rng class..

common/GameCommon.js

@@ -7,9 +7,10 @@ function exists(gameId) {
   return (!!GAMES[gameId]) || false
 }
 
-function createGame(id, puzzle, players, sockets, evtInfos) {
+function createGame(id, rng, puzzle, players, sockets, evtInfos) {
   return {
     id: id,
+    rng: rng,
     puzzle: puzzle,
     players: players,
     sockets: sockets,
@@ -31,8 +32,8 @@ function createPlayer(id, ts) {
   }
 }
 
-function newGame({id, puzzle, players, sockets, evtInfos}) {
-  const game = createGame(id, puzzle, players, sockets, evtInfos)
+function newGame({id, rng, puzzle, players, sockets, evtInfos}) {
+  const game = createGame(id, rng, puzzle, players, sockets, evtInfos)
   setGame(id, game)
   return game
 }

common/Rng.js

@@ -0,0 +1,27 @@
+export class Rng {
+  constructor(seed) {
+    this.rand_high = seed || 0xDEADC0DE
+    this.rand_low = seed ^ 0x49616E42
+  }
+
+  random (min, max) {
+    this.rand_high = ((this.rand_high << 16) + (this.rand_high >> 16) + this.rand_low) & 0xffffffff;
+    this.rand_low = (this.rand_low + this.rand_high) & 0xffffffff;
+    var n = (this.rand_high >>> 0) / 0xffffffff;
+    return (min + n * (max-min+1))|0;
+  }
+
+  static serialize (rng) {
+    return {
+      rand_high: rng.rand_high,
+      rand_low: rng.rand_low
+    }
+  }
+
+  static unserialize (rngSerialized) {
+    const rng = new Rng(0)
+    rng.rand_high = rngSerialized.rand_high
+    rng.rand_low = rngSerialized.rand_low
+    return rng
+  }
+}

common/Util.js

@@ -1,11 +1,20 @@
+import { Rng } from './Rng.js'
+
 // get a unique id
 export const uniqId = () => Date.now().toString(36) + Math.random().toString(36).substring(2)
 
 // get a random int between min and max (inclusive)
-export const randomInt = (min, max) => Math.floor(Math.random() * (max - min + 1)) + min
+export const randomInt = (
+  /** @type Rng */ rng,
+  min,
+  max
+) => rng.random(min, max)
 
 // get one random item from the given array
-export const choice = (array) => array[randomInt(0, array.length - 1)]
+export const choice = (
+  /** @type Rng */ rng,
+  array
+) => array[randomInt(rng, 0, array.length - 1)]
 
 export const throttle = (fn, delay) => {
   let canCall = true
@@ -21,11 +30,14 @@ export const throttle = (fn, delay) => {
 }
 
 // return a shuffled (shallow) copy of the given array
-export const shuffle = (array) => {
+export const shuffle = (
+  /** @type Rng */ rng,
+  array
+) => {
   let arr = array.slice()
   for (let i = 0; i <= arr.length - 2; i++)
   {
-    const j = randomInt(i, arr.length -1);
+    const j = randomInt(rng, i, arr.length -1);
     const tmp = arr[i];
     arr[i] = arr[j];
     arr[j] = tmp;