import React, { Component, createRef } from 'react'

import "./counter.css"

export default class Counter extends Component {
  constructor(props) {
    super(props)
    this.ref = createRef()
    this.update = this.update.bind(this)
  }

  componentDidMount() {
    this.update()
  }

  componentWillUnmount() {
    clearTimeout(this.timeout)
  }

  update() {
    this.timeout = setTimeout(this.update, 250)
    const population = getPopulation()
    if (this.ref.current) {
      this.ref.current.innerHTML = commatize(population)
    }
  }

  render() {
    return (
      <div className="counter">
        <div className="countValue" ref={this.ref} />
        <div className="description">
          CURRENT GLOBAL POPULATION
        </div>
      </div>
    )
  }
}

const aprilFirst = new Date(2021, 3, 1)

function getPopulation() {
  const popAprilFirst = 7855013899
  const popChangePerDay = 219251.934066
  const secondsDelta = (new Date() - aprilFirst) / 86400000  // april = month 3
  const population = popAprilFirst + secondsDelta * popChangePerDay
  return Math.round(population)
}

const commatize = (n, radix) => {
  radix = radix || -1
  var nums = [], i, counter = 0, r = Math.floor
  if (radix !== -1 && n > radix) {
    n /= radix
    nums.unshift(r((n * 10) % 10))
    nums.unshift(".")
  }
  do {
    i = r(n % 10)
    n = r(n / 10)
    counter += 1
    if (n && ! (counter % 3))
      { i = ',' + r(i) }
    nums.unshift(i)
  }
  while (n)
  return nums.join("")
}