/**
 *  @title pkg-name-check
 *  @version 0.0.1
 *
 *  @fileoverview A utiliy script to help identify whether your chosen package
 *  name already exists with a similar name in the npm registry. See:
 *  https://blog.npmjs.org/post/168978377570/new-package-moniker-rules)
 *
 *  Prior to usage you'll need to:
 *
 *  1. Download npm registry (approx 124Mb of JSON) by running:
 *
 *     curl -X GET https://replicate.npmjs.com/_all_docs > /path/to/npm-registry.json
 *
 *  @example
 *     node path/to/pkg-name-check.js "<pkg-name>"
 */

const tick = process.platform === 'win32' ? '√' : '✔';
const cross = process.platform === 'win32' ? '×' : '✖';

const npmRegistry = require('./npm-registry.json');
const pkgName = process.argv[2];
const CHARSET = '[_\\.\\-]*?';

if (!pkgName) {
  console.log('\x1b[31mERR!\x1b[0m %s', 'pkg name argument must be provided.');
  process.exit(1);
}

// Construct the regex pattern.
const regex = RegExp(pkgName
    .split('')
    .map(function (char, i, arr) {

      // If last letter is `s` then add `?` qualifier (i.e. zero or one)
      // to test for non-plural instances.
      if (arr.length - 1 === i && char === 's') {
        char = char + '?'
      }

      // If character equals `-`, `_`, or `.` then add `*?` qualifier
      // (i.e. zero to unlimited) to test for names without `-`, `_`, or `.`
      return (char === '-' || char === '_' || char === '.') ? char + '*?' : char
    })

    // Insert $CHARSET between each letter
    .join(CHARSET)

     // Prefix string with $CHARSET
    .replace(/^/, CHARSET)

     // Suffix string with $CHARSET
    .replace(/$/, CHARSET)

    // Prefix string with ^
    .replace(/^/, '^')

    // Suffix string with `s` and `?` qualifier
    // (i.e. zero or one) to test for plural names.
    .concat('[s]?$')
    , 'g');


const result = npmRegistry.rows
    .filter(function (pkg) {
      return regex.test(pkg.id);
    })
    .map(function (pkg) {
      return pkg.id;
    });


if (result.length) {
  console.log('\x1b[31m%s\x1b[0m  "%s" is unavailable:', cross, pkgName);
  console.log(result.join('\n'));
} else {
  console.log('\x1b[32m%s\x1b[0m  "%s" is available.', tick, pkgName);
}