import { RsvTimetableService } from '../services/RsvTimetableService.js';

class RsvTimeline extends HTMLElement {
  static get observedAttributes() {
    return ['timetable-id', 'date'];
  }

  // ---- Attribute accessors ------------------------------------------------

  get timetableId() { return parseInt(this.getAttribute('timetable-id')); }

  get date() {
    const attr = this.getAttribute('date');
    // Parse as local midnight so setHours() in block rendering stays in local time.
    return attr ? new Date(attr + 'T12:00:00') : new Date();
  }

  set date(value) {
    const d   = new Date(value);
    const str = `${d.getFullYear()}-${String(d.getMonth() + 1).padStart(2, '0')}-${String(d.getDate()).padStart(2, '0')}`;
    this.setAttribute('date', str);
  }

  // ---- Lifecycle ----------------------------------------------------------

  connectedCallback() {
    this._version = 0;
    this.classList.add('rsv-slots-list');
    this.addEventListener('click', this._on_click.bind(this));
    this._render();
  }

  attributeChangedCallback(_attr, oldVal, newVal) {
    if (oldVal === newVal || !this.isConnected) return;
    this._render();
  }

  // ---- Public API ---------------------------------------------------------

  // Re-fetch availability for the current date, e.g. after a booking occupied
  // some slots. The date is unchanged, so attributeChangedCallback won't fire.
  refresh() {
    this._render();
  }

  // ---- Private ------------------------------------------------------------

  _on_click(event) {
    const slot = event.target.closest('.rsv-slots-slot');
    if (slot && !slot.classList.contains('rsv-slots-slot-full') && !slot.classList.contains('rsv-slots-slot-too-soon')) {
      slot.classList.toggle('rsv-slots-slot-selected');
      slot.dispatchEvent(new Event('input', { bubbles: true }));
    }
  }

  async _render() {
    // Version guard: discard renders that were superseded by a newer call.
    const v   = ++this._version;
    const s   = ReservairStrings.timeline;

    if (this.timetableId === null) {
      this.replaceChildren(this._notice(s.not_reservable));
      return;
    }

    try {
      const occupancy = await RsvTimetableService.get_availability_for_date(this.timetableId, this.date);
      if (v !== this._version) return;


      const header = document.createElement('div');
      header.classList.add('rsv-slots-label');
      header.textContent = this.date.toLocaleDateString(navigator.language, {
        weekday: 'long', day: 'numeric', month: 'long',
      }).replace(',', '');

      if(occupancy.length === 0) {
        this.replaceChildren(header, this._notice(s.no_blocks));
        return;
      }

      const blocks = [];

      for (const { from_minutes, to_minutes, block_size_in_minutes, occupancy: block_occ, lead_time_minutes } of occupancy) {
        if (from_minutes === to_minutes || block_occ.length === 0) {
          continue;
        }

        const from_block = parseInt(from_minutes) / block_size_in_minutes;

        const time_slots = block_occ.map((occ, i) =>
          this._block(this.date, occ, block_size_in_minutes, from_block + i, lead_time_minutes?.[i] ?? 0)
        );

        const time_slot_group = document.createElement('div');
        time_slot_group.classList.add('rsv-slots-group');
        time_slot_group.replaceChildren(...time_slots);
        blocks.push(time_slot_group);
      }

      this.replaceChildren(header, ...blocks);
    } catch (_e) {
      if (v !== this._version) return;
      this.replaceChildren(this._notice(s.no_blocks));
    }
  }

  _block(date, left, block_size, idx, min_lead_time_minutes = 0) {
    const from = new Date(date);
    from.setHours(0, idx * block_size, 0, 0);

    const to = new Date(from);
    to.setMinutes(to.getMinutes() + block_size);

    const cell = document.createElement('div');
    cell.classList.add('rsv-slots-slot', 'rsv-slots-slot-available');
    cell.dataset.start_utc = from.toISOString();
    cell.dataset.end_utc   = to.toISOString();
    if (left <= 0) cell.classList.add('rsv-slots-slot-full');
    else if (from < new Date(Date.now() + min_lead_time_minutes * 60_000)) cell.classList.add('rsv-slots-slot-too-soon');

    const time_el = document.createElement('span');
    time_el.classList.add('rsv-slots-slot-time');
    time_el.textContent = `${this._fmt(from)} – ${this._fmt(to)}`;

    const badge = document.createElement('span');
    badge.classList.add('rsv-slots-slot-badge');
    const remaining_seats = left;

    if (remaining_seats > 0) badge.classList.add('rsv-slots-slot-badge-available');

    if (remaining_seats === 1) badge.textContent = `${remaining_seats} místo`;
    else if (remaining_seats >= 2 && remaining_seats <= 4) badge.textContent = `${remaining_seats} místa`;
    else badge.textContent = `${remaining_seats} míst`;


    cell.append(time_el, badge);
    return cell;
  }

  _notice(text) {
    const p = document.createElement('p');
    p.classList.add('rsv-slots-notice');
    p.textContent = text;
    return p;
  }

  _fmt(dt) {
    return dt.getHours() + ':' + String(dt.getMinutes()).padStart(2, '0');
  }
}

customElements.define('rsv-timeline', RsvTimeline);