(() => {

  const baseUrl = document.querySelector('[data-seance-url]').dataset.seanceUrl || 'http://localhost:4000'

  function resetTitle() {
    document.title = document.title.replace('[Loading...] ', '')
  }

  // Check that we're not on a Seance page
  if (window.location.href.startsWith(baseUrl)) {
    alert('That\'s not how to do it, silly!\n\nYou\'re supposed to BOOKMARK this link (by dragging it to the bookmarks bar or right-clicking and saying "save bookmark").\n\nWait till you\'re on a Medium page; don\'t try to start clicking on it right now ;)')

    // Reset title
    resetTitle()
    return
  }

  // Keep the user engaged with a nice bannery message
  
  var d1 = document.createElement('div')
  d1.style="position: absolute; top:0; right: 0; left: 0; background-color: turquoise; min-height: 2em; z-index: 1000; text-align: center;"
  
  var p1 = document.createElement('p')
  p1.innerHTML = 'Seance loading in progress...'
  p1.style='font-size: 2rem; margin: 2rem; color: white;'
  
  d1.appendChild(p1)
  document.body.appendChild(d1)
  
  // Form sending function
  function handleJSON(data) {
    try {
      data = JSON.parse(data.slice(data.indexOf('{')))
    } catch (err) {
      alert('Something went wrong fetching the post. Please make sure you\'re on a Medium site and try again.')

      // Hide the loading screen
      d1.parentElement.removeChild(d1)

      // Reset the title
      resetTitle()

      // Give up
      return
    }
  
    // Create a form to hold the data
    var f = document.createElement('form')
    f.action=baseUrl + '/fetch/'
    f.method='post'
  
    // Create hidden input to hold data
    i = document.createElement('input')
    i.name='data'
    i.type='hidden'
    i.value=JSON.stringify(data)
  
    // Assign children to parents
    f.appendChild(i)
    document.body.appendChild(f)
  
    // Submit the form  
    f.submit()
  }

  // fetch the XML
  var r = new XMLHttpRequest()
  r.open('GET', window.location + '?format=json')
  r.onreadystatechange = function () {
    if (r.readyState == 4 && r.status == 200) {
      handleJSON(r.responseText)
    }
  }
  r.setRequestHeader("Content-Type", "application/json;charset=utf-8")
  r.send(null)

})()