Syntriax.Engine/Engine.Core/Abstract/ITransform.cs

using System;
using System.Collections.Generic;

namespace Syntriax.Engine.Core.Abstract;

/// <summary>
/// Represents the transformation properties of an object such as position, scale, and rotation.
/// </summary>
public interface ITransform : IAssignableGameObject, IEnumerable<ITransform>
{
    /// <summary>
    /// Event triggered when the <see cref="Position"/> of the <see cref="ITransform"/> changes.
    /// </summary>
    event OnPositionChangedEventHandler? OnPositionChanged;

    /// <summary>
    /// Event triggered when the <see cref="Scale"/> of the <see cref="ITransform"/> changes.
    /// </summary>
    event OnScaleChangedEventHandler? OnScaleChanged;

    /// <summary>
    /// Event triggered when the <see cref="Rotation"/> of the <see cref="ITransform"/> changes.
    /// </summary>
    event OnRotationChangedEventHandler? OnRotationChanged;

    /// <summary>
    /// Event triggered when the <see cref="Parent"/> of the <see cref="ITransform"/> changes. The second parameter is the old <see cref="ITransform"/>.
    /// </summary>
    event OnParentChangedEventHandler? OnParentChanged;

    /// <summary>
    /// Event triggered when a new <see cref="ITransform"/> is added to the <see cref="Children"/>.
    /// </summary>
    event OnChildrenAddedEventHandler? OnChildrenAdded;

    /// <summary>
    /// Event triggered when an <see cref="ITransform"/> is removed from the <see cref="Children"/>.
    /// </summary>
    event OnChildrenRemovedEventHandler? OnChildrenRemoved;

    /// <summary>
    /// The world position of the <see cref="ITransform"/> in 2D space.
    /// </summary>
    Vector2D Position { get; set; }

    /// <summary>
    /// The world scale of the <see cref="ITransform"/>.
    /// </summary>
    Vector2D Scale { get; set; }

    /// <summary>
    /// The world rotation of the <see cref="ITransform"/> in degrees.
    /// </summary>
    float Rotation { get; set; }

    /// <summary>
    /// The local position of the <see cref="ITransform"/> in 2D space.
    /// </summary>
    Vector2D LocalPosition { get; set; }

    /// <summary>
    /// The local scale of the <see cref="ITransform"/>.
    /// </summary>
    Vector2D LocalScale { get; set; }

    /// <summary>
    /// The local rotation of the <see cref="ITransform"/> in degrees.
    /// </summary>
    float LocalRotation { get; set; }

    /// <summary>
    /// The parent <see cref="ITransform"/> of the <see cref="ITransform"/>.
    /// </summary>
    ITransform? Parent { get; }

    /// <summary>
    /// The <see cref="ITransform"/>s that have this <see cref="ITransform"/> as their <see cref="Parent"/>.
    /// </summary>
    IReadOnlyList<ITransform> Children { get; }

    /// <summary>
    /// Sets the parent <see cref="ITransform"/> of this <see cref="ITransform"/>.
    /// </summary>
    /// <param name="transform">The parent <see cref="ITransform"/> to set.</param>
    void SetParent(ITransform? transform);

    /// <summary>
    /// Adds a child <see cref="ITransform"/> to this <see cref="ITransform"/>.
    /// </summary>
    /// <param name="transform">The child <see cref="ITransform"/> to add.</param>
    void AddChild(ITransform transform);

    /// <summary>
    /// Removes a child <see cref="ITransform"/> from this <see cref="ITransform"/>.
    /// </summary>
    /// <param name="transform">The child <see cref="ITransform"/> to remove.</param>
    void RemoveChild(ITransform transform);

    delegate void OnPositionChangedEventHandler(ITransform sender);
    delegate void OnScaleChangedEventHandler(ITransform sender);
    delegate void OnRotationChangedEventHandler(ITransform sender);
    delegate void OnParentChangedEventHandler(ITransform sender, ITransform? previousParent, ITransform? newParent);
    delegate void OnChildrenAddedEventHandler(ITransform sender, ITransform childrenAdded);
    delegate void OnChildrenRemovedEventHandler(ITransform sender, ITransform childrenRemoved);
}