source: branches/New Persistence Exploration/Persistence/Persistence/DeSerializer.cs @ 1349

using System.Collections.Generic;
using System;

namespace Persistence {

  public class DeSerializer {

    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);
        }        
      }
    }

    private delegate void Handler(IParseToken token);

    private readonly Dictionary<int, object> id2obj;
    private readonly Dictionary<Type, Handler> handlers;
    private readonly Stack<IAccessibleObject> compositeStack;
    private readonly PersistenceConfiguration persistenceConfiguration;

    delegate void Thunk();
    private List<Thunk> finalFixes;

    public DeSerializer() : this(PersistenceConfiguration.Instance) {}
  
    public DeSerializer(PersistenceConfiguration persistenceConfiguration) {
      this.persistenceConfiguration = persistenceConfiguration;
      id2obj = new Dictionary<int, object>();
      compositeStack = new Stack<IAccessibleObject>();
      handlers = new Dictionary<Type, Handler> {
                     {typeof (CompositeStart), CompositeStartHandler},
                     {typeof (CompositeEnd), CompositeEndHandler},
                     {typeof (Primitive), PrimitiveHandler},
                     {typeof (Reference), ReferenceHandler},
                     {typeof (Null), NullHandler}
                   };      
    }

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

    private void CompositeStartHandler(IParseToken token) {
      CompositeStart start = (CompositeStart)token;
      object instance;
      if (persistenceConfiguration.GetDecomposer(start.Type) != null) {
        instance = new ParentReference();
        compositeStack.Push(new CustomObject(instance));        
      } else {        
        instance = Activator.CreateInstance(start.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(IParseToken token) {
      CompositeEnd end = (CompositeEnd)token;      
      IDecomposer decomposer = persistenceConfiguration.GetDecomposer(end.Type);
      if (decomposer != null) {
        CustomObject customObject = (CustomObject)compositeStack.Pop();
        object deserializedObject =
          decomposer.DeSerialize(customObject.customValues, end.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(IParseToken token) {
      Primitive primitive = (Primitive)token;
      object value = persistenceConfiguration
        .GetFormatter(XmlFormat.Instance, primitive.Type)
        .DeSerialize(primitive.SerializedValue);
      if ( ! value.GetType().IsValueType )
        id2obj[(int)primitive.Id] = value;
      SetValue(primitive.Name, value);
    }
    private void ReferenceHandler(IParseToken token) {
      Reference reference = (Reference)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(IParseToken token) {
      Null nil = (Null)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);
        }
      }
    }
  }
}