using System.Collections.Generic;

namespace Encompass
{
    internal abstract class TypedMessageStore
    {
        public abstract void ProcessDelayedMessages(double dilatedDelta, double realtimeDelta);
        public abstract void Clear();
    }

    internal class TypedMessageStore<TMessage> : TypedMessageStore where TMessage : struct, IMessage
    {
        private readonly List<int> _indices = new List<int>();
        private readonly TMessage[] _store = new TMessage[128];
        private readonly List<(TMessage, double)> _delayedStore = new List<(TMessage, double)>(128);
        private readonly List<(TMessage, double)> _delayedStoreIgnoringTimeDilation = new List<(TMessage, double)>(128);
        private readonly Dictionary<int, HashSet<int>> _entityToIndices = new Dictionary<int, HashSet<int>>();
        private readonly IDManager _idManager = new IDManager();

        public override void ProcessDelayedMessages(double dilatedDelta, double realtimeDelta)
        {
            for (var i = _delayedStore.Count - 1; i >= 0; i--)
            {
                var (message, time) = _delayedStore[i];

                var updatedTime = time - dilatedDelta;

                if (updatedTime <= 0)
                {
                    Add(message);
                    _delayedStore.RemoveAt(i);
                }
                else
                {
                    _delayedStore[i] = (message, updatedTime);
                }
            }

            for (var i = _delayedStoreIgnoringTimeDilation.Count - 1; i >= 0; i--)
            {
                var (message, time) = _delayedStoreIgnoringTimeDilation[i];

                var updatedTime = time - realtimeDelta;

                if (updatedTime <= 0)
                {
                    Add(message);
                    _delayedStoreIgnoringTimeDilation.RemoveAt(i);
                }
                else
                {
                    _delayedStoreIgnoringTimeDilation[i] = (message, updatedTime);
                }
            }
        }

        public void Add(in TMessage message)
        {
            var index = _idManager.NextID();
            _indices.Add(index);
            _store[index] = message;
            if (message is IHasEntity entityMessage)
            {
                var entityID = entityMessage.Entity.ID;
                if (!_entityToIndices.ContainsKey(entityID)) { _entityToIndices.Add(entityID, new HashSet<int>()); }
                _entityToIndices[entityID].Add(index);
            }
        }

        public void Add(in TMessage message, double time)
        {
            _delayedStore.Add((message, time));
        }

        public void AddIgnoringTimeDilation(in TMessage message, double time)
        {
            _delayedStoreIgnoringTimeDilation.Add((message, time));
        }

        public TMessage First()
        {
            return _store[_indices[0]];
        }

        public bool Any()
        {
            return _indices.Count > 0;
        }

        public IEnumerable<TMessage> All()
        {
            foreach (var index in _indices)
            {
                yield return _store[index];
            }
        }

        public IEnumerable<TMessage> WithEntity(int entityID)
        {
            if (_entityToIndices.ContainsKey(entityID))
            {
                foreach (var index in _entityToIndices[entityID])
                {
                    yield return _store[index];
                }
            }
        }

        public bool SomeWithEntity(int entityID)
        {
            return _entityToIndices.ContainsKey(entityID) && _entityToIndices[entityID].Count > 0;
        }

        public override void Clear()
        {
            _indices.Clear();
            foreach (var set in _entityToIndices.Values)
            {
                set.Clear();
            }
        }
    }
}