Monogame-Extended/source/MonoGame.Extended/Tilemaps/TilemapLayers/TilemapGroupLayer.cs

using System;
using System.Collections.Generic;
using Microsoft.Xna.Framework;

namespace MonoGame.Extended.Tilemaps
{
    /// <summary>
    /// Represents a layer that contains other layers as children.
    /// </summary>
    /// <remarks>
    /// Group layers allow for hierarchical organization of layers and can apply
    /// transformations and effects to all child layers collectively.
    /// </remarks>
    public class TilemapGroupLayer : TilemapLayer
    {
        private readonly List<TilemapLayer> _childLayers = new List<TilemapLayer>();

        /// <summary>
        /// Gets the collection of child layers.
        /// </summary>
        public IReadOnlyList<TilemapLayer> ChildLayers
        {
            get
            {
                return _childLayers;
            }
        }

        /// <inheritdoc/>
        public override Rectangle Bounds
        {
            get
            {
                if (_childLayers.Count == 0)
                {
                    return Rectangle.Empty;
                }

                // Calculate bounds as the union of all child layer bounds
                Rectangle bounds = _childLayers[0].Bounds;

                for (int i = 1; i < _childLayers.Count; i++)
                {
                    bounds = Rectangle.Union(bounds, _childLayers[i].Bounds);
                }

                return bounds;
            }
        }

        /// <summary>
        /// Initializes a new instance of the <see cref="TilemapGroupLayer"/> class.
        /// </summary>
        /// <param name="name">The name of the layer.</param>
        public TilemapGroupLayer(string name) : base(name)
        {
        }

        /// <summary>
        /// Adds a child layer to this group.
        /// </summary>
        /// <param name="layer">The layer to add.</param>
        public void AddLayer(TilemapLayer layer)
        {
            _childLayers.Add(layer);
        }

        /// <summary>
        /// Removes a child layer from this group.
        /// </summary>
        /// <param name="layer">The layer to remove.</param>
        /// <returns><see langword="true"/> if the layer was removed; otherwise, <see langword="false"/>.</returns>
        public bool RemoveLayer(TilemapLayer layer)
        {
            return _childLayers.Remove(layer);
        }

        /// <summary>
        /// Gets the child layer with the specified name.
        /// </summary>
        /// <param name="name">The name of the layer.</param>
        /// <returns>The layer with the specified name, or <see langword="null"/> if not found.</returns>
        /// <remarks>
        /// This method searches recursively through all child layers and their descendants.
        /// </remarks>
        public TilemapLayer GetLayer(string name)
        {
            if (string.IsNullOrEmpty(name))
            {
                return null;
            }

            // Search immediate children first
            foreach (TilemapLayer layer in _childLayers)
            {
                if (layer.Name == name)
                {
                    return layer;
                }
            }

            // Recursively search in child group layers
            foreach (TilemapLayer layer in _childLayers)
            {
                if (layer is TilemapGroupLayer groupLayer)
                {
                    TilemapLayer found = groupLayer.GetLayer(name);

                    if (found != null)
                    {
                        return found;
                    }
                }
            }

            return null;
        }
    }
}