using System.Collections.Generic;
using TriangleNet.Geometry;
using TriangleNet.Topology;

namespace TriangleNet.Meshing.Iterators
{
	public class VertexCirculator
	{
		private List<Otri> cache = new List<Otri>();

		public VertexCirculator(Mesh mesh)
		{
			mesh.MakeVertexMap();
		}

		public IEnumerable<Vertex> EnumerateVertices(Vertex vertex)
		{
			BuildCache(vertex, vertices: true);
			foreach (Otri item in cache)
			{
				yield return item.Dest();
			}
		}

		public IEnumerable<ITriangle> EnumerateTriangles(Vertex vertex)
		{
			BuildCache(vertex, vertices: false);
			foreach (Otri item in cache)
			{
				yield return item.tri;
			}
		}

		private void BuildCache(Vertex vertex, bool vertices)
		{
			cache.Clear();
			Otri tri = vertex.tri;
			Otri ot = default(Otri);
			Otri ot2 = default(Otri);
			tri.Copy(ref ot);
			while (ot.tri.id != -1)
			{
				cache.Add(ot);
				ot.Copy(ref ot2);
				ot.Onext();
				if (ot.Equals(tri))
				{
					break;
				}
			}
			if (ot.tri.id != -1)
			{
				return;
			}
			tri.Copy(ref ot);
			if (vertices)
			{
				ot2.Lnext();
				cache.Add(ot2);
			}
			ot.Oprev();
			while (ot.tri.id != -1)
			{
				cache.Insert(0, ot);
				ot.Oprev();
				if (ot.Equals(tri))
				{
					break;
				}
			}
		}
	}
}