// Copyright (C) 2015 Rémi Bèges
// This file is part of the "Nazara Engine - Noise module"
// For conditions of distribution and use, see copyright notice in Config.hpp

#include <Nazara/Noise/NoiseBase.hpp>
#include <Nazara/Core/Error.hpp>
#include <Nazara/Noise/Config.hpp>
#include <Nazara/Noise/Debug.hpp>

NzNoiseBase::NzNoiseBase(unsigned int seed)
{
	Ua = 16807;
	Uc = 0;
	Um = 2147483647;
	UcurrentSeed = 0;
	Uprevious = 0;

	SetNewSeed(seed);

	for(int i(0) ; i < 512 ; i++)
		perm[i] = i & 255;

}

void NzNoiseBase::SetNewSeed(unsigned int seed)
{
	Uprevious = seed;
	UcurrentSeed = seed;
}

unsigned int NzNoiseBase::GetUniformRandomValue()
{
	Ulast = Ua*Uprevious + Uc%Um;
	Uprevious = Ulast;
	return Ulast;
}

void NzNoiseBase::ShufflePermutationTable()
{
	int xchanger;
	unsigned int ncase;

	for(unsigned int i(0) ; i < 256 ; i++)
		perm[i] = i;

	for(unsigned int j(0) ; j < 20 ; ++j)
		for (unsigned int i(0); i < 256 ; ++i)
		{
			ncase = this->GetUniformRandomValue() & 255;
			xchanger = perm[i];
			perm[i] = perm[ncase];
			perm[ncase] = xchanger;
		}

	for(unsigned int i(256) ; i < 512; ++i)
		perm[i] = perm[i & 255];
}

int NzNoiseBase::fastfloor(float n)
{
	return (n >= 0) ? static_cast<int>(n) : static_cast<int>(n-1);
}

int NzNoiseBase::JenkinsHash(int a, int b, int c)
{
	a = a-b;  a = a - c;  a = a^(static_cast<unsigned int>(c) >> 13);
	b = b-c;  b = b - a;  b = b^(a << 8);
	c = c-a;  c = c - b;  c = c^(static_cast<unsigned int>(b) >> 13);
	a = a-b;  a = a - c;  a = a^(static_cast<unsigned int>(c) >> 12);
	b = b-c;  b = b - a;  b = b^(a << 16);
	c = c-a;  c = c - b;  c = c^(static_cast<unsigned int>(b) >> 5);
	a = a-b;  a = a - c;  a = a^(static_cast<unsigned int>(c) >> 3);
	b = b-c;  b = b - a;  b = b^(a << 10);
	c = c-a;  c = c - b;  c = c^(static_cast<unsigned int>(b) >> 15);
	return c;
}