dungeons/Assets/Scripts/Managers/SceneManager.cs

using Sirenix.OdinInspector;
using System.Collections;
using Unity.Netcode;
using UnityEngine;
using UnityEngine.Events;
using UnityEngine.SceneManagement;
using Zenject;

public class SceneManager : NetworkBehaviour
{
    [SerializeField]
    private Level lobbyLevel;

    [SerializeField]
    private Level entranceLevel;

    [SerializeField]
    private Level forgeLevel;

    public Level[] Levels => new []{ entranceLevel, forgeLevel };

    [Inject]
    [ReadOnly]
    [SerializeField]
    private GameManager gameManager;

    [ReadOnly]
    [SerializeField]
    private float fadeDuration = 2f;

    [ReadOnly]
    [SerializeField]
    private Scene loadedScene;

    public Scene LoadedScene => loadedScene;

    public bool IsInLobby => loadedScene.name == lobbyLevel.sceneName;

    public UnityEvent SceneLoaded;

    private bool isMultiplayer => gameManager.IsMultiplayer;

    private void Awake()
    {
        loadedScene = UnityEngine.SceneManagement.SceneManager.GetActiveScene();
    }

    public override void OnNetworkSpawn()
    {
        NetworkManager.SceneManager.OnSceneEvent += OnSceneEvent;

        Debug.Log("network spawn");

        base.OnNetworkSpawn();
    }

    private void OnSceneEvent(SceneEvent sceneEvent)
    {
        var clientOrServer = sceneEvent.ClientId == NetworkManager.ServerClientId ? "server" : "client";

        switch (sceneEvent.SceneEventType)
        {
            case SceneEventType.LoadComplete:
                {
                    // We want to handle this for only the server-side
                    if (sceneEvent.ClientId == NetworkManager.ServerClientId)
                    {
                        // Keep track of the loaded scene, you need this to unload it
                        loadedScene = sceneEvent.Scene;
                        SceneLoaded.Invoke();
                    }

                    Debug.Log($"Loaded the {sceneEvent.SceneName} scene on " +
                        $"{clientOrServer}-({sceneEvent.ClientId}).");

                    break;
                }
            case SceneEventType.UnloadComplete:
                {
                    Debug.Log($"Unloaded the {sceneEvent.SceneName} scene on " +
                        $"{clientOrServer}-({sceneEvent.ClientId}).");

                    break;
                }
            case SceneEventType.LoadEventCompleted:
            case SceneEventType.UnloadEventCompleted:
                {
                    var loadUnload = sceneEvent.SceneEventType == SceneEventType.LoadEventCompleted ? "Load" : "Unload";

                    Debug.Log($"{loadUnload} event completed for the following client " +
                        $"identifiers:({sceneEvent.ClientsThatCompleted})");

                    if (sceneEvent.ClientsThatTimedOut.Count > 0)
                    {
                        Debug.LogWarning($"{loadUnload} event timed out for the following client " +
                            $"identifiers:({sceneEvent.ClientsThatTimedOut})");
                    }

                    break;
                }
        }
    }

    private void CheckStatus(SceneEventProgressStatus status, bool isLoading = true)
    {
        var sceneEventAction = isLoading ? "load" : "unload";
        if (status != SceneEventProgressStatus.Started)
        {
            Debug.LogWarning($"Failed to {sceneEventAction} with" +
                $" a {nameof(SceneEventProgressStatus)}: {status}");
        }
    }

    private void UnloadScene()
    {
        // Assure only the server calls this when the NetworkObject is
        // spawned and the scene is loaded.
        if (!IsServer || !IsSpawned || !loadedScene.IsValid() || !loadedScene.isLoaded)
        {
            return;
        }

        var status = NetworkManager.SceneManager.UnloadScene(loadedScene);
        CheckStatus(status, false);
    }

    [Button]
    public void SwitchToLobbyLevel()
    {
        SwitchToScene(lobbyLevel.sceneName);
    }

    [Button]
    public void SwitchToEntranceLevel()
    {
        SwitchToScene(entranceLevel.sceneName);
    }

    [Button]
    public void SwitchToForgeLevel()
    {
        SwitchToScene(forgeLevel.sceneName);
    }

    private void SwitchToScene(string sceneName)
    {
        if (isMultiplayer)
        {
            StartCoroutine(SwitchToSceneMultiplayer(sceneName));
        }
        else
        {
            StartCoroutine(SwitchToSceneSolo(sceneName));
        }
    }

    private IEnumerator SwitchToSceneMultiplayer(string scene)
    {
        //gameManager.LocalPlayer.FadeScreen(1, fadeDuration);

        NetworkManager.SceneManager.LoadScene(scene, LoadSceneMode.Single);

        //var operation = UnityEngine.SceneManagement.SceneManager
        //    .LoadSceneAsync((int)scene);

        //operation.allowSceneActivation = false;

        //float timer = 0;

        //while (timer <= fadeDuration && !operation.isDone)
        //{
        //    timer += Time.deltaTime;
            yield return null;
        //}

        //operation.allowSceneActivation = true;

        //this.scene = scene;

        //gameManager.LocalPlayer.FadeScreen(0, fadeDuration);
    }

    private IEnumerator SwitchToSceneSolo(string scene)
    {
        gameManager.LocalPlayer.FadeScreen(1, fadeDuration);

        var operation = UnityEngine.SceneManagement.SceneManager
            .LoadSceneAsync(scene);

        operation.allowSceneActivation = false;

        float timer = 0;

        while (timer <= fadeDuration && !operation.isDone)
        {
            timer += Time.deltaTime;
            yield return null;
        }

        operation.allowSceneActivation = true;

        gameManager.LocalPlayer.FadeScreen(0, fadeDuration);

        loadedScene = UnityEngine.SceneManagement.SceneManager.GetActiveScene();
    }
}