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

namespace Encompass
{
    internal class DrawLayerManager
    {
        private readonly SortedList<int, int> _layerOrder = new SortedList<int, int>();

        private readonly Dictionary<int, Dictionary<Type, HashSet<int>>> _layerIndexToTypeToID = new Dictionary<int, Dictionary<Type, HashSet<int>>>();
        private readonly Dictionary<int, HashSet<GeneralRenderer>> _layerIndexToGeneralRenderers = new Dictionary<int, HashSet<GeneralRenderer>>(512);

        private readonly Dictionary<Type, Dictionary<int, int>> _typeToEntityToLayer = new Dictionary<Type, Dictionary<int, int>>(512);
        public IEnumerable<int> LayerOrder { get { return _layerOrder.Values; } }

        public DrawLayerManager()
        {
            RegisterDrawLayer(0);
        }

        public void RegisterDrawLayer(int layer)
        {
            if (!_layerIndexToTypeToID.ContainsKey(layer))
            {
                _layerOrder.Add(layer, layer);
                _layerIndexToGeneralRenderers.Add(layer, new HashSet<GeneralRenderer>());
                _layerIndexToTypeToID.Add(layer, new Dictionary<Type, HashSet<int>>());
            }
        }

        public void RegisterOrderedDrawable<TComponent>() where TComponent : struct
        {
            if (!_typeToEntityToLayer.ContainsKey(typeof(TComponent)))
            {
                _typeToEntityToLayer.Add(typeof(TComponent), new Dictionary<int, int>(128));
            }

            foreach (var pair in _layerIndexToTypeToID)
            {
                if (!pair.Value.ContainsKey(typeof(TComponent)))
                {
                    pair.Value.Add(typeof(TComponent), new HashSet<int>());
                }
            }
        }

        public void RegisterGeneralRendererWithLayer(GeneralRenderer renderer, int layer)
        {
            RegisterDrawLayer(layer);
            var set = _layerIndexToGeneralRenderers[layer];
            set.Add(renderer);
        }

        public void RegisterComponentWithLayer<TComponent>(int entityID, int layer) where TComponent : struct
        {
            if (!_layerIndexToTypeToID.ContainsKey(layer))
            {
                throw new UndefinedLayerException("Layer {0} is not defined. Use WorldBuilder.RegisterDrawLayer to register the layer.", layer);
            }

            if (_typeToEntityToLayer[typeof(TComponent)].ContainsKey(entityID))
            {
                if (_typeToEntityToLayer[typeof(TComponent)][entityID] != layer)
                {
                    UnRegisterComponentWithLayer<TComponent>(entityID);

                    var set = _layerIndexToTypeToID[layer][typeof(TComponent)];
                    set.Add(entityID);

                    _typeToEntityToLayer[typeof(TComponent)].Add(entityID, layer);
                }
            }
            else
            {
                var set = _layerIndexToTypeToID[layer][typeof(TComponent)];
                set.Add(entityID);

                _typeToEntityToLayer[typeof(TComponent)].Add(entityID, layer);
            }
        }

        public void UnRegisterComponentWithLayer<TComponent>(int entityID) where TComponent : struct
        {
            if (!_typeToEntityToLayer.ContainsKey(typeof(TComponent))) { return; }

            if (_typeToEntityToLayer[typeof(TComponent)].ContainsKey(entityID))
            {
                var layer = _typeToEntityToLayer[typeof(TComponent)][entityID];
                _layerIndexToTypeToID[layer][typeof(TComponent)].Remove(entityID);
            }
            _typeToEntityToLayer[typeof(TComponent)].Remove(entityID);
        }

        public void UnRegisterEntityWithLayer(int entityID)
        {
            foreach (var store in _layerIndexToTypeToID.Values)
            {
                foreach (var typeToSet in store)
                {
                    var type = typeToSet.Key;
                    var set = typeToSet.Value;

                    if (set.Contains(entityID))
                    {
                        _typeToEntityToLayer[type].Remove(entityID);
                        set.Remove(entityID);
                    }
                }
            }
        }

        public IEnumerable<GeneralRenderer> GeneralRenderersByLayer(int layer)
        {
            return _layerIndexToGeneralRenderers.ContainsKey(layer) ?
                _layerIndexToGeneralRenderers[layer] :
                Enumerable.Empty<GeneralRenderer>();
        }

        public IEnumerable<(int, Type)> AllInLayer(int layer)
        {
            foreach (var kvp in _layerIndexToTypeToID[layer])
            {
                foreach (var id in kvp.Value)
                {
                    yield return (id, kvp.Key);
                }
            }
        }
    }
}