soundtrack/Runtime/SoundtrackManager.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using Sirenix.OdinInspector;
using UnityEngine.SceneManagement;
using KairoEngine.Core;

namespace KairoEngine.SoundtrackSystem
{
    public class SoundtrackManager : MonoBehaviour
    {
        #region Singleton
        private static SoundtrackManager soundtrackManager;
        public static SoundtrackManager instance
        {
            get {
                if(!soundtrackManager)
                {
                    soundtrackManager = FindObjectOfType (typeof(SoundtrackManager)) as SoundtrackManager;
                    if(!soundtrackManager)
                    {
                        //Debug.LogError("There need to one active SountrackManager script on the scene.");
                        return null;
                    }
                }
                return soundtrackManager;
            }
        }
        #endregion

        public AudioSource audioSource1;
        public AudioSource audioSource2;
        public Soundtrack currentTrack;
        public Playlist playlist;
        public int currentTrackIndex;
        public bool playOnStart = true;
        public bool showDebug = false;

        private int currentAudioSourceIndex = 1;
        private bool isPlaying = false;
        private bool playlistEnded = false;

        void Start()
        {
            if(playOnStart) 
            {
                if(playlist != null) StartPlaylist(playlist, currentTrackIndex);
                else if(currentTrack != null) PlayTrack(currentTrack);
            }
        }

        void FixedUpdate()
        {
            if(!isPlaying) return;
            AudioSource currentAudioSource = GetAudioSource(currentAudioSourceIndex);
            if (!currentAudioSource.isPlaying && !playlistEnded)
            {
                // Song endend in current audio source
                
                if(playlist == null) return;
                currentTrackIndex += 1;
                if(playlist.soundtracks.Count <= currentTrackIndex)
                {
                    // Reached the end of the playlist
                    playlistEnded = true;
                    if(showDebug) Debug.Log($"Reached the end of the playlist \'{playlist.title}\'");
                }
                else
                {
                    // Play next song
                    PlayTrack(playlist.soundtracks[currentTrackIndex]);
                }
            }
        }

        public static void StartPlaylist(Playlist newPlaylist, int index = 0)
        {
            if(instance == null) return;
            if(newPlaylist == null)
            {
                Debug.LogWarning("Missing playlist... music wont play");
                return;
            }
            if(instance.showDebug) Debug.Log($"Starting playlist \'{newPlaylist.title}\'");
            instance.playlist = newPlaylist;
            instance.currentTrackIndex = index;
            instance.playlistEnded = false;
            PlayTrack(instance.playlist.soundtracks[instance.currentTrackIndex]);
        }

        public static void PlayTrack(Soundtrack soundtrack)
        {
            if(instance == null) return;
            if(instance.showDebug) Debug.Log($"{(soundtrack.fadeIn ? "Fading in" : "Playing")} song \'{soundtrack.name}\'");
            instance.isPlaying = true;
            instance.currentTrack = soundtrack;
            instance.SwitchAudioSource();
            instance.Play(soundtrack, instance.currentAudioSourceIndex);
            if(soundtrack.fadeIn) instance.StartCoroutine(SoundtrackManager.StartFade(instance.currentAudioSourceIndex, soundtrack.fadeTime, 1f, false));
            else instance.audioSource1.volume = 1f;
        }

        public static void FadeOutSoundtrack(float time = 1f)
        {
            if(instance == null) return;
            if(instance.showDebug) Debug.Log($"Fading out song \'{instance.playlist.soundtracks[instance.currentTrackIndex].name}\'");
            instance.StartCoroutine(SoundtrackManager.StartFade(instance.currentAudioSourceIndex, time, 0f, true));
        }

        public static IEnumerator StartFade(int audioSourceIndex, float duration, float targetVolume, bool stop = false)
        {
            if(instance == null) yield break;
            
            AudioSource audioSource = instance.GetAudioSource(audioSourceIndex);
            if(stop == false) audioSource.Play();
            float currentTime = 0;
            float start = audioSource.volume;

            while (currentTime < duration)
            {
                currentTime += Time.deltaTime;
                audioSource.volume = Mathf.Lerp(start, targetVolume, currentTime / duration);
                yield return null;
            }
            if(stop == true) 
            {   
                audioSource.Stop();
                audioSource.clip = null;
            }
            if(instance.showDebug) Debug.Log($"Song \'{instance.currentTrack.name}\' ended");
            yield break;
        }

        private void Play(Soundtrack soundtrack, int index)
        {
            if(index == 1)
            {
                audioSource1.clip = soundtrack.audioClip;
                audioSource1.Play();
            }
            else if(index == 2)
            {
                audioSource2.clip = soundtrack.audioClip;
                audioSource2.Play();
            }
        }

        private AudioSource GetAudioSource(int index)
        {
            if(index == 1) return audioSource1;
            else return audioSource2;
        }

        private void SwitchAudioSource()
        {
            if(currentAudioSourceIndex == 1) currentAudioSourceIndex = 2;
            else if(currentAudioSourceIndex == 2) currentAudioSourceIndex = 1;
        }
    }
}