using UniRx;
using UnityEngine;
using UnityEngine.Audio;
using UnityEngine.UI;

/// <summary>
/// ボリュームの設定
/// </summary>
public class VolumeSettings : MonoBehaviour
{
    /// <summary>
    /// Mixer
    /// </summary>
    [SerializeField] private AudioMixer _mixer;

    /// <summary>
    /// MasterVolumeのスライダー
    /// </summary>
    [SerializeField] private Slider _masterVolumeSlider;

    /// <summary>
    /// BGMのスライダー
    /// </summary>
    [SerializeField] private Slider _bgmSlider;

    /// <summary>
    /// SEのスライダー
    /// </summary>
    [SerializeField] private Slider _seSlider;

    /// <summary>
    /// インスタンス
    /// </summary>
    private static VolumeSettings _instance;

    void Awake()
    {
        if (_instance == null)
        {
            _instance = this;
            DontDestroyOnLoad (gameObject);
        }
        else 
        {
            Destroy (gameObject);
        }
    }

    private void Start()
    {
        //================================
        // Sliderの値をMiserへ
        //================================

        SetSliderValueToMixer("Master", _masterVolumeSlider);
        SetSliderValueToMixer("BGM", _bgmSlider);
        SetSliderValueToMixer("SE", _seSlider);
    }

    /// <summary>
    /// 0 ~ 1の値をdB( デシベル )に変換
    /// </summary>
    /// <param name="volume">ボリューム</param>
    /// <returns>変換後のデシベル</returns>
    private float ConvertVolume2dB(float volume) =>
        Mathf.Clamp(20f * Mathf.Log10(Mathf.Clamp(volume, 0f, 1f)), -80f, 0f);

    /// <summary>
    /// Sliderの値をMixerに設定
    /// </summary>
    /// <param name="groupName">グループ名</param>
    /// <param name="slider">値を通知するスライダー</param>
    private void SetSliderValueToMixer(string groupName,Slider slider)
    {
        slider.OnValueChangedAsObservable()
            .Subscribe(value => _mixer.SetFloat(groupName, ConvertVolume2dB(value)))
            .AddTo(this);
    }
}