using System;
using System.Collections.Generic;

namespace Chernobyl.Update
{
    /// <summary>
    /// An <see cref="IUpdateable"/> that allows for at runtime switching of
    /// it's implementation and makes creating new <see cref="IUpdateable"/>s
    /// easier through the use of other <see cref="IUpdateable"/> implementations.
    /// This is an implementation of the decorator pattern 
    /// (http://en.wikipedia.org/wiki/Decorator_pattern).
    /// </summary>
    public abstract class UpdateableDecorator : IUpdateable
    {
        /// <summary>
        /// Updates this <see cref="IUpdateable"/> object and it's children if
        /// the <see cref="IUpdateable"/> feels it's necessary.
        /// </summary>
        /// <param name="deltaTime">The amount of time that has passed since
        /// this update was last called.</param>
        public void Update(TimeSpan deltaTime)
        {
            DecoratedUpdateable.Update(deltaTime);
        }

        /// <summary>
        /// The parent of this IUpdateable or null if this IUpdateable does not
        /// have a parent.
        /// </summary>
        public IUpdateable UpdateableParent
        {
            get { return DecoratedUpdateable.UpdateableParent; }
            set { DecoratedUpdateable.UpdateableParent = value; }
        }

        /// <summary>
        /// Holds a collection of children that should be updated when this
        /// <see cref="IUpdateable"/> decides they should be updated.
        /// </summary>
        public ICollection<IUpdateable> UpdateableChildren
        {
            get { return DecoratedUpdateable.UpdateableChildren; }
        }

        /// <summary>
        /// The <see cref="IUpdateable"/> that implements the functionality of
        /// this <see cref="IUpdateable"/>. Note that, when setting this property,
        /// the data from the previous value of this property will be copied to
        /// the new value using 
        /// <see cref="Updateable.ShallowCopy(IUpdateable, IUpdateable)"/>.
        /// </summary>
        protected abstract IUpdateable DecoratedUpdateable { get; }
    }
}