#include "prand.h"
#include <stdint.h>
#include <stdio.h>
#include <time.h>
#include <unistd.h>

#define PRAND_BUILD_SEED                                                                                               \
    ((uint64_t)(__TIME__[0]) * (uint64_t)(__TIME__[1]) * (uint64_t)(__TIME__[3]) * (uint64_t)(__TIME__[4]) *           \
     (uint64_t)(__TIME__[6]) * (uint64_t)(__TIME__[7]))

static uint64_t seed = PRAND_BUILD_SEED * 6364136223846793005ULL + 1;

uint64_t prand() {
    seed = seed * 6364136223846793005ULL + 1;
    return seed;
}

inline uint64_t prand_range(uint64_t min, uint64_t max) {
    uint64_t range = max - min + 1;
    uint64_t x;
    uint64_t limit = UINT64_MAX - (UINT64_MAX % range);

    do {
        x = prand();
    } while (x > limit);

    return min + (x % range);
}

void sprand(uint64_t s) {
    if (s) {
        seed ^= (s * 0x9e3779b97f4a7c15ULL) + (seed << 6) + (seed >> 2);
    } else {
        seed ^= PRAND_BUILD_SEED;
    }
}

#undef PRAND_BUILD_SEED

#define PRAND_MAIN
#ifdef PRAND_MAIN
int main() {
    // time(NULL) provides a somewhat unique seed at runtime
    sprand(time(NULL));
    sprand(getpid());
    sprand(0);

    uint64_t rn1 = prand();
    uint64_t rn2 = prand();

    printf("rn1 = %lu\n", rn1);
    printf("rn2 = %lu\n", rn2);

    for (int i = 0; i < 40; i++) {
        uint64_t random = prand_range(0, 1000);
        printf("random = %lu\n", random);
    }
}
#endif