using System;
using System.Collections;
using UnityEngine;
using UnityEngine.UI;

public class Fader : MonoBehaviour
{
  private CanvasGroup canvasGroup;
  [SerializeField] private float fadeDuration = 1f;

  [SerializeField] private bool isFullBlack = false;

  private bool isFading = false;

  public static Fader instance => CanvasManager.singleton.fader;

  void Start()
  {
    canvasGroup = GetComponent<CanvasGroup>();
    StartCoroutine(FadeIn());
  }

  public void SetFullBlack()
  {
    isFullBlack = true;
    canvasGroup.alpha = 1;
  }

  public void SetTransparent()
  {
    isFullBlack = false;
    canvasGroup.alpha = 0;
  }


  // from black to transparent
  public static IEnumerator FadeIn()
  {
    instance.isFading = true;
    instance.SetFullBlack();
    float t = 0;
    while (t < instance.fadeDuration)
    {
      t += Time.deltaTime;
      instance.canvasGroup.alpha = 1 - t / instance.fadeDuration;
      yield return null;
    }
    instance.isFading = false;
    instance.SetTransparent();
  }

  // from transparent to black
  public static IEnumerator FadeOut()
  {
    instance.isFading = true;
    instance.SetTransparent();
    float t = 0;
    while (t < instance.fadeDuration)
    {
      t += Time.deltaTime;
      instance.canvasGroup.alpha = t / instance.fadeDuration;
      yield return null;
    }
    instance.isFading = false;
    instance.SetFullBlack();
  }

  public static void Fade(Action fullBlackCallBack, Action endFadeOutCallBack = null, bool fadeOut = true)
  {
    instance.StartCoroutine(FadeCoroutine(fullBlackCallBack, endFadeOutCallBack, fadeOut));
  }


  private static IEnumerator FadeCoroutine(Action fullBlackCallBack, Action endFadeOutCallBack = null, bool fadeOut = true)
  {
    yield return FadeOut();
    fullBlackCallBack.Invoke();
    if (fadeOut)
    {
      yield return FadeIn();
      endFadeOutCallBack?.Invoke();
    }
  }
}