/*=========================================================================

  Program:   Visualization Toolkit
  Module:    vtkMinimalStandardRandomSequence.cxx

  Copyright (c) Ken Martin, Will Schroeder, Bill Lorensen
  All rights reserved.
  See Copyright.txt or http://www.kitware.com/Copyright.htm for details.

     This software is distributed WITHOUT ANY WARRANTY; without even
     the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
     PURPOSE.  See the above copyright notice for more information.
=========================================================================*/
#include "vtkMinimalStandardRandomSequence.h"

#include <cassert>
#include "vtkObjectFactory.h"

vtkStandardNewMacro(vtkMinimalStandardRandomSequence);

const int VTK_K_A=16807;
const int VTK_K_M=2147483647; // Mersenne prime 2^(31)-1
const int VTK_K_Q=127773; // M/A
const int VTK_K_R=2836; // M%A

// ----------------------------------------------------------------------------
vtkMinimalStandardRandomSequence::vtkMinimalStandardRandomSequence()
{
  this->Seed=1;
}

// ----------------------------------------------------------------------------
vtkMinimalStandardRandomSequence::~vtkMinimalStandardRandomSequence()
{
}

// ----------------------------------------------------------------------------
void vtkMinimalStandardRandomSequence::SetSeedOnly(int value)
{
  this->Seed=value;
  
  // fit the seed to the valid range [1,2147483646]
  if(this->Seed<1)
    {
    this->Seed+=2147483646;
    }
  else
    {
    if(this->Seed==2147483647)
      {
      this->Seed=1;
      }
    }
}

// ----------------------------------------------------------------------------
void vtkMinimalStandardRandomSequence::SetSeed(int value)
{
  this->SetSeedOnly(value);
  
  // the first random number after setting the seed is proportional to the
  // seed value. To help solve this, call Next() a few times.
  // This doesn't ruin the repeatability of Next().
  this->Next();
  this->Next();
  this->Next();
}

// ----------------------------------------------------------------------------
int vtkMinimalStandardRandomSequence::GetSeed(void)
{
  return this->Seed;
}

// ----------------------------------------------------------------------------
double vtkMinimalStandardRandomSequence::GetValue()
{
  double result=static_cast<double>(this->Seed)/VTK_K_M;
  
  assert("post: unit_range" && result>=0.0 && result<=1.0);
  return result;
}

// ----------------------------------------------------------------------------
void vtkMinimalStandardRandomSequence::Next()
{
  int hi=this->Seed/VTK_K_Q;
  int lo=this->Seed%VTK_K_Q;
  this->Seed=VTK_K_A*lo-VTK_K_R*hi;
  if(this->Seed<=0)
    {
    this->Seed+=VTK_K_M;
    }
}

// ----------------------------------------------------------------------------
double vtkMinimalStandardRandomSequence::GetRangeValue(double rangeMin,
                                                       double rangeMax)
{
  double result;
  if(rangeMin==rangeMax)
    {
    result=rangeMin;
    }
  else
    {
    result=rangeMin+this->GetValue()*(rangeMax-rangeMin);
    }
  assert("post: valid_result" &&
         ((rangeMin<=rangeMax && result>=rangeMin && result<=rangeMax)
          || (rangeMax<=rangeMin && result>=rangeMax && result<=rangeMin)));
  return result;
}

// ----------------------------------------------------------------------------
void vtkMinimalStandardRandomSequence::PrintSelf(ostream& os, vtkIndent indent)
{
  this->Superclass::PrintSelf(os, indent);
}