using System;
using System.Collections;
using System.Collections.Generic;
using Svelto.Common;
using Svelto.DataStructures;
using Svelto.ECS.Internal;
using Svelto.ECS.Schedulers;

namespace Svelto.ECS
{
    public sealed partial class EnginesRoot
    {
        public struct EntitiesSubmitter
        {
            public EntitiesSubmitter(EnginesRoot enginesRoot) : this()
            {
                _weakReference = new Svelto.DataStructures.WeakReference<EnginesRoot>(enginesRoot);
            }

            public bool IsUnused => _weakReference.IsValid == false;

            public IEnumerator Invoke(uint maxNumberOfOperationsPerFrame)
            {
                var entitiesSubmissionScheduler = _weakReference.Target._scheduler;
                if (_weakReference.IsValid && entitiesSubmissionScheduler.paused == false)
                {
                    var submitEntityComponents =
                        _weakReference.Target.SubmitEntityComponents(maxNumberOfOperationsPerFrame);
                    DBC.ECS.Check.Require(entitiesSubmissionScheduler.isRunning == false
                                        , "A submission started while the previous one was still flushing");
                    entitiesSubmissionScheduler.isRunning = true;
                    while (submitEntityComponents.MoveNext() == true)
                        yield return null;

                    entitiesSubmissionScheduler.isRunning = false;
                    ++entitiesSubmissionScheduler.iteration;
                }
            }

            readonly Svelto.DataStructures.WeakReference<EnginesRoot> _weakReference;
        }

        readonly EntitiesSubmissionScheduler _scheduler;
        public   EntitiesSubmissionScheduler scheduler => _scheduler;

        /// <summary>
        /// Engines root contextualize your engines and entities. You don't need to limit yourself to one EngineRoot
        /// as multiple engines root could promote separation of scopes. The EntitySubmissionScheduler checks
        /// periodically if new entity must be submitted to the database and the engines. It's an external
        /// dependencies to be independent by the running platform as the user can define it.
        /// The EntitySubmissionScheduler cannot hold an EnginesRoot reference, that's why
        /// it must receive a weak reference of the EnginesRoot callback.
        /// </summary>
        public EnginesRoot(EntitiesSubmissionScheduler entitiesComponentScheduler)
        {
            _entitiesOperations                = new FasterDictionary<ulong, EntitySubmitOperation>();
            serializationDescriptorMap         = new SerializationDescriptorMap();
            _reactiveEnginesAddRemove          = new FasterDictionary<RefWrapperType, FasterList<IReactEngine>>();
            _reactiveEnginesAddRemoveOnDispose = new FasterDictionary<RefWrapperType, FasterList<IReactEngine>>();
            _reactiveEnginesSwap               = new FasterDictionary<RefWrapperType, FasterList<IReactEngine>>();
            _reactiveEnginesSubmission         = new FasterList<IReactOnSubmission>();
            _enginesSet                        = new FasterList<IEngine>();
            _enginesTypeSet                    = new HashSet<Type>();
            _disposableEngines                 = new FasterList<IDisposable>();
            _transientEntitiesOperations       = new FasterList<EntitySubmitOperation>();

            _groupEntityComponentsDB =
                new FasterDictionary<ExclusiveGroupStruct, FasterDictionary<RefWrapperType, ITypeSafeDictionary>>();
            _groupsPerEntity =
                new FasterDictionary<RefWrapperType, FasterDictionary<ExclusiveGroupStruct, ITypeSafeDictionary>>();
            _groupedEntityToAdd = new DoubleBufferedEntitiesToAdd();

            _entityStreams = EntitiesStreams.Create();
            _groupFilters =
                new FasterDictionary<RefWrapperType, FasterDictionary<ExclusiveGroupStruct, GroupFilters>>();
            _entitiesDB = new EntitiesDB(this);

            _scheduler        = entitiesComponentScheduler;
            _scheduler.onTick = new EntitiesSubmitter(this);
#if UNITY_NATIVE
            AllocateNativeOperations();
#endif
        }

        public EnginesRoot
            (EntitiesSubmissionScheduler entitiesComponentScheduler, bool isDeserializationOnly) :
            this(entitiesComponentScheduler)
        {
            _isDeserializationOnly = isDeserializationOnly;
        }

        /// <summary>
        /// Dispose an EngineRoot once not used anymore, so that all the
        /// engines are notified with the entities removed.
        /// It's a clean up process.
        /// </summary>
        public void Dispose()
        {
            _isDisposing = true;

            using (var profiler = new PlatformProfiler("Final Dispose"))
            {
                //Note: The engines are disposed before the the remove callback to give the chance to behave
                //differently if a remove happens as a consequence of a dispose
                //The pattern is to implement the IDisposable interface and set a flag in the engine. The 
                //remove callback will then behave differently according the flag.
                foreach (var engine in _disposableEngines)
                {
                    try
                    {
                        if (engine is IDisposingEngine dengine)
                            dengine.isDisposing = true;
                        engine.Dispose();
                    }
                    catch (Exception e)
                    {
                        Svelto.Console.LogException(e);
                    }
                }

                foreach (var groups in _groupEntityComponentsDB)
                {
                    foreach (var entityList in groups.Value)
                        try
                        {
                            entityList.Value.ExecuteEnginesRemoveCallbacks(_reactiveEnginesAddRemoveOnDispose, profiler
                                                                         , new ExclusiveGroupStruct(groups.Key));
                        }
                        catch (Exception e)
                        {
                            Svelto.Console.LogException(e);
                        }
                }

                foreach (var groups in _groupEntityComponentsDB)
                {
                    foreach (var entityList in groups.Value)
                        entityList.Value.Dispose();
                }

                foreach (var type in _groupFilters)
                    foreach (var group in type.Value)
                        group.Value.Dispose();

                _groupFilters.Clear();

#if UNITY_NATIVE
                _addOperationQueue.Dispose();
                _removeOperationQueue.Dispose();
                _swapOperationQueue.Dispose();
#endif
                _groupEntityComponentsDB.Clear();
                _groupsPerEntity.Clear();

                _disposableEngines.Clear();
                _enginesSet.Clear();
                _enginesTypeSet.Clear();
                _reactiveEnginesSwap.Clear();
                _reactiveEnginesAddRemove.Clear();
                _reactiveEnginesAddRemoveOnDispose.Clear();
                _reactiveEnginesSubmission.Clear();

                _entitiesOperations.Clear();
                _transientEntitiesOperations.Clear();

                _groupedEntityToAdd.Dispose();
                _entityStreams.Dispose();
                scheduler.Dispose();
            }

            GC.SuppressFinalize(this);
        }

        ~EnginesRoot()
        {
            Console.LogWarning("Engines Root has been garbage collected, don't forget to call Dispose()!");

            Dispose();
        }

        public void AddEngine(IEngine engine)
        {
            var type       = engine.GetType();
            var refWrapper = new RefWrapperType(type);
            DBC.ECS.Check.Require(engine != null, "Engine to add is invalid or null");
            DBC.ECS.Check.Require(
                _enginesTypeSet.Contains(refWrapper) == false
             || type.ContainsCustomAttribute(typeof(AllowMultipleAttribute)) == true
              , "The same engine has been added more than once, if intentional, use [AllowMultiple] class attribute "
                   .FastConcat(engine.ToString()));
            try
            {
                if (engine is IReactOnAddAndRemove viewEngine)
                    CheckReactEngineComponents(viewEngine, _reactiveEnginesAddRemove);

                if (engine is IReactOnDispose viewEngineDispose)
                    CheckReactEngineComponents(viewEngineDispose, _reactiveEnginesAddRemoveOnDispose);

                if (engine is IReactOnSwap viewEngineSwap)
                    CheckReactEngineComponents(viewEngineSwap, _reactiveEnginesSwap);

                if (engine is IReactOnSubmission submissionEngine)
                    _reactiveEnginesSubmission.Add(submissionEngine);

                _enginesTypeSet.Add(refWrapper);
                _enginesSet.Add(engine);

                if (engine is IDisposable)
                    _disposableEngines.Add(engine as IDisposable);

                if (engine is IQueryingEntitiesEngine queryableEntityComponentEngine)
                {
                    queryableEntityComponentEngine.entitiesDB = _entitiesDB;
                    queryableEntityComponentEngine.Ready();
                }
            }
            catch (Exception e)
            {
                throw new ECSException("Code crashed while adding engine ".FastConcat(engine.GetType().ToString(), " ")
                                     , e);
            }
        }

        void CheckReactEngineComponents<T>(T engine, FasterDictionary<RefWrapperType, FasterList<IReactEngine>> engines)
            where T : class, IReactEngine
        {
            var interfaces = engine.GetType().GetInterfaces();

            foreach (var interf in interfaces)
            {
                if (interf.IsGenericTypeEx() && typeof(T).IsAssignableFrom(interf))
                {
                    var genericArguments = interf.GetGenericArgumentsEx();

                    AddEngineToList(engine, genericArguments, engines);
                }
            }
        }

        static void AddEngineToList<T>
            (T engine, Type[] entityComponentTypes, FasterDictionary<RefWrapperType, FasterList<IReactEngine>> engines)
            where T : class, IReactEngine
        {
            for (var i = 0; i < entityComponentTypes.Length; i++)
            {
                var type = entityComponentTypes[i];

                if (engines.TryGetValue(new RefWrapperType(type), out var list) == false)
                {
                    list = new FasterList<IReactEngine>();

                    engines.Add(new RefWrapperType(type), list);
                }

                list.Add(engine);
            }
        }

        readonly FasterDictionary<RefWrapperType, FasterList<IReactEngine>> _reactiveEnginesAddRemove;
        readonly FasterDictionary<RefWrapperType, FasterList<IReactEngine>> _reactiveEnginesAddRemoveOnDispose;
        readonly FasterDictionary<RefWrapperType, FasterList<IReactEngine>> _reactiveEnginesSwap;
        readonly FasterList<IReactOnSubmission>                             _reactiveEnginesSubmission;
        readonly FasterList<IDisposable>                                    _disposableEngines;
        readonly FasterList<IEngine>                                        _enginesSet;
        readonly HashSet<Type>                                              _enginesTypeSet;
        internal bool                                                       _isDisposing;
    }
}