//========= Copyright Valve Corporation, All rights reserved. ============//
//
// Purpose: Random number generator
//
// $Workfile: $
// $NoKeywords: $
//===========================================================================//

#ifndef VSTDLIB_RANDOM_H
#define VSTDLIB_RANDOM_H

#include "../tier0/basetypes.h"
#include "../tier0/threadtools.h"
#include "../tier1/interface.h"
#include "vstdlib.h"

#define NTAB 32

#pragma warning(push)
#pragma warning(disable : 4251)

//-----------------------------------------------------------------------------
// A generator of uniformly distributed random numbers
//-----------------------------------------------------------------------------
class VSTDLIB_CLASS IUniformRandomStream {
   public:
    // virtual ~IUniformRandomStream() { }

    // Sets the seed of the random number generator
    virtual void SetSeed(int iSeed) = 0;

    // Generates random numbers
    virtual float RandomFloat(float flMinVal = 0.0f, float flMaxVal = 1.0f) = 0;
    virtual int RandomInt(int iMinVal, int iMaxVal) = 0;
    virtual float RandomFloatExp(float flMinVal = 0.0f, float flMaxVal = 1.0f,
                                 float flExponent = 1.0f) = 0;
};

//-----------------------------------------------------------------------------
// The standard generator of uniformly distributed random numbers
//-----------------------------------------------------------------------------
class VSTDLIB_CLASS CUniformRandomStream : public IUniformRandomStream {
   public:
    CUniformRandomStream();

    // Sets the seed of the random number generator
    virtual void SetSeed(int iSeed);

    // Generates random numbers
    virtual float RandomFloat(float flMinVal = 0.0f, float flMaxVal = 1.0f);
    virtual int RandomInt(int iMinVal, int iMaxVal);
    virtual float RandomFloatExp(float flMinVal = 0.0f, float flMaxVal = 1.0f,
                                 float flExponent = 1.0f);

   private:
    int GenerateRandomNumber();

    int m_idum;
    int m_iy;
    int m_iv[NTAB];

    CThreadFastMutex m_mutex;
};

//-----------------------------------------------------------------------------
// A generator of gaussian distributed random numbers
//-----------------------------------------------------------------------------
class VSTDLIB_CLASS CGaussianRandomStream {
   public:
    // Passing in NULL will cause the gaussian stream to use the
    // installed global random number generator
    CGaussianRandomStream(IUniformRandomStream *pUniformStream = NULL);

    // Attaches to a random uniform stream
    void AttachToStream(IUniformRandomStream *pUniformStream = NULL);

    // Generates random numbers
    float RandomFloat(float flMean = 0.0f, float flStdDev = 1.0f);

   private:
    IUniformRandomStream *m_pUniformStream;
    bool m_bHaveValue;
    float m_flRandomValue;

    CThreadFastMutex m_mutex;
};

//-----------------------------------------------------------------------------
// A couple of convenience functions to access the library's global uniform
// stream
//-----------------------------------------------------------------------------
VSTDLIB_INTERFACE void RandomSeed(int iSeed);
VSTDLIB_INTERFACE float RandomFloat(float flMinVal = 0.0f,
                                    float flMaxVal = 1.0f);
VSTDLIB_INTERFACE float RandomFloatExp(float flMinVal = 0.0f,
                                       float flMaxVal = 1.0f,
                                       float flExponent = 1.0f);
VSTDLIB_INTERFACE int RandomInt(int iMinVal, int iMaxVal);
VSTDLIB_INTERFACE float RandomGaussianFloat(float flMean = 0.0f,
                                            float flStdDev = 1.0f);

//-----------------------------------------------------------------------------
// IUniformRandomStream interface for free functions
//-----------------------------------------------------------------------------
class VSTDLIB_CLASS CDefaultUniformRandomStream : public IUniformRandomStream {
   public:
    virtual void SetSeed(int iSeed) OVERRIDE { RandomSeed(iSeed); }
    virtual float RandomFloat(float flMinVal, float flMaxVal) OVERRIDE {
        return ::RandomFloat(flMinVal, flMaxVal);
    }
    virtual int RandomInt(int iMinVal, int iMaxVal) OVERRIDE {
        return ::RandomInt(iMinVal, iMaxVal);
    }
    virtual float RandomFloatExp(float flMinVal, float flMaxVal,
                                 float flExponent) OVERRIDE {
        return ::RandomFloatExp(flMinVal, flMaxVal, flExponent);
    }
};

//-----------------------------------------------------------------------------
// Installs a global random number generator, which will affect the Random
// functions above
//-----------------------------------------------------------------------------
VSTDLIB_INTERFACE void InstallUniformRandomStream(
    IUniformRandomStream *pStream);

#pragma warning(pop)

#endif  // VSTDLIB_RANDOM_H