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

namespace LibMMD.Unity3D
{
    /// <summary>Owns main-thread Unity Mesh creation from background-prepared model data.</summary>
    internal static class MmdMeshBuilder
    {
        internal static IEnumerator BuildIncremental(ModelLoadPreparer.Result prepared,
            MmdModelOptions options, Action<Mesh> singleMeshCreated,
            Action<List<Mesh>, List<List<int>>> partMeshesCreated)
        {
            var slice = new MmdLoadTimeSlicer(options);
            if (!prepared.UsesParts)
            {
                var mesh = new Mesh();
                singleMeshCreated(mesh);
                mesh.vertices = prepared.Vertices;
                if (slice.ShouldYield()) yield return null;
                mesh.normals = prepared.Normals;
                if (slice.ShouldYield()) yield return null;
                mesh.uv = prepared.Uv;
                if (slice.ShouldYield()) yield return null;
                mesh.boneWeights = prepared.BoneWeights;
                if (slice.ShouldYield()) yield return null;
                mesh.subMeshCount = prepared.SubMeshTriangles.Length;
                for (var i = 0; i < prepared.SubMeshTriangles.Length; i++)
                {
                    mesh.SetTriangles(prepared.SubMeshTriangles[i], i);
                    if (slice.ShouldYield()) yield return null;
                }
                mesh.RecalculateBounds();
                yield break;
            }

            var meshes = new List<Mesh>();
            var indexes = new List<List<int>>();
            partMeshesCreated(meshes, indexes);
            foreach (var part in prepared.Parts)
            {
                var mesh = new Mesh();
                meshes.Add(mesh);
                indexes.Add(part.VertexIndexes);
                mesh.vertices = part.Vertices;
                if (slice.ShouldYield()) yield return null;
                mesh.normals = part.Normals;
                if (slice.ShouldYield()) yield return null;
                mesh.uv = part.Uv;
                if (slice.ShouldYield()) yield return null;
                mesh.boneWeights = part.BoneWeights;
                if (slice.ShouldYield()) yield return null;
                mesh.triangles = part.Triangles;
                mesh.RecalculateBounds();
                if (slice.ShouldYield()) yield return null;
            }
        }
    }
}