#include "rng.h"

// Linear congruential generator (LCG) state
static unsigned int g_seed = 1;

// LCG parameters (from numerical recipes)
#define LCG_A 1664525
#define LCG_C 1013904223
#define LCG_MOD 4294967294  // 2^32 - 2 (avoid 0)

void rng_seed(unsigned int seed) {
  // Ensure seed is never 0
  g_seed = (seed == 0) ? 1 : seed;
}

int rng_int(int min, int max) {
  // Generate next value
  g_seed = (LCG_A * g_seed + LCG_C) % LCG_MOD;

  // Map to [min, max] range
  return min + (int)((unsigned long long)g_seed % (max - min + 1));
}