/**
 * Convert number to words in Indian Rupees
 *
 * @param {number} input The value to convert.
 * @return The number in lakhs and crores.
 * @customfunction
 */
function INR(input) {
  const rupees = Number(parseInt(input, 10));
  const output = [];

  if (rupees === 0) {
    output.push('zero');
  } else if (rupees === 1) {
    output.push('one');
  } else {
    const crores = Math.floor(rupees / 10000000) % 100;
    if (crores > 0) {
      output.push(`${getHundreds(crores)} crore`);
    }

    const lakhs = Math.floor(rupees / 100000) % 100;
    if (lakhs > 0) {
      output.push(`${getHundreds(lakhs)} lakh`);
    }

    const thousands = Math.floor(rupees / 1000) % 100;
    if (thousands > 0) {
      output.push(`${getHundreds(thousands)} thousand`);
    }

    const hundreds = Math.floor((rupees % 1000) / 100);
    if (hundreds > 0 && hundreds < 10) {
      output.push(`${getOnes(hundreds)} hundred`);
    }

    const tens = rupees % 100;
    if (tens > 0) {
      if (rupees > 100) output.push('and');
      output.push(`${getHundreds(tens)}`);
    }
  }

  return ['Rupees', ...output, 'only']
    .join(' ')
    .split(/\s/)
    .filter((e) => e)
    .map((e) => e.substr(0, 1).toUpperCase() + e.substr(1))
    .join(' ');
}

function getOnes(number) {
  const ones = ['', 'one', 'two', 'three', 'four', 'five', 'six', 'seven', 'eight', 'nine'];
  return ones[number] || '';
}

function getTeens(number) {
  const teens = [
    'ten',
    'eleven',
    'twelve',
    'thirteen',
    'fourteen',
    'fifteen',
    'sixteen',
    'seventeen',
    'eighteen',
    'nineteen',
  ];
  return teens[number] || '';
}

function getTens(number) {
  const tens = ['', '', 'twenty', 'thirty', 'forty', 'fifty', 'sixty', 'seventy', 'eighty', 'ninety'];
  return tens[number] || '';
}

function getHundreds(num) {
  if (num > 0 && num < 10) {
    return getOnes(num);
  }
  if (num >= 10 && num < 20) {
    return getTeens(num % 10);
  }
  if (num >= 20 && num < 100) {
    return `${getTens(Math.floor(num / 10))} ${getOnes(num % 10)}`;
  }
  return '';
}