(function() {
'use strict';

let reqBoxes;
let excBoxes;
let allBoxes;
let tags;
let itemsByYear;

let showSingles = false;


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 [year, items] of itemsByYear) {
    let hide = true;

    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));
      let hidden = exc || (anyReq && !req);

      item.hidden = hidden;
      hide &&= hidden;
    }

    document.getElementById(`marker-${year}`).hidden = hide;
  }
}

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) {
  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 toggleSingles(e) {
  showSingles = !showSingles;

  for (let li of document.querySelectorAll('#filters li')) {
    let count = li.querySelector('label').dataset.count;
    if (count <= 1) {
      li.hidden = !showSingles;
    }
  }

  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() {
  let frag = decodeURIComponent(location.hash).replace(/^#/, '');

  if (frag == 'all' || !frag) {
    clearForm();
  } else {
    let set = new Set(frag.split(';'));
    if (new Array(...set).every(x => /^(require|exclude)_/.test(x))) {
      allBoxes.forEach(b => b.checked = set.has(b.id));
      let details = document.getElementById('filters-details');
      details.open = !set.has('hide_filters');
    }
  }

  updateItems();
}


function setup() {
  function inputs(id) {
    let iter = document.getElementById(id).getElementsByTagName('input');
    return Array.from(iter);
  }

  let items = Array.from(document.getElementsByClassName('post'));
  itemsByYear = new Map;

  for (let item of items) {
    let year = item.dataset.year;
    if (!itemsByYear.has(year)) itemsByYear.set(year, new Set);
    itemsByYear.get(year).add(item);
  }

  reqBoxes = inputs('require');
  excBoxes = inputs('exclude');
  allBoxes = [...reqBoxes, ...excBoxes];

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


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

  document.getElementById('clear').addEventListener('click', clear);
  document.getElementById('singles').addEventListener('click', toggleSingles);

  window.addEventListener('popstate', useFragment);

  useFragment();
}

window.addEventListener('DOMContentLoaded', setup);

})();