net.peeweek.gameplay-ingredients/Runtime/Managers/Implementations/GameManager.cs

using GameplayIngredients;
using GameplayIngredients.Actions;
using GameplayIngredients.LevelStreaming;
using NaughtyAttributes;
using System.Linq;
using System.Collections.Generic;
using UnityEngine;
using GameplayIngredients.Logic;

[ManagerDefaultPrefab("GameManager")]
public class GameManager : Manager
{
    [Header("Events")]
    [ReorderableList]
    public Callable[] OnGameStart;
    [ReorderableList]
    public Callable[] OnLevelLoaded;
    [ReorderableList]
    public Callable[] OnMainMenuLoaded;

    [Header("Levels"),NonNullCheck]
    public GameLevel MainMenuGameLevel;
    [ReorderableList,NonNullCheck]
    public GameLevel[] MainGameLevels;

    [Header("Save")]
    public string ProgressSaveName = "Progress";

    [Header("Messages")]
    public string MainMenuStartMessage = "MAINMENU_START";
    public string GameLevelStartMessage = "GAME_START";

    public int currentLevel { get; private set; } = -2;

    public int currentSaveProgress {
        get { Manager.Get<GameSaveManager>().LoadUserSave(0); return Manager.Get<GameSaveManager>().GetInt(ProgressSaveName, GameSaveManager.Location.User);  }
        set { Manager.Get<GameSaveManager>().SetInt(ProgressSaveName, GameSaveManager.Location.User, value); Manager.Get<GameSaveManager>().SaveUserSave(0); }
    }

    GameObject m_CurrentLevelSwitch;

    public void Start()
    {
        currentLevel = int.MinValue;
        Callable.Call(OnGameStart);
        Manager.Get<GameSaveManager>().LoadUserSave(0);
    }

    Callable GetCurrentLevelSwitch(int targetLevel, bool showUI = false, Callable[] onComplete = null)
    {
        GameObject go = new GameObject();
        go.name = $"LevelSwtich {currentLevel} -> {targetLevel}";
        go.transform.parent = this.transform;
        m_CurrentLevelSwitch = go;

        var cameraFade = go.AddComponent<FullScreenFadeAction>();
        var loadLevel = go.AddComponent<StreamingLevelAction>();
        var sendMessage = go.AddComponent<SendMessageAction>();
        var destroy = go.AddComponent<DestroyObjectAction>();
        var next = go.AddComponent<Logic>();

        cameraFade.Fading = FullScreenFadeManager.FadeMode.ToBlack;
        cameraFade.Name = "Fade to Black";
        cameraFade.Duration = 1.0f;
        cameraFade.OnComplete = new Callable[]{ loadLevel };

        loadLevel.Name = $"Load {(targetLevel < 0? "Main menu" : MainGameLevels[targetLevel].name)}";
        loadLevel.ShowUI = showUI;
        loadLevel.Action = LevelStreamingManager.StreamingAction.Replace;
        var level = targetLevel < 0 ? MainMenuGameLevel : MainGameLevels[targetLevel];
        loadLevel.SceneToActivate = level.StartupScenes[0];
        loadLevel.Scenes = level.StartupScenes;
        loadLevel.OnLoadComplete = new Callable[] { sendMessage, destroy, next };

        string message = targetLevel == -1 ? MainMenuStartMessage : GameLevelStartMessage;
        sendMessage.Name = $"Send {message}";
        sendMessage.MessageToSend = message;

        destroy.ObjectsToDestroy = new GameObject[] { go };

        var nextActions = targetLevel < 0 ? OnMainMenuLoaded : OnLevelLoaded;
        next.Calls =  nextActions.Concat(onComplete).ToArray();

        // Return first callable
        return cameraFade;
    }

    public void SwitchLevel(int nextLevel, bool showUI = false, Callable[] onComplete = null)
    {
        if (m_CurrentLevelSwitch == null)
        {
            var call = GetCurrentLevelSwitch(nextLevel, showUI, onComplete);
            call.Execute();
            currentLevel = nextLevel;
        }
        else
            Debug.LogWarning("SwitchLevel : an Operation was still in progress and switching level could not be done. ");
    }
    
}