source: branches/ParameterBinding/HeuristicLab.Core/3.3/ItemBinding.cs @ 6514

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using HeuristicLab.Persistence.Default.CompositeSerializers.Storable;
using HeuristicLab.Common;
using System.Reflection;
using System.Reflection.Emit;
using System.ComponentModel;
using System.Linq.Expressions;

namespace HeuristicLab.Core {
  [StorableClass]
  public sealed class ItemBinding : IItemBinding {
    private static readonly BindingFlags Flags = BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic;
    [Storable]
    private IDeepCloneable target;
    [Storable]
    private string targetPath;
    [Storable]
    private IDeepCloneable source;
    [Storable]
    private string sourcePath;
    [Storable]
    private bool bound;
    [Storable]
    private LambdaExpression bindingExpression;

    private Delegate bindingFunc;
    private static object evhCacheLock = new object();
    private static Dictionary<Type, DynamicMethod> eventHandlerCache = new Dictionary<Type, DynamicMethod>();

    [StorableConstructor]
    private ItemBinding(bool deserializing) { }
    private ItemBinding(ItemBinding original, Cloner cloner) {
      this.target = cloner.Clone(original.target);
      this.targetPath = original.targetPath;
      this.source = cloner.Clone(original.source);
      this.sourcePath = original.sourcePath;
      this.bindingExpression = original.bindingExpression;
      if (this.bindingExpression != null)
        this.bindingFunc = this.bindingExpression.Compile();
      if (original.bound) Bind();
    }
    public ItemBinding(IDeepCloneable target, string targetPath, IDeepCloneable source, string sourcePath) {
      this.target = target;
      this.targetPath = targetPath;
      this.source = source;
      this.sourcePath = sourcePath;
      this.bound = false;
    }
    public ItemBinding(IDeepCloneable target, string targetPath, IDeepCloneable source, string sourcePath, LambdaExpression func)
      : this(target, targetPath, source, sourcePath) {
      this.bindingExpression = func;
      this.bindingFunc = this.bindingExpression.Compile();
    }

    public IDeepCloneable Clone(Cloner cloner) {
      return new ItemBinding(this, cloner);
    }

    public object Clone() {
      return Clone(new Cloner());
    }

    [StorableHook(HookType.AfterDeserialization)]
    private void AfterDeserialization() {
      if (bound) RegisterEventHandlers();
      if (bindingExpression != null)
        bindingFunc = bindingExpression.Compile();
    }

    public void Bind() {
      RegisterEventHandlers();
      bound = true;
      ExecuteBinding(null);
    }

    public void Unbind() {
      DeregisterEventHandlers();
      bound = false;
    }

    private void RegisterEventHandlers() {
      string[] properties = sourcePath.Split('.');
      object current = source;
      foreach (string property in properties) {
        TryHookToChangedEvent(current, property);
        MethodInfo mInfo = current.GetType().GetProperty(property, Flags).GetGetMethod(true);
        object next = mInfo.Invoke(current, null);
        if (next == null) return;
        current = next;
      }
    }

    private void DeregisterEventHandlers() {
      string[] properties = sourcePath.Split('.');
      object current = source;
      foreach (string property in properties) {
        TryUnhookFromChangedEvent(current, property);
        MethodInfo mInfo = current.GetType().GetProperty(property, Flags).GetGetMethod(true);
        object next = mInfo.Invoke(current, null);
        if (next == null) return;
        current = next;
      }
    }

    // DO NOT RENAME (string reference to this method name in CreateAndAddDynamicEventHandler)
    private void ExecuteBinding(object sender) {
      string[] sourceProperties = sourcePath.Split('.');
      object cSource = source;
      #region Navigate to source property (readd bindings if necessary)
      bool reregister = false;
      for (int i = 0; i < sourceProperties.Length; i++) {
        if (cSource == null) return;
        string property = sourceProperties[i];
        if (reregister) TryHookToChangedEvent(cSource, property);
        if (cSource == sender) reregister = true;
        PropertyInfo pInfo = cSource.GetType().GetProperty(property, Flags);
        if (pInfo == null) return;
        object next = pInfo.GetGetMethod(true).Invoke(cSource, null);
        cSource = next;
      }
      #endregion

      string[] targetProperties = targetPath.Split('.');
      object cTarget = target;
      MethodInfo targetSetter = null;
      #region Navigate to target property
      for (int i = 0; i < targetProperties.Length - 1; i++) {
        PropertyInfo pInfo = cTarget.GetType().GetProperty(targetProperties[i], Flags);
        if (pInfo == null) return;
        cTarget = pInfo.GetGetMethod(true).Invoke(cTarget, null);
        if (cTarget == null) return;
      }
      targetSetter = cTarget.GetType().GetProperty(targetProperties.Last(), Flags).GetSetMethod(true);
      if (targetSetter == null) return;
      #endregion

      if (bindingFunc != null) {
        targetSetter.Invoke(cTarget, new object[] { bindingFunc.DynamicInvoke(new object[] { cSource }) });
      } else if (cSource == null && !targetSetter.GetParameters().First().ParameterType.IsValueType
        || cSource != null && cSource.GetType().IsValueType)
        targetSetter.Invoke(cTarget, new object[] { cSource });
      else if (cSource is ICloneable)
        targetSetter.Invoke(cTarget, new object[] { ((ICloneable)cSource).Clone() });
      else throw new InvalidOperationException("Can only bind to targets which are either a ValueType or an ICloneable.");
    }

    private bool TryHookToChangedEvent(object obj, string property) {
      INotifyPropertyChanged npc = (obj as INotifyPropertyChanged);
      if (npc != null) {
        npc.PropertyChanged += new PropertyChangedEventHandler(source_PropertyChanged);
        return true;
      } else {
        EventInfo eInfo = obj.GetType().GetEvent(property + "Changed", Flags);
        if (eInfo != null) {
          Type[] methodParams = eInfo.EventHandlerType.GetMethod("Invoke").GetParameters().Select(x => x.ParameterType).ToArray();
          if (!eventHandlerCache.ContainsKey(methodParams[1]))
            CreateAndAddDynamicEventHandler(eInfo, methodParams);
          eInfo.AddEventHandler(obj, eventHandlerCache[methodParams[1]].CreateDelegate(eInfo.EventHandlerType, this));
        }
        return eInfo != null;
      }
    }

    private bool TryUnhookFromChangedEvent(object obj, string property) {
      INotifyPropertyChanged npc = (obj as INotifyPropertyChanged);
      if (npc != null) {
        npc.PropertyChanged -= new PropertyChangedEventHandler(source_PropertyChanged);
        return true;
      } else {
        EventInfo eInfo = obj.GetType().GetEvent(property, Flags);
        if (eInfo != null) {
          Type[] methodParams = eInfo.EventHandlerType.GetMethod("Invoke").GetParameters().Select(x => x.ParameterType).ToArray();
          if (eventHandlerCache.ContainsKey(methodParams[1]))
            eInfo.RemoveEventHandler(obj, eventHandlerCache[methodParams[1]].CreateDelegate(eInfo.EventHandlerType, this));
        }
        return eInfo != null;
      }
    }

    private void source_PropertyChanged(object sender, PropertyChangedEventArgs e) {
      ExecuteBinding(sender);
    }

    private void CreateAndAddDynamicEventHandler(EventInfo eInfo, Type[] methodParams) {
      lock (evhCacheLock) {
        if (!eventHandlerCache.ContainsKey(methodParams[1])) {
          Type[] instanceMethodParams = new Type[] { GetType() }.Concat(methodParams).ToArray();
          DynamicMethod dynamicEventHandler = new DynamicMethod("source_Changed", null, instanceMethodParams, GetType());
          MethodInfo executeBindingMethodInfo = GetType().GetMethod("ExecuteBinding", Flags);
          ILGenerator iLG = dynamicEventHandler.GetILGenerator();
          iLG.Emit(OpCodes.Ldarg_0); // load 'this' pointer
          iLG.Emit(OpCodes.Ldarg_1); // load sender parameter
          iLG.Emit(OpCodes.Call, executeBindingMethodInfo); // call method to execute the binding
          iLG.Emit(OpCodes.Ret);
          eventHandlerCache.Add(methodParams[1], dynamicEventHandler);
        }
      }
    }
  }
}