using System.Collections.Generic;
using System;
using HeuristicLab.Persistence.Interfaces;

namespace HeuristicLab.Persistence {


  struct ParentReference { }
  delegate void Setter(object value);


  interface IAccessibleObject {
    object Obj { get; }
    Setter GetSetter(string name);
  }


  class CustomObject : IAccessibleObject {

    public object Obj { get; private set; }
    public readonly List<object> customValues;

    public CustomObject(object obj) {
      Obj = obj;
      customValues = new List<object>();
    }

    public void AddValue(object value) {
      customValues.Add(value);
    }

    public Setter GetSetter(string name) {
      int index = customValues.Count - 1;
      return value => customValues[index] = value;
    }
  }


  class CompositeObject : IAccessibleObject {

    public object Obj { get; private set; }
    public readonly Dictionary<string, DataMemberAccessor> accessorDict;

    public CompositeObject(object obj, Dictionary<string, DataMemberAccessor> accessorDict) {
      Obj = obj;
      this.accessorDict = new Dictionary<string, DataMemberAccessor>();
      foreach (KeyValuePair<string, DataMemberAccessor> pair in accessorDict) {
        this.accessorDict.Add(
          pair.Value.Name,
          pair.Value);
      }
    }

    public void SetValue(string name, object value) {
      accessorDict[name].Set(value);
      accessorDict.Remove(name);
    }

    public Setter GetSetter(string name) {
      return value => accessorDict[name].Set(value);
    }

    public void PopulateDefaultValues() {
      foreach (var pair in accessorDict) {
        pair.Value.Set(pair.Value.DefaultValue);
      }
    }
  }


  public class DeSerializer {

    private delegate void Handler(ISerializationToken token);
    private delegate void Thunk();

    private readonly Dictionary<int, object> id2obj;
    private readonly Dictionary<Type, Handler> handlers;
    private readonly Stack<IAccessibleObject> compositeStack;
    private readonly Configuration configuration;
    private readonly Dictionary<int, Type> typeIds;    
    private List<Thunk> finalFixes;

    public DeSerializer(
      IEnumerable<KeyValuePair<string, int>> typeCache,
      Configuration configuration) {
      this.configuration = configuration;
      id2obj = new Dictionary<int, object>();
      compositeStack = new Stack<IAccessibleObject>();
      handlers = new Dictionary<Type, Handler> {
                     {typeof (BeginToken), CompositeStartHandler},
                     {typeof (EndToken), CompositeEndHandler},
                     {typeof (PrimitiveToken), PrimitiveHandler},
                     {typeof (ReferenceToken), ReferenceHandler},
                     {typeof (NullReferenceToken), NullHandler}
                   };      
      typeIds = new Dictionary<int, Type>();
      foreach ( var pair in typeCache ) {
        Type type = Type.GetType(pair.Key);
        typeIds.Add(pair.Value, type);
      }
    }

    public object DeSerialize(IEnumerable<ISerializationToken> tokens) {
      finalFixes = new List<Thunk>();
      foreach (ISerializationToken token in tokens) {
        handlers[token.GetType()].Invoke(token);
      }
      foreach (Thunk fix in finalFixes) {
        fix();
      }
      return compositeStack.Pop().Obj;
    }

    private void CompositeStartHandler(ISerializationToken token) {
      BeginToken start = (BeginToken)token;
      object instance;      
      Type type = typeIds[(int)start.TypeId];
      if (configuration.GetDecomposer(type) != null) {
        instance = new ParentReference();
        compositeStack.Push(new CustomObject(instance));        
      } else {        
        instance = Activator.CreateInstance(type, true);
        Dictionary<string, DataMemberAccessor> accessorDict =
          StorableAttribute.GetAutostorableAccessors(instance);
        compositeStack.Push(new CompositeObject(instance, accessorDict));        
      }
      if ( start.Id != null )
        id2obj.Add((int)start.Id, instance);
    }

    private void CompositeEndHandler(ISerializationToken token) {
      EndToken end = (EndToken)token;
      Type type = typeIds[(int)end.TypeId];
      IDecomposer decomposer = configuration.GetDecomposer(type);
      if (decomposer != null) {
        CustomObject customObject = (CustomObject)compositeStack.Pop();
        object deserializedObject =
          decomposer.DeSerialize(customObject.customValues, type);
        if ( end.Id != null )
          id2obj[(int)end.Id] = deserializedObject;        
        SetValue(end.Name, deserializedObject);          
      } else {
        CompositeObject compositeObject = (CompositeObject)compositeStack.Pop();
        compositeObject.PopulateDefaultValues();
        SetValue(end.Name, compositeObject.Obj);
      }
    }

    private void PrimitiveHandler(ISerializationToken token) {
      PrimitiveToken primitive = (PrimitiveToken)token;
      Type type = typeIds[(int)primitive.TypeId];
      object value = configuration
        .GetFormatter(type)
        .DeSerialize(primitive.SerialData);
      if ( ! value.GetType().IsValueType )
        id2obj[(int)primitive.Id] = value;
      SetValue(primitive.Name, value);
    }

    private void ReferenceHandler(ISerializationToken token) {
      ReferenceToken reference = (ReferenceToken)token;
      object referredObject = id2obj[reference.Id];
      SetValue(reference.Name, id2obj[reference.Id]);
      if (referredObject is ParentReference) {
        Setter set = compositeStack.Peek().GetSetter(reference.Name);        
        int id = reference.Id;
        finalFixes.Add(() => set(id2obj[id]));
      } 
    }

    private void NullHandler(ISerializationToken token) {
      NullReferenceToken nil = (NullReferenceToken)token;
      SetValue(nil.Name, null);
    }

    private void SetValue(string name, object value) {
      if (compositeStack.Count == 0) {
        compositeStack.Push(new CompositeObject(value, new Dictionary<string, DataMemberAccessor>()));
      } else {
        object accessibleObject = compositeStack.Peek();
        if (accessibleObject is CompositeObject) {
          ((CompositeObject)accessibleObject).SetValue(name, value);
        } else if (accessibleObject is CustomObject) {
          ((CustomObject)accessibleObject).AddValue(value);
        }
      }
    }
  }
}