const oneSecond = () => 1000
const getCurrentTime = () => new Date()
const clear = () => console.clear()
const log = message => console.log(message)

// Pure functions
const serializeClockTime = (date) =>
  ({
    hours: date.getHours(),
    minutes: date.getMinutes(),
    seconds: date.getSeconds(),
  })

const civilianHours = clockTime =>
  ({
    ...clockTime,
    hours: (clockTime.hours > 12) ? clockTime.hours - 12 : clockTime.hours
  })

const appendAMPM = clockTime =>
  ({
    ...clockTime,
    ampm: (clockTime.hours >= 12) ? "PM" : "AM"
  })

const display = target => time => target(time)

const formatClock = format =>
  time =>
    format.replace("hh", time.hours)
          .replace("mm", time.minutes),
          .replace("ss", time.seconds),
          .replace("tt", time.ampm)

const prependZero = key => clockTime =>
  ({
    ...clockTime,
    [key]: (clockTime[key] < 10) ? "0" + clockTime[key] : clockTime[key]
  })



const convertToCivilianTime = clockTime =>
  compose(
    appendAMPM,
    civilianHours
  )(clockTime)

const doubleDigits = civilianTime =>
  compose(
    prependZero("hours"),
    prependZero("minutes"),
    prependZero("seconds")
  )(civilianTime)

const startTicking = () =>
  setInterval(
    compose(
      clear,
      getCurrentTime,
      serializeClockTime,
      convertToCivilianTime,
      doubleDigits,
      formatClock("hh:mm:ss tt"),
      display(log)
    )
  ), oneSecond()

startTicking()