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/**
* @module uuids
*/
/**
* A string or number representing a start state for a random generator
* @typedef {(Number|String)} Seed
*/
/**
* A UUIDv4 string in the format <code>Hex{8}-Hex{4}-4Hex{3}-[89ab]Hex{3}-Hex{12}</code>
* @typedef {String} UUIDv4
*/
import { MersenneTwister } from 'fast-mersenne-twister';
import stringHash from 'string-hash';
import { isString } from 'lodash';
import { v4 } from 'uuid';
function getSeed(seeds) {
return seeds.reduce((seedling, seed, i) => {
let thisSeed = 0;
if (Number.isInteger(seed)) {
thisSeed = seed;
} else if (isString(seed)) {
thisSeed = stringHash(seed);
}
return seedling + (seeds.length - i) * thisSeed;
}, 0);
}
function getPseudoRandomNumberGenerator(...seeds) {
let seedNumber;
if (seeds.length) {
seedNumber = getSeed(seeds);
} else {
seedNumber = Math.floor(Math.random() * 10 ** 15);
}
return new MersenneTwister(seedNumber);
}
function randomValuesForUuid(prng) {
const randomValues = [];
for (let i = 0; i <= 3; i += 1) {
const buffer = new ArrayBuffer(4);
const view = new DataView(buffer);
view.setUint32(0, prng.randomNumber());
randomValues.push(view.getUint8(0), view.getUint8(1), view.getUint8(2), view.getUint8(3));
}
return randomValues;
}
/**
* Get an array of UUIDv4s
* @param {Object} [options={}]
* @param {Seed[]} [options.seeds=[]] - A list of mixed strings or numbers to seed the UUIDv4 generator
* @param {Number} [options.count=1] - A total number of UUIDv4s to generate
* @returns {UUIDv4[]} An array of UUIDv4s
*/
export function uuids({ seeds = [], count = 1 } = {}) {
const rng = getPseudoRandomNumberGenerator(...seeds);
return (
// Create an array the same size as the number of UUIDs requested
Array(count)
.fill(0)
// Replace each slot in the array with a UUID which needs 16 (pseudo)random values to generate
.map(() => v4({ random: randomValuesForUuid(rng) }))
);
}
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