// Custom date-range picker. The two native <input type=date> (#date-start /
// #date-end) stay in the DOM (hidden) as the source of truth — all filter code
// keeps reading/writing them. The calendar selects into a temporary state; the
// filter is applied (and the popup closed) only when the user presses «Применить».
//
// Two endpoint pills «С» / «По» sit above the grid: one is active, and clicking a
// day writes into the active endpoint, then focus auto-advances to the other. Each
// pill has a × to clear just that endpoint, so an OPEN range is possible — «с X»
// (no end) or «по Y» (no start). «Применить» is enabled once at least one endpoint
// is set; «Сбросить» clears both.

const MONTHS = ['Январь', 'Февраль', 'Март', 'Апрель', 'Май', 'Июнь', 'Июль', 'Август', 'Сентябрь', 'Октябрь', 'Ноябрь', 'Декабрь'];
const WEEKDAYS = ['пн', 'вт', 'ср', 'чт', 'пт', 'сб', 'вс'];

function parseISO(iso: string): Date | null {
  return iso ? new Date(iso + 'T00:00:00') : null;
}
function toISO(d: Date): string {
  return `${d.getFullYear()}-${String(d.getMonth() + 1).padStart(2, '0')}-${String(d.getDate()).padStart(2, '0')}`;
}
function fmt(iso: string): string {
  const p = iso.split('-');
  // Short 2-digit year so the full range fits the compact "Период" field.
  return p.length === 3 ? `${p[2]}.${p[1]}.${p[0].slice(2)}` : iso;
}

export interface DateRange {
  /** Refresh the field text (+ open calendar) from the hidden inputs. */
  sync(): void;
}

export function createDateRange(): DateRange {
  const startInput = document.getElementById('date-start') as HTMLInputElement;
  const endInput = document.getElementById('date-end') as HTMLInputElement;
  const field = document.getElementById('dr-field') as HTMLElement;
  const text = document.getElementById('dr-text') as HTMLElement;
  const clearBtn = document.getElementById('dr-clear') as HTMLElement;
  const cal = document.getElementById('dr-cal') as HTMLElement;

  let viewY = new Date().getFullYear();
  let viewM = new Date().getMonth();
  // In-progress selection (committed to the inputs on «Применить»). Either end may
  // stay empty → an open range. `activeEnd` is the endpoint the next day-click fills.
  let selStart = '';
  let selEnd = '';
  let activeEnd: 'start' | 'end' = 'start';

  function updateText(): void {
    const s = startInput.value;
    const e = endInput.value;
    if (s && e) text.textContent = `${fmt(s)} — ${fmt(e)}`;
    else if (s) text.textContent = `с ${fmt(s)}`;
    else if (e) text.textContent = `по ${fmt(e)}`;
    else text.textContent = 'Период';
    clearBtn.style.display = s || e ? '' : 'none';
    field.classList.toggle('has-value', !!(s || e));
  }

  function render(): void {
    const s = parseISO(selStart);
    const e = parseISO(selEnd);
    const endPill = (which: 'start' | 'end', label: string, val: string): string =>
      `<button type="button" class="dr-end${activeEnd === which ? ' active' : ''}${val ? ' set' : ''}" data-end="${which}">` +
      `<span class="dr-end-lbl">${label}</span>` +
      `<span class="dr-end-val">${val ? fmt(val) : '—'}</span>` +
      (val ? `<span class="dr-end-x" data-clear="${which}" aria-label="Очистить">×</span>` : '') +
      `</button>`;
    const parts: string[] = [
      `<div class="dr-ends">${endPill('start', 'С', selStart)}${endPill('end', 'По', selEnd)}</div>`,
      `<div class="dr-cal-h"><button type="button" class="dr-nav" data-nav="-1" aria-label="Предыдущий месяц">‹</button>` +
      `<span class="dr-cal-title">${MONTHS[viewM]} ${viewY}</span>` +
      `<button type="button" class="dr-nav" data-nav="1" aria-label="Следующий месяц">›</button></div>`,
      '<div class="dr-grid">',
    ];
    for (const w of WEEKDAYS) parts.push(`<span class="dr-wd">${w}</span>`);
    const lead = (new Date(viewY, viewM, 1).getDay() + 6) % 7; // Monday-first
    const days = new Date(viewY, viewM + 1, 0).getDate();
    for (let i = 0; i < lead; i++) parts.push('<span class="dr-blank"></span>');
    for (let d = 1; d <= days; d++) {
      const cur = new Date(viewY, viewM, d);
      const iso = toISO(cur);
      let cls = 'dr-day';
      if (iso === selStart) cls += ' s';
      if (iso === selEnd) cls += ' e';
      if (s && e && cur > s && cur < e) cls += ' rng';
      parts.push(`<button type="button" class="${cls}" data-iso="${iso}"><span class="dr-num">${d}</span></button>`);
    }
    parts.push('</div>');
    const ready = !!(selStart || selEnd); // at least one endpoint → applyable (open range OK)
    parts.push(
      '<div class="dr-foot">' +
      `<button type="button" class="dr-reset" data-act="reset">Сбросить</button>` +
      `<button type="button" class="dr-apply" data-act="apply"${ready ? '' : ' disabled'}>Применить</button>` +
      '</div>'
    );
    cal.innerHTML = parts.join('');
  }

  // Write the completed selection to the hidden inputs → triggers the filter reload.
  function applyRange(): void {
    startInput.value = selStart;
    endInput.value = selEnd;
    startInput.dispatchEvent(new Event('change', { bubbles: true }));
    endInput.dispatchEvent(new Event('change', { bubbles: true }));
    updateText();
  }

  function pick(iso: string): void {
    if (activeEnd === 'start') {
      selStart = iso;
      // Крест начала за концом — конец больше не валиден, очищаем его.
      if (selEnd && selStart > selEnd) selEnd = '';
      if (!selEnd) activeEnd = 'end'; // авто-переход к незаданному концу
    } else {
      selEnd = iso;
      if (selStart && selEnd < selStart) selStart = '';
      if (!selStart) activeEnd = 'start';
    }
    render();
  }

  function open(): void {
    selStart = startInput.value;
    selEnd = endInput.value;
    // Start filling whichever endpoint is empty (start first).
    activeEnd = !selStart ? 'start' : !selEnd ? 'end' : 'start';
    const base = parseISO(selStart) || parseISO(selEnd) || new Date();
    viewY = base.getFullYear();
    viewM = base.getMonth();
    render();
    cal.hidden = false;
  }
  function close(): void {
    cal.hidden = true;
  }

  field.addEventListener('click', (ev) => {
    if ((ev.target as HTMLElement).closest('.dr-clear')) return;
    if (cal.hidden) open();
    else close();
  });
  field.addEventListener('keydown', (ev) => {
    if (ev.key === 'Enter' || ev.key === ' ') { ev.preventDefault(); if (cal.hidden) open(); else close(); }
  });
  clearBtn.addEventListener('click', (ev) => {
    ev.stopPropagation();
    selStart = '';
    selEnd = '';
    startInput.value = '';
    endInput.value = '';
    startInput.dispatchEvent(new Event('change', { bubbles: true }));
    endInput.dispatchEvent(new Event('change', { bubbles: true }));
    updateText();
    close();
  });
  cal.addEventListener('click', (ev) => {
    // Keep the click inside the calendar so re-rendering a clicked day doesn't
    // detach the target and trip the outside-click close below.
    ev.stopPropagation();
    const target = ev.target as HTMLElement;
    const nav = target.closest<HTMLElement>('.dr-nav');
    if (nav) {
      viewM += Number(nav.dataset.nav);
      if (viewM < 0) { viewM = 11; viewY--; } else if (viewM > 11) { viewM = 0; viewY++; }
      render();
      return;
    }
    const act = target.closest<HTMLElement>('[data-act]');
    if (act) {
      if (act.dataset.act === 'apply') {
        if (selStart || selEnd) { applyRange(); close(); }
      } else if (act.dataset.act === 'reset') {
        selStart = '';
        selEnd = '';
        activeEnd = 'start';
        render();
      }
      return;
    }
    // Clear one endpoint via its × (→ open range on that side). Checked before the
    // pill activate below, since the × lives inside the pill button.
    const clr = target.closest<HTMLElement>('[data-clear]');
    if (clr) {
      const which = clr.dataset.clear as 'start' | 'end';
      if (which === 'start') selStart = ''; else selEnd = '';
      activeEnd = which; // focus the emptied end for the next pick
      render();
      return;
    }
    const endBtn = target.closest<HTMLElement>('[data-end]');
    if (endBtn) {
      activeEnd = endBtn.dataset.end as 'start' | 'end';
      render();
      return;
    }
    const day = target.closest<HTMLElement>('.dr-day');
    if (day && day.dataset.iso) pick(day.dataset.iso);
  });
  document.addEventListener('click', (ev) => {
    if (!(ev.target as HTMLElement).closest('#daterange')) close();
  });

  updateText();
  return {
    sync(): void {
      updateText();
      if (!cal.hidden) {
        selStart = startInput.value;
        selEnd = endInput.value;
        activeEnd = !selStart ? 'start' : !selEnd ? 'end' : 'start';
        render();
      }
    },
  };
}