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

namespace Encompass
{
    internal struct EntitySetQuery
    {
        private BitSet WithImmediateMask { get; }
        private BitSet WithExistingMask { get; }
        private BitSet WithoutImmediateMask { get; }
        private BitSet WithoutExistingMask { get; }
        private BitSet NotWithMask { get; }

        internal EntitySetQuery(BitSet withImmediateMask, BitSet withExistingMask, BitSet withoutImmediateMask, BitSet withoutExistingMask, BitSet notWithMask)
        {
            WithImmediateMask = withImmediateMask;
            WithExistingMask = withExistingMask;
            WithoutImmediateMask = withoutImmediateMask;
            WithoutExistingMask = withoutExistingMask;
            NotWithMask = notWithMask;
        }

        public IEnumerable<Entity> FilterEntities(IEnumerable<Entity> entities, ComponentBitSet immediateBitLookup, ComponentBitSet existingBitLookup)
        {
            foreach (var entity in entities)
            {
                var immediateBits = immediateBitLookup.EntityBitArray(entity.ID);
                var existingBits = existingBitLookup.EntityBitArray(entity.ID);

                var immediate = WithImmediateMask.And(immediateBits);
                var existing = WithExistingMask.And(existingBits);
                var withCheck = immediate.Or(existing).Or(NotWithMask);

                var immediateForbidden = WithoutImmediateMask.And(immediateBits).Not();
                var existingForbidden = WithoutExistingMask.And(existingBits).Not();
                var withoutCheck = immediateForbidden.And(existingForbidden);

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