/* Resi Cues — the tile.
 *
 * One number matters: how long until the next cue. It is drawn as large as the
 * tile allows, with the cue's name above it, because on a wall the operator reads
 * it from across the booth.
 *
 * The countdown ticks locally. The server sends the playhead with the instant it
 * was true (`estMs` at `estAt`) and whether playback is running; this adds the
 * elapsed time since. That is what keeps the digits moving every second while
 * Resi itself only reports every few seconds, and it means a slow poll never
 * shows as a stalled clock.
 */

const TICK_MS = 250; // redraw faster than a second so the digit turns on time

export default function create({ root, moduleApi }) {
  let stream = null;
  let ticker = null;
  let state = null;

  const settings = () => moduleApi.instanceSettings;

  function el(tag, className, text) {
    const node = document.createElement(tag);
    if (className) node.className = className;
    if (text !== undefined) node.textContent = text;
    return node;
  }

  function hms(ms) {
    const total = Math.max(0, Math.round(ms / 1000));
    const h = Math.floor(total / 3600);
    const m = Math.floor((total % 3600) / 60);
    const s = total % 60;
    const pad = (n) => String(n).padStart(2, '0');
    return h > 0 ? `${h}:${pad(m)}:${pad(s)}` : `${m}:${pad(s)}`;
  }

  /** Where the playhead is right now, extrapolated from the last server word. */
  function playheadMs() {
    if (!state || state.estMs === null || state.estMs === undefined) return null;
    return state.estMs + (state.playing ? Date.now() - state.estAt : 0);
  }

  function render() {
    root.textContent = '';
    const set = settings();

    if (!state || state.status === 'error') {
      const box = el('div', 'resi-empty');
      box.append(el('div', 'resi-empty-line', (state && state.message) || 'Not connected'));
      root.append(box);
      return;
    }

    const here = playheadMs();
    const wrap = el('div', 'resi-wrap');

    if (state.next) {
      if (set.showCueName !== false) wrap.append(el('div', 'resi-label', 'NEXT'));
      if (set.showCueName !== false) wrap.append(el('div', 'resi-cue', state.next.name || 'Next cue'));
      const remaining = here === null ? null : state.next.ms - here;
      const count = el('div', 'resi-count', remaining === null ? '—' : hms(remaining));
      if (remaining !== null && remaining <= 30000) count.classList.add('is-soon');
      if (!state.playing) count.classList.add('is-held');
      wrap.append(count);
    } else {
      wrap.append(el('div', 'resi-label', state.event ? 'NO CUES LEFT' : 'NOTHING PLAYING'));
      wrap.append(el('div', 'resi-cue', state.event || state.decoder || ''));
    }

    const foot = el('div', 'resi-foot');
    if (set.showPrevious !== false && state.prev) {
      foot.append(el('span', 'resi-foot-item',
        `after ${state.prev.name}${here === null ? '' : ` · ${hms(here - state.prev.ms)} ago`}`));
    }
    if (set.showPosition !== false && here !== null) {
      foot.append(el('span', 'resi-foot-item', `playhead ${hms(here)}`));
    }
    if (!state.playing && state.estMs !== null) foot.append(el('span', 'resi-foot-item is-held', 'paused'));
    if (foot.childElementCount) wrap.append(foot);

    if (set.showCueList && state.cues && state.cues.length) {
      const list = el('ul', 'resi-list');
      for (const cue of state.cues) {
        const row = el('li', 'resi-list-row');
        if (here !== null && cue.ms <= here) row.classList.add('is-past');
        if (state.next && cue.ms === state.next.ms) row.classList.add('is-next');
        row.append(el('span', 'resi-list-name', cue.name));
        row.append(el('span', 'resi-list-at', hms(cue.ms)));
        list.append(row);
      }
      wrap.append(list);
    }

    root.append(wrap);
  }

  function applyStatus() {
    if (!state) return moduleApi.setStatus('connecting', 'Waiting for the server');
    if (state.status !== 'ok') return moduleApi.setStatus('error', state.message || 'Not connected');
    if (!state.playing) return moduleApi.setStatus('connecting', `Playback stopped — ${state.decoder}`);
    const cadence = state.cadenceMs ? ` · Resi updates every ${Math.round(state.cadenceMs / 1000)}s` : '';
    return moduleApi.setStatus('ok', `${state.decoder}${cadence}`);
  }

  return {
    start() {
      moduleApi.setStatus('connecting', 'Connecting');
      stream = moduleApi.sse('/stream', {
        state: (data) => {
          try {
            state = JSON.parse(data);
          } catch {
            return;
          }
          applyStatus();
          render();
        },
        error: () => moduleApi.setStatus('error', 'Lost the connection to ProdDash'),
      });
      ticker = setInterval(render, TICK_MS);
      render();
    },

    stop() {
      if (stream) stream.close();
      if (ticker) clearInterval(ticker);
      stream = null;
      ticker = null;
      root.textContent = '';
    },

    onConfigChange() {
      render();
    },
  };
}