refactor: align with Node's behavior for randomInt()

Author: webdeveric

src/randomInt.ts

@@ -1,4 +1,4 @@
-import { assertIsInteger } from './assertion/assertIsInteger.js';
+import { assertIsSafeInteger } from './assertion/assertIsSafeInteger.js';
 import { isObject } from './predicate/isObject.js';
 
 import type { RequireAtLeastOne } from './types/records.js';
@@ -18,20 +18,26 @@ export function randomInt(options?: RandomIntOptions): number;
 export function randomInt(min: number, max?: number): number;
 
 export function randomInt(arg1?: number | RandomIntOptions, arg2?: number): number {
-  const { min = Number.MIN_SAFE_INTEGER, max = Number.MAX_SAFE_INTEGER } = isObject(arg1)
-    ? arg1
-    : { min: arg1, max: arg2 };
+  const { min = 0, max = Number.MAX_SAFE_INTEGER } = isObject(arg1) ? arg1 : { min: arg1, max: arg2 };
 
-  assertIsInteger(min, 'min must be an integer');
-  assertIsInteger(max, 'max must be an integer');
+  assertIsSafeInteger(min, 'min must be a safe integer');
+  assertIsSafeInteger(max, 'max must be a safe integer');
 
-  if (min === max) {
-    return min;
-  }
-
-  if (min > max) {
+  if (min >= max) {
     throw new RangeError('min must be less than max');
   }
 
-  return Math.floor(Math.random() * (max - min)) + min;
+  const minBigInt = BigInt(min);
+  const range = BigInt(max) - minBigInt;
+  const limit = (2n ** 64n / range) * range;
+  const data = new BigInt64Array(1);
+
+  let value: bigint;
+
+  do {
+    crypto.getRandomValues(data);
+    value = BigInt.asUintN(64, data[0]!);
+  } while (value >= limit);
+
+  return Number(minBigInt + (value % range));
 }

test/randomInt.test.ts

@@ -3,10 +3,6 @@ import { describe, expect, it } from 'vitest';
 import { randomInt } from '../src/randomInt.js';
 
 describe('randomInt()', () => {
-  it('Returns early when min and max are the same', () => {
-    expect(randomInt(0, 0)).toEqual(0);
-  });
-
   it('Returns a random integer', () => {
     const value = randomInt(100, 200);
 
@@ -27,16 +23,28 @@ describe('randomInt()', () => {
     expect(value).lessThan(1000);
   });
 
-  it('Defaults to SAFE_INTEGER range', () => {
+  it('Defaults to [0, MAX_SAFE_INTEGER) range', () => {
     const value = randomInt();
 
-    expect(value).greaterThanOrEqual(Number.MIN_SAFE_INTEGER);
+    expect(value).greaterThanOrEqual(0);
     expect(value).lessThan(Number.MAX_SAFE_INTEGER);
   });
 
+  it('Throws when min and max are equal', () => {
+    expect(() => {
+      randomInt(0, 0);
+    }).toThrow();
+  });
+
   it('Throws when min > max', () => {
     expect(() => {
       randomInt(100, 0);
     }).toThrow();
   });
+
+  it('Throws when range is too large', () => {
+    expect(() => {
+      randomInt(Number.MIN_VALUE, Number.MAX_VALUE);
+    }).toThrow();
+  });
 });