svcorelib/src/functions/seededRNG/generateNumbers.js

Core library used in the projects of Sv443 and the Sv443 Network. Contains tons of miscellaneous QoL features.

const isEmpty = require("../isEmpty");
const generateRandomSeed = require("./randomSeed");
const validateSeed = require("./validateSeed");

// thanks to olsn for this code snippet: http://indiegamr.com/generate-repeatable-random-numbers-in-js/
function generateSeededNumbers(count = 16, seed)
{
    let result = [];

    if(isEmpty(seed))
        seed = generateRandomSeed();

    if(!validateSeed(seed))
        throw new Error("Error while validating seed in generateSeededNumbers() - Seeds cannot start with 0 and can only contain numerical digits between 0 and 9");

    let initialSeed = seed;

    let seededRandom = (min, max) => {
        max = max || 1;
        min = min || 0;
    
        seed = (seed * 9301 + 49297) % 233280;
        let rnd = seed / 233280;
    
        return Math.floor(min + rnd * (max - min));
    }

    for(let i = 0; i < count; i++)
        result.push(seededRandom(0, 9));

    if(result[0] == 0)
        result[0] = 1; // make sure the first item is not 0, so we can parse it as an int without losing the first digit - this can't be a random number since it needs to be the same every time

    return {
        numbers: result,
        stringified: result.join(""),
        integer: parseInt(result.join("")),
        seed: initialSeed,
    }
}

module.exports = generateSeededNumbers;