using TriangleNet.Geometry;

namespace TriangleNet.Topology
{
	public struct Osub
	{
		internal SubSegment seg;

		internal int orient;

		public SubSegment Segment => seg;

		public override string ToString()
		{
			if (seg == null)
			{
				return "O-TID [null]";
			}
			return $"O-SID {seg.hash}";
		}

		public void Sym(ref Osub os)
		{
			os.seg = seg;
			os.orient = 1 - orient;
		}

		public void Sym()
		{
			orient = 1 - orient;
		}

		public void Pivot(ref Osub os)
		{
			os = seg.subsegs[orient];
		}

		internal void Pivot(ref Otri ot)
		{
			ot = seg.triangles[orient];
		}

		public void Next(ref Osub ot)
		{
			ot = seg.subsegs[1 - orient];
		}

		public void Next()
		{
			this = seg.subsegs[1 - orient];
		}

		public Vertex Org()
		{
			return seg.vertices[orient];
		}

		public Vertex Dest()
		{
			return seg.vertices[1 - orient];
		}

		internal void SetOrg(Vertex vertex)
		{
			seg.vertices[orient] = vertex;
		}

		internal void SetDest(Vertex vertex)
		{
			seg.vertices[1 - orient] = vertex;
		}

		internal Vertex SegOrg()
		{
			return seg.vertices[2 + orient];
		}

		internal Vertex SegDest()
		{
			return seg.vertices[3 - orient];
		}

		internal void SetSegOrg(Vertex vertex)
		{
			seg.vertices[2 + orient] = vertex;
		}

		internal void SetSegDest(Vertex vertex)
		{
			seg.vertices[3 - orient] = vertex;
		}

		internal void Bond(ref Osub os)
		{
			seg.subsegs[orient] = os;
			os.seg.subsegs[os.orient] = this;
		}

		internal void Dissolve(SubSegment dummy)
		{
			seg.subsegs[orient].seg = dummy;
		}

		internal bool Equal(Osub os)
		{
			if (seg == os.seg)
			{
				return orient == os.orient;
			}
			return false;
		}

		internal void TriDissolve(Triangle dummy)
		{
			seg.triangles[orient].tri = dummy;
		}

		internal static bool IsDead(SubSegment sub)
		{
			return sub.subsegs[0].seg == null;
		}

		internal static void Kill(SubSegment sub)
		{
			sub.subsegs[0].seg = null;
			sub.subsegs[1].seg = null;
		}
	}
}