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

namespace Assets.ThoMagic.Renderer
{
    public class DrawCall
    {
        public readonly Mesh Mesh;
        public readonly Material[] Materials;
        public readonly RenderParams[] RenderParams;
        private readonly Matrix4x4 _localToWorldMatrix;
        private readonly uint baseIndirectArgsIndex;
        private readonly int lodNr;
        public DrawCall(
          int lodNr,
          Mesh mesh,
          Material[] materials,
          Matrix4x4 localToWorldMatrix,
          uint baseIndirectArgsIndex,
          List<GraphicsBuffer.IndirectDrawIndexedArgs> indirectDrawIndexedArgs,
          in RenderParams renderParams)
        {            
            if (mesh == null)
                throw new ArgumentNullException(nameof(mesh));
            if (materials == null)
                throw new ArgumentNullException(nameof(materials));
            if (materials.Length != mesh.subMeshCount)
                throw new IndexOutOfRangeException(nameof(materials));

            this.baseIndirectArgsIndex = baseIndirectArgsIndex;
            _localToWorldMatrix = localToWorldMatrix;
            Mesh = mesh;
            Materials = materials;
            RenderParams = new RenderParams[mesh.subMeshCount];

            this.lodNr = lodNr;

            for (int index = 0; index < mesh.subMeshCount; ++index)
            {
                RenderParams[index] = renderParams;
                RenderParams[index].material = materials[index];
                RenderParams[index].matProps = new MaterialPropertyBlock();
                RenderParams[index].matProps.SetMatrix("trInstanceMatrix", _localToWorldMatrix);
                RenderParams[index].matProps.SetInteger("trLodNr", lodNr + 1);
                
                RenderParams[index].worldBounds = new Bounds(Vector3.zero, 1000f * Vector3.one);

                indirectDrawIndexedArgs.Add(new GraphicsBuffer.IndirectDrawIndexedArgs
                {
                    indexCountPerInstance = mesh.GetIndexCount(index),
                    baseVertexIndex = mesh.GetBaseVertex(index),
                    startIndex = mesh.GetIndexStart(index),
                    startInstance = 0,
                    instanceCount = 0
                });
            }
        }

        public virtual void SetInstances(ComputeBuffer instances, ComputeBuffer visibleIndexBuffer, ComputeBuffer metaBuffer)
        {
            for (int index = 0; index < this.RenderParams.Length; ++index)
            {
                RenderParams[index].matProps.SetBuffer("trInstances", instances);
                RenderParams[index].matProps.SetBuffer("trPerCamVisibleIndexesBuffer", visibleIndexBuffer);
                RenderParams[index].matProps.SetBuffer("trPerCamMeta", metaBuffer);                
            }
        }

        public virtual void Draw(Camera camera, ObjectData obj, GraphicsBuffer indirectDrawIndexedArgs)
        {
            if (Materials == null)
                throw new ObjectDisposedException("Materials");

            if (Mesh == null)
                throw new ObjectDisposedException("Mesh");

            var bounds = new Bounds(camera.transform.position, Vector3.one * 1000f);

            for (int index = 0; index < RenderParams.Length; ++index)
            {
                var renderParam = RenderParams[index];
                if (renderParam.material != null)
                {
                    renderParam.camera = camera;
                    renderParam.worldBounds = bounds;
                    Graphics.RenderMeshIndirect(in renderParam, Mesh, indirectDrawIndexedArgs, 1, obj.indirectArgsPerSubmeshOffsets[(int)baseIndirectArgsIndex + index]);                    
                }
            }
        }

        internal virtual void Dispose()
        {

        }
    }
}