using System;
using System.Collections.Generic;

namespace Chernobyl.Update
{
    /// <summary>
    /// Used to work with objects that can be updated. <see cref="IUpdateable"/>'s 
    /// have a set of children <see cref="IUpdateable"/>s that they call update 
    /// on. This structure forms a tree of <see cref="IUpdateable"/>s and allows
    /// for each <see cref="IUpdateable"/> to have it's own rules for when and 
    /// how it and its children objects are updated.
    /// </summary>
    public interface 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>
        void Update(TimeSpan deltaTime);

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

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