Add seed functionality

src/index.d.ts

@@ -16,9 +16,10 @@ type RenderFunction = (resolution: number, indexX: number, indexY: number) => st
  * Returns a randomly generated string representation code of an avatar for a given `complexity`
  * @param {number} [complexity] - A positive integer that represents the number of rows and columns to be drawn
  * @param {string} [avatarDataSeparator] - A character to be used as data separator
+ * @param {any} [seed] - A value to be used as the seed for generating the avatar data; accepts any value that the `String` constructor would accept
  * @return {string} Output example: 0-6-6te25-9d9p0-xd5g
  */
-export function generateRandomAvatarData(complexity?: number, avatarDataSeparator?: string): string;
+export function generateRandomAvatarData(complexity?: number, avatarDataSeparator?: string, seed?: any): string;
 
 /**
  * Returns a string with a valid SVG markup for a given `avatarData`

src/index.js

@@ -39,16 +39,56 @@ function parseAvatarData(data, separator) {
   return ret;
 }
 
-export function generateRandomAvatarData(complexity = 16, avatarDataSeparator = '-') {
-  const xAxis = Math.floor(Math.random() * Math.pow(2, complexity - 1));
-  const yAxis = Math.floor(Math.random() * (Math.pow(2, complexity) - 1)) + 1;
+// https://stackoverflow.com/a/47593316/1714997
+function cyrb128(str) {
+  let h1 = 1779033703, h2 = 3144134277,
+      h3 = 1013904242, h4 = 2773480762;
+  for (let i = 0, k; i < str.length; i++) {
+      k = str.charCodeAt(i);
+      h1 = h2 ^ Math.imul(h1 ^ k, 597399067);
+      h2 = h3 ^ Math.imul(h2 ^ k, 2869860233);
+      h3 = h4 ^ Math.imul(h3 ^ k, 951274213);
+      h4 = h1 ^ Math.imul(h4 ^ k, 2716044179);
+  }
+  h1 = Math.imul(h3 ^ (h1 >>> 18), 597399067);
+  h2 = Math.imul(h4 ^ (h2 >>> 22), 2869860233);
+  h3 = Math.imul(h1 ^ (h3 >>> 17), 951274213);
+  h4 = Math.imul(h2 ^ (h4 >>> 19), 2716044179);
+  h1 ^= (h2 ^ h3 ^ h4), h2 ^= h1, h3 ^= h1, h4 ^= h1;
+  return [h1>>>0, h2>>>0, h3>>>0, h4>>>0];
+}
+
+// https://stackoverflow.com/a/47593316/1714997
+function sfc32(a, b, c, d) {
+  return function() {
+    a |= 0; b |= 0; c |= 0; d |= 0;
+    let t = (a + b | 0) + d | 0;
+    d = d + 1 | 0;
+    a = b ^ b >>> 9;
+    b = c + (c << 3) | 0;
+    c = (c << 21 | c >>> 11);
+    c = c + t | 0;
+    return (t >>> 0) / 4294967296;
+  }
+}
+
+function getRandomNumberGenerator(seed) {
+  const seedString = String(seed); // Making sure that the seed is a string.
+  const seedHashed = cyrb128(seedString);
+  return sfc32(seedHashed[0], seedHashed[1], seedHashed[2], seedHashed[3]);
+}
+
+export function generateRandomAvatarData(complexity = 16, avatarDataSeparator = '-', seed = Math.random()) {
+  const getRandomNumber = getRandomNumberGenerator(seed);
+  const xAxis = Math.floor(getRandomNumber() * Math.pow(2, complexity - 1));
+  const yAxis = Math.floor(getRandomNumber() * (Math.pow(2, complexity) - 1)) + 1;
 
   const rows = getBinaryList(yAxis, complexity);
   let ret = `${xAxis.toString(36)}${avatarDataSeparator}${yAxis.toString(36)}`;
   let color;
 
   rows.forEach(() => {
-    color = Math.floor(Math.random() * 16777215);
+    color = Math.floor(getRandomNumber() * 16777215);
     ret += `${avatarDataSeparator}${color.toString(36)}`;
   });
 

src/index.test.js

@@ -1,6 +1,6 @@
 import { getRandomAvatar, getAvatarFromData, generateRandomAvatarData } from './index.js';
 
-describe('Generate random avatar Ddta', () => {
+describe('Generate random avatar Data', () => {
   it('should return a random code from default values', () => {
     const avatarCode = generateRandomAvatarData();
     expect(avatarCode.split('-').length).toEqual(18);
@@ -11,6 +11,27 @@ describe('Generate random avatar Ddta', () => {
   });
 });
 
+describe('Generate random avatar data with seed', () => {
+  it('should return the same code for the same seed', () => {
+    const seed = "apples";
+    const avatarCode1 = generateRandomAvatarData(16, '-', seed);
+    const avatarCode2 = generateRandomAvatarData(16, '-', seed);
+    expect(avatarCode1).toEqual(avatarCode2);
+  });
+  it('should return different codes for different seeds', () => {
+    const seed1 = "apples";
+    const seed2 = "oranges";
+    const avatarCode1 = generateRandomAvatarData(16, '-', seed1);
+    const avatarCode2 = generateRandomAvatarData(16, '-', seed2);
+    expect(avatarCode1).not.toEqual(avatarCode2);
+  });
+  it('should return different codes when no seed is provided', () => {
+    const avatarCode1 = generateRandomAvatarData();
+    const avatarCode2 = generateRandomAvatarData();
+    expect(avatarCode1).not.toEqual(avatarCode2);
+  });
+});
+
 describe('Get svg from avatar data', () => {
   it('should fail if wrong avatar code is submited', () => {
     expect(() => getAvatarFromData('')).toThrow('Incorrect avatar data');
@@ -41,4 +62,4 @@ describe('Get a random svg avatar', () => {
     expect(getRandomAvatar(2, 'circle')).toMatch(/<svg xmlns="http:\/\/www.w3.org\/2000\/svg" width="100%" height="100%" viewBox="0 0 256 256">.+<\/svg>/);
     expect(getRandomAvatar(2, 'circle', 16)).toMatch(/<svg xmlns="http:\/\/www.w3.org\/2000\/svg" width="100%" height="100%" viewBox="0 0 16 16">.+<\/svg>/);
   });
-});
+});