send2streamer/public/overlay.js

const box = document.getElementById('box');
const fromEl = document.getElementById('from');
const textEl = document.getElementById('text');

const token = location.pathname.split('/').filter(Boolean).pop();
const socket = io({ query: { role: 'overlay', token } });

const FADE_MS = 400; // matches the CSS transition duration on #box

const queue = [];
let current = null; // { id, text, from, durationMs, audio }
let audioCtx = null;

function getAudioCtx() {
  audioCtx = audioCtx || new (window.AudioContext || window.webkitAudioContext)();
  return audioCtx;
}

// Browsers suspend AudioContext until a user gesture happens on the page.
// OBS's Browser Source doesn't enforce this, but for testing in a normal
// tab, unlock it on the first click/keypress anywhere on the page.
['click', 'keydown'].forEach((eventName) => {
  document.addEventListener(eventName, () => {
    const ctx = getAudioCtx();
    if (ctx.state === 'suspended') ctx.resume();
  }, { once: true });
});

function playNotificationSound() {
  try {
    const ctx = getAudioCtx();
    const osc = ctx.createOscillator();
    const gain = ctx.createGain();
    osc.type = 'sine';
    osc.frequency.setValueAtTime(880, ctx.currentTime);
    osc.frequency.setValueAtTime(1320, ctx.currentTime + 0.1);
    gain.gain.setValueAtTime(0.2, ctx.currentTime);
    gain.gain.exponentialRampToValueAtTime(0.001, ctx.currentTime + 0.35);
    osc.connect(gain);
    gain.connect(ctx.destination);
    osc.start();
    osc.stop(ctx.currentTime + 0.35);
  } catch (err) {
    console.error('Could not play notification sound:', err);
  }
}

function playSpeech(base64Audio, mimeType, onEnded) {
  const audio = new Audio(`data:${mimeType};base64,${base64Audio}`);
  const done = () => { if (onEnded) onEnded(); };
  audio.addEventListener('ended', done);
  audio.addEventListener('error', done);
  audio.play().catch((err) => {
    console.error('Could not play TTS audio:', err);
    done();
  });
}

function advanceQueue() {
  if (current || queue.length === 0) return;

  current = queue.shift();
  fromEl.textContent = current.from || '';
  fromEl.style.display = current.from ? 'block' : 'none';
  textEl.textContent = current.text;
  // force reflow so the transition re-triggers even if a message was already visible
  void box.offsetWidth;
  box.classList.add('visible');

  playNotificationSound();

  // The message stays up for at least durationMs (streamer's configured
  // display time), but if its TTS audio is still playing when that timer
  // fires (e.g. a long question read aloud), we must not start the next
  // message's audio on top of it — so we also wait for the audio to
  // actually finish before advancing.
  let minTimeElapsed = false;
  let audioFinished = !current.audio;

  const maybeAdvance = () => {
    if (!minTimeElapsed || !audioFinished) return;
    box.classList.remove('visible');
    current = null;
    setTimeout(advanceQueue, FADE_MS);
  };

  current.startAudio = (audio) => {
    audioFinished = false;
    playSpeech(audio.data, audio.mimeType, () => {
      audioFinished = true;
      maybeAdvance();
    });
  };

  if (current.audio) {
    current.startAudio(current.audio);
  }

  setTimeout(() => {
    minTimeElapsed = true;
    maybeAdvance();
  }, current.durationMs || 10000);
}

socket.on('display_message', (payload) => {
  queue.push({
    id: payload.id,
    text: payload.text,
    from: payload.from,
    durationMs: payload.durationMs,
    audio: null,
  });
  advanceQueue();
});

socket.on('display_audio', (payload) => {
  const audio = { data: payload.audio, mimeType: payload.mimeType };
  if (current && current.id === payload.id) {
    current.startAudio(audio);
    return;
  }
  const queued = queue.find((item) => item.id === payload.id);
  if (queued) queued.audio = audio;
});

socket.on('invalid_link', () => {
  console.error('Invalid overlay link — check the URL from your dashboard.');
});