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

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

        private Dictionary<int, HashSet<Guid>> layerIndexToComponentIDs = new Dictionary<int, HashSet<Guid>>();
        private Dictionary<int, HashSet<GeneralRenderer>> layerIndexToGeneralRenderers = new Dictionary<int, HashSet<GeneralRenderer>>();

        private Dictionary<Guid, int> componentIDToLayerIndex = new Dictionary<Guid, int>();
        
        public IEnumerable<int> LayerOrder { get { return layerOrder.Values; } }

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

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

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

        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.Add(id);
            }
            else
            {
                var set = new HashSet<Guid>();
                layerIndexToComponentIDs.Add(layer, set);
                set.Add(id);
            }

            componentIDToLayerIndex[id] = layer;

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

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

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

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

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