bannerbanner/src

import browser from 'webextension-polyfill'
import throttle from 'lodash/throttle'

import { onEnabledChange, isEnabled } from './perOrigin'


function hideBanners() {
  const revertSteps = []

  /* Hide all elements with position:fixed */
  const fixedElements = Array.from(document.querySelectorAll('*'))
    .filter(el => (
      getComputedStyle(el).position === 'fixed'
      && el.style.opacity !== '0' // ignore if we already hid this one
    ))

  fixedElements.forEach(el => {
    const originalVisibility = el.style.visibility
    const originalOpacity = el.style.opacity
    const originalTransition = el.style.transition
    el.style.transition = 'opacity 1s'
    el.style.opacity = '0'

    const hiderTimeoutId = window.setTimeout(() => {
      el.style.visibility = 'hidden'
    }, 1000)

    revertSteps.push(() => {
      window.clearTimeout(hiderTimeoutId)
      const reverterTimeoutId = window.setTimeout(() => {
        el.style.transition = originalTransition
      }, 1000)
      el.style.visibility = originalVisibility
      el.style.opacity = originalOpacity
    })
  })

  /* Stop position:sticky elements from sticking. */
  const stickyElements = Array.from(document.querySelectorAll('*'))
    .filter(el => getComputedStyle(el).position === 'sticky')

  stickyElements.forEach(el => {
    const originalPosition = el.style.position
    el.style.position = 'relative'
    revertSteps.push(() => {
      el.style.position = originalPosition
    })
  })

  return revertSteps
}

function main() {
  let revertSteps = []

  // XXX We read the location only once, but it may be changed by page scripts.
  // Fortunately we only need the origin, which should remain the same.
  const url = window.location.href

  async function run() {
    const enabled = await isEnabled(url)
    if (enabled && window.scrollY > 20) {
      // Hide everything that looks annoying. Remember the steps to revert this.
      revertSteps = hideBanners().concat(revertSteps)
    } else if (!enabled || window.scrollY <= 0) {
      // Unhide everything we have hidden.
      revertSteps.forEach(step => step())
      revertSteps = []
    }
  }

  window.addEventListener('scroll', throttle(run, 300))
  onEnabledChange(url, run)
}

main()