using System.Collections.Generic;
using System.Linq;

namespace Encompass
{
    internal class ComponentManager
    {
        private readonly DrawLayerManager drawLayerManager;
        private readonly ComponentUpdateManager componentUpdateManager;

        private readonly ComponentStore componentStore = new ComponentStore();
        private readonly HashSet<Entity> entitiesMarkedForRemoval = new HashSet<Entity>();

        public ComponentManager(DrawLayerManager drawLayerManager, ComponentUpdateManager componentUpdateManager)
        {
            this.drawLayerManager = drawLayerManager;
            this.componentUpdateManager = componentUpdateManager;
        }

        internal void SetComponentStore(ComponentStore componentStore)
        {
            this.componentStore.SwapWith(componentStore);
        }

        internal void RegisterDrawableComponent<TComponent>(Entity entity, TComponent component, int layer) where TComponent : struct, IComponent
        {
            drawLayerManager.RegisterComponentWithLayer(entity, component, layer);
        }

        internal void AddComponent<TComponent>(Entity entity, TComponent component) where TComponent : struct, IComponent
        {
            componentStore.Set(entity, component);
        }

        internal void WriteComponents()
        {
            componentStore.SwapWith(componentUpdateManager.UpToDateComponentStore);
        }

        internal IEnumerable<(TComponent, Entity)> GetComponentsIncludingEntity<TComponent>() where TComponent : struct, IComponent
        {
            return componentStore.All<TComponent>().Select(pair => (pair.Item2, pair.Item1));
        }

        internal IEnumerable<TComponent> GetComponentsByType<TComponent>() where TComponent : struct, IComponent
        {
            return componentStore.All<TComponent>().Select(pair => pair.Item2);
        }

        internal TComponent GetComponentByEntityAndType<TComponent>(Entity entity) where TComponent : struct, IComponent
        {
            return componentStore.Get<TComponent>(entity);
        }

        internal bool EntityHasComponentOfType<TComponent>(Entity entity) where TComponent : struct, IComponent
        {
            return componentStore.Has<TComponent>(entity);
        }

        internal bool ComponentOfTypeExists<TComponent>() where TComponent : struct, IComponent
        {
            return componentStore.Any<TComponent>();
        }

        internal void MarkAllComponentsOnEntityForRemoval(Entity entity)
        {
            entitiesMarkedForRemoval.Add(entity);
        }

        internal void RemoveMarkedComponents()
        {
            foreach (var entity in entitiesMarkedForRemoval)
            {
                componentStore.Remove(entity);
                drawLayerManager.UnRegisterEntityWithLayer(entity);
            }

            entitiesMarkedForRemoval.Clear();
        }

        public void Remove<TComponent>(Entity entity) where TComponent : struct, IComponent
        {
            componentUpdateManager.Remove<TComponent>(entity);
            drawLayerManager.UnRegisterComponentWithLayer<TComponent>(entity);
        }
    }
}