// guide.js — "The Almanac": 1994-style scrolling EPG overlay.
// Virtualized rows (fixed height) so thousands of channels stay smooth.

const ROW_H = 46;
const CH_COL = 150;
const HOUR_W = 180;          // px per hour
const WINDOW_HRS = 6;        // how far right the grid extends
const OVERSCAN = 4;

export class Guide {
  /**
   * @param {object} els
   * @param {import('./providers/source-provider.js').ChannelAggregator} agg
   * @param {(ch:any)=>void} onTune
   */
  constructor(els, agg, onTune) {
    this.els = els;
    this.agg = agg;
    this.onTune = onTune;
    this.open = false;
    this.focusRow = 0;
    this._programCache = new Map();   // channelId -> Program[]
    this._health = new Map();         // channelId -> bool
    this.scroll = els.guideScroll;
    this.rowsEl = els.guideRows;
    this.scroll.addEventListener('scroll', () => this._renderViewport(), { passive: true });
    this.scroll.addEventListener('keydown', (e) => this._onKey(e));
    els.guideClose.addEventListener('click', () => this.hide());
    this._baseT = 0;
  }

  async toggle() { this.open ? this.hide() : this.show(); }

  async show() {
    const list = this.agg.channels;
    if (!list.length) return;
    this.open = true;
    const g = this.els.guide;
    g.hidden = false;
    g.setAttribute('aria-hidden', 'false');
    requestAnimationFrame(() => g.classList.add('show'));
    // time base = top of current half-hour
    const now = Date.now();
    this._baseT = now - (now % (30 * 60 * 1000));
    this.rowsEl.style.setProperty('--row-h', ROW_H + 'px');
    this.scroll.style.setProperty('--ch-col', CH_COL + 'px');
    this.scroll.style.setProperty('--hour-w', HOUR_W + 'px');
    this.rowsEl.style.height = (list.length * ROW_H) + 'px';
    this._buildTimeHeader();
    this._renderViewport();
    this._positionPlayhead();
    this._clockTimer = setInterval(() => { this._tickClock(); this._positionPlayhead(); }, 30000);
    this._tickClock();
    this.scroll.focus();
  }

  hide() {
    this.open = false;
    const g = this.els.guide;
    g.classList.remove('show');
    g.setAttribute('aria-hidden', 'true');
    clearInterval(this._clockTimer);
    setTimeout(() => { if (!this.open) g.hidden = true; }, 300);
  }

  setHealth(channelId, ok) { this._health.set(channelId, ok); }

  _tickClock() {
    const t = new Date();
    this.els.guideClock.textContent =
      `${String(t.getHours()).padStart(2,'0')}:${String(t.getMinutes()).padStart(2,'0')}`;
  }

  _buildTimeHeader() {
    const hdr = this.els.guideTimehdr;
    hdr.innerHTML = '';
    hdr.style.marginLeft = CH_COL + 'px';
    for (let h = 0; h < WINDOW_HRS; h++) {
      const t = new Date(this._baseT + h * 3600 * 1000);
      const tick = document.createElement('div');
      tick.className = 'tick';
      tick.style.flex = `0 0 ${HOUR_W}px`;
      tick.textContent = `${String(t.getHours()).padStart(2,'0')}:${String(t.getMinutes()).padStart(2,'0')}`;
      hdr.appendChild(tick);
    }
  }

  _positionPlayhead() {
    const ph = this.els.guidePlayhead;
    const offset = ((Date.now() - this._baseT) / 3600000) * HOUR_W;
    if (offset < 0 || offset > WINDOW_HRS * HOUR_W) { ph.style.display = 'none'; return; }
    ph.style.display = '';
    ph.style.left = (CH_COL + offset - this.scroll.scrollLeft) + 'px';
  }

  async _renderViewport() {
    const list = this.agg.channels;
    const top = this.scroll.scrollTop;
    const h = this.scroll.clientHeight;
    const first = Math.max(0, Math.floor(top / ROW_H) - OVERSCAN);
    const last = Math.min(list.length, Math.ceil((top + h) / ROW_H) + OVERSCAN);
    this.rowsEl.innerHTML = '';
    for (let i = first; i < last; i++) {
      this.rowsEl.appendChild(this._renderRow(list[i], i));
    }
    this._positionPlayhead();
    // lazily fetch programs for visible rows
    for (let i = first; i < last; i++) this._ensurePrograms(list[i]);
  }

  _renderRow(ch, idx) {
    const row = document.createElement('div');
    row.className = 'guide-row';
    row.style.position = 'absolute';
    row.style.top = (idx * ROW_H) + 'px';
    row.style.left = '0'; row.style.right = '0';
    row.setAttribute('role', 'row');

    const cell = document.createElement('div');
    cell.className = 'guide-chcell';
    cell.setAttribute('role', 'rowheader');
    const num = document.createElement('span'); num.className = 'num'; num.textContent = ch.number;
    const nm = document.createElement('span'); nm.className = 'nm'; nm.textContent = ch.name; // safe
    cell.append(num, nm);
    if (this._health.get(ch.id) === false) {
      const sk = document.createElement('span'); sk.className = 'skull'; sk.textContent = '☠';
      sk.title = 'no signal'; cell.appendChild(sk);
    }
    cell.addEventListener('click', () => { this.onTune(ch); this.hide(); });

    const progs = document.createElement('div');
    progs.className = 'guide-progs';
    const cached = this._programCache.get(ch.id);
    if (cached) this._layoutPrograms(progs, cached, ch);

    row.append(cell, progs);
    return row;
  }

  _layoutPrograms(container, programs, ch) {
    const now = Date.now();
    const winEnd = this._baseT + WINDOW_HRS * 3600 * 1000;
    for (const p of programs) {
      if (p.stop <= this._baseT || p.start >= winEnd) continue;
      const left = ((Math.max(p.start, this._baseT) - this._baseT) / 3600000) * HOUR_W;
      const right = ((Math.min(p.stop, winEnd) - this._baseT) / 3600000) * HOUR_W;
      const el = document.createElement('div');
      el.className = 'guide-prog' + (p.start <= now && now < p.stop ? ' airing' : '');
      el.style.left = left + 'px';
      el.style.width = Math.max(8, right - left - 2) + 'px';
      el.setAttribute('role', 'gridcell');
      el.tabIndex = -1;
      const tEl = document.createElement('span'); tEl.className = 't';
      const s = new Date(p.start);
      tEl.textContent = `${String(s.getHours()).padStart(2,'0')}:${String(s.getMinutes()).padStart(2,'0')} `;
      el.appendChild(tEl);
      el.appendChild(document.createTextNode(p.title)); // safe
      el.addEventListener('click', () => { this.onTune(ch); this.hide(); });
      container.appendChild(el);
    }
  }

  async _ensurePrograms(ch) {
    if (this._programCache.has(ch.id)) return;
    this._programCache.set(ch.id, []); // mark in-flight
    const progs = await this.agg.getPrograms(ch.id, {
      from: this._baseT - 3600 * 1000,
      to: this._baseT + WINDOW_HRS * 3600 * 1000,
    });
    this._programCache.set(ch.id, progs);
    if (this.open) this._renderViewport();
  }

  _onKey(e) {
    const list = this.agg.channels;
    switch (e.key) {
      case 'ArrowDown': e.preventDefault(); this.focusRow = Math.min(list.length-1, this.focusRow+1); this._scrollToFocus(); break;
      case 'ArrowUp':   e.preventDefault(); this.focusRow = Math.max(0, this.focusRow-1); this._scrollToFocus(); break;
      case 'Enter':     e.preventDefault(); { const ch = list[this.focusRow]; if (ch){ this.onTune(ch); this.hide(); } } break;
      case 'Escape':    e.preventDefault(); this.hide(); break;
    }
  }
  _scrollToFocus() {
    const y = this.focusRow * ROW_H;
    if (y < this.scroll.scrollTop) this.scroll.scrollTop = y;
    else if (y + ROW_H > this.scroll.scrollTop + this.scroll.clientHeight)
      this.scroll.scrollTop = y + ROW_H - this.scroll.clientHeight;
  }
}