using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.InteropServices;
using System.Text;
using System.Threading.Tasks;
using Xenko.Core.Mathematics;
using Xenko.Engine;
using Xenko.Graphics;
using Xenko.Input;
using Xenko.Rendering;
using MeshExtensions;
using Buffer = Xenko.Graphics.Buffer;

namespace LoadMesh
{
    public class LoadMeshScript : AsyncScript
    {
        [StructLayout(LayoutKind.Sequential, Pack = 4)]
        public struct MyVertex : IVertex
        {
            Vector3 Position;
            Vector3 Normal;

            public static readonly VertexDeclaration Layout =
                new VertexDeclaration(VertexElement.Position<Vector3>(), VertexElement.Normal<Vector3>());

            public void FlipWinding()
            {
                throw new NotImplementedException();
            }

            public VertexDeclaration GetLayout()
            {
                return Layout;
            }
        }

        public Model TargetModel;

        public override async Task Execute()
        {
            var processedTargetModel = false;
            var processedTargetUrl = false;

            while(Game.IsRunning)
            {
                await Script.NextFrame();

                // Modelから読み込む
                if (!processedTargetModel && Input.IsKeyPressed(Keys.M))
                {
                    AddEntity(new Vector3(-5, 5, 0), Content.GetMeshData<MyVertex>(TargetModel));
                    processedTargetModel = true;
                }

                // アセットURLから読み込む
                if (!processedTargetUrl && Input.IsKeyPressed(Keys.U))
                {
                    if (Content.TryGetAssetUrl(TargetModel, out var url))
                    {
                        AddEntity(new Vector3(5, 5, 0), Content.GetMeshData<MyVertex>(url));
                    }
                    processedTargetUrl = true;
                }
            }
        }

        public void AddEntity(Vector3 position, VertexAndIndexExtensions.MeshData<MyVertex, int> meshData)
        {
            // 取得したmeshDataからModelを再現する(Skeletonは考慮されていない)

            if (meshData == null)
            {
                return;
            }

            var vertexBufferList = new List<Buffer>();
            var indexBufferList = new List<Buffer>();
            var is32Bit = meshData.IndexStride == sizeof(int);

            foreach (var vertices in meshData.Vertices)
            {
                vertexBufferList.Add(Buffer.Vertex.New(GraphicsDevice, vertices));
            }
            foreach (var indices in meshData.Indices)
            {
                indexBufferList.Add(Buffer.Index.New(GraphicsDevice, indices));
            }

            var newModel = new Model();

            foreach (var meshInfo in meshData.MeshInfos)
            {
                var vertexBufferBinginds = new VertexBufferBinding[meshInfo.VertexBufferInfos.Length];
                for (int i = 0; i < vertexBufferBinginds.Length; ++i)
                {
                    vertexBufferBinginds[i] = new VertexBufferBinding(vertexBufferList[meshInfo.VertexBufferInfos[i].BufferIndex], MyVertex.Layout, meshInfo.VertexBufferInfos[i].Count, meshData.VertexStride, meshInfo.VertexBufferInfos[i].Offset);
                }

                var indexBufferBinding = new IndexBufferBinding(indexBufferList[meshInfo.IndexBufferInfo.BufferIndex], is32Bit, meshInfo.IndexBufferInfo.Count, meshInfo.IndexBufferInfo.Offset);

                var meshDraw = new MeshDraw
                {
                    PrimitiveType = PrimitiveType.TriangleList,
                    VertexBuffers = vertexBufferBinginds,
                    IndexBuffer = indexBufferBinding,
                    StartLocation = 0,
                    DrawCount = meshInfo.IndexBufferInfo.Count,
                };

                newModel.Meshes.Add(new Mesh { Draw = meshDraw, });
            }

            var entity = new Entity(position);
            entity.Add(new ModelComponent(newModel));

            SceneSystem.SceneInstance.RootScene.Entities.Add(entity);
        }
    }
}