From 2d1355fc27832360d48c13d2e1431a8776e36bf4 Mon Sep 17 00:00:00 2001
From: Mahmoud Zalt <mahmoud@zalt.me>
Date: Fri, 24 May 2024 22:11:37 +0200
Subject: [PATCH] improve audio playbacks transition for smooth interruptions

---
 src/core/AiAssistantEngine.ts |  5 +++++
 src/core/AudioPlayer.ts       | 21 ++++++++++++++++++---
 src/core/AudioRecorder.ts     |  4 ++--
 src/core/SpeechRecognizer.ts  |  4 ++--
 src/core/User.ts              |  2 +-
 5 files changed, 28 insertions(+), 8 deletions(-)

diff --git a/src/core/AiAssistantEngine.ts b/src/core/AiAssistantEngine.ts
index 5b42752..5adf836 100644
--- a/src/core/AiAssistantEngine.ts
+++ b/src/core/AiAssistantEngine.ts
@@ -99,6 +99,9 @@ class AiAssistantEngine extends EventEmitter {
     startProcessing = async (): Promise<void> => {
         Logger.log('F: startProcessing');
 
+        // Lower the volume of any currently playing audio
+        this.audioPlayer.setVolume(0.5);
+
         // Reset the assistant before starting processing
         this._resetEngine();
 
@@ -252,6 +255,8 @@ class AiAssistantEngine extends EventEmitter {
         }
 
         // ----[ Step 4: Play AI Audio Reply ]----
+        // Stop any currently playing audio
+        this.audioPlayer.stopCurrentSound();
         // Handle audio response if available as a Stream
         if (response.data.shouldStreamAudioReply) {
             this._handleAudioStreamResponse(response.data.outputTextReply);
diff --git a/src/core/AudioPlayer.ts b/src/core/AudioPlayer.ts
index 9f29bba..f44eac7 100644
--- a/src/core/AudioPlayer.ts
+++ b/src/core/AudioPlayer.ts
@@ -1,6 +1,6 @@
 // src/core/AudioPlayer.ts
 
-import { Howl } from 'howler';
+import { Howl, Howler } from 'howler';
 import config from './config';
 import Logger from './Logger';
 
@@ -11,6 +11,7 @@ interface SoundCallback {
 class AudioPlayer {
     private readonly startSound: Howl;
     private readonly endSound: Howl;
+    private currentSound: Howl | null = null;
 
     constructor() {
         // Specify volume at 50% for start and end tones (0.5 = 50%)
@@ -82,7 +83,7 @@ class AudioPlayer {
     ): void => {
         Logger.log('F: playAiReplyFromUrl');
         // Play AI reply at 100% volume (1.0 = 100%)
-        this.playSound(audioFileUrl, callback, 1.0);
+        this.currentSound = this.playSound(audioFileUrl, callback, 1.0);
     };
 
     playStartTone = (): void => {
@@ -93,6 +94,19 @@ class AudioPlayer {
         this.endSound.play();
     };
 
+    setVolume = (volume: number): void => {
+        if (this.currentSound) {
+            this.currentSound.volume(volume);
+        }
+    };
+
+    stopCurrentSound = (): void => {
+        if (this.currentSound) {
+            this.currentSound.stop();
+            this.currentSound = null;
+        }
+    };
+
     private initializeSound = (soundFileUrl: string, volume = 1.0): Howl => {
         return new Howl({
             src: [soundFileUrl],
@@ -108,7 +122,7 @@ class AudioPlayer {
         soundFileUrl: string,
         callback?: SoundCallback,
         volume?: number,
-    ): void => {
+    ): Howl => {
         Logger.log('F: playSound');
         const sound = new Howl({
             src: [soundFileUrl],
@@ -123,6 +137,7 @@ class AudioPlayer {
         });
 
         sound.play();
+        return sound;
     };
 }
 
diff --git a/src/core/AudioRecorder.ts b/src/core/AudioRecorder.ts
index 100dfc2..3d77585 100644
--- a/src/core/AudioRecorder.ts
+++ b/src/core/AudioRecorder.ts
@@ -22,13 +22,13 @@ class AudioRecorder {
         this.handleStop = this.handleStop.bind(this);
     }
 
-    public async test_startRecording(): Promise<Blob> {
+    async test_startRecording(): Promise<Blob> {
         return new Promise((resolve, reject) => {
             reject(new Error('TEST Error starting recording...'));
         });
     }
 
-    public async startRecording(): Promise<Blob> {
+    async startRecording(): Promise<Blob> {
         Logger.log('F: startRecording');
         try {
             if (
diff --git a/src/core/SpeechRecognizer.ts b/src/core/SpeechRecognizer.ts
index 9e61cd6..f2f75c8 100644
--- a/src/core/SpeechRecognizer.ts
+++ b/src/core/SpeechRecognizer.ts
@@ -69,13 +69,13 @@ class SpeechRecognizer {
         this.isInitialized = true;
     }
 
-    public async test_startListening(): Promise<string> {
+    async test_startListening(): Promise<string> {
         return new Promise((resolve, reject) => {
             reject(new Error('TEST Error starting listening...'));
         });
     }
 
-    public async startListening(): Promise<string> {
+    async startListening(): Promise<string> {
         Logger.log('F: startListening');
 
         if (!this.isInitialized) {
diff --git a/src/core/User.ts b/src/core/User.ts
index 32b2ba6..eb76595 100644
--- a/src/core/User.ts
+++ b/src/core/User.ts
@@ -15,7 +15,7 @@ class User {
         this.generatedUserId = this._generateEndUserId();
     }
 
-    public getEndUserDetails(): EndUserDetails {
+    getEndUserDetails(): EndUserDetails {
         return {
             endUserAgent: navigator.userAgent,
             generatedEndUserId: this.generatedUserId,