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

namespace Encompass
{
    internal class DrawLayerManager
    {
        private readonly object layerOrderLock = new object();

        private readonly SortedList<int, int> layerOrder = new SortedList<int, int>();

        private readonly ConcurrentDictionary<int, ConcurrentDictionary<Guid, byte>> layerIndexToComponentIDs = new ConcurrentDictionary<int, ConcurrentDictionary<Guid, byte>>();
        private readonly ConcurrentDictionary<int, ConcurrentDictionary<GeneralRenderer, byte>> layerIndexToGeneralRenderers = new ConcurrentDictionary<int, ConcurrentDictionary<GeneralRenderer, byte>>();

        private readonly ConcurrentDictionary<Guid, int> componentIDToLayerIndex = new ConcurrentDictionary<Guid, int>();

        public IEnumerable<int> LayerOrder { get { lock(layerOrderLock) { return layerOrder.Values; } } }

        public void RegisterGeneralRendererWithLayer(GeneralRenderer renderer, int layer)
        {
            if (layerIndexToGeneralRenderers.ContainsKey(layer))
            {
                var set = layerIndexToGeneralRenderers[layer];
                set[renderer] = 0;
            }
            else
            {
                var set = new ConcurrentDictionary<GeneralRenderer, byte>();
                layerIndexToGeneralRenderers[layer] = set;
                set[renderer] = 0;
            }

            lock (layerOrderLock)
            {
                if (!layerOrder.ContainsKey(layer))
                {
                    layerOrder.Add(layer, layer);
                }
            }
        }

        public void UnregisterGeneralRendererWithLayer(GeneralRenderer renderer, int layer)
        {
            if (layerIndexToGeneralRenderers.ContainsKey(layer))
            {
                layerIndexToGeneralRenderers[layer].TryRemove(renderer, out _);
            }
        }

        public void AdjustRendererLayer(GeneralRenderer renderer, int oldLayer, int newLayer)
        {
            UnregisterGeneralRendererWithLayer(renderer, oldLayer);
            RegisterGeneralRendererWithLayer(renderer, newLayer);
        }

        public void RegisterComponentWithLayer(Guid id, int layer)
        {
            if (layerIndexToComponentIDs.ContainsKey(layer))
            {
                var set = layerIndexToComponentIDs[layer];
                set[id] = 0;
            }
            else
            {
                var set = new ConcurrentDictionary<Guid, byte>();
                layerIndexToComponentIDs[layer] = set;
                set[id] = 0;
            }

            componentIDToLayerIndex[id] = layer;

            lock (layerOrderLock)
            {
                if (!layerOrder.ContainsKey(layer))
                {
                    layerOrder.Add(layer, layer);
                }
            }
        }

        public void UnRegisterComponentWithLayer(Guid id)
        {
            if (componentIDToLayerIndex.ContainsKey(id))
            {
                var layer = componentIDToLayerIndex[id];
                layerIndexToComponentIDs[layer].TryRemove(id, out _);
            }
        }

        public void AdjustComponentLayer(Guid id, int layer)
        {
            UnRegisterComponentWithLayer(id);
            RegisterComponentWithLayer(id, layer);
        }

        public IEnumerable<Guid> ComponentIDsByLayer(int layer)
        {
            return layerIndexToComponentIDs.ContainsKey(layer) ?
                layerIndexToComponentIDs[layer].Keys :
                Enumerable.Empty<Guid>();
        }

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