAC_RC_GW_H */
