namespace Mapbox.Unity.MeshGeneration.Modifiers
{
	using System.Collections.Generic;
	using UnityEngine;
	using Mapbox.Unity.MeshGeneration.Data;
	using System;

	[CreateAssetMenu(menuName = "Mapbox/Modifiers/Smooth Height for Buildings Modifier")]
	public class ChamferHeightModifier : MeshModifier
	{
		[SerializeField]
		[Tooltip("Flatten top polygons to prevent unwanted slanted roofs because of the bumpy terrain")]
		private bool _flatTops;
		[SerializeField]
		[Tooltip("Fixed height value for ForceHeight option")]
		private float _height;
		[SerializeField]
		[Tooltip("Fix all features to certain height, suggested to be used for pushing roads above terrain level to prevent z-fighting.")]
		private bool _forceHeight;
		[SerializeField]
		[Range(0.1f,2)]
		[Tooltip("Chamfer width value")]
		private float _offset = 0.2f;

		public override ModifierType Type { get { return ModifierType.Preprocess; } }

		public override void Run(VectorFeatureUnity feature, MeshData md, UnityTile tile = null)
		{
			if (md.Vertices.Count == 0 || feature == null || feature.Points.Count < 1)
				return;

			var minHeight = 0f;
			float hf = _height;

			if (!_forceHeight)
			{
				GetHeightData(feature, tile.TileScale, ref minHeight, ref hf);
			}

			var max = md.Vertices[0].y;
			var min = md.Vertices[0].y;
			if (_flatTops)
			{
				FlattenTops(md, minHeight, ref hf, ref max, ref min);
			}
			else
			{
				for (int i = 0; i < md.Vertices.Count; i++)
				{
					md.Vertices[i] = new Vector3(md.Vertices[i].x, md.Vertices[i].y + minHeight + hf, md.Vertices[i].z);
				}
			}

			var originalVertexCount = md.Vertices.Count;
			Chamfer(feature, md, tile);

			Sides(feature, md, hf, originalVertexCount);
		}

		private void Sides(VectorFeatureUnity feature, MeshData meshData, float hf, int originalVertexCount)
		{


			float d = 0f;
			Vector3 v1;
			Vector3 v2 = Mapbox.Unity.Constants.Math.Vector3Zero;
			int ind = 0;

			var wallTri = new List<int>();
			var wallUv = new List<Vector2>();
			meshData.Vertices.Add(new Vector3(meshData.Vertices[originalVertexCount - 1].x, meshData.Vertices[originalVertexCount - 1].y - hf, meshData.Vertices[originalVertexCount - 1].z));
			meshData.Tangents.Add(meshData.Tangents[originalVertexCount - 1]);
			wallUv.Add(new Vector2(0, -hf));
			meshData.Normals.Add(meshData.Normals[originalVertexCount - 1]);

			for (int i = 0; i < meshData.Edges.Count; i += 2)
			{
				v1 = meshData.Vertices[meshData.Edges[i]];
				v2 = meshData.Vertices[meshData.Edges[i + 1]];
				ind = meshData.Vertices.Count;
				meshData.Vertices.Add(v1);
				meshData.Vertices.Add(v2);
				meshData.Vertices.Add(new Vector3(v1.x, v1.y - hf, v1.z));
				meshData.Vertices.Add(new Vector3(v2.x, v2.y - hf, v2.z));

				meshData.Normals.Add(meshData.Normals[meshData.Edges[i]]);
				meshData.Normals.Add(meshData.Normals[meshData.Edges[i + 1]]);
				meshData.Normals.Add(meshData.Normals[meshData.Edges[i]]);
				meshData.Normals.Add(meshData.Normals[meshData.Edges[i + 1]]);

				meshData.Tangents.Add(v2 - v1.normalized);
				meshData.Tangents.Add(v2 - v1.normalized);
				meshData.Tangents.Add(v2 - v1.normalized);
				meshData.Tangents.Add(v2 - v1.normalized);

				d = (v2 - v1).magnitude;

				wallUv.Add(new Vector2(0, 0));
				wallUv.Add(new Vector2(d, 0));
				wallUv.Add(new Vector2(0, -hf));
				wallUv.Add(new Vector2(d, -hf));

				wallTri.Add(ind);
				wallTri.Add(ind + 1);
				wallTri.Add(ind + 2);

				wallTri.Add(ind + 1);
				wallTri.Add(ind + 3);
				wallTri.Add(ind + 2);
			}

			meshData.Triangles.Add(wallTri);
			meshData.UV[0].AddRange(wallUv);
		}

		private static void FlattenTops(MeshData meshData, float minHeight, ref float hf, ref float max, ref float min)
		{
			for (int i = 0; i < meshData.Vertices.Count; i++)
			{
				if (meshData.Vertices[i].y > max)
					max = meshData.Vertices[i].y;
				else if (meshData.Vertices[i].y < min)
					min = meshData.Vertices[i].y;
			}
			for (int i = 0; i < meshData.Vertices.Count; i++)
			{
				meshData.Vertices[i] = new Vector3(meshData.Vertices[i].x, max + minHeight + hf, meshData.Vertices[i].z);
			}
			hf += max - min;
		}

		private static void GetHeightData(VectorFeatureUnity feature, float scale, ref float minHeight, ref float hf)
		{
			if (feature.Properties.ContainsKey("height"))
			{
				hf = Convert.ToSingle(feature.Properties["height"]);
				hf *= scale;
				if (feature.Properties.ContainsKey("min_height"))
				{
					minHeight = Convert.ToSingle(feature.Properties["min_height"]) * scale;
					hf -= minHeight;
				}

			}
			if (feature.Properties.ContainsKey("ele"))
			{
				hf = Convert.ToSingle(feature.Properties["ele"]);
				hf *= scale;
			}
		}

		public void Chamfer(VectorFeatureUnity feature, MeshData md, UnityTile tile = null)
		{
			if (md.Vertices.Count == 0 || feature.Points.Count < 1)
				return;

			List<Vector3> newVertices = new List<Vector3>();
			List<Vector2> newUV = new List<Vector2>();
			md.Normals.Clear();
			md.Edges.Clear();
			md.Tangents.Clear();

			for (int t = 0; t < md.Triangles[0].Count; t++)
			{
				md.Triangles[0][t] *= 3;
			}

			var next = 0; var current = 0; var prev = 0;
			Vector3 v1, v2, n1, n2, pij1, pij2, pjk1, pjk2;
			Vector3 poi, close1, close2;

			var start = 0;
			for (int i = 0; i < feature.Points.Count; i++)
			{
				var count = feature.Points[i].Count;
				var cst = newVertices.Count;
				for (int j = 0; j < count; j++)
				{
					if (j == count - 1)
					{
						newVertices.Add(newVertices[cst]);
						newVertices.Add(newVertices[cst + 1]);
						newVertices.Add(newVertices[cst + 2]);
						newUV.Add(newUV[cst]);
						newUV.Add(newUV[cst + 1]);
						newUV.Add(newUV[cst + 2]);
						md.Normals.Add(md.Normals[cst]);
						md.Normals.Add(md.Normals[cst + 1]);
						md.Normals.Add(md.Normals[cst + 2]);

						md.Tangents.Add(md.Tangents[cst]);
						md.Tangents.Add(md.Tangents[cst + 1]);
						md.Tangents.Add(md.Tangents[cst + 2]);

						continue;
					}

					current = start + j;
					if (j > 0)
						next = start + j - 1;
					else
						next = start + j - 1 + count - 1; //another -1  as last item equals first
					prev = start + j + 1;


					v1 = new Vector3(
							md.Vertices[current].x - md.Vertices[next].x, 0,
							md.Vertices[current].z - md.Vertices[next].z);
					v1.Normalize();
					v1 *= -_offset;
					n1 = new Vector3(-v1.z, 0, v1.x);

					pij1 = new Vector3(
						(float)(md.Vertices[next].x + n1.x), 0,
						(float)(md.Vertices[next].z + n1.z));
					pij2 = new Vector3(
						(float)(md.Vertices[current].x + n1.x), 0,
						(float)(md.Vertices[current].z + n1.z));

					v2 = new Vector3(
						md.Vertices[prev].x - md.Vertices[current].x, 0,
						md.Vertices[prev].z - md.Vertices[current].z);

					v2.Normalize();
					v2 *= -_offset;
					n2 = new Vector3(-v2.z, 0, v2.x);
					pjk1 = new Vector3(
						(float)(md.Vertices[current].x + n2.x), 0,
						(float)(md.Vertices[current].z + n2.z));
					pjk2 = new Vector3(
						(float)(md.Vertices[prev].x + n2.x), 0,
						(float)(md.Vertices[prev].z + n2.z));

					// See where the shifted lines ij and jk intersect.
					bool lines_intersect, segments_intersect;

					FindIntersection(pij1, pij2, pjk1, pjk2,
						out lines_intersect, out segments_intersect,
						out poi, out close1, out close2);

					var d = Vector3.Distance(poi, pij2);
					if (d > 10 * _offset)
					{
						poi = new Vector3((md.Vertices[current].x + (poi - (-v1 - v2)).normalized.x), 0,
							(md.Vertices[current].z + (poi - (-v1 - v2)).normalized.z));
					}

					newVertices.Add(new Vector3(poi.x, poi.y + _offset + md.Vertices[current].y, poi.z));
					newVertices.Add(md.Vertices[current] + v1);
					newVertices.Add(md.Vertices[current] - v2);

					md.Normals.Add(Constants.Math.Vector3Up);
					md.Normals.Add(-n1);
					md.Normals.Add(-n2);

					md.Tangents.Add(v1 - v2);
					md.Tangents.Add(v1 - v2);
					md.Tangents.Add(v1 - v2);

					newUV.Add(md.UV[0][current]);
					newUV.Add(md.UV[0][current]);
					newUV.Add(md.UV[0][current]);

					md.Triangles[0].Add(3 * current);
					md.Triangles[0].Add(3 * current + 1);
					md.Triangles[0].Add(3 * current + 2);

					md.Edges.Add(3 * current + 2);
					md.Edges.Add(3 * current + 1);

					md.Triangles[0].Add(3 * prev);
					md.Triangles[0].Add(3 * current + 2);
					md.Triangles[0].Add(3 * prev + 1);

					md.Triangles[0].Add(3 * current);
					md.Triangles[0].Add(3 * current + 2);
					md.Triangles[0].Add(3 * prev);

					md.Edges.Add(3 * prev + 1);
					md.Edges.Add(3 * current + 2);
				}
				start += count;
			}

			md.Vertices = newVertices;
			md.UV[0] = newUV;
		}

		private List<Vector3> GetEnlargedPolygon(List<Vector3> old_points, float offset)
		{
			List<Vector3> enlarged_points = new List<Vector3>();
			int num_points = old_points.Count;
			for (int j = 0; j < num_points; j++)
			{
				// Find the new location for point j.
				// Find the points before and after j.
				int i = (j - 1);
				if (i < 0) i += num_points;
				int k = (j + 1) % num_points;

				// Move the points by the offset.
				Vector3 v1 = new Vector3(
					old_points[j].x - old_points[i].x, 0,
					old_points[j].z - old_points[i].z);
				v1.Normalize();
				v1 *= offset;
				Vector3 n1 = new Vector3(-v1.z, 0, v1.x);

				Vector3 pij1 = new Vector3(
					(float)(old_points[i].x + n1.x), 0,
					(float)(old_points[i].z + n1.z));
				Vector3 pij2 = new Vector3(
					(float)(old_points[j].x + n1.x), 0,
					(float)(old_points[j].z + n1.z));

				Vector3 v2 = new Vector3(
					old_points[k].x - old_points[j].x, 0,
					old_points[k].z - old_points[j].z);
				v2.Normalize();
				v2 *= offset;
				Vector3 n2 = new Vector3(-v2.z, 0, v2.x);

				Vector3 pjk1 = new Vector3(
					(float)(old_points[j].x + n2.x), 0,
					(float)(old_points[j].z + n2.z));
				Vector3 pjk2 = new Vector3(
					(float)(old_points[k].x + n2.x), 0,
					(float)(old_points[k].z + n2.z));

				// See where the shifted lines ij and jk intersect.
				bool lines_intersect, segments_intersect;
				Vector3 poi, close1, close2;
				FindIntersection(pij1, pij2, pjk1, pjk2,
					out lines_intersect, out segments_intersect,
					out poi, out close1, out close2);
				Debug.Assert(lines_intersect,
					"Edges " + i + "-->" + j + " and " +
					j + "-->" + k + " are parallel");

				enlarged_points.Add(poi);
			}

			return enlarged_points;
		}

		// Find the point of intersection between
		// the lines p1 --> p2 and p3 --> p4.
		private void FindIntersection(
			Vector3 p1, Vector3 p2, Vector3 p3, Vector3 p4,
			out bool lines_intersect, out bool segments_intersect,
			out Vector3 intersection,
			out Vector3 close_p1, out Vector3 close_p2)
		{
			// Get the segments' parameters.
			float dx12 = p2.x - p1.x;
			float dy12 = p2.z - p1.z;
			float dx34 = p4.x - p3.x;
			float dy34 = p4.z - p3.z;

			// Solve for t1 and t2
			float denominator = (dy12 * dx34 - dx12 * dy34);

			float t1 =
				((p1.x - p3.x) * dy34 + (p3.z - p1.z) * dx34)
					/ denominator;
			if (float.IsInfinity(t1))
			{
				// The lines are parallel (or close enough to it).
				lines_intersect = false;
				segments_intersect = false;
				intersection = new Vector3(float.NaN, 0, float.NaN);
				close_p1 = new Vector3(float.NaN, 0, float.NaN);
				close_p2 = new Vector3(float.NaN, 0, float.NaN);
				return;
			}
			lines_intersect = true;

			float t2 =
				((p3.x - p1.x) * dy12 + (p1.z - p3.z) * dx12)
					/ -denominator;

			// Find the point of intersection.
			intersection = new Vector3(p1.x + dx12 * t1, 0, p1.z + dy12 * t1);

			// The segments intersect if t1 and t2 are between 0 and 1.
			segments_intersect =
				((t1 >= 0) && (t1 <= 1) &&
				 (t2 >= 0) && (t2 <= 1));

			// Find the closest points on the segments.
			if (t1 < 0)
			{
				t1 = 0;
			}
			else if (t1 > 1)
			{
				t1 = 1;
			}

			if (t2 < 0)
			{
				t2 = 0;
			}
			else if (t2 > 1)
			{
				t2 = 1;
			}

			close_p1 = new Vector3(p1.x + dx12 * t1, 0, p1.z + dy12 * t1);
			close_p2 = new Vector3(p3.x + dx34 * t2, 0, p3.z + dy34 * t2);
		}
	}
}