using System.Collections.Generic;

namespace Dbscan
{

	/// <summary>
	/// Provides the base interface for the abstraction of
	/// an index to find points.
	/// </summary>
	/// <typeparam name="T">The type of elements in the index.</typeparam>
	public interface ISpatialIndex<out T>
	{
		/// <summary>
		/// Get all of the elements within the current <see cref="T:Dbscan.ISpatialIndex`1" />.
		/// </summary>
		/// <returns>
		/// A list of every element contained in the <see cref="T:Dbscan.ISpatialIndex`1" />.
		/// </returns>
		IReadOnlyList<T> Search();

		/// <summary>
		/// Get all of the elements from this <see cref="T:Dbscan.ISpatialIndex`1" />
		/// within a circle centered at the point <see cref="P:Dbscan.IPointData.Point" />
		/// with a radius of <paramref name="epsilon" />.
		/// </summary>
		/// <param name="p">The center of the search circle.</param>
		/// <param name="epsilon">The radius of the search circle.</param>
		/// <returns>
		/// A list of the points that are within the search area.
		/// </returns>
		IReadOnlyList<T> Search(in IPointData p, double epsilon);
	}
}