;(function () {
  'use strict'
  const revealEl = document.querySelectorAll('[class*=reveal-]')
  let viewportHeight = window.innerHeight

  function throttle (delay, fn) {
    var lastCall = 0
    return function () {
      var now = new Date().getTime()
      if (now - lastCall < delay) {
        return
      }
      lastCall = now
      return fn.apply(void 0, arguments)
    }
  }

  function elementIsVisible (el, offset) {
    return (el.getBoundingClientRect().top <= viewportHeight - offset)
  }

  function revealElements () {
    for (let i = 0; i < revealEl.length; i++) {
      let el = revealEl[i]
      let revealDelay = el.getAttribute('data-reveal-delay')
      let revealOffset = (el.getAttribute('data-reveal-offset') ? el.getAttribute('data-reveal-offset') : '200')
      let listenedEl = (el.getAttribute('data-reveal-container') ? el.closest(el.getAttribute('data-reveal-container')) : el)
      if (elementIsVisible(listenedEl, revealOffset) && !el.classList.contains('is-revealed')) {
        if (revealDelay && revealDelay !== 0) {
          setTimeout(function () {
            el.classList.add('is-revealed')
          }, revealDelay)
        } else {
          el.classList.add('is-revealed')
        }
      }
    }
    revealDone()
  }

  function revealScroll () {
    throttle(30, revealElements())
  }

  function revealResize () {
    viewportHeight = window.innerHeight
    throttle(30, revealElements())
  }

  function revealDone () {
    if (revealEl.length > document.querySelectorAll('[class*=reveal-].is-revealed').length) return
    window.removeEventListener('load', revealElements)
    window.removeEventListener('scroll', revealScroll)
    window.removeEventListener('resize', revealResize)
  }

  if (revealEl.length > 0 && document.body.classList.contains('has-animations')) {
    window.addEventListener('load', revealElements)
    window.addEventListener('scroll', revealScroll)
    window.addEventListener('resize', revealResize)
  }
}())