#if UNITY_2017
using UnityEngine;
using System.Collections.Generic;

public static class SubMeshFix {
	private class Vertices {
		List<Vector3> verts = null;
		List<Vector2> uv1 = null;
		List<Vector2> uv2 = null;
		List<Vector2> uv3 = null;
		List<Vector2> uv4 = null;
		List<Vector3> normals = null;
		List<Vector4> tangents = null;
		List<Color32> colors = null;
		List<BoneWeight> boneWeights = null;

		public Vertices() {
			verts = new List<Vector3>();
		}

		public Vertices(Mesh aMesh) {
			verts = CreateList(aMesh.vertices);
			uv1 = CreateList(aMesh.uv);
			uv2 = CreateList(aMesh.uv2);
			uv3 = CreateList(aMesh.uv3);
			uv4 = CreateList(aMesh.uv4);
			normals = CreateList(aMesh.normals);
			tangents = CreateList(aMesh.tangents);
			colors = CreateList(aMesh.colors32);
			boneWeights = CreateList(aMesh.boneWeights);
		}

		private List<T> CreateList<T>(T[] aSource) {
			if (aSource == null || aSource.Length == 0)
				return null;
			return new List<T>(aSource);
		}

		private void Copy<T>(ref List<T> aDest, List<T> aSource, int aIndex) {
			if (aSource == null)
				return;
			if (aDest == null)
				aDest = new List<T>();
			aDest.Add(aSource[aIndex]);
		}

		public int Add(Vertices aOther, int aIndex) {
			int i = verts.Count;
			Copy(ref verts, aOther.verts, aIndex);
			Copy(ref uv1, aOther.uv1, aIndex);
			Copy(ref uv2, aOther.uv2, aIndex);
			Copy(ref uv3, aOther.uv3, aIndex);
			Copy(ref uv4, aOther.uv4, aIndex);
			Copy(ref normals, aOther.normals, aIndex);
			Copy(ref tangents, aOther.tangents, aIndex);
			Copy(ref colors, aOther.colors, aIndex);
			Copy(ref boneWeights, aOther.boneWeights, aIndex);
			return i;
		}

		public void AssignTo(Mesh aTarget) {
			aTarget.SetVertices(verts);
			if (uv1 != null) aTarget.SetUVs(0, uv1);
			if (uv2 != null) aTarget.SetUVs(1, uv2);
			if (uv3 != null) aTarget.SetUVs(2, uv3);
			if (uv4 != null) aTarget.SetUVs(3, uv4);
			if (normals != null) aTarget.SetNormals(normals);
			if (tangents != null) aTarget.SetTangents(tangents);
			if (colors != null) aTarget.SetColors(colors);
			if (boneWeights != null) aTarget.boneWeights = boneWeights.ToArray();
		}
	}

	public static Mesh GetSubmesh(this Mesh aMesh, int aSubMeshIndex) {
		if (aSubMeshIndex < 0 || aSubMeshIndex >= aMesh.subMeshCount)
			return null;
		int[] indices = aMesh.GetTriangles(aSubMeshIndex);
		Vertices source = new Vertices(aMesh);
		Vertices dest = new Vertices();
		Dictionary<int, int> map = new Dictionary<int, int>();
		int[] newIndices = new int[indices.Length];
		for (int i = 0; i < indices.Length; i++) {
			int o = indices[i];
			int n;
			if (!map.TryGetValue(o, out n)) {
				n = dest.Add(source, o);
				map.Add(o, n);
			}
			newIndices[i] = n;
		}
		Mesh m = new Mesh();
		dest.AssignTo(m);
		m.triangles = newIndices;
		return m;
	}
}
#endif