bill-calculator.js

function parseLogs(logs) {
  const logsArray = logs.split('\n').map(eachLog => eachLog.split(','))
  const normalisedArray = normaliseArray(logsArray)
  const logsWithSeconds = normalisedArray.map(([timestamp, phoneNumber]) =>
    [calculateTotalSeconds(timestamp), phoneNumber])
  const grouped = groupByPhoneNumber(logsWithSeconds)
  const phoneNumberWithLargestTotal = getPhoneNumberWithLargestTotalSeconds(grouped)
  grouped[phoneNumberWithLargestTotal] = 0
  return calculateTotalBill(logsWithSeconds, phoneNumberWithLargestTotal)
}

function normaliseArray(logsArray) {
  const lastElementIdx = logsArray.length - 1
  if (logsArray[lastElementIdx].length === 1 && logsArray[lastElementIdx][0] === '') {
    return logsArray.slice(0, -1)
  }
  return logsArray
}

function calculateTotalBill(logsWithSeconds, phoneNumberWithLargestTotal) {
  const FIVE_MINUTES = 5 * 60
  return logsWithSeconds.reduce((acc, [totalSeconds, phoneNumber]) => {
    if (phoneNumber !== phoneNumberWithLargestTotal) {
      switch (true) {
        case totalSeconds < FIVE_MINUTES:
          acc = acc + totalSeconds * 3
          break;
        
        case totalSeconds >= FIVE_MINUTES:
          const numOfMinutes = Math.trunc(totalSeconds / 60)
          acc = acc + numOfMinutes * 150
        default:
          break;
      }
    }
    return acc
  }, 0)
}

function calculateTotalSeconds(timestamp) {
  const [hours, minutes, seconds] = timestamp.split(':')
  return Number(hours) * 60 * 60 + Number(minutes) * 60 + Number(seconds)
}

function groupByPhoneNumber(logs) {
  return logs.reduce((acc, val) => {
    const [ seconds, phoneNumber ] = val
    if (!acc.hasOwnProperty(phoneNumber)) {
      acc[phoneNumber] = seconds
    } else {
      acc[phoneNumber] = acc[phoneNumber] + seconds
    }
    return acc
  }, {})
}

function getPhoneNumberWithLargestTotalSeconds(logs) {
  const logsArray = Object.keys(logs).map(key => [key, logs[key]])
  let largestTotal = 0
  let phoneNumberWithLargestTotal = ''
  logsArray.forEach(([phoneNumber, totalSeconds]) => {
    if (totalSeconds > largestTotal) {
      largestTotal = totalSeconds
      phoneNumberWithLargestTotal = phoneNumber
    } else if (totalSeconds === largestTotal) {
      if (Number(phoneNumber.replace(/-/g, '')) < Number(phoneNumberWithLargestTotal.replace(/-/g, ''))) {
        phoneNumberWithLargestTotal = phoneNumber
      }
    }
  })
  return phoneNumberWithLargestTotal
}

module.exports = parseLogs