ip-address 10.7.0: Address6.fromAddress4

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 Address6.fromAddress4 in pkg:npm/ip-address@10.7.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/ip-address@10.7.0
Demonstrate these symbols/APIs:
  - Address6.fromAddress4

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:sha256:3407d4a204d17132880e01fe81d25c31f5089b7ba1821e837bb461c08399014d","contract":["Address6.fromAddress4 creates valid IPv4-mapped IPv6 Address6 instance","Address6.fromAddress4 marks parsed address with isMapped4 as true","Address6.fromAddress4 maps IPv4 subnet CIDR mask to corresponding IPv6 prefix length","Address6.fromAddress4 instance formats correct compressed form and to4in6 representation","Address6.fromAddress4 converts back to original Address4 instance using to4","Address6.fromAddress4 throws AddressError on invalid IPv4 input strings"],"goal":"verify Address6.fromAddress4 in pkg:npm/ip-address@10.7.0","kind":"HOW","packages":["pkg:npm/ip-address@10.7.0"],"schemaVersion":1,"symbols":["Address6.fromAddress4"]},"contractCommand":["node","test/contract.cjs"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"npm","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/ip-address@10.7.0"],"schemaVersion":1,"subject":"pkg:npm/ip-address@10.7.0","symbols":["Address6.fromAddress4"],"verifierAdapter":"node-typescript@1"}

{
  "name": "ip-address-sample",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "ip-address-sample",
      "version": "1.0.0",
      "dependencies": {
        "ip-address": "10.7.0"
      }
    },
    "node_modules/ip-address": {
      "version": "10.7.0",
      "resolved": "https://registry.npmjs.org/ip-address/-/ip-address-10.7.0.tgz",
      "integrity": "sha512-BGFsyJd5mpXp3rK6jIdADLNgpJUK1jnjzvYF8lK+VyDab9JAmqN0YOKDdP17HlgKb2+ehPgDc8EtnRLbGCAMhA==",
      "license": "MIT",
      "engines": {
        "node": ">= 12"
      }
    }
  }
}

{
  "name": "ip-address-sample",
  "version": "1.0.0",
  "private": true,
  "description": "Verification sample for Address6.fromAddress4 in ip-address 10.7.0",
  "dependencies": {
    "ip-address": "10.7.0"
  }
}

{
  "schemaVersion": 1,
  "goal": "verify Address6.fromAddress4 in pkg:npm/ip-address@10.7.0",
  "kind": "HOW",
  "packages": [
    "pkg:npm/ip-address@10.7.0"
  ],
  "symbols": [
    "Address6.fromAddress4"
  ]
}

const assert = require("node:assert/strict");
const { Address6, AddressError } = require("ip-address");

// 1. Address6.fromAddress4 creates valid IPv4-mapped IPv6 Address6 instance
const mapped = Address6.fromAddress4("192.168.1.1");
assert.ok(mapped instanceof Address6);
assert.equal(Address6.isValid(mapped.address), true);
assert.equal(mapped.address, "::ffff:192.168.1.1/128");

// 2. Address6.fromAddress4 marks parsed address with isMapped4 as true
assert.equal(mapped.isMapped4(), true);
assert.equal(mapped.isLoopback(), false);
assert.equal(mapped.isLinkLocal(), false);
assert.equal(mapped.isMulticast(), false);

// 3. Address6.fromAddress4 maps IPv4 subnet CIDR mask to corresponding IPv6 prefix length
const mappedCidr = Address6.fromAddress4("10.0.0.0/24");
assert.equal(mappedCidr.subnetMask, 120);
assert.equal(mappedCidr.subnet, "/120");
const hostInSubnet = Address6.fromAddress4("10.0.0.42");
const hostOutOfSubnet = Address6.fromAddress4("10.0.1.42");
assert.equal(hostInSubnet.isInSubnet(mappedCidr), true);
assert.equal(hostOutOfSubnet.isInSubnet(mappedCidr), false);

// 4. Address6.fromAddress4 instance formats correct compressed form and to4in6 representation
assert.equal(mapped.correctForm(), "::ffff:c0a8:101");
assert.equal(mapped.to4in6(), "::ffff:192.168.1.1");
assert.equal(mapped.canonicalForm(), "0000:0000:0000:0000:0000:ffff:c0a8:0101");

// 5. Address6.fromAddress4 converts back to original Address4 instance using to4
const originalV4 = mapped.to4();
assert.equal(originalV4.correctForm(), "192.168.1.1");
assert.equal(originalV4.isCorrect(), true);

// 6. Address6.fromAddress4 throws AddressError on invalid IPv4 input strings
assert.throws(
  () => Address6.fromAddress4("invalid-ipv4"),
  (err) => err instanceof AddressError || err.name === "AddressError" || /Invalid/i.test(err.message)
);
assert.throws(
  () => Address6.fromAddress4("999.999.999.999"),
  (err) => err instanceof AddressError || err.name === "AddressError" || /Invalid/i.test(err.message)
);
assert.throws(
  () => Address6.fromAddress4(""),
  (err) => err instanceof AddressError || err.name === "AddressError" || /Invalid/i.test(err.message)
);