using System.Collections;
using System.Collections.Generic;
using Encompass.Collections;

namespace Encompass
{
    public struct EntitySetQuery : IEnumerable<Entity>
    {
        private EntityManager EntityManager { get; }
        private ComponentUpdateManager ComponentUpdateManager { get; }
        private BitSet1024 WithPendingMask { get; }
        private BitSet1024 WithExistingMask { get; }
        private BitSet1024 WithoutPendingMask { get; }
        private BitSet1024 WithoutExistingMask { get; }
        private BitSet1024 NotWithMask { get; }

        internal EntitySetQuery(EntityManager entityManager, ComponentUpdateManager componentUpdateManager, BitSet1024 withPendingMask, BitSet1024 withExistingMask, BitSet1024 withoutPendingMask, BitSet1024 withoutExistingMask, BitSet1024 notWithMask)
        {
            EntityManager = entityManager;
            ComponentUpdateManager = componentUpdateManager;
            WithPendingMask = withPendingMask;
            WithExistingMask = withExistingMask;
            WithoutPendingMask = withoutPendingMask;
            WithoutExistingMask = withoutExistingMask;
            NotWithMask = notWithMask;
        }

        public IEnumerator<Entity> GetEnumerator()
        {
            foreach (var entity in EntityManager.Entities)
            {
                var pendingBits = ComponentUpdateManager.PendingBits(entity);
                var existingBits = ComponentUpdateManager.ExistingBits(entity);

                var pending = WithPendingMask.And(pendingBits);
                var existing = WithExistingMask.And(existingBits);
                var withCheck = pending.Or(existing).Or(NotWithMask);

                var pendingForbidden = WithoutPendingMask.And(pendingBits);
                var existingForbidden = WithoutExistingMask.And(existingBits);
                var withoutCheck = pendingForbidden.And(existingForbidden);

                if (withCheck.And(withoutCheck).AllTrue()) { yield return entity; }
            }
        }

        IEnumerator IEnumerable.GetEnumerator()
        {
            return GetEnumerator();
        }
    }
}