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

namespace Encompass
{
    internal class ComponentManager
    {
        private Dictionary<uint, List<IComponent>> entityIDToComponents = new Dictionary<uint, List<IComponent>>();
        private Dictionary<IComponent, uint> componentToEntityID = new Dictionary<IComponent, uint>();

        private Dictionary<Type, List<IComponent>> activeComponents = new Dictionary<Type, List<IComponent>>();
        private Dictionary<Type, List<IComponent>> inactiveComponents = new Dictionary<Type, List<IComponent>>();

        private List<IComponent> componentsToActivate = new List<IComponent>();
        private List<IComponent> componentsToDeactivate = new List<IComponent>();
        private List<IComponent> componentsToRemove = new List<IComponent>();

        internal void AddComponent<TComponent>(uint entityID, TComponent component) where TComponent : struct, IComponent
        {
            if (!entityIDToComponents.ContainsKey(entityID))
            {
                entityIDToComponents.Add(entityID, new List<IComponent>());
            }

            entityIDToComponents[entityID].Add(component);
            componentToEntityID[component] = entityID;

            if (!activeComponents.ContainsKey(typeof(TComponent)))
            {
                activeComponents.Add(typeof(TComponent), new List<IComponent>());
                inactiveComponents.Add(typeof(TComponent), new List<IComponent>());
            }

            MarkForActivation(component);
        }

        internal IEnumerable<IComponent> GetComponentsByEntity(uint entityID)
        {
            return entityIDToComponents[entityID];
        }

        internal IEnumerable<TComponent> GetActiveComponentsByType<TComponent>() where TComponent : struct, IComponent
        {
            return activeComponents[typeof(TComponent)].Cast<TComponent>();
        }

        internal TComponent GetActiveComponentByType<TComponent>() where TComponent : struct, IComponent
        {
            return GetActiveComponentsByType<TComponent>().Single();
        }

        internal IEnumerable<TComponent> GetComponentsByEntityAndType<TComponent>(uint entityID) where TComponent : struct, IComponent
        {
            var entity_components = GetComponentsByEntity(entityID).Cast<TComponent>();
            var active_components_by_type = GetActiveComponentsByType<TComponent>();
            return entity_components.Intersect(active_components_by_type).Cast<TComponent>();
        }

        internal bool EntityHasComponentOfType<TComponent>(uint entityID) where TComponent : struct, IComponent
        {
            return GetComponentsByEntityAndType<TComponent>(entityID).Any();
        }

        /** Replaces the component with another. */
        internal void UpdateComponent<TComponent>(TComponent originalComponent, TComponent newComponent) where TComponent : struct, IComponent
        {
            var entityID = componentToEntityID[originalComponent];

            entityIDToComponents[entityID].Remove(originalComponent);
            entityIDToComponents[entityID].Add(newComponent);

            componentToEntityID.Remove(originalComponent);
            componentToEntityID.Add(newComponent, entityID);

            if (activeComponents[originalComponent.GetType()].Remove(originalComponent))
            {
                activeComponents[originalComponent.GetType()].Add(newComponent);
            }

            if (inactiveComponents[originalComponent.GetType()].Remove(originalComponent))
            {
                inactiveComponents[originalComponent.GetType()].Add(newComponent);
            }

            if (componentsToActivate.Remove(originalComponent))
            {
                componentsToActivate.Add(newComponent);
            }

            if (componentsToDeactivate.Remove(originalComponent))
            {
                componentsToDeactivate.Add(newComponent);
            }

            if (componentsToRemove.Remove(originalComponent))
            {
                componentsToRemove.Add(newComponent);
            }
        }

        internal void RemoveAllComponentsFromEntity(uint entityID)
        {
            var components = GetComponentsByEntity(entityID);

            foreach (var component in components)
            {
                activeComponents[component.GetType()].Remove(component);
                inactiveComponents[component.GetType()].Remove(component);
            }

            entityIDToComponents.Remove(entityID);
        }

        internal void MarkForActivation(IComponent component)
        {
            componentsToActivate.Add(component);
        }

        internal void MarkForDeactivation(IComponent component)
        {
            componentsToDeactivate.Add(component);
        }

        internal void MarkForRemoval(IComponent component)
        {
            componentsToRemove.Add(component);
        }

        internal void ActivateComponents()
        {
            foreach (var component in componentsToActivate)
            {
                activeComponents[component.GetType()].Add(component);
                inactiveComponents[component.GetType()].Remove(component);
            }

            componentsToActivate.Clear();
        }

        internal void DeactivateComponents()
        {
            foreach (var component in componentsToDeactivate)
            {
                activeComponents[component.GetType()].Remove(component);
                inactiveComponents[component.GetType()].Add(component);
            }
        }

        internal void RemoveComponents()
        {
            foreach (var component in componentsToRemove)
            {
                activeComponents[component.GetType()].Remove(component);
                inactiveComponents[component.GetType()].Remove(component);
            }

            componentsToRemove.Clear();
        }
    }
}