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

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

        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, Dictionary<Type, HashSet<Guid>>> entityToTypeToExistingComponentIDs = new Dictionary<Entity, Dictionary<Type, HashSet<Guid>>>();
        private readonly Dictionary<Entity, Dictionary<Type, HashSet<Guid>>> entityToTypeToPendingComponentIDs = new Dictionary<Entity, Dictionary<Type, HashSet<Guid>>>();
        private readonly Dictionary<Entity, Dictionary<Type, HashSet<Guid>>> entityToTypeToComponentIDs = new Dictionary<Entity, Dictionary<Type, HashSet<Guid>>>();

        internal void ClearMessages()
        {
            componentIDToComponent.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 entityToTypeToExistingComponentIDs.Values)
            {
                foreach (var set in dictionary.Values)
                {
                    set.Clear();
                }
            }

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

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

        internal void RegisterDestroyedEntity(Entity entity)
        {
            entityToTypeToComponentIDs.Remove(entity);
            entityToTypeToPendingComponentIDs.Remove(entity);
            entityToTypeToExistingComponentIDs.Remove(entity);
        }

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

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

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

            if (!entityToTypeToExistingComponentIDs.ContainsKey(componentMessage.entity))
            {
                entityToTypeToExistingComponentIDs.Add(componentMessage.entity, new Dictionary<Type, HashSet<Guid>>());
            }
            if (!entityToTypeToExistingComponentIDs[componentMessage.entity].ContainsKey(typeof(TComponent)))
            {
                entityToTypeToExistingComponentIDs[componentMessage.entity].Add(typeof(TComponent), new HashSet<Guid>());
            }

            entityToTypeToExistingComponentIDs[componentMessage.entity][typeof(TComponent)].Add(componentMessage.componentID);
        }

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

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

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

            if (!entityToTypeToPendingComponentIDs.ContainsKey(pendingComponentMessage.entity))
            {
                entityToTypeToPendingComponentIDs.Add(pendingComponentMessage.entity, new Dictionary<Type, HashSet<Guid>>());
            }
            if (!entityToTypeToPendingComponentIDs[pendingComponentMessage.entity].ContainsKey(typeof(TComponent)))
            {
                entityToTypeToPendingComponentIDs[pendingComponentMessage.entity].Add(typeof(TComponent), new HashSet<Guid>());
            }

            entityToTypeToPendingComponentIDs[pendingComponentMessage.entity][typeof(TComponent)].Add(pendingComponentMessage.componentID);
        }

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

        // general component reads by type

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

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

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

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

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

            return false;
        }

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

            return false;
        }

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

            return false;
        }

        // read components by entity and type

        internal IEnumerable<(Guid, TComponent)> ReadExistingAndPendingComponentsByEntityAndType<TComponent>(Entity entity) where TComponent : struct, IComponent
        {
            HashSet<Guid> idSet;
            if (entityToTypeToComponentIDs.ContainsKey(entity) && entityToTypeToComponentIDs[entity].TryGetValue(typeof(TComponent), out idSet))
            {
                return idSet.Select(id => (id, (TComponent)componentIDToComponent[id]));
            }

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

        internal IEnumerable<(Guid, TComponent)> ReadExistingComponentsByEntityAndType<TComponent>(Entity entity) where TComponent : struct, IComponent
        {
            HashSet<Guid> idSet;
            if (entityToTypeToExistingComponentIDs.ContainsKey(entity) && entityToTypeToExistingComponentIDs[entity].TryGetValue(typeof(TComponent), out idSet))
            {
                return idSet.Select(id => (id, (TComponent)componentIDToComponent[id]));
            }

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

        internal IEnumerable<(Guid, TComponent)> ReadPendingComponentsByEntityAndType<TComponent>(Entity entity) where TComponent : struct, IComponent
        {
            HashSet<Guid> idSet;
            if (entityToTypeToPendingComponentIDs.ContainsKey(entity) && entityToTypeToPendingComponentIDs[entity].TryGetValue(typeof(TComponent), out idSet))
            {
                return idSet.Select(id => (id, (TComponent)componentIDToComponent[id]));
            }

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

        // singular read components by entity and type

        internal (Guid, TComponent) ReadFirstExistingOrPendingComponentByEntityAndType<TComponent>(Entity entity) where TComponent : struct, IComponent
        {
            return ReadExistingAndPendingComponentsByEntityAndType<TComponent>(entity).First();
        }

        internal (Guid, TComponent) ReadFirstExistingComponentByEntityAndType<TComponent>(Entity entity) where TComponent : struct, IComponent
        {
            return ReadExistingComponentsByEntityAndType<TComponent>(entity).First();
        }

        internal (Guid, TComponent) ReadFirstPendingComponentByEntityAndType<TComponent>(Entity entity) where TComponent : struct, IComponent
        {
            return ReadPendingComponentsByEntityAndType<TComponent>(entity).First();
        }

        // check if entity has component of type

        internal bool HasExistingOrPendingComponent<TComponent>(Entity entity) where TComponent : struct, IComponent
        {
            HashSet<Guid> idSet;
            if (entityToTypeToComponentIDs.TryGetValue(entity, out _) && entityToTypeToComponentIDs[entity].TryGetValue(typeof(TComponent), out idSet))
            {
                return idSet.Count > 0;
            }

            return false;
        }

        internal bool HasExistingComponent<TComponent>(Entity entity) where TComponent : struct, IComponent
        {
            HashSet<Guid> idSet;
            if (entityToTypeToExistingComponentIDs.TryGetValue(entity, out _) && entityToTypeToExistingComponentIDs[entity].TryGetValue(typeof(TComponent), out idSet))
            {
                return idSet.Count > 0;
            }

            return false;
        }

        internal bool HasPendingComponent<TComponent>(Entity entity) where TComponent : struct, IComponent
        {
            HashSet<Guid> idSet;
            if (entityToTypeToPendingComponentIDs.TryGetValue(entity, out _) && entityToTypeToPendingComponentIDs[entity].TryGetValue(typeof(TComponent), out idSet))
            {
                return idSet.Count > 0;
            }

            return false;
        }
    }
}