#include "kknd.h"

/* xoroshiro128** deterministic RNG */

void rng_seed(RNG *r, uint64_t seed) {
    if (seed == 0) seed = 0x9E3779B97F4A7C15ULL;
    r->s[0] = seed;
    r->s[1] = seed ^ 0xBF58476D1CE4E5B9ULL;
    if (r->s[0] == 0) r->s[0] = 1;
    if (r->s[1] == 0) r->s[1] = 2;
}

static inline uint64_t rotl(uint64_t x, int k) {
    return (x << k) | (x >> (64 - k));
}

uint64_t rng_u64(RNG *r) {
    uint64_t s0 = r->s[0];
    uint64_t s1 = r->s[1];
    uint64_t result = rotl(s0 * 5, 7) * 9;
    s1 ^= s0;
    r->s[0] = rotl(s0, 24) ^ s1 ^ (s1 << 16);
    r->s[1] = rotl(s1, 37);
    return result;
}

uint32_t rng_u32(RNG *r) {
    return (uint32_t)(rng_u64(r) >> 32);
}

int rng_range(RNG *r, int lo, int hi) {
    if (hi <= lo) return lo;
    return lo + (int)(rng_u32(r) % (uint32_t)(hi - lo + 1));
}

float rng_f32(RNG *r) {
    return (float)(rng_u32(r) >> 8) / (float)(1 << 24);
}

float rng_frange(RNG *r, float lo, float hi) {
    return lo + rng_f32(r) * (hi - lo);
}