docbrown/app/assets/javascripts/initializers/initializeAllFollowButts.js

function initializeAllFollowButts() {
  var followButts = document.getElementsByClassName('follow-action-button');
  for(var i = 0; i < followButts.length; i++) {
    initializeFollowButt(followButts[i]);
  }
}

//private

function initializeFollowButt(butt) {
  var user = userData()
  var deviceWidth = (window.innerWidth > 0) ? window.innerWidth : screen.width;
  var buttInfo = JSON.parse(butt.dataset.info);
  var userStatus = document.getElementsByTagName('body')[0].getAttribute('data-user-status');
  if (userStatus === 'logged-out') {
    addModalEventListener(butt);
    return;
  }
  if (buttInfo.className === 'Tag' && user) {
    handleTagButtAssignment(user, butt, buttInfo);
    return;
  }
  else {
    fetchButt(butt, buttInfo);
  }
}

function addModalEventListener(butt) {
  assignState(butt, 'login');
  butt.onclick = function (e) {
    e.preventDefault();
    showModal('follow-button');
    return;
  }
}

function fetchButt(butt, buttInfo) {
  var dataRequester;
  if (window.XMLHttpRequest) {
      dataRequester = new XMLHttpRequest();
  } else {
      dataRequester = new ActiveXObject('Microsoft.XMLHTTP');
  }
  dataRequester.onreadystatechange = function() {
    if (dataRequester.readyState === XMLHttpRequest.DONE && dataRequester.status === 200) {
      addButtClickHandle(dataRequester.response, butt);
    }
  }
  dataRequester.open('GET', '/follows/' + buttInfo.id + '?followable_type=' + buttInfo.className, true);
  dataRequester.send();
}

function addButtClickHandle(response, butt) {
  // currently lacking error handling
  var buttInfo = JSON.parse(butt.dataset.info);
  assignInitialButtResponse(response, butt);
  butt.onclick = function(e) {
    e.preventDefault();
    handleOptimisticButtRender(butt);
  }
}

function handleTagButtAssignment(user, butt, buttInfo) {
  var buttAssignmentBoolean = JSON.parse(user.followed_tags).map(function (a) { return a.id; }).indexOf(buttInfo.id) !== -1;
  var buttAssignmentBoolText = buttAssignmentBoolean ? 'true' : 'false';
  addButtClickHandle(buttAssignmentBoolText, butt);
  shouldNotFetch = true;
}

function assignInitialButtResponse(response, butt) {
  butt.classList.add('showing');
  if (response === 'true') {
    assignState(butt, 'unfollow');
  }
  else if (response === 'false') {
    assignState(butt, 'follow');
  }
  else if (response === 'self') {
    assignState(butt, 'self');
  }
  else {
    assignState(butt, 'login');
  }
}

function handleOptimisticButtRender(butt) {
  if (butt.dataset.verb === 'self') {
    window.location.href = '/settings';
  } else if (butt.dataset.verb === 'login') {
    showModal('follow-button');
  } else {
    // Handles actual following of tags/users
    assignState(butt, butt.dataset.verb);
    handleFollowButtPress(butt);
  }
}

function handleFollowButtPress(butt) {
  var buttonDataInfo = JSON.parse(butt.dataset.info);
  var formData = new FormData();
  formData.append('followable_type', buttonDataInfo.className);
  formData.append('followable_id', buttonDataInfo.id);
  formData.append('verb', butt.dataset.verb);
  getCsrfToken().then(sendFetch('follow-creation', formData));
}

function assignState(butt, newState) {
  var style = '';
  if (butt.dataset.info) {
    style = JSON.parse(butt.dataset.info).style;
  }
  butt.classList.add('showing');
  if (newState === 'follow') {
    butt.dataset.verb = 'unfollow';
    butt.classList.remove('following-butt');
    addFollowText(butt, style);
  } else if (newState === 'login') {
    addFollowText(butt, style);
  } else if (newState === 'self') {
    butt.dataset.verb = 'self';
    butt.innerHTML = 'EDIT PROFILE';
  } else {
    butt.dataset.verb = 'follow';
    addFollowingText(butt, style);
    butt.classList.add('following-butt');
  }
}

function addFollowText(butt, style) {
  if (style === 'small') {
    butt.innerHTML = '+';
  } else if (style === 'follow-back') {
    butt.innerHTML = '+ FOLLOW BACK';
  } else {
    butt.innerHTML = '+ FOLLOW';
  }
}

function addFollowingText(butt, style) {
  if (style === 'small') {
    butt.innerHTML = '✓';
  } else {
    butt.innerHTML = '✓ FOLLOWING';
  }
}