using System;
using System.Collections.Generic;
using System.Linq;
using Collections.Pooled;
using Encompass.Exceptions;

namespace Encompass
{
    class ComponentMessageManager
    {
        private readonly Dictionary<Guid, IComponent> componentIDToComponent = new Dictionary<Guid, IComponent>();
        private readonly Dictionary<Guid, Type> componentIDToType = new Dictionary<Guid, Type>();

        private readonly Dictionary<Guid, Guid> componentIDToEntityID = new Dictionary<Guid, Guid>();
        
        private readonly Dictionary<Type, HashSet<Guid>> componentMessageTypeToExistingComponentIDs = new Dictionary<Type, HashSet<Guid>>();
        private readonly Dictionary<Type, HashSet<Guid>> componentMessageTypeToPendingComponentIDs = new Dictionary<Type, HashSet<Guid>>();
        private readonly Dictionary<Type, HashSet<Guid>> componentMessageTypeToComponentIDs = new Dictionary<Type, HashSet<Guid>>();

        private readonly Dictionary<Entity, PooledDictionary<Type, Guid>> entityToTypeToExistingComponentID = new Dictionary<Entity, PooledDictionary<Type, Guid>>();
        private readonly Dictionary<Entity, PooledDictionary<Type, Guid>> entityToTypeToPendingComponentID = new Dictionary<Entity, PooledDictionary<Type, Guid>>();
        private readonly Dictionary<Entity, PooledDictionary<Type, Guid>> entityToTypeToComponentID = new Dictionary<Entity, PooledDictionary<Type, Guid>>();

        internal void RegisterEntity(Entity entity)
        {
            entityToTypeToComponentID[entity] = new PooledDictionary<Type, Guid>();
            entityToTypeToPendingComponentID[entity] = new PooledDictionary<Type, Guid>();
            entityToTypeToExistingComponentID[entity] = new PooledDictionary<Type, Guid>();
        }

        internal void RegisterDestroyedEntity(Entity entity)
        {
            entityToTypeToComponentID[entity].Dispose();
            entityToTypeToComponentID.Remove(entity);

            entityToTypeToPendingComponentID[entity].Dispose();
            entityToTypeToPendingComponentID.Remove(entity);

            entityToTypeToExistingComponentID[entity].Dispose();
            entityToTypeToExistingComponentID.Remove(entity);
        }

        internal void ClearMessages()
        {
            componentIDToComponent.Clear();
            componentIDToType.Clear();
            componentIDToEntityID.Clear();

            foreach (var set in componentMessageTypeToExistingComponentIDs.Values)
            {
                set.Clear();
            }

            foreach (var set in componentMessageTypeToPendingComponentIDs.Values)
            {
                set.Clear();
            }

            foreach (var set in componentMessageTypeToComponentIDs.Values)
            {
                set.Clear();
            }

            foreach (var dictionary in entityToTypeToExistingComponentID.Values)
            {
                dictionary.Clear();
            }

            foreach (var dictionary in entityToTypeToPendingComponentID.Values)
            {
                dictionary.Clear();
            }

            foreach (var dictionary in entityToTypeToComponentID.Values)
            {
                dictionary.Clear();
            }
        }

        internal void AddExistingComponentMessage<TComponent>(ComponentMessage<TComponent> componentMessage) where TComponent : struct, IComponent
        {
            RegisterExistingOrPendingComponentMessage(componentMessage.entity, componentMessage.componentID, componentMessage.component);

            if (!componentMessageTypeToExistingComponentIDs.ContainsKey(typeof(TComponent)))
            {
                componentMessageTypeToExistingComponentIDs.Add(typeof(TComponent), new HashSet<Guid>());
            }

            componentMessageTypeToExistingComponentIDs[typeof(TComponent)].Add(componentMessage.componentID);

            if (!entityToTypeToExistingComponentID[componentMessage.entity].ContainsKey(typeof(TComponent)))
            {
                entityToTypeToExistingComponentID[componentMessage.entity].Add(typeof(TComponent), componentMessage.componentID);
            }
            else
            {
                throw new MultipleComponentOfSameTypeException("Entity {0} cannot have multiple components of type {1}", componentMessage.entity.ID, typeof(TComponent).Name);
            }
        }

        internal void AddPendingComponentMessage<TComponent>(PendingComponentMessage<TComponent> pendingComponentMessage) where TComponent : struct, IComponent
        {
            RegisterExistingOrPendingComponentMessage(pendingComponentMessage.entity, pendingComponentMessage.componentID, pendingComponentMessage.component);

            if (!componentMessageTypeToPendingComponentIDs.ContainsKey(typeof(TComponent)))
            {
                componentMessageTypeToPendingComponentIDs.Add(typeof(TComponent), new HashSet<Guid>());
            }

            componentMessageTypeToPendingComponentIDs[typeof(TComponent)].Add(pendingComponentMessage.componentID);

            if (!entityToTypeToPendingComponentID[pendingComponentMessage.entity].ContainsKey(typeof(TComponent)))
            {
                entityToTypeToPendingComponentID[pendingComponentMessage.entity].Add(typeof(TComponent), pendingComponentMessage.componentID);
            }
            else
            {
                throw new MultipleComponentOfSameTypeException("Entity {0} cannot have multiple components of type {1}", pendingComponentMessage.entity.ID, typeof(TComponent).Name);
            }
        }

        private void RegisterExistingOrPendingComponentMessage<TComponent>(Entity entity, Guid componentID, TComponent component) where TComponent: struct, IComponent
        {
            componentIDToComponent[componentID] = component;
            componentIDToEntityID[componentID] = entity.ID;
            componentIDToType[componentID] = typeof(TComponent);
            
            if (!componentMessageTypeToComponentIDs.ContainsKey(typeof(TComponent)))
            {
                componentMessageTypeToComponentIDs.Add(typeof(TComponent), new HashSet<Guid>());
            }
            componentMessageTypeToComponentIDs[typeof(TComponent)].Add(componentID);

            entityToTypeToComponentID[entity][typeof(TComponent)] = componentID;
        }

        // general component reads by type

        internal IEnumerable<(Guid, TComponent)> ReadExistingAndPendingComponentsByType<TComponent>() where TComponent : struct, IComponent
        {
            if (componentMessageTypeToComponentIDs.TryGetValue(typeof(TComponent), out HashSet<Guid> idSet))
            {
                return idSet.Select(id => (id, (TComponent)componentIDToComponent[id]));
            }

            return Enumerable.Empty<(Guid, TComponent)>();
        }

        internal IEnumerable<(Guid, TComponent)> ReadExistingComponentsByType<TComponent>() where TComponent: struct, IComponent
        {
            if (componentMessageTypeToExistingComponentIDs.TryGetValue(typeof(TComponent), out HashSet<Guid> idSet))
            {
                return idSet.Select(id => (id, (TComponent)componentIDToComponent[id]));
            }

            return Enumerable.Empty<(Guid, TComponent)>();
        }

        internal IEnumerable<(Guid, TComponent)> ReadPendingComponentsByType<TComponent>() where TComponent : struct, IComponent
        {
            if (componentMessageTypeToPendingComponentIDs.TryGetValue(typeof(TComponent), out HashSet<Guid> idSet))
            {
                return idSet.Select(id => (id, (TComponent)componentIDToComponent[id]));
            }

            return Enumerable.Empty<(Guid, TComponent)>();
        }

        // singular component reads by type

        internal (Guid, TComponent) ReadFirstExistingOrPendingComponentByType<TComponent>() where TComponent : struct, IComponent
        {
            return ReadExistingAndPendingComponentsByType<TComponent>().First();
        }

        internal (Guid, TComponent) ReadFirstExistingComponentByType<TComponent>() where TComponent : struct, IComponent
        {
            return ReadExistingComponentsByType<TComponent>().First();
        }

        internal (Guid, TComponent) ReadFirstPendingComponentByType<TComponent>() where TComponent : struct, IComponent
        {
            return ReadPendingComponentsByType<TComponent>().First();
        }

        // check if some component of type exists in the world

        internal bool SomeExistingOrPendingComponent<TComponent>() where TComponent : struct, IComponent
        {
            if (componentMessageTypeToComponentIDs.TryGetValue(typeof(TComponent), out HashSet<Guid> idSet))
            {
                return idSet.Count > 0;
            }

            return false;
        }

        internal bool SomeExistingComponent<TComponent>() where TComponent : struct, IComponent
        {
            if (componentMessageTypeToExistingComponentIDs.TryGetValue(typeof(TComponent), out HashSet<Guid> idSet))
            {
                return idSet.Count > 0;
            }

            return false;
        }

        internal bool SomePendingComponent<TComponent>() where TComponent : struct, IComponent
        {
            if (componentMessageTypeToPendingComponentIDs.TryGetValue(typeof(TComponent), out HashSet<Guid> idSet))
            {
                return idSet.Count > 0;
            }

            return false;
        }

        // read components by entity and type

        internal (Guid, TComponent) ReadExistingComponentByEntityAndType<TComponent>(Entity entity) where TComponent : struct, IComponent
        {
            if (entityToTypeToExistingComponentID.ContainsKey(entity) && entityToTypeToExistingComponentID[entity].TryGetValue(typeof(TComponent), out Guid id))
            {
                return (id, (TComponent)componentIDToComponent[id]);
            }
            else
            {
                throw new NoComponentOfTypeOnEntityException("No Component of type {0} exists on Entity {1}", typeof(TComponent).Name, entity.ID);
            }
        }

        internal (Guid, TComponent) ReadPendingComponentByEntityAndType<TComponent>(Entity entity) where TComponent : struct, IComponent
        {
            if (entityToTypeToPendingComponentID.ContainsKey(entity) && entityToTypeToPendingComponentID[entity].TryGetValue(typeof(TComponent), out Guid id))
            {
                return (id, (TComponent)componentIDToComponent[id]);
            }
            else
            {
                throw new NoComponentOfTypeOnEntityException("No Component of type {0} exists on Entity {1}", typeof(TComponent).Name, entity.ID);
            }
        }

        // check if entity has component of type

        internal bool HasExistingOrPendingComponent<TComponent>(Entity entity) where TComponent : struct, IComponent
        {
            return entityToTypeToComponentID.ContainsKey(entity) && entityToTypeToComponentID[entity].ContainsKey(typeof(TComponent));
        }

        internal bool HasExistingComponent<TComponent>(Entity entity) where TComponent : struct, IComponent
        {
            return entityToTypeToExistingComponentID.ContainsKey(entity) && entityToTypeToExistingComponentID[entity].ContainsKey(typeof(TComponent));
        }

        internal bool HasPendingComponent<TComponent>(Entity entity) where TComponent : struct, IComponent
        {
            return entityToTypeToPendingComponentID.ContainsKey(entity) && entityToTypeToPendingComponentID[entity].ContainsKey(typeof(TComponent));
        }

        internal IComponent GetComponentByID(Guid componentID)
        {
            return componentIDToComponent[componentID];
        }

        internal Type GetComponentTypeByID(Guid componentID)
        {
            return componentIDToType[componentID];
        }

        internal Guid GetEntityIDByComponentID(Guid componentID)
        {
            return componentIDToEntityID[componentID];
        }
    }
}