using System.Collections;
using UnityEngine;
using UnityEngine.Rendering;

/// <summary>
/// Smoothly fades a post-process Volume's weight in or out (e.g. from UnityEvents when the player
/// changes area), instead of switching the look abruptly.
/// </summary>
[RequireComponent(typeof(Volume))]
public class VolumeWeightFader : MonoBehaviour
{
    [SerializeField, Min(0f)] private float _duration = 1.5f;

    private Volume _volume;
    private Coroutine _fade;

    private void Awake()
    {
        _volume = GetComponent<Volume>();
    }

    public void FadeIn() => FadeTo(1f);

    public void FadeOut() => FadeTo(0f);

    public void FadeTo(float weight)
    {
        if (_fade != null)
            StopCoroutine(_fade);

        _fade = StartCoroutine(Fade(Mathf.Clamp01(weight)));
    }

    private IEnumerator Fade(float target)
    {
        float start = _volume.weight;

        for (float t = 0f; t < _duration; t += Time.deltaTime)
        {
            _volume.weight = Mathf.Lerp(start, target, Mathf.SmoothStep(0f, 1f, t / _duration));
            yield return null;
        }

        _volume.weight = target;
        _fade = null;
    }
}