using MoonTools.ECS;
using Nerfed.Runtime.Components;

namespace Nerfed.Runtime.Systems
{
    //public class ParentSystem : MoonTools.ECS.System
    //{
    //    private readonly Filter parentsAddedFilter;
    //    private readonly Filter parentsRemovedFilter;
    //    private readonly Filter parentsFilter;

    //    public ParentSystem(World world) : base(world)
    //    {
    //        parentsAddedFilter = FilterBuilder.Include<Parent>().Exclude<PreviousParent>().Build();
    //        parentsRemovedFilter = FilterBuilder.Include<PreviousParent>().Exclude<Parent>().Build();
    //        parentsFilter = FilterBuilder.Include<Parent>().Include<PreviousParent>().Build();
    //    }

    //    public override void Update(TimeSpan delta)
    //    {
    //        // Update removed parents.
    //        foreach (Entity entity in parentsRemovedFilter.Entities)
    //        {
    //            // Do stuff here to update/remove child relations etc.
    //            //PreviousParent previousParent = Get<PreviousParent>(entity);
    //            //World.Unrelate<ChildParentRelation>(previousParent.parentEntity, entity);
    //            Remove<PreviousParent>(entity);
    //        }

    //        // Update added parents.
    //        foreach (Entity entity in parentsAddedFilter.Entities)
    //        {
    //            Parent parent = Get<Parent>(entity);

    //            if (Has<Parent>(parent.parentEntity) && Get<Parent>(parent.parentEntity).parentEntity == entity)
    //            {
    //                Log.Warning($"Entity {entity} cannot be a parent of entity {parent.parentEntity}, because {parent.parentEntity} is the parent of {entity}");
    //                Remove<Parent>(entity);
    //                continue;
    //            }

    //            PreviousParent previousParent = new(parent.parentEntity);
    //            Set(entity, previousParent);
    //            World.Relate(parent.parentEntity, entity, new ChildParentRelation());
    //        }

    //        // Update relations if the parent has changed.
    //        foreach (Entity entity in parentsFilter.Entities)
    //        {
    //            Parent parent = Get<Parent>(entity);
    //            PreviousParent previousParent = Get<PreviousParent>(entity);

    //            if(parent.parentEntity != previousParent.parentEntity)
    //            {
    //                World.Unrelate<ChildParentRelation>(previousParent.parentEntity, entity);
    //                Set(entity, new PreviousParent(parent.parentEntity));
    //                World.Relate(parent.parentEntity, entity, new ChildParentRelation());
    //            }
    //        }

    //        // TODO:
    //        // What if an parent entity gets destroyed?
    //        // How does the child know if the parent is in valid. Also we need to remove the parent component.
    //        // Maybe if we also relate the other way around child -> parent via relations, and the relation is gone that means the parent is gone so we should remove the component.
    //    }
    //}
}