random-without-winning-streaks

.gitignore

node_modules

index.js

const seedrandom = require('seedrandom'); // Because JS doesn't let you set the seed on Math.random.
const { WebClient } = require('@slack/web-api');

const util = require('util');
const fs = require('fs');
const readFile = util.promisify(fs.readFile);
const writeFile = util.promisify(fs.writeFile);

let candidates = [
 "Xiao Yu'er",
 "Hua Wu Que",
 "Tie Xin Lan",
 "Su Ying",
];

const prngFile = '/tmp/prng.tmp';

async function loadPrngStateFile() {
  return await readFile(prngFile, 'utf8')
    .then(JSON.parse)
    .catch(()=>{return createRngWithSeed("something")});
}

function createRngWithSeed(seed) {
  const prng = seedrandom(seed, {state: true});
  const p = seedrandom("", {state: prng.state});
  return prng.state();
}

function selectCandidate(random) {
  return candidates[Math.floor(random * candidates.length)];
}

function selectNextCandidate(prng, lastCandidate) {
  let nextCandidateState = prng.state(); // "next", because prng() was called.
  let nextCandidate = selectCandidate(prng());

  const next = {
    candidate: nextCandidate,
    state: nextCandidateState
  };

  // Prevents "streaks".
  while (lastCandidate === next.candidate) {
    next.state = prng.state();
    next.candidate = selectCandidate(prng());
  }

  return next;
}

// Fyi: This function is async, so be sure to call it sequentially if you put
// this into an array.
async function main() {
  const initialPrngState = await loadPrngStateFile()
  const prng = seedrandom("", {state: initialPrngState});

  let lastCandidate = selectCandidate(prng());
  let next = selectNextCandidate(prng, lastCandidate)

  await writeFile(prngFile, JSON.stringify(next.state), 'utf8');

  // return next.candidate;
}
main();

/*
No streaks.

However, it has a slightly uneven distribution after 1000 runs
{
  '0': 103, // **********
  '1': 103, // **********
  '2': 89,  // ********
  '3': 108, // **********
  '4': 107, // **********
  '5': 98,  // *********
  '6': 103, // **********
  '7': 87,  // ********
  '8': 97,  // *********
  '9': 105  // **********
}
*/

package-lock.json

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package.json

{
  "name": "less-annoying-rand",
  "version": "0.1.0",
  "description": "Making Random draws less annoying",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "",
  "license": "ISC",
  "dependencies": {
    "@slack/web-api": "^5.11.0",
    "seedrandom": "^3.0.5"
  }
}