#region License Information
/* HeuristicLab
 * Copyright (C) 2002-2015 Heuristic and Evolutionary Algorithms Laboratory (HEAL)
 *
 * This file is part of HeuristicLab.
 *
 * HeuristicLab is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * HeuristicLab is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with HeuristicLab. If not, see <http://www.gnu.org/licenses/>.
 */
#endregion

using System;
using System.Collections.Generic;
using System.Linq;
using Google.Protobuf;

namespace HeuristicLab.Persistence {
  public sealed class Mapper {
    internal class MappingEqualityComparer : IEqualityComparer<object> {
      bool IEqualityComparer<object>.Equals(object x, object y) {
        if (x == null && y == null) return true;
        if (x == null ^ y == null) return false;
        if (x.GetType() != y.GetType()) return false;

        var type = x.GetType();
        if (type.IsValueType || type == typeof(string)) return x.Equals(y);
        return object.ReferenceEquals(x, y);
      }

      int IEqualityComparer<object>.GetHashCode(object obj) {
        return obj == null ? 0 : obj.GetHashCode();
      }
    }

    private static StaticCache staticCache;
    private static object locker = new object();
    public static StaticCache StaticCache {
      get {
        lock (locker) {
          if (staticCache == null) staticCache = new StaticCache();
          return staticCache;
        }
      }
    }

    private Index<ITransformer> transformers;
    private Index<Type> types;

    private Dictionary<uint, Box> boxId2Box;
    private Dictionary<object, uint> object2BoxId;
    private Dictionary<uint, object> boxId2Object;
    private Index<string> strings;

    public uint BoxCount { get; private set; }

    public Mapper() {
      transformers = new Index<ITransformer>();
      types = new Index<Type>();

      boxId2Box = new Dictionary<uint, Box>();
      object2BoxId = new Dictionary<object, uint>(new MappingEqualityComparer());
      boxId2Object = new Dictionary<uint, object>();
      strings = new Index<string>();

      BoxCount = 0;
    }

    #region Transformers
    public uint GetTransformerId(ITransformer transformer) {
      return transformers.GetIndex(transformer);
    }

    public ITransformer GetTransformer(uint transformerId) {
      return transformers.GetValue(transformerId);
    }
    #endregion

    #region Types
    public uint GetTypeId(Type type) {
      return types.GetIndex(type);
    }

    public Type GetType(uint typeId) {
      return types.GetValue(typeId);
    }
    #endregion

    #region Boxes
    public uint GetBoxId(object o) {
      uint boxId;

      if (o == null)
        boxId = 0;
      else {
        if (object2BoxId.TryGetValue(o, out boxId)) return boxId;
        var type = o.GetType();
        var typeInfo = StaticCache.GetTypeInfo(type);
        if (typeInfo.Transformer == null) throw new ArgumentException("Cannot serialize object of type " + o.GetType());
        boxId = ++BoxCount;
        typeInfo.Used++;
        object2BoxId.Add(o, boxId);
        boxId2Box.Add(boxId, typeInfo.Transformer.ToBox(o, this));
      }
      return boxId;
    }

    public Box GetBox(uint boxId) {
      return boxId2Box[boxId];
    }

    public object GetObject(uint boxId) {
      object o;
      if (boxId2Object.TryGetValue(boxId, out o)) return o;

      Box box;
      boxId2Box.TryGetValue(boxId, out box);

      if (box == null)
        o = null;
      else {
        var transformer = transformers.GetValue(box.TransformerId);
        o = transformer.ToObject(box, this);
        boxId2Object.Add(boxId, o);
        transformer.FillFromBox(o, box, this);
      }

      return o;
    }
    #endregion

    #region Strings
    public uint GetStringId(string str) {
      return strings.GetIndex(str);
    }
    public string GetString(uint stringId) {
      return strings.GetValue(stringId);
    }
    #endregion

    public object CreateInstance(Type type) {
      try {
        return StaticCache.GetTypeInfo(type).GetConstructor()();
      } catch (Exception e) {
        throw new PersistenceException("Deserialization failed.", e);
      }
    }

    public static Bundle ToBundle(object o) {
      var mapper = new Mapper();
      var bundle = new Bundle();

      bundle.RootBoxId = mapper.GetBoxId(o);
      bundle.TransformerGuids.AddRange(mapper.transformers.GetValues().Select(x => x.Guid).Select(x => ByteString.CopyFrom(x.ToByteArray())));
      bundle.TypeGuids.AddRange(mapper.types.GetValues().Select(x => ByteString.CopyFrom(StaticCache.GetGuid(x).ToByteArray())));
      bundle.Boxes.AddRange(mapper.boxId2Box.OrderBy(x => x.Key).Select(x => x.Value));
      bundle.Strings.AddRange(mapper.strings.GetValues());

      return bundle;
    }
    public static object ToObject(Bundle bundle) {
      var mapper = new Mapper();

      mapper.transformers = new Index<ITransformer>(bundle.TransformerGuids.Select(x => new Guid(x.ToByteArray())).Select(StaticCache.GetTransformer));
      mapper.types = new Index<Type>(bundle.TypeGuids.Select(x => StaticCache.GetType(new Guid(x.ToByteArray()))));
      mapper.boxId2Box = bundle.Boxes.Select((b, i) => new { Box = b, Index = i }).ToDictionary(k => (uint)k.Index + 1, v => v.Box);
      mapper.strings = new Index<string>(bundle.Strings);

      return mapper.GetObject(bundle.RootBoxId);
    }
  }
}