plugin-library/Assets/04.AudioCore/RunTime/MusicPlayer.cs

using System.Collections;
using UnityEngine;

public class MusicPlayer
{
    private AudioSourcePool audioSourcePool;

    public MusicPlayer(AudioSourcePool audioSourcePool)
    {
        this.audioSourcePool = audioSourcePool;
    }

    public void Play(AudioClip clip, float fadeDuration)
    {
        AudioSource source = audioSourcePool.GetAudioSource("Music");
        if (source == null) return;

        CoroutineHelper.StartCoroutine(FadeMusic(source, clip, fadeDuration));
    }

    public void Stop(float fadeDuration)
    {
        AudioSource source = audioSourcePool.GetAudioSource("Music");
        if (source == null) return;

        CoroutineHelper.StartCoroutine(FadeOutMusic(source, fadeDuration));
    }

    private IEnumerator FadeMusic(AudioSource source, AudioClip clip, float fadeDuration)
    {
        yield return FadeOutMusic(source, fadeDuration);

        source.clip = clip;
        source.Play();

        yield return FadeInMusic(source, fadeDuration);
    }

    private IEnumerator FadeOutMusic(AudioSource source, float fadeDuration)
    {
        float startVolume = source.volume;

        while (source.volume > 0)
        {
            source.volume -= startVolume * Time.deltaTime / fadeDuration;
            yield return null;
        }

        source.Stop();
        source.volume = startVolume;
    }

    private IEnumerator FadeInMusic(AudioSource source, float fadeDuration)
    {
        float targetVolume = source.volume;
        source.volume = 0;

        while (source.volume < targetVolume)
        {
            source.volume += targetVolume * Time.deltaTime / fadeDuration;
            yield return null;
        }
    }
}