#include <types.h>

#include <math/random.h>


/*
  This code uses Xorshift (high speed, small) and PCG (Permuted Congruential Generator).
  PCG may or may not be slightly slower than Xorshift.
*/

static uint32_t xorshift_state = 2463534242;

static void srand_xorshift(uint32_t seed)
{
  xorshift_state = seed;
}

static inline uint32_t rand_xorshift(void)
{
  uint32_t x = xorshift_state;
  x ^= x << 13;
  x ^= x >> 17;
  x ^= x << 5;
  
  return xorshift_state = x;
}

static uint64_t state = 0x853c49e6748fea9bULL;
static uint64_t inc   = 0xda3e39cb94b95bdbULL;

static inline uint32_t rand_pcg32(void)
{
  uint64_t oldstate = state;
  state = oldstate * 6364136223846793005ULL + (inc | 1);
  uint32_t xorshifted = ((oldstate >> 18u) ^ oldstate) >> 27u;
  uint32_t rot = oldstate >> 59u;
  
  return (xorshifted >> rot) | (xorshifted << ((-rot) & 31));
}

void seed_rand(uint32_t seed)
{
  srand_xorshift(seed);
  state = seed * 6364136223846793005ULL + (seed | 1);
}

uint32_t uirand(void)
{
  return rand_pcg32() ^ rand_xorshift();
}

/* get a number between 0 and max-1 */
uint32_t uirand_range(uint32_t max)
{
  if (max == 0)
  {
    return 0;
  }

  return uirand() % max;
}

uint64_t ulrand(void)
{
  uint64_t hi = uirand();
  uint64_t lo = uirand();
  return (hi << 32) | lo;
}

/* get a number between 0 and max-1 */
uint64_t ulrand_range(uint64_t max)
{
  if (max == 0)
  {
    return 0;
  }

  return ulrand() % max;
}