type Boxes = Set<HTMLInputElement>;

let reqBoxes: Boxes;
let excBoxes: Boxes;
let allBoxes: Boxes;
let tags: Map<HTMLElement, string[]>;
let itemsByYear: Map<string, Set<HTMLElement>>;

let showSingles = false;


function fillSets(): [Set<string>, Set<string>] {
  function checkedValues(boxes: Boxes) {
    return new Set([...boxes].filter(b => b.checked).map(b => b.value));
  }

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

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

  for (const [year, items] of itemsByYear) {
    let hideMarker = true;

    for (const item of items) {
      const req = tags.get(item)?.some(x => reqTags.has(x)) ?? false;
      const exc = tags.get(item)?.some(x => excTags.has(x)) ?? false;
      const hidden = exc || (anyReq && !req);

      item.hidden = hidden;
      hideMarker &&= hidden;
    }

    const marker = document.getElementById(`marker-${year}`);
    if (marker !== null) marker.hidden = hideMarker;
  }

  function disp(pfx: string, tags: Iterable<string>) {
    return [...tags].map(x => pfx + x).join('\u2003'); // em space
  }
  const plus  = disp('+\u2009', reqTags); // thin space
  const minus = disp('-\u2009', excTags);
  document.getElementById('filters-details')!.dataset.filters =
    `${plus}\u2003${minus}`.trim();
}

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

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

function toggle(checkbox: HTMLInputElement) {
  if (checkbox.checked) {
    const converse = document.getElementById(converseId(checkbox.id)) as HTMLInputElement;
    converse.checked = false;
  }
  update();
}


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

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

function toggleSingles(e: Event) {
  showSingles = !showSingles;

  const elems = Array.from(document.querySelectorAll('.filterlist li')) as HTMLElement[];
  for (const li of elems) {
    const countStr = li.querySelector('label')?.dataset.count;
    const count = countStr ? +countStr : 0;
    if (count <= 1 && li instanceof HTMLElement) {
      li.hidden = !showSingles;
    }
  }

  e.preventDefault();
}


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

function useFragment() {
  const frag = decodeURIComponent(location.hash).replace(/^#/, '');
  const details = document.getElementById('filters-details') as HTMLDetailsElement;

  if (!frag) {
    clearForm();
  } else if (frag == 'all') {
    allBoxes.forEach(b => b.checked = false);
    details.open = false;
  } else {
    const set = new Set(frag.split(';'));
    const re = /^(require|exclude)_|hide_filters/;
    if (Array.from(set).every(x => re.test(x))) {
      allBoxes.forEach(b => b.checked = set.has(b.id));
      details.open = !frag.match(/hide_filters|example\b/);
    }
  }

  updateItems();
}


function sortFilters(cmp: (a: Node, b: Node) => number) {
  function sort1(id: string) {
    const elt = document.getElementById(id);
    if (elt === null) return;

    const children = Array.from(elt.childNodes);
    children.sort(cmp);
    for (const c of children) {
      elt.removeChild(c);
      elt.appendChild(c);
    }
  }

  sort1('require');
  sort1('exclude');
}

function sortFiltersAlpha(e: Event) {
  function getName(node: Node): string {
    if (node instanceof Element) {
      return node.getElementsByTagName('input')[0].value;
    } else {
      return '';
    }
  }
  sortFilters((a, b) => getName(a).localeCompare(getName(b)));
  e.preventDefault();
}

function sortFiltersUses(e: Event) {
  function getUses(node: Node) {
    if (node instanceof Element) {
      const countStr = node.getElementsByTagName('label')[0].dataset.count;
      return countStr ? +countStr : 0;
    } else {
      return 0;
    }
  }
  sortFilters((a, b) => getUses(b) - getUses(a));
  e.preventDefault();
}


function setup() {
  function inputs(id: string): Boxes {
    const iter = document.getElementById(id)!.getElementsByTagName('input');
    return new Set(Array.from(iter));
  }

  const items = Array.from(document.getElementsByClassName('post')) as HTMLElement[];

  itemsByYear = new Map;
  for (const item of items) {
    const year = item.dataset.year;
    if (year !== undefined) {
      if (!itemsByYear.has(year)) {
        itemsByYear.set(year, new Set([item]));
      } else {
        itemsByYear.get(year)?.add(item);
      }
    }
  }

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

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


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

  function addClick(id: string, f: (e: Event) => void) {
    document.getElementById(id)!.addEventListener('click', f);
  }
  addClick('clear',     clear);
  addClick('sortalpha', sortFiltersAlpha);
  addClick('sortuses',  sortFiltersUses);
  addClick('singles',   toggleSingles);

  window.addEventListener('popstate', useFragment);

  useFragment();
}

window.addEventListener('DOMContentLoaded', setup);

export {};