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

namespace MonoGame.Extended.Tilemaps
{
    /// <summary>
    /// Represents a layer containing drawable objects.
    /// </summary>
    public class TilemapObjectLayer : TilemapLayer
    {
        private readonly List<TilemapObject> _objects = new();

        /// <summary>
        /// Gets the collection of objects in this layer.
        /// </summary>
        public IReadOnlyList<TilemapObject> Objects
        {
            get
            {
                return _objects;
            }
        }

        /// <summary>
        /// Gets or sets the rendering order for objects in this layer.
        /// </summary>
        public TilemapObjectDrawOrder DrawOrder { get; set; }

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

                // Calculate bounds as the union of all object bounds
                RectangleF? unionBounds = null;

                foreach (TilemapObject obj in _objects)
                {
                    RectangleF objBounds = obj.Bounds;

                    if (unionBounds == null)
                    {
                        unionBounds = objBounds;
                    }
                    else
                    {
                        unionBounds = RectangleF.Union(unionBounds.Value, objBounds);
                    }
                }

                RectangleF bounds = unionBounds.Value;

                return new Rectangle(
                    (int)bounds.X,
                    (int)bounds.Y,
                    (int)Math.Ceiling(bounds.Width),
                    (int)Math.Ceiling(bounds.Height)
                );
            }
        }

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

        /// <summary>
        /// Adds an object to the layer.
        /// </summary>
        /// <param name="obj">The object to add.</param>
        public void AddObject(TilemapObject obj)
        {
            _objects.Add(obj);
        }

        /// <summary>
        /// Removes an object from the layer.
        /// </summary>
        /// <param name="obj">The object to remove.</param>
        /// <returns><see langword="true"/> if the object was removed; otherwise, <see langword="false"/>.</returns>
        public bool RemoveObject(TilemapObject obj)
        {
            return _objects.Remove(obj);
        }

        /// <summary>
        /// Gets the object with the specified ID.
        /// </summary>
        /// <param name="id">The object ID.</param>
        /// <returns>The object with the specified ID, or <see langword="null"/> if not found.</returns>
        public TilemapObject GetObject(int id)
        {
            foreach (TilemapObject obj in _objects)
            {
                if (obj.Id == id)
                {
                    return obj;
                }
            }

            return null;
        }

        /// <summary>
        /// Gets all objects within the specified rectangular region.
        /// </summary>
        /// <param name="region">The region in world coordinates.</param>
        /// <returns>An enumerable of objects within the region.</returns>
        public IEnumerable<TilemapObject> GetObjectsInRegion(RectangleF region)
        {
            foreach (TilemapObject obj in _objects)
            {
                if (region.Intersects(obj.Bounds))
                {
                    yield return obj;
                }
            }
        }

        /// <summary>
        /// Gets all objects of the specified type.
        /// </summary>
        /// <typeparam name="T">The type of objects to retrieve.</typeparam>
        /// <returns>An enumerable of objects of the specified type.</returns>
        public IEnumerable<T> GetObjects<T>() where T : TilemapObject
        {
            foreach (TilemapObject obj in _objects)
            {
                if (obj is T typedObj)
                {
                    yield return typedObj;
                }
            }
        }
    }
}