Syntriax.Engine/Engine.Core/GameObject.cs

using Syntriax.Engine.Core.Abstract;
using Syntriax.Engine.Core.Exceptions;

namespace Syntriax.Engine.Core;

[System.Diagnostics.DebuggerDisplay("Name: {Name}, Initialized: {Initialized}")]
public class GameObject : BaseEntity, IGameObject
{
    public event IHierarchyObject.OnEnteredHierarchyEventHandler? OnEnteredHierarchy = null;
    public event IHierarchyObject.OnExitedHierarchyEventHandler? OnExitedHierarchy = null;

    public event IAssignableTransform.OnTransformAssignedEventHandler? OnTransformAssigned = null;
    public event IAssignableBehaviourController.OnBehaviourControllerAssignedEventHandler? OnBehaviourControllerAssigned = null;

    public event INameable.OnNameChangedEventHandler? OnNameChanged = null;

    public event IGameObject.OnUpdatedEventHandler? OnUpdated = null;

    private ITransform _transform = null!;
    private IBehaviourController _behaviourController = null!;
    private IGameManager _gameManager = null!;

    private string _name = nameof(GameObject);

    public ITransform Transform => _transform;
    public IBehaviourController BehaviourController => _behaviourController;
    public IGameManager GameManager => _gameManager;
    public bool IsInHierarchy => GameManager is not null;

    public string Name
    {
        get => _name;
        set
        {
            if (value == _name) return;

            string previousName = _name;
            _name = value;
            OnNameChanged?.Invoke(this, previousName);
        }
    }

    protected override void InitializeInternal()
    {
        base.InitializeInternal();

        NotAssignedException.Check(this, _transform);
        NotAssignedException.Check(this, _behaviourController);

        if (!_behaviourController.Initialize())
            throw new System.Exception($"Failed to Initialize {BehaviourController.GetType().Name} on {Transform.GameObject.Name}");
    }

    public void Update()
    {
        if (!StateEnable.Enabled)
            return;

        OnUpdated?.Invoke(this);
    }

    protected override void FinalizeInternal()
    {
        base.FinalizeInternal();

        if (!_behaviourController.Finalize())
            throw new System.Exception($"Failed to Finalize {BehaviourController.GetType().Name} on {Transform.GameObject.Name}");
    }

    public bool Assign(ITransform transform)
    {
        if (IsInitialized)
            return false;

        _transform = transform;
        OnTransformAssigned?.Invoke(this);
        transform.OnParentChanged += OnParentChangedInternal;
        OnParentChangedInternal(transform, null, transform.Parent);
        return true;
    }

    public bool Assign(IBehaviourController behaviourController)
    {
        if (IsInitialized)
            return false;

        _behaviourController = behaviourController;
        OnBehaviourControllerAssigned?.Invoke(this);
        return true;
    }

    protected override void UnassignInternal()
    {
        base.UnassignInternal();

        _transform.OnParentChanged -= OnParentChangedInternal;
        OnParentChangedInternal(_transform, _transform.Parent, null);
        _transform = null!;
        _behaviourController = null!;
        _gameManager = null!;
    }

    public GameObject() { OnBehaviourControllerAssigned += ConnectBehaviourController; }

    private void ConnectBehaviourController(IAssignableBehaviourController controller)
    {
        controller.BehaviourController.OnBehaviourAdded += OnBehaviourAdded;
        controller.BehaviourController.OnBehaviourRemoved += OnBehaviourRemoved;
    }
    private void OnBehaviourRemoved(IBehaviourController _, IBehaviour behaviour) { if (IsInitialized) behaviour.Finalize(); }
    private void OnBehaviourAdded(IBehaviourController _, IBehaviour behaviour) { if (!IsInitialized) behaviour.Initialize(); }

    private void OnParentChangedInternal(ITransform sender, ITransform? previousParent, ITransform? newParent)
    {
        if (previousParent is not null)
        {
            previousParent.OnParentChanged -= OnParentChangedInternal;
            previousParent.GameObject.OnEnteredHierarchy -= EnterHierarchyInternal;
            previousParent.GameObject.OnExitedHierarchy -= ExitHierarchyInternal;
        }
        if (newParent is not null)
        {
            newParent.OnParentChanged += OnParentChangedInternal;
            newParent.GameObject.OnEnteredHierarchy += EnterHierarchyInternal;
            newParent.GameObject.OnExitedHierarchy += ExitHierarchyInternal;
        }
    }

    private void EnterHierarchyInternal(IHierarchyObject sender, IGameManager gameManager) => ((IHierarchyObject)this).EnterHierarchy(gameManager);
    private void ExitHierarchyInternal(IHierarchyObject sender, IGameManager gameManager) => ((IHierarchyObject)this).ExitHierarchy();

    bool IHierarchyObject.EnterHierarchy(IGameManager gameManager)
    {
        if (IsInHierarchy)
            return false;

        _gameManager = gameManager;
        OnEnteredHierarchy?.Invoke(this, gameManager);
        return true;
    }

    bool IHierarchyObject.ExitHierarchy()
    {
        if (!IsInHierarchy || _gameManager is not IGameManager gameManager)
            return false;

        _gameManager = null!;
        OnExitedHierarchy?.Invoke(this, gameManager);
        return true;
    }
}