using System.Collections.Generic;

namespace Chernobyl.Mathematics.Collision
{
    /// <summary>
    /// An <see cref="IExtendedCollidable{T}"/> and <see cref="IEnumerable{T}"/> 
    /// that can check for collisions with many different objects. This collision 
    /// group builds a collision graph for optimized collision detection. Each 
    /// <see cref="ICollidable2D"/> held within this group must be derive from 
    /// <see cref="IExtendedCollidable{TCollider}"/>.
    /// </summary>
    /// <typeparam name="TContainedCollidable">The type of 
    /// <see cref="ICollidable"/> being held 
    /// within this <see cref="ICollidableEnumerable{TContainedCollidable, TCollider}"/>. 
    /// This ICollidable type must derive from <see cref="IExtendedCollidable{T}"/>.</typeparam>
    /// <typeparam name="TCollider">The <see cref="ICollidable"/> type that will 
    /// be passed in to check for collisions against the 
    /// <typeparamref name="TContainedCollidable"/> instances contained within 
    /// this <see cref="ICollection{T}"/>.</typeparam>
    public interface ICollidableEnumerable<TContainedCollidable, TCollider>
        : IEnumerable<TContainedCollidable>, IExtendedCollidable<TCollider>
        where TContainedCollidable : IExtendedCollidable<TCollider>
    {
        /// <summary>
        /// Returns an <see cref="IEnumerable{T}"/> that can be iterated 
        /// over to collect the objects that are colliding with the passed in 
        /// <paramref name="collidable"/>. Note this method should never 
        /// pre-compute the collisions. It should return an
        /// <see cref="IEnumerable{T}"/> that returns an 
        /// <see cref="IEnumerator{T}"/> that checks for collisions as it 
        /// iterates.
        /// </summary>
        /// <param name="collidable">The <see cref="ICollidable"/> to check 
        /// against for collisions.</param>
        /// <returns>The <see cref="IEnumerable{T}"/> that can be iterated over
        /// to get the <see cref="ICollidable2D"/>s that are being collided 
        /// against.</returns>
        IEnumerable<TContainedCollidable> GetCollidables(TCollider collidable);
    }
}