using System;
using Svelto.ECS.Internal;

namespace Svelto.ECS
{
    public interface IEntityViewBuilder
    {
        void BuildEntityViewAndAddToList(ref ITypeSafeList list, int entityID, out IEntityView entityView);
        ITypeSafeList Preallocate(ref ITypeSafeList list, int size);

        Type GetEntityViewType();
        void MoveEntityView(int entityID, ITypeSafeList fromSafeList, ITypeSafeList toSafeList);
    }

    public class EntityViewBuilder<EntityViewType> : IEntityViewBuilder where EntityViewType : EntityView, new()
    {
        public void BuildEntityViewAndAddToList(ref ITypeSafeList list, int entityID, out IEntityView entityView)
        {
            if (list == null)
                list = new TypeSafeFasterListForECSForClasses<EntityViewType>();

            var castedList = list as TypeSafeFasterListForECSForClasses<EntityViewType>;

            var lentityView = EntityView<EntityViewType>.BuildEntityView(entityID);

            castedList.Add(lentityView);

            entityView = lentityView;
        }

        public ITypeSafeList Preallocate(ref ITypeSafeList list, int size)
        {
            if (list == null)
                list = new TypeSafeFasterListForECSForClasses<EntityViewType>(size);
            else
                list.ReserveCapacity(size);

            return list;
        }

        public Type GetEntityViewType()
        {
            return _entityViewType;
        }

        public void MoveEntityView(int entityID, ITypeSafeList fromSafeList, ITypeSafeList toSafeList)
        {
            var fromCastedList = fromSafeList as TypeSafeFasterListForECSForClasses<EntityViewType>;
            var toCastedList = toSafeList as TypeSafeFasterListForECSForClasses<EntityViewType>;

            toCastedList.Add(fromCastedList[entityID]);
        }

        readonly Type _entityViewType = typeof(EntityViewType);
    }

    public class EntityStructBuilder<EntityViewType> : IEntityViewBuilder where EntityViewType : struct, IEntityStruct
    {
        public void BuildEntityViewAndAddToList(ref ITypeSafeList list, int entityID, out IEntityView entityView)
        {
            var lentityView = default(EntityViewType);
            lentityView.ID = entityID;
            
            if (list == null)
                list = new TypeSafeFasterListForECSForStructs<EntityViewType>();

            var castedList = list as TypeSafeFasterListForECSForStructs<EntityViewType>;

            castedList.Add(lentityView);

            entityView = null;
        }

        public ITypeSafeList Preallocate(ref ITypeSafeList list, int size)
        {
            if (list == null)
                list = new TypeSafeFasterListForECSForStructs<EntityViewType>(size);
            else
                list.ReserveCapacity(size);

            return list;
        }

        public Type GetEntityViewType()
        {
            return _entityViewType;
        }

        public void MoveEntityView(int entityID, ITypeSafeList fromSafeList, ITypeSafeList toSafeList)
        {
            var fromCastedList = fromSafeList as TypeSafeFasterListForECSForStructs<EntityViewType>;
            var toCastedList = toSafeList as TypeSafeFasterListForECSForStructs<EntityViewType>;

            toCastedList.Add(fromCastedList[entityID]);
        }

        readonly Type _entityViewType = typeof(EntityViewType);
    }    
}