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// Copyright 2024 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
class AudioHandler {
constructor() {
// Initialize the audio element and event listeners on it.
this.audioElement_ = document.createElement('audio');
document.body.appendChild(this.audioElement_);
this.audioElement_.addEventListener(
'canplaythrough', () => this.onCanPlayThrough_(), false);
this.audioElement_.addEventListener('ended', () => this.onEnded_(), false);
// The extension system does not keep the main service worker awake even if
// we're doing work in this offscreen doc. Keep it awake while we're playing
// speech via this interval.
this.heartbeatId_ = 0;
chrome.runtime.onMessage.addListener(message => {
switch (message['command']) {
case 'pause':
this.audioElement_.pause();
break;
case 'play':
this.audioElement_.play();
break;
case 'setCurrentUtterance':
this.currentUtterance_ = message.currentUtterance;
break;
case 'setUrl':
this.audioElement_.src = message.url;
break;
}
});
}
/**
* Handler for the canplaythrough event on the audio element.
* Called when the audio element has buffered enough audio to begin
* playback. Send the 'start' event to the ttsEngine callback and
* then begin playing the audio element.
* @private
*/
onCanPlayThrough_() {
if (!this.currentUtterance_) {
return;
}
if (this.currentUtterance_.options.volume !== undefined) {
// Both APIs use the same range for volume, between 0.0 and 1.0.
this.audioElement_.volume = this.currentUtterance_.options.volume;
}
this.audioElement_.play();
chrome.runtime.sendMessage({command: 'onCanPlayThrough'});
this.heartbeatId_ = setInterval(this.onHeartbeat_, 1000);
}
onEnded_() {
this.currentUtterance_ = null;
chrome.runtime.sendMessage({command: 'onEnded'});
clearInterval(this.heartbeatId_);
}
onHeartbeat_() {
chrome.runtime.sendMessage({command: 'heartbeat'});
}
}
document.addEventListener('DOMContentLoaded', () => {
new AudioHandler();
chrome.runtime.sendMessage({command: 'loaded'});
});
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