99bottles_v2.js

import { downTo } from './helpers';

export class Bottles {
  song() {
    return this.verses(99, 0);
  }

  verses(start, end) {
    return downTo(start, end)
      .map((i) => this.verse(i))
      .join('\n');
  }

  verse(number) {
    const [current, next] = downTo(number, number - 1);
    const nextText = next === 0 ? 'no more' : next;
    const takeText = current === 1 ? 'it' : 'one';
    const currentBottles = this.pluralizeBottles(current);
    const nextBottles = this.pluralizeBottles(next);

    if (number === 0) {
      return (
        'No more bottles of beer on the wall, ' +
        'no more bottles of beer.\n' +
        'Go to the store and buy some more, ' +
        '99 bottles of beer on the wall.\n'
      );
    }

    return (
      `${current} ${currentBottles} of beer on the wall, ` +
      `${current} ${currentBottles} of beer.\n` +
      `Take ${takeText} down and pass it around, ` +
      `${nextText} ${nextBottles} of beer on the wall.\n`
    );
  }

  pluralizeBottles(number) {
    return `bottle${number === 1 ? '' : 's'}`;
  }
}