using MoonTools.ECS;
using Nerfed.Runtime.Components;
using Nerfed.Runtime.Util;
using System.Numerics;

namespace Nerfed.Runtime.Systems
{
    public class LocalToWorldThreadedSystem : MoonTools.ECS.System
    {
        private readonly Filter rootEntitiesFilter;
        private readonly Action<int> forEntity;

        public LocalToWorldThreadedSystem(World world) : base(world)
        {
            rootEntitiesFilter = FilterBuilder.Include<LocalTransform>().Exclude<Child>().Build();
            forEntity = UpdateEntity;
        }

        public override void Update(TimeSpan delta)
        {
            Parallel.For(0, rootEntitiesFilter.Count, forEntity);
        }

        private void UpdateEntity(int entityFilterIndex)
        {
            Entity entity = rootEntitiesFilter.NthEntity(entityFilterIndex);
            UpdateWorldTransform(entity, Matrix4x4.Identity);
        }

        private void UpdateWorldTransform(Entity entity, Matrix4x4 localToWorldMatrix)
        {
            // TODO: Only update dirty transforms.
            // If a parent is dirty all the children need to update their localToWorld matrix.
            // How do we check if something is dirty? How do we know if a LocalTransform has been changed?

            if (Has<LocalTransform>(entity))
            {
                LocalTransform localTransform = Get<LocalTransform>(entity);
                localToWorldMatrix = Matrix4x4.Multiply(localToWorldMatrix, localTransform.TRS());
                LocalToWorld localToWorld = new(localToWorldMatrix);
                Set(entity, localToWorld);
                //Task.Delay(10).Wait();
                //Log.Info($"Entity {entity} | local position {localTransform.position} | world position {localToWorldMatrix.Translation}");
            }

            ReverseSpanEnumerator<Entity> childEntities = World.InRelations<ChildParentRelation>(entity);
            foreach (Entity childEntity in childEntities)
            {
                UpdateWorldTransform(childEntity, localToWorldMatrix);
            }
        }
    }
}


//System.Random rnd = new System.Random();

//World world = new World();
//Filter filter = world.FilterBuilder.Include<Test>().Build();

//for (int i = 0; i < 100; i++)
//{
//    Entity e = world.CreateEntity(i.ToString());
//    world.Set(e, new Test());
//}

//Action<int> forEntityIndex = ForEntityIndex;
//ParallelLoopResult result = Parallel.For(0, filter.Count, forEntityIndex);
//Console.WriteLine(result.IsCompleted);

//void ForEntityIndex(int entity)
//{
//    int delay = rnd.Next(1, 1000);
//    Task.Delay(delay).Wait();
//    Console.WriteLine($"ForEntityIndex | {filter.NthEntity(entity).ID}");
//}

//namespace Hoi
//{
//    public readonly record struct Test;
//}