#ifndef _random_h_INCLUDED
#define _random_h_INCLUDED

#include <assert.h>
#include <stdbool.h>
#include <stdint.h>

typedef uint64_t generator;

static inline uint64_t kissat_next_random64(generator *rng)
{
    *rng *= 6364136223846793005ul;
    *rng += 1442695040888963407ul;
    return *rng;
}

static inline unsigned kissat_next_random32(generator *rng)
{
    return kissat_next_random64(rng) >> 32;
}

static inline unsigned kissat_pick_random(generator *rng, unsigned l, unsigned r)
{
    assert(l < r);
    const unsigned delta = r - l;
    const unsigned tmp = kissat_next_random32(rng);
    const double fraction = tmp / 4294967296.0;
    assert(0 <= fraction), assert(fraction < 1);
    const unsigned scaled = delta * fraction;
    assert(scaled < delta);
    const unsigned res = l + scaled;
    assert(l <= res), assert(res < r);
    return res;
}

static inline bool kissat_pick_bool(generator *rng)
{
    return kissat_pick_random(rng, 0, 2);
}

static inline double kissat_pick_double(generator *rng)
{
    return kissat_next_random32(rng) / 4294967296.0;
}

#endif
