using System.Collections;
using UnityEngine;
using UnityEngine.SceneManagement;
using OctoCore.Navigation;

[DisallowMultipleComponent]
public sealed class PersistentWwiseFadeInPlayer : MonoBehaviour
{
    private static PersistentWwiseFadeInPlayer _instance;

    [SerializeField] private AK.Wwise.Event _fadeInEvent;

    private const int BindRetryFrames = 120;

    private OctoSceneFade _boundFade;
    private Coroutine _bindRoutine;

    [RuntimeInitializeOnLoadMethod(
        RuntimeInitializeLoadType.SubsystemRegistration)]
    private static void ResetInstance()
    {
        _instance = null;
    }

    private void Awake()
    {
        if (_instance != null && _instance != this)
        {
            Destroy(gameObject);
            return;
        }

        _instance = this;

        // Required because DontDestroyOnLoad should preserve a root object.
        if (transform.parent != null)
            transform.SetParent(null, true);

        DontDestroyOnLoad(gameObject);
    }

    private void OnEnable()
    {
        SceneManager.sceneLoaded += OnSceneLoaded;
    }

    private void Start()
    {
        StartBinding(SceneManager.GetActiveScene());
    }

    private void OnDisable()
    {
        SceneManager.sceneLoaded -= OnSceneLoaded;

        if (_bindRoutine != null)
        {
            StopCoroutine(_bindRoutine);
            _bindRoutine = null;
        }

        Unbind();
    }

    private void OnDestroy()
    {
        if (_instance == this)
            _instance = null;
    }

    private void OnSceneLoaded(Scene scene, LoadSceneMode mode)
    {
        StartBinding(scene);
    }

    private void StartBinding(Scene scene)
    {
        if (_bindRoutine != null)
            StopCoroutine(_bindRoutine);

        _bindRoutine = StartCoroutine(BindWhenAvailable(scene));
    }

    private IEnumerator BindWhenAvailable(Scene scene)
    {
        for (int frame = 0; frame < BindRetryFrames; frame++)
        {
            OctoSceneFade fade = FindFade(scene);

            if (fade != null)
            {
                Bind(fade);
                _bindRoutine = null;
                yield break;
            }

            yield return null;
        }

        Debug.LogWarning(
            $"[{nameof(PersistentWwiseFadeInPlayer)}] " +
            $"Could not find OctoSceneFade for scene '{scene.name}'.",
            this
        );

        _bindRoutine = null;
    }

    private static OctoSceneFade FindFade(Scene scene)
    {
        if (scene.IsValid() && scene.isLoaded)
        {
            foreach (GameObject root in scene.GetRootGameObjects())
            {
                OctoSceneFade fade =
                    root.GetComponentInChildren<OctoSceneFade>(true);

                if (fade != null) return fade;
            }
        }

        return OctoSceneFade.Instance;
    }

    private void Bind(OctoSceneFade fade)
    {
        if (_boundFade == fade)
            return;

        Unbind();

        _boundFade = fade;
        _boundFade.OnFadeIn += OnFadeIn;
    }

    private void Unbind()
    {
        if (_boundFade != null)
            _boundFade.OnFadeIn -= OnFadeIn;

        _boundFade = null;
    }

    private void OnFadeIn()
    {
        if (_fadeInEvent == null) return;

        _fadeInEvent.Post(gameObject);
    }
}