// Seeded RNG (mulberry32). All sim/mapgen randomness goes through this so a
// shared seed produces identical maps on both peers.
export function mulberry32(seed) {
  let a = seed >>> 0;
  return function () {
    a |= 0; a = (a + 0x6D2B79F5) | 0;
    let t = Math.imul(a ^ (a >>> 15), 1 | a);
    t = (t + Math.imul(t ^ (t >>> 7), 61 | t)) ^ t;
    return ((t ^ (t >>> 14)) >>> 0) / 4294967296;
  };
}

export function makeRng(seed) {
  const f = mulberry32(seed);
  return {
    f,
    int: (a, b) => a + Math.floor(f() * (b - a + 1)),
    pick: (arr) => arr[Math.floor(f() * arr.length)],
    chance: (p) => f() < p,
  };
}

// UI-side only (room keys, match seeds) — never inside the sim.
export function randomSeed() {
  return Math.floor(Math.random() * 0xffffffff) >>> 0;
}