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

namespace TriangleNet.Tools
{
	public static class PolygonValidator
	{
		public static bool IsConsistent(IPolygon poly)
		{
			ILog<LogItem> instance = Log.Instance;
			List<Vertex> points = poly.Points;
			int num = 0;
			int num2 = 0;
			int count = points.Count;
			if (count < 3)
			{
				instance.Warning("Polygon must have at least 3 vertices.", "PolygonValidator.IsConsistent()");
				return false;
			}
			foreach (Vertex item in points)
			{
				if (item == null)
				{
					num++;
					instance.Warning($"Point {num2} is null.", "PolygonValidator.IsConsistent()");
				}
				else if (double.IsNaN(item.x) || double.IsNaN(item.y))
				{
					num++;
					instance.Warning($"Point {num2} has invalid coordinates.", "PolygonValidator.IsConsistent()");
				}
				else if (double.IsInfinity(item.x) || double.IsInfinity(item.y))
				{
					num++;
					instance.Warning($"Point {num2} has invalid coordinates.", "PolygonValidator.IsConsistent()");
				}
				num2++;
			}
			num2 = 0;
			foreach (ISegment segment in poly.Segments)
			{
				if (segment == null)
				{
					num++;
					instance.Warning($"Segment {num2} is null.", "PolygonValidator.IsConsistent()");
					return false;
				}
				Vertex vertex = segment.GetVertex(0);
				Vertex vertex2 = segment.GetVertex(1);
				if (vertex.x == vertex2.x && vertex.y == vertex2.y)
				{
					num++;
					instance.Warning($"Endpoints of segment {num2} are coincident (IDs {vertex.id} / {vertex2.id}).", "PolygonValidator.IsConsistent()");
				}
				num2++;
			}
			num = ((points[0].id != points[1].id) ? (num + CheckDuplicateIDs(poly)) : (num + CheckVertexIDs(poly, count)));
			return num == 0;
		}

		public static bool HasDuplicateVertices(IPolygon poly)
		{
			ILog<LogItem> instance = Log.Instance;
			int num = 0;
			Vertex[] array = poly.Points.ToArray();
			VertexSorter.Sort(array);
			for (int i = 1; i < array.Length; i++)
			{
				if (array[i - 1] == array[i])
				{
					num++;
					instance.Warning($"Found duplicate point {array[i]}.", "PolygonValidator.HasDuplicateVertices()");
				}
			}
			return num > 0;
		}

		public static bool HasBadAngles(IPolygon poly, double threshold = 2E-12)
		{
			ILog<LogItem> instance = Log.Instance;
			int num = 0;
			int num2 = 0;
			Point point = null;
			Point point2 = null;
			_ = poly.Points.Count;
			foreach (ISegment segment in poly.Segments)
			{
				Point point3 = point;
				Point point4 = point2;
				point = segment.GetVertex(0);
				point2 = segment.GetVertex(1);
				if (!(point == point2) && !(point3 == point4))
				{
					if (point3 != null && point4 != null && point == point4 && point2 != null && IsBadAngle(point3, point, point2, threshold))
					{
						num++;
						instance.Warning($"Bad segment angle found at index {num2}.", "PolygonValidator.HasBadAngles()");
					}
					num2++;
				}
			}
			return num > 0;
		}

		private static bool IsBadAngle(Point a, Point b, Point c, double threshold = 0.0)
		{
			double x = DotProduct(a, b, c);
			return Math.Abs(Math.Atan2(CrossProductLength(a, b, c), x)) <= threshold;
		}

		private static double DotProduct(Point a, Point b, Point c)
		{
			return (a.x - b.x) * (c.x - b.x) + (a.y - b.y) * (c.y - b.y);
		}

		private static double CrossProductLength(Point a, Point b, Point c)
		{
			return (a.x - b.x) * (c.y - b.y) - (a.y - b.y) * (c.x - b.x);
		}

		private static int CheckVertexIDs(IPolygon poly, int count)
		{
			ILog<LogItem> instance = Log.Instance;
			int num = 0;
			int num2 = 0;
			foreach (ISegment segment in poly.Segments)
			{
				Vertex vertex = segment.GetVertex(0);
				Vertex vertex2 = segment.GetVertex(1);
				if (vertex.id < 0 || vertex.id >= count)
				{
					num++;
					instance.Warning($"Segment {num2} has invalid startpoint.", "PolygonValidator.IsConsistent()");
				}
				if (vertex2.id < 0 || vertex2.id >= count)
				{
					num++;
					instance.Warning($"Segment {num2} has invalid endpoint.", "PolygonValidator.IsConsistent()");
				}
				num2++;
			}
			return num;
		}

		private static int CheckDuplicateIDs(IPolygon poly)
		{
			HashSet<int> hashSet = new HashSet<int>();
			foreach (Vertex point in poly.Points)
			{
				if (!hashSet.Add(point.id))
				{
					Log.Instance.Warning("Found duplicate vertex ids.", "PolygonValidator.IsConsistent()");
					return 1;
				}
			}
			return 0;
		}
	}
}