using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UI;
using UnityEngine.SceneManagement;

public class FadeTransition : MonoBehaviour
{
  public static FadeTransition instance = null;

  public Image blackFadeImage;
  public Image whiteFadeImage;

  void Awake()
  {
    //Check if instance already exists
    if (instance == null)
    {
      //if not, set instance to this
      instance = this;
    }
    //If instance already exists and it's not this:
    else if (instance != this)
    {
      //Then destroy this. This enforces our singleton pattern, meaning there can only ever be one instance of a GameManager.
      Destroy(gameObject);
    }

    DontDestroyOnLoad(gameObject);

    blackFadeImage.gameObject.SetActive(false);
    whiteFadeImage.gameObject.SetActive(false);
  }

  public void FadeInDark(float time, System.Action action = null)
  {
    StartCoroutine(FadeIn(blackFadeImage, time, 1, action));
  }

  public void FadeInLight(float time, System.Action action = null)
  {
    StartCoroutine(FadeIn(whiteFadeImage, time, 1, action));
  }

  public void FadeOutDark(float time, System.Action action = null)
  {
    StartCoroutine(FadeOut(blackFadeImage, time, 0, action));
  }

  public void FadeOutLight(float time, System.Action action = null)
  {
    StartCoroutine(FadeOut(whiteFadeImage, time, 0, action));
  }

  public IEnumerator FadeIn(Image image, float time, float alpha = 1, System.Action action = null)
  {
    Color color = image.color;
    WaitForEndOfFrame waitForEndOfFrame = new WaitForEndOfFrame();

    image.gameObject.SetActive(true);
    float updatedTime = time;
    color.a = 0;
    image.color = color;

    while (updatedTime > 0.0)
    {
      yield return new WaitForEndOfFrame();
      updatedTime -= Time.deltaTime;
      color.a = alpha * (1 - (updatedTime / time));
      image.color = color;
    }

    if (action != null)
      action();
  }

  public IEnumerator FadeOut(Image image, float time, float alpha = 0, System.Action action = null)
  {
    Color color = image.color;
    WaitForEndOfFrame waitForEndOfFrame = new WaitForEndOfFrame();

    image.gameObject.SetActive(true);
    float updatedTime = time;

    while (updatedTime > 0.0)
    {
      yield return new WaitForEndOfFrame();
      updatedTime -= Time.deltaTime;
      color.a = updatedTime / time;
      image.color = color;
    }
    image.gameObject.SetActive(false);

    if (action != null)
      action();
  }


  public void OnFadeOutComplete()
  {
    int activeSceneBuildIndex = SceneManager.GetActiveScene().buildIndex;

    SceneManager.LoadScene(activeSceneBuildIndex != 0 ? activeSceneBuildIndex - 1 : activeSceneBuildIndex + 1);
  }
}