dtp-base/client/js/base-audio.js

// base-audio.js
// Copyright (C) 2024 DTP Technologies, LLC
// All Rights Reserved

'use strict';

import DtpLog from 'lib/dtp-log';

const AudioContext = window.AudioContext || window.webkitAudioContext;

export default class BaseAudio {

  constructor ( ) {
    this.log = new DtpLog('BaseAudio');
  }

  start ( ) {
    this.log.info('start', 'starting Web Audio API main context');
    this.ctx = new AudioContext();

    this.masterVolume = this.ctx.createGain();
    this.masterVolume.connect(this.ctx.destination);

    this.musicGain = this.ctx.createGain();
    this.musicGain.value = 0.7;
    this.musicGain.connect(this.masterVolume);

    this.sounds = { };
  }

  async loadSound (soundId, url) {
    if (this.sounds[soundId]) {
      throw new Error('Already have sound registered for soundId');
    }

    const audioBuffer = await this.loadAudioBuffer(url);
    const sound = { soundId, url, audioBuffer };
    this.sounds[soundId] = sound;

    return sound;
  }

  hasSound (soundId) {
    return !!this.sounds[soundId];
  }

  playSound (soundId, options) {
    const sound = this.sounds[soundId];
    if (!sound) {
      throw new Error(`Invalid soundId: ${soundId}`);
    }

    this.log.info('playSound', 'playing sound', { soundId });
    return { soundId, ...this.playAudioBuffer(sound.audioBuffer, options) };
  }

  loadAudioBuffer (url) {
    return new Promise(async (resolve, reject) => {
      const response = await fetch(url);
      const audioData = await response.arrayBuffer();
      this.ctx.decodeAudioData(audioData, resolve, reject);
    });
  }

  playAudioBuffer (buffer, options) {
    options = Object.assign({
      gain: 0.4,
      loop: false,
    }, options);

    const source = this.ctx.createBufferSource();
    source.buffer = buffer;
    source.loop = options.loop;

    const gainNode = this.ctx.createGain();
    gainNode.gain.value = options.gain;

    source.connect(gainNode);
    gainNode.connect(this.masterVolume);

    source.start();

    return { gain: gainNode, source };
  }

  setMusicStream (url) {
    let source;

    this.stopMusicStream();
    this.log.debug('setMusicStream', 'setting new music stream', { url });
    this.music = new Audio();
    this.music.setAttribute('loop', 'loop');

    source = document.createElement('source');
    source.setAttribute('src', `${url}.ogg`);
    source.setAttribute('type', 'audio/ogg');
    this.music.appendChild(source);

    source = document.createElement('source');
    source.setAttribute('src', `${url}.mp3`);
    source.setAttribute('type', 'audio/mp3');
    this.music.appendChild(source);
  }

  playMusicStream ( ) {
    if (this.musicSource) {
      return;
    }

    this.musicSource = this.ctx.createMediaElementSource(this.music);
    this.musicSource.connect(this.musicGain);

    this.log.debug('playMusicStream', 'starting music stream playback');
    this.music.play();
  }

  stopMusicStream ( ) {
    if (!this.musicSource) {
      return;
    }

    this.log.debug('pauseMusicStream', 'stopping music stream playback');
    this.music.pause();

    this.musicGain.value = 0;

    this.musicSource.disconnect(this.musicGain);
    delete this.musicSource;
  }

  get musicVolume ( ) { return this.musicGain.gain.value; }
  set musicVolume (volume) {
    this.musicGain.gain.value = volume;
  }

  get haveMusicStream ( ) {
    return !!this.music &&
           !!this.musicSource &&
           !!this.musicGain
    ;
  }

  get isMusicPaused ( ) {
    if (!this.music) {
      return true;
    }
    return this.music.paused;
  }
}