using System.Collections.Generic;
using System.Linq;
using Chernobyl.Collections.Generic.Event;
using Chernobyl.Collections.Generic.Hierarchy;
using Chernobyl.Mathematics.Geometry;
using Chernobyl.Values;
using Chernobyl.Collections.Generic;
using Enumerable = System.Linq.Enumerable;

namespace Chernobyl.Mathematics.Space
{
    /// <summary>
    /// An implementation of an <see cref="ICell"/> whose purpose is to only hold
    /// sub-cells (see <see cref="Children"/>).
    /// </summary>
    public class CellCollection : Shape, ICell
    {
        /// <summary>
        /// Initializes a new instance of the <see cref="CellCollection"/> class.
        /// </summary>
        public CellCollection() : this(null)
        { }

        /// <summary>
        /// Initializes a new instance of the <see cref="CellCollection"/> class.
        /// </summary>
        /// <param name="parent">The immediate superior of this node in the 
        /// hierarchy or null if this node has no superior.</param>
        public CellCollection(ICell parent)
            : this(parent, Enumerable.Empty<ICell>())
        {}

        /// <summary>
        /// Initializes a new instance of the <see cref="CellCollection"/> class.
        /// </summary>
        /// <param name="parent">The immediate superior of this node in the 
        /// hierarchy or null if this node has no superior.</param>
        /// <param name="children">The immediate subordinates of this node in 
        /// the hierarchy.</param>
        public CellCollection(ICell parent, IEnumerable<ICell> children)
        {
            Children = new DecoratingEventCollection<ICell>(new HierarchalChildren<ICell>(this));
            Children.ItemsAdded += (sender, args) => _shapeCollection.AddRange(args.Items);
            Children.ItemsRemoved += (sender, args) => _shapeCollection.RemoveRange(args.Items);
            Parent = new HierarchalParent<ICell>(this);

            Parent.Value = parent;
            Children.AddRange(children);
        }

        /// <summary>
        /// The immediate superior of this node in the hierarchy or null if this
        /// node has no superior.
        /// </summary>
        public IDynamicContainer<ICell> Parent { get; private set; }

        /// <summary>
        /// The immediate subordinates of this node in the hierarchy.
        /// </summary>
        public IEventCollection<ICell> Children { get; private set; }

        /// <summary>
        /// True if this <see cref="IShape" /> is convex, false if it is concave
        /// or has 0 <see cref="Dimensions" /> (such as a point). A
        /// <see cref="IShape" /> is convex if for every pair of points within
        /// the object, every point on the straight line segment that joins them
        /// is also within the object. A concave <see cref="IShape" /> is the
        /// opposite of this.
        /// </summary>
        public override bool IsConvex
        {
            get { return _shapeCollection.IsConvex; }
        }

        /// <summary>
        /// The amount of space taken up by an object on a flat plane in
        /// square metres (m^2).
        /// </summary>
        public override float Area
        {
            get { return _shapeCollection.Area; }
        }

        /// <summary>
        /// The amount of 3D space this object consumes in cubic metres (m^3).
        /// If this object is 2D, then the value of this property is zero.
        /// </summary>
        public override float Volume
        {
            get { return _shapeCollection.Volume; }
        }

        /// <summary>
        /// The length of the path that surrounds a shape specified in metres (m).
        /// in the case of a closed curve such as a circle, this value represents
        /// the circumference of the object.
        /// </summary>
        public override float Perimeter
        {
            get { return _shapeCollection.Perimeter; }
        }

        /// <summary>
        /// The minimum number of coordinates needed to specify each point
        /// within this object. For example: a point has 0 dimensions, a
        /// line has 1 dimension, a circle or rectangle has 2 dimensions, a
        /// cube or sphere has 3 dimensions, and a moving cube or sphere has 4.
        /// </summary>
        public override uint Dimensions
        {
            get { return _shapeCollection.Dimensions; }
        }

        /// <summary>
        /// The instance that manages that manages that <see cref="IShape"/>
        /// aspect of this type.
        /// </summary>
        readonly ShapeCollection _shapeCollection = new ShapeCollection();
    }
}