Syntriax.Engine/Engine.Core/Transform2D.cs

using Engine.Core.Serialization;

namespace Engine.Core;

[System.Diagnostics.DebuggerDisplay("Name: {UniverseObject.Name, nq} Position: {Position.ToString(), nq}, Scale: {Scale.ToString(), nq}, Rotation: {Rotation}")]
public class Transform2D : Behaviour, ITransform2D
{
    public Event<ITransform2D, ITransform2D.PositionChangedArguments> OnPositionChanged { get; } = new();
    public Event<ITransform2D, ITransform2D.ScaleChangedArguments> OnScaleChanged { get; } = new();
    public Event<ITransform2D, ITransform2D.RotationChangedArguments> OnRotationChanged { get; } = new();
    public Event<ITransform2D> OnTransformUpdated { get; } = new();

    private Vector2D _position = Vector2D.Zero;
    private Vector2D _scale = Vector2D.One;
    private float _rotation = 0f;

    [Serialize] private Vector2D _localPosition = Vector2D.Zero;
    [Serialize] private Vector2D _localScale = Vector2D.One;
    [Serialize] private float _localRotation = 0f;

    private ITransform2D? parentTransform = null;

    public Vector2D Up => Vector2D.Up.Rotate(Rotation * Math.DegreeToRadian);
    public Vector2D Down => Vector2D.Down.Rotate(Rotation * Math.DegreeToRadian);
    public Vector2D Left => Vector2D.Left.Rotate(Rotation * Math.DegreeToRadian);
    public Vector2D Right => Vector2D.Right.Rotate(Rotation * Math.DegreeToRadian);

    public Vector2D Position
    {
        get => _position;
        set
        {
            if (value == _position)
                return;

            Vector2D previousPosition = _position;
            _position = value;

            UpdateLocalPosition();
            OnPositionChanged.Invoke(this, new(previousPosition));
            OnTransformUpdated.Invoke(this);
        }
    }

    public Vector2D Scale
    {
        get => _scale;
        set
        {
            if (value == _scale)
                return;

            Vector2D previousScale = _scale;
            _scale = value;

            UpdateLocalScale();
            OnScaleChanged.Invoke(this, new(previousScale));
            OnTransformUpdated.Invoke(this);
        }
    }

    public float Rotation
    {
        get => _rotation;
        set
        {
            if (value == _rotation)
                return;

            float previousRotation = _rotation;
            _rotation = value;

            UpdateLocalRotation();
            OnRotationChanged.Invoke(this, new(previousRotation));
            OnTransformUpdated.Invoke(this);
        }
    }

    public Vector2D LocalPosition
    {
        get => _localPosition;
        set
        {
            if (value == _localPosition)
                return;

            Vector2D previousPosition = _position;
            _localPosition = value;

            UpdatePosition();
            OnPositionChanged.Invoke(this, new(previousPosition));
            OnTransformUpdated.Invoke(this);
        }
    }

    public Vector2D LocalScale
    {
        get => _localScale;
        set
        {
            if (value == _localScale)
                return;

            Vector2D previousScale = _scale;
            Vector2D previousPosition = _position;
            _localScale = value;

            UpdateScale();
            UpdatePosition();
            OnScaleChanged.Invoke(this, new(previousScale));
            OnPositionChanged.Invoke(this, new(previousPosition));
            OnTransformUpdated.Invoke(this);
        }
    }

    public float LocalRotation
    {
        get => _localRotation;
        set
        {
            if (value == _localRotation)
                return;

            float previousRotation = _rotation;
            _localRotation = value;

            UpdateRotation();
            OnRotationChanged.Invoke(this, new(previousRotation));
            OnTransformUpdated.Invoke(this);
        }
    }

    private void RecalculatePosition(ITransform2D _, ITransform2D.PositionChangedArguments args)
    {
        if (parentTransform is null)
            return;

        UpdatePosition();

        OnPositionChanged.Invoke(this, args);
        OnTransformUpdated.Invoke(this);
    }

    private void RecalculateScale(ITransform2D _, ITransform2D.ScaleChangedArguments args)
    {
        if (parentTransform is null)
            return;

        Vector2D previousPosition = _position;

        UpdateScale();
        UpdatePosition();

        OnScaleChanged.Invoke(this, args);
        OnPositionChanged.Invoke(this, new(previousPosition));
        OnTransformUpdated.Invoke(this);
    }

    private void RecalculateRotation(ITransform2D _, ITransform2D.RotationChangedArguments args)
    {
        if (parentTransform is null)
            return;

        Vector2D previousPosition = Position;

        UpdateRotation();
        UpdatePosition();

        OnRotationChanged.Invoke(this, args);
        OnPositionChanged.Invoke(this, new(previousPosition));
        OnTransformUpdated.Invoke(this);
    }

    private void UpdateLocalPosition()
    {
        if (parentTransform is null)
            _localPosition = Position;
        else
            _localPosition = parentTransform.Position.FromTo(Position).Scale(parentTransform.Scale);
    }

    private void UpdateLocalScale()
    {
        if (parentTransform is null)
            _localScale = Scale;
        else
            _localScale = Scale.Scale(new(1f / parentTransform.Scale.X, 1f / parentTransform.Scale.Y));
    }

    private void UpdateLocalRotation()
    {
        if (parentTransform is null)
            _localRotation = Rotation;
        else
            _localRotation = Rotation - parentTransform.Rotation;
    }

    private void UpdatePosition()
    {
        if (parentTransform is null)
            _position = LocalPosition.Rotate(0f * Math.DegreeToRadian);
        else
            _position = parentTransform.Position + LocalPosition.Scale(new(parentTransform.Scale.X, parentTransform.Scale.Y)).Rotate(parentTransform.Rotation * Math.DegreeToRadian);
    }

    private void UpdateScale()
    {
        if (parentTransform is null)
            _scale = LocalScale;
        else
            _scale = (parentTransform?.Scale ?? Vector2D.One).Scale(_localScale);
    }

    private void UpdateRotation()
    {
        if (parentTransform is null)
            _rotation = LocalRotation;
        else
            _rotation = parentTransform.Rotation + LocalRotation;
    }

    protected override void InitializeInternal()
    {
        UpdateReferences(UniverseObject.Parent);
        UniverseObject.OnParentChanged.AddListener(OnParentChanged);
    }

    protected override void FinalizeInternal()
    {
        UniverseObject.OnParentChanged.RemoveListener(OnParentChanged);
    }

    private void UpdateReferences(IUniverseObject? parent)
    {
        ITransform2D? previousParent = parentTransform;
        if (previousParent is not null)
        {
            previousParent.OnPositionChanged.RemoveListener(RecalculatePosition);
            previousParent.OnScaleChanged.RemoveListener(RecalculateScale);
            previousParent.OnRotationChanged.RemoveListener(RecalculateRotation);
            previousParent.BehaviourController.UniverseObject.OnParentChanged.RemoveListener(OnParentChanged);
            previousParent.BehaviourController.OnBehaviourAdded.RemoveListener(LookForTransform2D);
        }

        parentTransform = parent?.BehaviourController.GetBehaviour<ITransform2D>();

        if (parentTransform is not null)
        {
            parentTransform.OnPositionChanged.AddListener(RecalculatePosition);
            parentTransform.OnScaleChanged.AddListener(RecalculateScale);
            parentTransform.OnRotationChanged.AddListener(RecalculateRotation);
            parentTransform.BehaviourController.UniverseObject.OnParentChanged.AddListener(OnParentChanged);

            UpdatePosition();
            UpdateScale();
            UpdateRotation();
        }
        else if (UniverseObject.Parent is not null)
            UniverseObject.Parent.BehaviourController.OnBehaviourAdded.AddListener(LookForTransform2D);

        UpdateLocalPosition();
        UpdateLocalScale();
        UpdateLocalRotation();

        OnPositionChanged.Invoke(this, new(Position));
        OnScaleChanged.Invoke(this, new(Scale));
        OnRotationChanged.Invoke(this, new(Rotation));
        OnTransformUpdated.Invoke(this);
    }

    private void LookForTransform2D(IBehaviourController sender, IBehaviourController.BehaviourAddedArguments args)
    {
        if (args.BehaviourAdded is not ITransform2D)
            return;

        UpdateReferences(UniverseObject.Parent);
    }

    private void OnParentChanged(IUniverseObject sender, IUniverseObject.ParentChangedArguments args)
    {
        UpdateReferences(args.CurrentParent);
    }
}