negotiator 0.6.4

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/negotiator@0.6.4
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/negotiator@0.6.4

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:sha256:609e13737290a6963fb5c402ff2e97acbed58d3fa2170475a077be4be193504e","contract":["Negotiator parses Accept header and selects the most preferred media type from available options","Negotiator parses Accept-Language header and returns preferred languages in prioritized order","Negotiator parses Accept-Encoding header and selects the best encoding from supported list","Negotiator parses Accept-Charset header and selects the best character set from supported list","Negotiator provides sensible defaults for empty headers"],"goal":"verify pkg:npm/negotiator@0.6.4","kind":"HOW","packages":["pkg:npm/negotiator@0.6.4"],"schemaVersion":1},"contractCommand":["node","test/contract.js"],"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/negotiator@0.6.4"],"schemaVersion":1,"subject":"pkg:npm/negotiator@0.6.4","verifierAdapter":"node-typescript@1"}

{
  "name": "negotiator-sample",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "negotiator-sample",
      "version": "1.0.0",
      "dependencies": {
        "negotiator": "0.6.4"
      }
    },
    "node_modules/negotiator": {
      "version": "0.6.4",
      "resolved": "https://registry.npmjs.org/negotiator/-/negotiator-0.6.4.tgz",
      "integrity": "sha512-myRT3DiWPHqho5PrJaIRyaMv2kgYf0mUVgBNOYMuCH5Ki1yEiQaf/ZJuQ62nvpc44wL5WDbTX7yGJi1Neevw8w==",
      "license": "MIT",
      "engines": {
        "node": ">= 0.6"
      }
    }
  }
}

{
  "name": "negotiator-sample",
  "version": "1.0.0",
  "dependencies": {
    "negotiator": "0.6.4"
  }
}

{
  "schemaVersion": 1,
  "goal": "verify pkg:npm/negotiator@0.6.4",
  "kind": "HOW",
  "packages": [
    "pkg:npm/negotiator@0.6.4"
  ]
}

const Negotiator = require('negotiator');

/**
 * Creates a Negotiator instance for the given request.
 *
 * @param {{ headers?: Record<string, string> }} req
 * @returns {Negotiator}
 */
function createNegotiator(req) {
  return new Negotiator(req);
}

/**
 * Returns the most preferred media type from the available options.
 *
 * @param {{ headers?: Record<string, string> }} req
 * @param {string[]} [available]
 * @returns {string | undefined}
 */
function getPreferredMediaType(req, available) {
  const negotiator = new Negotiator(req);
  return negotiator.mediaType(available);
}

/**
 * Returns all preferred media types ordered by quality.
 *
 * @param {{ headers?: Record<string, string> }} req
 * @param {string[]} [available]
 * @returns {string[]}
 */
function getMediaTypes(req, available) {
  const negotiator = new Negotiator(req);
  return negotiator.mediaTypes(available);
}

/**
 * Returns the most preferred language from the available options.
 *
 * @param {{ headers?: Record<string, string> }} req
 * @param {string[]} [available]
 * @returns {string | undefined}
 */
function getPreferredLanguage(req, available) {
  const negotiator = new Negotiator(req);
  return negotiator.language(available);
}

/**
 * Returns all preferred languages ordered by quality.
 *
 * @param {{ headers?: Record<string, string> }} req
 * @param {string[]} [available]
 * @returns {string[]}
 */
function getLanguages(req, available) {
  const negotiator = new Negotiator(req);
  return negotiator.languages(available);
}

/**
 * Returns the most preferred encoding from the available options.
 *
 * @param {{ headers?: Record<string, string> }} req
 * @param {string[]} [available]
 * @returns {string | undefined}
 */
function getPreferredEncoding(req, available) {
  const negotiator = new Negotiator(req);
  return negotiator.encoding(available);
}

/**
 * Returns all preferred encodings ordered by quality.
 *
 * @param {{ headers?: Record<string, string> }} req
 * @param {string[]} [available]
 * @returns {string[]}
 */
function getEncodings(req, available) {
  const negotiator = new Negotiator(req);
  return negotiator.encodings(available);
}

/**
 * Returns the most preferred charset from the available options.
 *
 * @param {{ headers?: Record<string, string> }} req
 * @param {string[]} [available]
 * @returns {string | undefined}
 */
function getPreferredCharset(req, available) {
  const negotiator = new Negotiator(req);
  return negotiator.charset(available);
}

/**
 * Returns all preferred charsets ordered by quality.
 *
 * @param {{ headers?: Record<string, string> }} req
 * @param {string[]} [available]
 * @returns {string[]}
 */
function getCharsets(req, available) {
  const negotiator = new Negotiator(req);
  return negotiator.charsets(available);
}

module.exports = {
  Negotiator,
  createNegotiator,
  getPreferredMediaType,
  getMediaTypes,
  getPreferredLanguage,
  getLanguages,
  getPreferredEncoding,
  getEncodings,
  getPreferredCharset,
  getCharsets,
};

const assert = require('node:assert/strict');
const {
  Negotiator,
  createNegotiator,
  getPreferredMediaType,
  getMediaTypes,
  getPreferredLanguage,
  getLanguages,
  getPreferredEncoding,
  getEncodings,
  getPreferredCharset,
  getCharsets,
} = require('../src/index.js');

async function main() {
  // Contract 1: Negotiator parses Accept header and selects the most preferred media type from available options
  {
    const req = {
      headers: {
        accept: 'text/html, application/xhtml+xml, application/xml;q=0.9, image/webp, */*;q=0.8',
      },
    };

    const mediaTypes = getMediaTypes(req);
    assert.strictEqual(Array.isArray(mediaTypes), true);
    assert.strictEqual(mediaTypes[0], 'text/html');
    assert.strictEqual(mediaTypes.includes('application/xhtml+xml'), true);
    assert.strictEqual(mediaTypes.includes('image/webp'), true);

    const preferredMatch = getPreferredMediaType(req, ['application/json', 'text/html']);
    assert.strictEqual(preferredMatch, 'text/html');

    const fallbackMatch = getPreferredMediaType(req, ['application/json']);
    assert.strictEqual(fallbackMatch, 'application/json');

    const negotiator = createNegotiator(req);
    assert.strictEqual(negotiator instanceof Negotiator, true);
  }

  // Contract 2: Negotiator parses Accept-Language header and returns preferred languages in prioritized order
  {
    const req = {
      headers: {
        'accept-language': 'en-US, en;q=0.9, fr;q=0.8, de;q=0.5',
      },
    };

    const languages = getLanguages(req);
    assert.deepStrictEqual(languages, ['en-US', 'en', 'fr', 'de']);

    const preferredLang = getPreferredLanguage(req, ['de', 'fr']);
    assert.strictEqual(preferredLang, 'fr');

    const exactMatch = getPreferredLanguage(req, ['en-US', 'en']);
    assert.strictEqual(exactMatch, 'en-US');
  }

  // Contract 3: Negotiator parses Accept-Encoding header and selects the best encoding from supported list
  {
    const req = {
      headers: {
        'accept-encoding': 'gzip, deflate, br;q=0.5',
      },
    };

    const encodings = getEncodings(req);
    assert.strictEqual(encodings.includes('gzip'), true);
    assert.strictEqual(encodings.includes('deflate'), true);
    assert.strictEqual(encodings.includes('br'), true);

    const preferredEncoding = getPreferredEncoding(req, ['br', 'gzip']);
    assert.strictEqual(preferredEncoding, 'gzip');

    const singleOption = getPreferredEncoding(req, ['deflate']);
    assert.strictEqual(singleOption, 'deflate');
  }

  // Contract 4: Negotiator parses Accept-Charset header and selects the best character set from supported list
  {
    const req = {
      headers: {
        'accept-charset': 'utf-8, iso-8859-1;q=0.7, utf-16;q=0.3',
      },
    };

    const charsets = getCharsets(req);
    assert.deepStrictEqual(charsets, ['utf-8', 'iso-8859-1', 'utf-16']);

    const preferredCharset = getPreferredCharset(req, ['iso-8859-1', 'utf-16']);
    assert.strictEqual(preferredCharset, 'iso-8859-1');

    const topCharset = getPreferredCharset(req, ['utf-8', 'iso-8859-1']);
    assert.strictEqual(topCharset, 'utf-8');
  }

  // Contract 5: Negotiator provides sensible defaults for empty headers
  {
    const req = { headers: {} };

    const mediaTypes = getMediaTypes(req);
    assert.deepStrictEqual(mediaTypes, ['*/*']);

    const languages = getLanguages(req);
    assert.deepStrictEqual(languages, ['*']);

    const encodings = getEncodings(req);
    assert.deepStrictEqual(encodings, ['identity']);

    const charsets = getCharsets(req);
    assert.deepStrictEqual(charsets, ['*']);

    const selectedMedia = getPreferredMediaType(req, ['application/json', 'text/plain']);
    assert.strictEqual(selectedMedia, 'application/json');
  }

  console.log('All pkg:npm/negotiator@0.6.4 contracts passed successfully.');
}

main().catch(err => {
  console.error(err);
  process.exit(1);
});