// Rand.cpp: implementation of the CRand class.
//
//////////////////////////////////////////////////////////////////////

#include "stdafx.h"
#include "FGrass.h"
#include "Rand.h"

#include<stdlib.h>
#include<math.h>

#ifdef _DEBUG
#undef THIS_FILE
static char THIS_FILE[]=__FILE__;
#define new DEBUG_NEW
#endif

#define _rand_table_size 101
#define _rand_init_seed 3030303l

static int first_time=1;
static int need_newvars = 1;
static int last_rand_int = _rand_init_seed;
static RandType rand_table[_rand_table_size];
static RandType last_rand;

void _srand(unsigned long iseed)
{
	srand(iseed);
	for(int i=0;i<_rand_table_size;i++)
		rand_table[i]=rand()/(RAND_MAX+RandType(1));
	last_rand=(last_rand_int=rand())/(RAND_MAX+RandType(1));
	first_time=0;
	need_newvars = 1;
}

RandType _rand(void)
{
	int index;
	if(first_time)
		_srand(_rand_init_seed);
	index=unsigned int(_rand_table_size*last_rand);
	last_rand=rand_table[index];
	rand_table[index]=(last_rand_int=rand())/(RAND_MAX+RandType(1));
	return last_rand;
}

RandType _randBiUniform(void)
{
	RandType x;

	x = _rand();
	if (_rand() < 0.5f) x *= -1;
	return x;
}

RandType _randExponential(void)
{
	RandType x;

	x = _rand();
	return RandType(-log(x));
}

RandType _randBiExponential(void)
{
	RandType x;

	x = _randExponential();
	if (_rand() < 0.5f) x *= -1;

	return x;
}

RandType _randgauss(void)
{ 
	static RandType factor,v1,v2;
	RandType result;
	
	if(need_newvars)
	{ 
		RandType r=RandType(1.1);
		while(r>=1||r==0)
		{ 
			v1=2*_rand()-1;
			v2=2*_rand()-1;
			r=v1*v1+v2*v2;
		}
		need_newvars=0;
		factor=RandType(sqrt(-2*log(r)/r));
		result=v1*factor;
	}
	else
	{ 
		need_newvars=1;
		result=v2*factor;
	}
	return result;
}

int _randGetSeed(void)
{
	return last_rand_int;
}

void CRandBase::setseed(long new_seed)
{ 
	m_seed=new_seed;
//	_srand(m_seed);
}

void CRandBase::setCurSeed(long new_seed)
{ 
	m_seed=new_seed;
	_srand(m_seed);
}

void CRandBase::setCurSeed()
{ 
	_srand(m_seed);
}

RandType CRandUniform::next(void)
{ 
//	return (_rand()*2*m_stdev+m_mean-m_stdev);
//	return (_rand()*(m_stdev-m_mean)+m_mean);
	setseed(_randGetSeed());
	return (2*(_rand()-0.5f)*m_stdev+m_mean);
}

RandType CRandGauss::next(void)
{ 
	setseed(_randGetSeed());
	return (_randgauss()*m_stdev+m_mean);
}

void CRandExponential::CalcRange()
{
	m_min=RandType(exp(-m_stdev-m_mean));
	m_max=RandType(exp( m_stdev-m_mean));
}

RandType CRandExponential::next(void)
{ 
	setseed(_randGetSeed());
	RandType x;

	x = _rand();
	return RandType(-log( x*(m_max-m_min) + m_min ));
//	return (_randExponential()*m_stdev+m_mean);
}