// vim:fileencoding=utf-8:foldmethod=marker

#include "splitmix64.h"
#include "../../common/aliases/aliases.h"
#include "../../common/assert/assert.h"
#include "../../common/platform/platform.h"
#include <stdlib.h>
#include <time.h>

wp_intern void seedOsGenerator(u64 seed);
wp_intern u64 genRandomNumber(void);

WpSplitmix64State wpPrngSplitmix64Init(void) {
	wp_persist b8 seeded = false;
	if (!seeded) {
		seeded = true;
		seedOsGenerator(0);
	}

	return (WpSplitmix64State){ .seed = genRandomNumber() };
}

WpSplitmix64State wpPrngSplitmix64InitWithSeed(u64 seed) {
	return (WpSplitmix64State){ .seed = seed };
}

u64 wpPrngSplitmix64(WpSplitmix64State *state) {
	state->seed += 0x9E3779B97f4A7C15;

	u64 result = state->seed;
	result = (result ^ (result >> 30)) * 0xBF58476D1CE4E5B9;
	result = (result ^ (result >> 27)) * 0x94D049BB133111EB;

	return result ^ (result >> 31);
}

u64 wpPrngSplitmix64InRange(WpSplitmix64State *state, u64 start, u64 end) {
	return wpPrngSplitmix64(state) % (end - start) + start;
}

u64 wpPrngSplitmix64Choice(WpSplitmix64State *state, u64 available_choices) {
	return wpPrngSplitmix64(state) % available_choices;
}

#if defined(WP_PLATFORM_C) && WP_PLATFORM_C_VERSION >= WP_PLATFORM_C11_VERSION
#ifdef WP_PLATFORM_POSIX
wp_intern void seedOsGenerator(u64 seed) {
	if (seed == 0) {
		struct timespec ts = {0};
		int result = clock_gettime(CLOCK_MONOTONIC_RAW, &ts);
		wpRuntimeAssert(result == 0, "Invalid seed value");
		seed = (u64)ts.tv_nsec;
	}

	srand48(seed);
}

wp_intern u64 genRandomNumber(void) {
	return lrand48();
}
#else
wp_intern void seedOsGenerator(u64 seed) {
	if (seed == 0) {
		struct timespec ts = {0};
		int result = timespec_get(&ts, TIME_UTC);
		wpRuntimeAssert(result != 0, "Invalid seed value");
		seed = (u64)ts.tv_nsec;
	}

	srand(seed);
}

wp_intern u64 genRandomNumber(void) {
	i32 n1 = rand();
	i32 n2 = rand();

	return (((u64)n1) << 32 | (u64)n2);
}
#endif // !WP_PLATFORM_POSIX
#else
wp_intern void seedOsGenerator(u64 seed) {
	if (seed == 0) {
		time_t result = time(NULL);
		wpRuntimeAssert(result != (time_t)(-1), "Invalid seed value");
		seed = (u64)result;
	}

	srand(seed);
}

wp_intern u64 genRandomNumber(void) {
	i32 n1 = rand();
	i32 n2 = rand();

	return (((u64)n1) << 32 | (u64)n2);
}
#endif // !WP_PLATFORM_C