1 files changed, 79 insertions, 0 deletions
diff --git a/app/assets/javascripts/diffs/utils/uuids.js b/app/assets/javascripts/diffs/utils/uuids.js
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index 00000000000..1a529c07ccc
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+++ b/app/assets/javascripts/diffs/utils/uuids.js
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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
+ */
+
+// https://gitlab.com/gitlab-org/frontend/rfcs/-/issues/20
+/* eslint-disable import/prefer-default-export */
+
+import MersenneTwister from '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.random_int());
+
+    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) }))
+  );
+}