leven 3.1.0

Clean-room public code sample — generation instructions

Write a brand-new, minimal, self-contained code sample in this clean-room directory.
Do not copy, paraphrase, or reference any existing project source. Work only from this spec.

A csx.json manifest scaffold already exists. Do not recreate it from memory. Preserve its case.goal, packages and symbols; fill its empty case.contract with exact assertions and correct its environment, commands and verifierAdapter for the files you generate.

Goal: verify pkg:npm/leven@3.1.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/leven@3.1.0

Rules:
  - One focused purpose; the smallest project that proves the goal.
  - Include a contract test (test/contract.*) that runs OFFLINE and exits 0 exactly when the goal behavior works.
  - Pin every dependency with a lockfile so resolution is reproducible.
  - No secrets, credentials, or tokens. No real URLs (only example.com or localhost). No absolute paths.
  - No personal names, emails, company names, or project identifiers of any kind.
  - No binaries and no generated output (node_modules, dist, target, venv, .git, .env).
  - Keep it under 200 files and 256KB packed.

{"case":{"caseId":"case:sha256:205eb74179d9f2c9fa58e152d36997f26ea61e4b52bd55029f0aefdcd0d06895","contract":["leven returns 0 for identical strings","leven returns string length when comparing against an empty string","leven calculates single character substitution insertion and deletion distances","leven calculates edit distance for arbitrary string transformations","leven produces symmetric distance results regardless of argument order","leven optimizes distance calculation for strings sharing common prefixes and suffixes","leven computes distance across multi-byte UTF-16 code units"],"goal":"verify pkg:npm/leven@3.1.0","kind":"HOW","packages":["pkg:npm/leven@3.1.0"],"schemaVersion":1},"contractCommand":["node","test/contract.mjs"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"npm","executionContext":"node","language":"javascript","libc":"glibc","libcVersion":"2.39","moduleSystem":"cjs","os":"linux","osVersionBucket":"24","packageManager":"npm","packageManagerVersion":"10.9.8","runtime":"node","runtimeVersion":"22.23.2","schemaVersion":1},"license":"MIT-0","packages":["pkg:npm/leven@3.1.0"],"schemaVersion":1,"subject":"pkg:npm/leven@3.1.0","verifierAdapter":"node-typescript@1"}

'use strict';

const leven = require('leven');

/**
 * Calculate the Levenshtein distance between two strings.
 *
 * @param {string} a - First string to compare.
 * @param {string} b - Second string to compare.
 * @returns {number} The edit distance between the two strings.
 */
function getDistance(a, b) {
  return leven(a, b);
}

module.exports = {
  getDistance,
  leven,
};

{
  "name": "sample",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "sample",
      "version": "1.0.0",
      "dependencies": {
        "leven": "3.1.0"
      }
    },
    "node_modules/leven": {
      "version": "3.1.0",
      "resolved": "https://registry.npmjs.org/leven/-/leven-3.1.0.tgz",
      "integrity": "sha512-qsda+H8jTaUaN/x5vzW2rzc+8Rw4TAQ/4KjB46IwK5VH+IlVeeeje/EoZRpiXvIqjFgK84QffqPztGI3VBLG1A==",
      "license": "MIT",
      "engines": {
        "node": ">=6"
      }
    }
  }
}

{
  "name": "sample",
  "version": "1.0.0",
  "private": true,
  "description": "Clean-room verification of leven",
  "main": "index.js",
  "scripts": {
    "test": "node test/contract.mjs"
  },
  "dependencies": {
    "leven": "3.1.0"
  }
}

{
  "schemaVersion": 1,
  "goal": "verify pkg:npm/leven@3.1.0",
  "kind": "HOW",
  "packages": [
    "pkg:npm/leven@3.1.0"
  ]
}

import assert from 'node:assert/strict';
import leven from 'leven';
import { getDistance } from '../index.js';

// 1. leven returns 0 for identical strings
assert.equal(leven('', ''), 0);
assert.equal(leven('a', 'a'), 0);
assert.equal(leven('kitten', 'kitten'), 0);
assert.equal(getDistance('hello', 'hello'), 0);

// 2. leven returns string length when comparing against an empty string
assert.equal(leven('', 'a'), 1);
assert.equal(leven('abc', ''), 3);
assert.equal(leven('', 'hello'), 5);
assert.equal(getDistance('testing', ''), 7);

// 3. leven calculates single character substitution insertion and deletion distances
assert.equal(leven('a', 'b'), 1);
assert.equal(leven('ab', 'abc'), 1);
assert.equal(leven('abc', 'ab'), 1);
assert.equal(getDistance('cat', 'bat'), 1);

// 4. leven calculates edit distance for arbitrary string transformations
assert.equal(leven('kitten', 'sitting'), 3);
assert.equal(leven('saturday', 'sunday'), 3);
assert.equal(leven('rosettacode', 'raisethysword'), 8);
assert.equal(getDistance('industry', 'interest'), 6);

// 5. leven produces symmetric distance results regardless of argument order
assert.equal(leven('a', 'b'), leven('b', 'a'));
assert.equal(leven('kitten', 'sitting'), leven('sitting', 'kitten'));
assert.equal(leven('abcde', '123'), leven('123', 'abcde'));
assert.equal(getDistance('algorithm', 'altruistic'), getDistance('altruistic', 'algorithm'));

// 6. leven optimizes distance calculation for strings sharing common prefixes and suffixes
assert.equal(leven('prefix_a', 'prefix_b'), 1);
assert.equal(leven('a_suffix', 'b_suffix'), 1);
assert.equal(leven('start_middle1_end', 'start_middle2_end'), 1);
assert.equal(getDistance('common_base_x', 'common_base_y'), 1);

// 7. leven computes distance across multi-byte UTF-16 code units
assert.equal(leven('한국', '한글'), 1);
assert.equal(leven('café', 'cafe'), 1);
assert.equal(leven('🎉', '✨'), 2);
assert.equal(getDistance('こんにちは', 'こんにちわ'), 1);

console.log('All contract assertions passed.');