/*
  Copyright (c) 2020 Alex Diener
  
  This software is provided 'as-is', without any express or implied
  warranty. In no event will the authors be held liable for any damages
  arising from the use of this software.
  
  Permission is granted to anyone to use this software for any purpose,
  including commercial applications, and to alter it and redistribute it
  freely, subject to the following restrictions:
  
  1. The origin of this software must not be misrepresented; you must not
     claim that you wrote the original software. If you use this software
     in a product, an acknowledgment in the product documentation would be
     appreciated but is not required.
  2. Altered source versions must be plainly marked as such, and must not be
     misrepresented as being the original software.
  3. This notice may not be removed or altered from any source distribution.
  
  Alex Diener alex@ludobloom.com
*/

#include "gamemath/PCGRandom.h"
#include <limits.h>

#define DEFAULT_MULTIPLIER_32 747796405u

void pcg32_seed(pcg_state * state, uint32_t initState, uint32_t initSeq) {
	state->state = 0u;
	state->inc = (initSeq << 1u) | 1u;
	state->state = state->state * DEFAULT_MULTIPLIER_32 + state->inc;
	state->state += initState;
	state->state = state->state * DEFAULT_MULTIPLIER_32 + state->inc;
}

static inline void pcg32_advance(pcg_state * state) {
	uint64_t lastState = state->state;
	state->state = lastState * 6364136223846793005ull + (state->inc | 1);
}

void pcg32_stir(pcg_state * state, unsigned int iterationCount) {
	while (iterationCount > 0) {
		pcg32_advance(state);
		iterationCount--;
	}
}

uint32_t pcg32_uirand(pcg_state * state) {
	uint32_t xorShifted = ((state->state >> 18u) ^ state->state) >> 27u;
	uint32_t rot = state->state >> 59u;
	pcg32_advance(state);
	return (xorShifted >> rot) | (xorShifted << (-rot & 31));
}

int32_t pcg32_irand(pcg_state * state) {
	return pcg32_uirand(state);
}

float pcg32_ufrand(pcg_state * state, float bound) {
	return bound * (double) pcg32_uirand(state) / UINT_MAX;
}

float pcg32_frand(pcg_state * state, float bound) {
	return bound * (double) pcg32_irand(state) / INT_MAX;
}