// Copyright 2009-2020 Intel Corporation
// SPDX-License-Identifier: Apache-2.0

#pragma once

#include "../math/vec.h"

namespace embree {

struct RandomSampler
{
  unsigned int s;
};

__forceinline unsigned int MurmurHash3_mix(unsigned int hash, unsigned int k)
{
  const unsigned int c1 = 0xcc9e2d51;
  const unsigned int c2 = 0x1b873593;
  const unsigned int r1 = 15;
  const unsigned int r2 = 13;
  const unsigned int m = 5;
  const unsigned int n = 0xe6546b64;

  k *= c1;
  k = (k << r1) | (k >> (32 - r1));
  k *= c2;

  hash ^= k;
  hash = ((hash << r2) | (hash >> (32 - r2))) * m + n;

  return hash;
}

__forceinline unsigned int MurmurHash3_finalize(unsigned int hash)
{
  hash ^= hash >> 16;
  hash *= 0x85ebca6b;
  hash ^= hash >> 13;
  hash *= 0xc2b2ae35;
  hash ^= hash >> 16;

  return hash;
}

__forceinline unsigned int LCG_next(unsigned int value)
{
  const unsigned int m = 1664525;
  const unsigned int n = 1013904223;

  return value * m + n;
}

__forceinline void RandomSampler_init(RandomSampler& self, int id)
{
  unsigned int hash = 0;
  hash = MurmurHash3_mix(hash, id);
  hash = MurmurHash3_finalize(hash);

  self.s = hash;
}

__forceinline void RandomSampler_init(RandomSampler& self, int pixelId, int sampleId)
{
  unsigned int hash = 0;
  hash = MurmurHash3_mix(hash, pixelId);
  hash = MurmurHash3_mix(hash, sampleId);
  hash = MurmurHash3_finalize(hash);

  self.s = hash;
}

__forceinline void RandomSampler_init(RandomSampler& self, int x, int y, int sampleId)
{
  RandomSampler_init(self, x | (y << 16), sampleId);
}

__forceinline int RandomSampler_getInt(RandomSampler& self) {
  self.s = LCG_next(self.s); return self.s >> 1;
}

__forceinline unsigned int RandomSampler_getUInt(RandomSampler& self) {
  self.s = LCG_next(self.s); return self.s;
}

__forceinline float RandomSampler_getFloat(RandomSampler& self) {
  return (float)RandomSampler_getInt(self) * 4.656612873077392578125e-10f;
}

__forceinline float RandomSampler_get1D(RandomSampler& self) {
  return RandomSampler_getFloat(self);
}

__forceinline Vec2f RandomSampler_get2D(RandomSampler& self)
{
  const float u = RandomSampler_get1D(self);
  const float v = RandomSampler_get1D(self);
  return Vec2f(u,v);
}

__forceinline Vec3fa RandomSampler_get3D(RandomSampler& self)
{
  /*
  const float u = RandomSampler_get1D(self);
  const float v = RandomSampler_get1D(self);
  const float w = RandomSampler_get1D(self);
  return Vec3fa(u,v,w);
  */
  const int u = RandomSampler_getUInt(self);
  const int v = RandomSampler_getUInt(self);
  const int w = RandomSampler_getUInt(self);
  return Vec3fa(srl(Vec3ia(u,v,w), 1)) * 4.656612873077392578125e-10f;
}

} // namespace embree
