(function() {
'use strict';

let items = Array.from(document.querySelectorAll('.item.post'));

let reqBoxes = Array.from(document.querySelectorAll('#require input'));
let excBoxes = Array.from(document.querySelectorAll('#exclude input'));
let allBoxes = [...reqBoxes, ...excBoxes];

let tags = new Map(items.map(item => [item, item.dataset.tags.split(';')]));


function fillSets() {
  let checkedValues = boxes =>
    new Set(boxes.filter(b => b.checked).map(b => b.value));

  return [checkedValues(reqBoxes), checkedValues(excBoxes)];
}

function updateItems() {
  let [reqTags, excTags] = fillSets();
  let anyReq = reqTags.size > 0;

  for (let item of items) {
    let req = tags.get(item).some(x => reqTags.has(x));
    let exc = tags.get(item).some(x => excTags.has(x));

    if ((req || !anyReq) && !exc) {
      item.classList.remove('hidden');
    } else {
      item.classList.add('hidden');
    }
  }
}

function update() {
  updateItems();
  history.pushState(null, "", makeFragment());
}

function converseId(id) {
  if (id.match(/^require/)) {
    return id.replace('require', 'exclude');
  } else {
    return id.replace('exclude', 'require');
  }
}

function toggle(checkbox, thisSet, thatSet) {
  if (checkbox.checked)
    document.getElementById(converseId(checkbox.id)).checked = false;

  update();
}


function clearForm() {
  allBoxes.forEach(b => b.checked = false);
}

function clear(e) {
  clearForm();
  update();
  if (e) e.preventDefault();
}

function resetForm() {
  allBoxes.forEach(b => b.checked = b.defaultChecked);
}

function reset(e) {
  resetForm();
  update();
  if (e) e.preventDefault();
}


function makeFragment() {
  let ids = allBoxes.filter(b => b.checked).map(b => b.id);
  if (ids.length == 0) {
    return '#all';
  } else if (allBoxes.every(b => b.checked == b.defaultChecked)) {
    return '#';
  } else {
    return '#' + ids.join(';');
  }
}

function useFragment(firstLoad) {
  let frag = document.location.hash.replace(/^#/, '');

  if (frag == 'all') {
    clearForm();
  } else if (frag) {
    let set = new Set(frag.split(';'));
    allBoxes.forEach(b => b.checked = set.has(b.id));
    if (firstLoad) document.getElementById('filters-details').open = true;
  } else {
    resetForm();
  }

  updateItems();
}


function setup() {
  allBoxes.forEach(b => b.addEventListener('change', () => toggle(b)));

  document.getElementById('clear').addEventListener('click', clear);
  document.getElementById('reset').addEventListener('click', reset);

  window.addEventListener('popstate', () => useFragment(false));
  useFragment(true);
}

window.addEventListener('load', setup);

})();