using System.Collections.Generic;

namespace Encompass
{
    public abstract class Renderer
    {
        internal EntityManager _entityManager;
        internal ComponentManager _componentManager;

        internal void AssignEntityManager(EntityManager entityManager)
        {
            _entityManager = entityManager;
        }

        internal void AssignComponentManager(ComponentManager componentManager)
        {
            _componentManager = componentManager;
        }

        protected IEnumerable<Entity> ReadEntities<TComponent>() where TComponent : struct
        {
            foreach (var pair in ReadComponentsIncludingEntity<TComponent>())
            {
                yield return pair.Item2;
            }
        }

        protected Entity ReadEntity<TComponent>() where TComponent : struct
        {
            return ReadComponentIncludingEntity<TComponent>().Item2;
        }

        protected IEnumerable<TComponent> ReadComponents<TComponent>() where TComponent : struct
        {
            return _componentManager.GetComponentsByType<TComponent>();
        }

        protected IEnumerable<(TComponent, Entity)> ReadComponentsIncludingEntity<TComponent>() where TComponent : struct
        {
            foreach (var (component, id) in _componentManager.GetComponentsIncludingEntity<TComponent>())
            {
                yield return (component, _entityManager.GetEntity(id));
            }
        }

        protected TComponent ReadComponent<TComponent>() where TComponent : struct
        {
            var enumerator = ReadComponents<TComponent>().GetEnumerator();
            enumerator.MoveNext();
            return enumerator.Current;
        }

        protected (TComponent, Entity) ReadComponentIncludingEntity<TComponent>() where TComponent : struct
        {
            var enumerator = ReadComponentsIncludingEntity<TComponent>().GetEnumerator();
            enumerator.MoveNext();
            return enumerator.Current;
        }

        protected ref readonly TComponent GetComponent<TComponent>(Entity entity) where TComponent : struct
        {
            return ref _componentManager.GetComponentByEntityAndType<TComponent>(entity.ID);
        }

        protected bool HasComponent<TComponent>(Entity entity) where TComponent : struct
        {
            return _componentManager.EntityHasComponentOfType<TComponent>(entity.ID);
        }

        protected bool SomeComponent<TComponent>() where TComponent : struct
        {
            return _componentManager.SomeExistingComponent<TComponent>();
        }
    }
}