using System.Collections.Generic;
using UnityEngine;
using UnityEngine.Rendering;

namespace NGS.MeshFusionPro;

public class MeshSeparatorSimple
{
	private const int MAX_UV_CHANNELS = 4;

	private static Dictionary<Mesh, Mesh[]> _meshToSubmeshes;

	private static List<Vector3> _srcVertices;

	private static List<Vector3> _srcNormals;

	private static List<Vector4> _srcTangents;

	private static List<Vector2> _srcUV;

	private static List<int> _triangles;

	private static List<Vector3> _vertices;

	private static List<Vector3> _normals;

	private static List<Vector4> _tangents;

	private static List<Vector2> _uv;

	static MeshSeparatorSimple()
	{
		_meshToSubmeshes = new Dictionary<Mesh, Mesh[]>();
		_srcVertices = new List<Vector3>();
		_srcNormals = new List<Vector3>();
		_srcTangents = new List<Vector4>();
		_srcUV = new List<Vector2>();
		_triangles = new List<int>();
		_vertices = new List<Vector3>();
		_normals = new List<Vector3>();
		_tangents = new List<Vector4>();
		_uv = new List<Vector2>();
	}

	public Mesh GetSubmesh(Mesh source, int submesh)
	{
		if (!_meshToSubmeshes.TryGetValue(source, out var value))
		{
			value = Separate(source);
			_meshToSubmeshes.Add(source, value);
		}
		return value[submesh];
	}

	private Mesh[] Separate(Mesh mesh)
	{
		int subMeshCount = mesh.subMeshCount;
		Mesh[] array = new Mesh[subMeshCount];
		CollectMeshData(mesh);
		for (int i = 0; i < subMeshCount; i++)
		{
			array[i] = CreateFromSubmesh(mesh, i);
		}
		ClearData();
		return array;
	}

	private void CollectMeshData(Mesh mesh)
	{
		mesh.GetVertices(_srcVertices);
		mesh.GetNormals(_srcNormals);
		mesh.GetTangents(_srcTangents);
	}

	private Mesh CreateFromSubmesh(Mesh mesh, int submesh)
	{
		SubMeshDescriptor subMesh = mesh.GetSubMesh(submesh);
		Mesh mesh2 = new Mesh();
		int indexCount = subMesh.indexCount;
		int vertexCount = subMesh.vertexCount;
		int firstVertex = subMesh.firstVertex;
		int num = firstVertex + vertexCount;
		_vertices.Clear();
		_normals.Clear();
		_tangents.Clear();
		mesh.GetIndices(_triangles, submesh);
		for (int i = firstVertex; i < num; i++)
		{
			_vertices.Add(_srcVertices[i]);
			_normals.Add(_srcNormals[i]);
			_tangents.Add(_srcTangents[i]);
		}
		for (int j = 0; j < indexCount; j++)
		{
			_triangles[j] -= firstVertex;
		}
		mesh2.SetVertices(_vertices);
		mesh2.SetNormals(_normals);
		mesh2.SetTangents(_tangents);
		mesh2.SetTriangles(_triangles, 0, calculateBounds: false);
		mesh2.bounds = subMesh.bounds;
		for (int k = 0; k < 4; k++)
		{
			mesh.GetUVs(k, _srcUV);
			if (_srcUV.Count != 0)
			{
				_uv.Clear();
				for (int l = firstVertex; l < num; l++)
				{
					_uv.Add(_srcUV[l]);
				}
				mesh2.SetUVs(k, _uv);
			}
		}
		return mesh2;
	}

	private void ClearData()
	{
		_srcVertices.Clear();
		_srcNormals.Clear();
		_srcTangents.Clear();
		_srcUV.Clear();
		_triangles.Clear();
		_vertices.Clear();
		_normals.Clear();
		_tangents.Clear();
		_uv.Clear();
	}
}