VoiceUtils.swift

import Foundation
import AVFoundation

class VoiceUtils {
  
  static var avSpeechSynthesizer = AVSpeechSynthesizer()
  
  static func textToSpeech(text: String, delegate: AVSpeechSynthesizerDelegate?) {
    /*
     Support langauges:
       Chinese (China) - zh-CN
       Chinese (Hong Kong SAR China) - zh-HK
       Chinese (Taiwan) - zh-TW
       English (Australia) - en-AU
       English (Ireland) - en-IE
       English (South Africa) - en-ZA
       English (United Kingdom) - en-GB
       English (United States) - en-US
     
     AVSpeechUtterance property
      voice, rate (Speed of speech), volume, pitchMultiplier
     
     /*!
     @property "rate"
     @abstract Changes the playback rate of the input signal
     @discussion
     A value of 2.0 results in the output audio playing one octave higher.
     A value of 0.5, results in the output audio playing one octave lower.
     
     Range:      0.5 -> 2.0
     Default:    1.0
     Mixer:      AVAudioEnvironmentNode
     */
     
     @property "pitchMultiplier"
     // [0.5 - 2] Default = 1
    */
    let utterance = AVSpeechUtterance(string: text)
    utterance.voice = AVSpeechSynthesisVoice(language: DataUtils.getTextToSpeechLang())
    utterance.rate = Float(DataUtils.selectedVoiceSpeed.rawValue) ?? 1.0
    utterance.pitchMultiplier = Float(DataUtils.selectedVoiceTone.rawValue) ?? 1.0
    stopSpeech()
    avSpeechSynthesizer = AVSpeechSynthesizer()
    avSpeechSynthesizer.delegate = delegate
    avSpeechSynthesizer.speak(utterance)
  }
  
  static func isSpeechPlaying() -> Bool {
    return avSpeechSynthesizer.isSpeaking
  }
  
  static func isSpeechPaused() -> Bool {
    return avSpeechSynthesizer.isPaused
  }
  
  static func stopSpeech() {
    avSpeechSynthesizer.stopSpeaking(at: .immediate)
  }
  
  static func pauseSpeech() {
    avSpeechSynthesizer.pauseSpeaking(at: .immediate)
  }
  
  static func resumeSpeech() {
    avSpeechSynthesizer.continueSpeaking()
  }
}