feat: implement basic object member iterator functionality, probably …

…will need more testing

src/ObjectTreeWalker/ObjectMemberIterator.cs

@@ -1,4 +1,6 @@
 using System.Collections.Concurrent;
+using System.Reflection;
+using System.Runtime.CompilerServices;
 using Microsoft.Extensions.ObjectPool;
 
 namespace ObjectTreeWalker
@@ -9,14 +11,74 @@ namespace ObjectTreeWalker
 	public class ObjectMemberIterator
 	{
 		private static readonly ConcurrentDictionary<Type, ObjectAccessor> ObjectAccessorCache = new();
-		private static readonly ObjectPool<Queue<KeyValuePair<string, object>>> TraversalQueuePool =
-			new DefaultObjectPoolProvider().Create<Queue<KeyValuePair<string, object>>>();
+		private static readonly ObjectPool<Queue<(IterationInfo iterationItem, ObjectGraphNode node)>> TraversalQueuePool =
+			new DefaultObjectPoolProvider().Create<Queue<(IterationInfo iterationItem, ObjectGraphNode node)>>();
 
-		/// <summary>
-		/// Initializes a new instance of the <see cref="ObjectMemberIterator"/> class
-		/// </summary>
-		public ObjectMemberIterator()
+		public void Traverse(object obj, Action<IterationInfo> visitor)
 		{
+			var objectGraph = ObjectEnumerator.Enumerate(obj.GetType());
+
+			var traversalQueue = TraversalQueuePool.Get();
+			try
+			{
+				var rootObjectAccessor = GetCachedObjectAccessor(objectGraph.Type);
+
+				foreach (var root in objectGraph.Roots)
+				{
+					traversalQueue.Enqueue(
+						(new IterationInfo(root.Name, obj, rootObjectAccessor), root));
+				}
+
+				while (traversalQueue.TryDequeue(out var current))
+				{
+					var objectAccessor = GetCachedObjectAccessor(current.node.Type);
+					var nodeInstance = current.iterationItem.GetValue();
+
+					// we are only interested in iterating over the "data" vertices
+					// otherwise, we would get "foo(obj)" and then all foo's properties
+					if (current.node.Children.Count == 0)
+					{
+						visitor(current.iterationItem);
+					}
+					else
+					{
+						foreach (var child in current.node.Children)
+						{
+							traversalQueue.Enqueue(
+								(new IterationInfo(child.Name, nodeInstance!, objectAccessor), child));
+						}
+					}
+				}
+			}
+			finally
+			{
+				TraversalQueuePool.Return(traversalQueue);
+			}
+		}
+
+		[MethodImpl(MethodImplOptions.AggressiveInlining)]
+		private static ObjectAccessor GetCachedObjectAccessor(Type type) =>
+			ObjectAccessorCache.GetOrAdd(type, t => new ObjectAccessor(t));
+
+		public class IterationInfo
+		{
+			private readonly ObjectAccessor _objectAccessor;
+			private readonly object _object;
+			private readonly string _memberName;
+
+			internal IterationInfo(string memberName, object obj, ObjectAccessor objectAccessor)
+			{
+				_memberName = memberName ?? throw new ArgumentNullException(nameof(memberName));
+				_object = obj ?? throw new ArgumentNullException(nameof(obj));
+				_objectAccessor = objectAccessor ?? throw new ArgumentNullException(nameof(objectAccessor));
+			}
+
+			public object? GetValue() =>
+				!_objectAccessor.TryGetValue(_object, _memberName, out var value) ?
+					null : value;
+
+			public void SetValue(object newValue) =>
+				_objectAccessor.TrySetValue(_object, _memberName, newValue);
 		}
 	}
 }