using System; 
using System.Collections.Generic; 
using System.Reflection; 
using System.Text; 

namespace Com.GuyMahieu.Util 
{ 
   /// <summary> 
   /// Helps to get and set property values on objects through reflection. 
   /// Properties of underlying objects can be accessed directly by separating 
   /// the levels in the hierarchy by dots. 
   /// To get/set the name of an Ancestor, for objects that have a Parent property, 
   /// you could use "Parent.Parent.Parent.Name". 
   /// </summary> 
   public class PropertyReflector 
   { 
      private const char PropertyNameSeparator = '.'; 

      private static readonly object[] NoParams = new object[0]; 
      private static readonly Type[] NoTypeParams = new Type[0]; 

      private IDictionary<Type, PropertyInfoCache> propertyCache = new Dictionary<Type, PropertyInfoCache>(); 
      private IDictionary<Type, ConstructorInfo> constructorCache = new Dictionary<Type, ConstructorInfo>(); 

      /// <summary> 
      /// Gets the Type of the given property of the given targetType. 
      /// The targetType and propertyName parameters can't be null. 
      /// </summary> 
      /// <param name="targetType">the target type which contains the property</param> 
      /// <param name="propertyName">the property to get, can be a property on a nested object (eg. "Child.Name")</param>

      public Type GetType(Type targetType, string propertyName) 
      { 
         if (propertyName.IndexOf(PropertyNameSeparator) > -1) 
         { 
            string[] propertyList = propertyName.Split(PropertyNameSeparator); 
            for (int i = 0; i < propertyList.Length; i++) 
            { 
               string currentProperty = propertyList[i]; 
               targetType = GetTypeImpl(targetType, currentProperty); 
            } 
            return targetType; 
         } 
         else 
         { 
            return GetTypeImpl(targetType, propertyName); 
         } 
      } 

      /// <summary> 
      /// Gets the value of the given property of the given target. 
      /// If objects within the property hierarchy are null references, null will be returned. 
      /// The target and propertyName parameters can't be null. 
      /// </summary> 
      /// <param name="target">the target object to get the value from</param> 
      /// <param name="propertyName">the property to get, can be a property on a nested object (eg. "Child.Name")</param>

      public object GetValue(object target, string propertyName) 
      { 
         if (propertyName.IndexOf(PropertyNameSeparator) > -1) 
         { 
            string[] propertyList = propertyName.Split(PropertyNameSeparator); 
            for (int i = 0; i < propertyList.Length; i++) 
            { 
               string currentProperty = propertyList[i]; 
               target = GetValueImpl(target, currentProperty); 
               if (target == null) 
               { 
                  return null; 
               } 
            } 
            return target; 
         } 
         else 
         { 
            return GetValueImpl(target, propertyName); 
         } 
      } 

      /// <summary> 
      /// Sets the value of the given property on the given target to the given value. 
      /// If objects within the property hierarchy are null references, an attempt will be 
      /// made to construct a new instance through a parameterless constructor. 
      /// The target and propertyName parameters can't be null. 
      /// </summary> 
      /// <param name="target">the target object to set the value on</param> 
      /// <param name="propertyName">the property to set, can be a property on a nested object (eg. "Child.Name")</param>

      /// <param name="value">the new value of the property</param> 
      public void SetValue(object target, string propertyName, object value) 
      { 
         if (propertyName.IndexOf(PropertyNameSeparator) > -1) 
         { 
            object originalTarget = target; 
            string[] propertyList = propertyName.Split(PropertyNameSeparator); 
            for (int i = 0; i < propertyList.Length - 1; i++) 
            { 
               propertyName = propertyList[i]; 
               target = GetValueImpl(target, propertyName); 
               if (target == null) 
               { 
                  string currentFullPropertyNameString = GetPropertyNameString(propertyList, i); 
                  target = Construct(GetType(originalTarget.GetType(), currentFullPropertyNameString)); 
                  SetValue(originalTarget, currentFullPropertyNameString, target); 
               } 
            } 
            propertyName = propertyList[propertyList.Length - 1]; 
         } 
         SetValueImpl(target, propertyName, value); 
      } 

      /// <summary> 
      /// Returns a string containing the properties in the propertyList up to the given 
      /// level, separated by dots. 
      /// For the propertyList { "Zero", "One", "Two" } and level 1, the string 
      /// "Zero.One" will be returned. 
      /// </summary> 
      /// <param name="propertyList">the array containing the properties in the corect order</param> 
      /// <param name="level">the level up to wich to include the properties in the returned string</param> 
      /// <returns>a dot-separated string containing the properties up to the given level</returns> 
      private static string GetPropertyNameString(string[] propertyList, int level) 
      { 
         StringBuilder currentFullPropertyName = new StringBuilder(); 
         for (int j = 0; j <= level; j++) 
         { 
            if (j > 0) 
            { 
               currentFullPropertyName.Append(PropertyNameSeparator); 
            } 
            currentFullPropertyName.Append(propertyList[j]); 
         } 
         return currentFullPropertyName.ToString(); 
      } 

      /// <summary> 
      /// Returns the type of the given property on the target instance. 
      /// The type and propertyName parameters can't be null. 
      /// </summary> 
      /// <param name="targetType">the type of the target instance</param> 
      /// <param name="propertyName">the property to retrieve the type for</param> 
      /// <returns>the typr of the given property on the target type</returns> 
      private Type GetTypeImpl(Type targetType, string propertyName) 
      { 
         return GetPropertyInfo(targetType, propertyName).PropertyType; 
      } 

      /// <summary> 
      /// Returns the value of the given property on the target instance. 
      /// The target instance and propertyName parameters can't be null. 
      /// </summary> 
      /// <param name="target">the instance on which to get the value</param> 
      /// <param name="propertyName">the property for which to get the value</param> 
      /// <returns>the value of the given property on the target instance</returns> 
      private object GetValueImpl(object target, string propertyName) 
      { 
         return GetPropertyInfo(target.GetType(), propertyName).GetValue(target, NoParams); 
      } 

      /// <summary> 
      /// Sets the given property of the target instance to the given value. 
      /// Type mismatches in the parameters of these methods will result in an exception. 
      /// Also, the target instance and propertyName parameters can't be null. 
      /// </summary> 
      /// <param name="target">the instance to set the value on</param> 
      /// <param name="propertyName">the property to set the value on</param> 
      /// <param name="value">the value to set on the target</param> 
      private void SetValueImpl(object target, string propertyName, object value) 
      { 
         GetPropertyInfo(target.GetType(), propertyName).SetValue(target, value, NoParams); 
      } 

      /// <summary> 
      /// Obtains the PropertyInfo for the given propertyName of the given type from the cache. 
      /// If it is not already in the cache, the PropertyInfo will be looked up and added to 
      /// the cache. 
      /// </summary> 
      /// <param name="type">the type to resolve the property on</param> 
      /// <param name="propertyName">the name of the property to return the PropertyInfo for</param> 
      /// <returns></returns> 
      private PropertyInfo GetPropertyInfo(Type type, string propertyName) 
      { 
         PropertyInfoCache propertyInfoCache = GetPropertyInfoCache(type); 
         if (!propertyInfoCache.ContainsKey(propertyName)) 
         { 
            PropertyInfo propertyInfo = GetBestMatchingProperty(propertyName, type); 
            if (propertyInfo == null) 
            { 
               throw new ArgumentException(string.Format("Unable to find public property named {0} on type {1}", propertyName, type.FullName), propertyName);

            } 
            propertyInfoCache.Add(propertyName, propertyInfo); 
         } 
         return propertyInfoCache[propertyName]; 
      } 

      /// <summary> 
      /// Gets the best matching property info for the given name on the given type if the same property is defined on 
      /// multiple levels in the object hierarchy. 
      /// </summary> 
      private static PropertyInfo GetBestMatchingProperty(string propertyName, Type type) 
      { 
         PropertyInfo[] propertyInfos = type.GetProperties(BindingFlags.Public | BindingFlags.Instance | BindingFlags.FlattenHierarchy);

         PropertyInfo bestMatch = null; 
         int bestMatchDistance = int.MaxValue; 
         for (int i = 0; i < propertyInfos.Length; i++) 
         { 
            PropertyInfo info = propertyInfos[i]; 
            if (info.Name == propertyName) 
            { 
               int distance = CalculateDistance(type, info.DeclaringType); 
               if (distance == 0) 
               { 
                  // as close as we're gonna get... 
                  return info; 
               } 
               if (distance > 0 && distance < bestMatchDistance) 
               { 
                  bestMatch = info; 
                  bestMatchDistance = distance;
               } 
            } 
         } 
         return bestMatch; 
      } 

      /// <summary> 
      /// Calculates the hierarchy levels between two classes. 
      /// If the targetObjectType is the same as the baseType, the returned distance will be 0. 
      /// If the two types do not belong to the same hierarchy, -1 will be returned. 
      /// </summary> 
      private static int CalculateDistance(Type targetObjectType, Type baseType) 
      { 
         if (!baseType.IsInterface) 
         { 
            Type currType = targetObjectType; 
            int level = 0; 
            while (currType != null) 
            { 
               if (baseType == currType) 
               { 
                  return level; 
               } 
               currType = currType.BaseType; 
               level++; 
            } 
         } 
         return -1; 
      } 

      /// <summary> 
      /// Returns the PropertyInfoCache for the given type. 
      /// If there isn't one available already, a new one will be created. 
      /// </summary> 
      /// <param name="type">the type to retrieve the PropertyInfoCache for</param> 
      /// <returns>the PropertyInfoCache for the given type</returns> 
      private PropertyInfoCache GetPropertyInfoCache(Type type) 
      { 
         if (!propertyCache.ContainsKey(type)) 
         { 
            lock(this)
            {
               if (!propertyCache.ContainsKey(type))
               {
            propertyCache.Add(type, new PropertyInfoCache()); 
         } 
            }
         }
         return propertyCache[type]; 
      } 

      /// <summary> 
      /// Creates a new object of the given type, provided that the type has a default (parameterless) 
      /// constructor. If it does not have such a constructor, an exception will be thrown. 
      /// </summary> 
      /// <param name="type">the type of the object to construct</param> 
      /// <returns>a new instance of the given type</returns> 
      private object Construct(Type type) 
      { 
         if (!constructorCache.ContainsKey(type)) 
         { 
            lock (this)
            {
               if (!constructorCache.ContainsKey(type))
               {
            ConstructorInfo constructorInfo = type.GetConstructor(NoTypeParams); 
            if (constructorInfo == null) 
            { 
               throw new Exception(string.Format("Unable to construct instance, no parameterless constructor found in type {0}", type.FullName));

            } 
            constructorCache.Add(type, constructorInfo); 
         } 
            }
         }
         return constructorCache[type].Invoke(NoParams); 
      } 
   } 

   /// <summary> 
   /// Keeps a mapping between a string and a PropertyInfo instance. 
   /// Simply wraps an IDictionary and exposes the relevant operations. 
   /// Putting all this in a separate class makes the calling code more 
   /// readable. 
   /// </summary> 
   internal class PropertyInfoCache 
   { 
      private IDictionary<string, PropertyInfo> propertyInfoCache; 

      public PropertyInfoCache() 
      { 
         propertyInfoCache = new Dictionary<string, PropertyInfo>(); 
      } 

      public bool ContainsKey(string key) 
      { 
         return propertyInfoCache.ContainsKey(key); 
      } 

      public void Add(string key, PropertyInfo value) 
      { 
         propertyInfoCache.Add(key, value); 
      } 

      public PropertyInfo this[string key] 
      { 
         get { return propertyInfoCache[key]; } 
         set { propertyInfoCache[key] = value; } 
      } 
   } 
}