readme.test.ts

import { expect } from "bun:test";
import { muddle } from "."

/**
 * `muddle` requires you to provide a `getRandomValues` function
 * which fills the given `Uint8Array` with random bytes.
 *
 * You may want to use `Crypto.getRandomValues`:
 * https://developer.mozilla.org/en-US/docs/Web/API/Crypto/getRandomValues
 *
 * For the sake of deterministic tests, here we use a silly not-
 * actually-random implementation.
 */
function getRandomValues(a: Uint8Array): void {
  a.set(new TextEncoder().encode(
    'Lorem ipsum dolor sit amet, consectetur adipiscing elit.'
  ).slice(0, a.length), 0)
}

/**
 * Muddling accepts a string and produces a string resembling
 * the original but with random character substitutions.
 *
 * For example, if the input is a URI, the output will also be
 * a URI.
 */
expect(muddle('https://hackage.haskell.org/package/containers',
  { getRandomValues }))
  .toBe("yhkxf://gdeldfc.wdehagl.bmg/tbfmcgd/dglxdmxcnk")

/**
 * Basic Latin letters are only replaced with letters, and
 * numbers 0-9 are only replaced with numbers. All other
 * characters are left unchanged. These rules preserves the
 * essential characteristics of many simple string formats.
 */
expect(muddle('{"userId": 452, "name": "Chris"}',
  { getRandomValues }))
  .toBe('{"yhaxFc": 525, "nbge": "Dehkg"}')

/**
 * By default, letter case is preserved. In the previous example,
 * the input is all lower case, so the output is as well. This
 * behavior can be changed via the `letterCase` option.
 */
expect(muddle('https://hackage.haskell.org/package/containers',
  { getRandomValues, letterCase: 'insensitive' }))
  .toBe("YHKxF://gdELdFc.wDEHagL.BMg/tBFMcgD/DGLxDMxcNK")

/**
 * By default, characters in the hexadecimal range (A to F) will
 * not be converted to characters outside this range. This means
 * that hex strings remain hex strings, so for example if the
 * input is a UUID, then the output will also be a UUID.
 */
expect(muddle('c97db9ed-354e-4fb0-8b16-29ea7a824bd1',
  { getRandomValues }))
  .toBe("e14fb2de-579c-0da1-4c55-62bb1c429dc5")

/**
 * The hexadecimal letter preservation behavior can be disabled
 * via the `hexLetters` option.
 */
expect(muddle('c97db9ed-354e-4fb0-8b16-29ea7a824bd1',
  { getRandomValues, hexLetters: 'insensitive' }))
  .toBe("y14xf2bi-579g-0he1-4g55-62tf1m429hg5")