Object Explorer Service (#311)

* moving OE service from an old branch

src/Microsoft.SqlTools.ServiceLayer/ObjectExplorer/ObjectExplorerUtils.cs

@@ -0,0 +1,76 @@
+//
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+//
+
+using System;
+using Microsoft.SqlTools.ServiceLayer.ObjectExplorer.Nodes;
+
+namespace Microsoft.SqlTools.ServiceLayer.ObjectExplorer
+{
+    /// <summary>
+    /// Utility class for Object Explorer related operations
+    /// </summary>
+    public static class ObjectExplorerUtils
+    {
+        /// <summary>
+        /// Visitor that walks all nodes from the child to the root node, unless the 
+        /// <paramref name="visitor"/> function indicates that this should stop traversing
+        /// </summary>
+        /// <param name="child">node to start traversing at</param>
+        /// <param name="visitor">Predicate function that accesses the tree and
+        /// determines whether to stop going further up the tree</param>
+        /// <returns>
+        /// boolean - true to continue navigating up the tree, false to end the loop
+        /// and return early
+        /// </returns>
+        public static bool VisitChildAndParents(TreeNode child, Predicate<TreeNode> visitor)
+        {
+            if (child == null)
+            {
+                // End case: all nodes have been visited
+                return true;
+            }
+
+            // Visit the child first, then go up the parents
+            if (!visitor(child))
+            {
+                return false;
+            }
+            return VisitChildAndParents(child.Parent, visitor);
+        }
+
+        /// <summary>
+        /// Finds a node by traversing the tree starting from the given node through all the children
+        /// </summary>
+        /// <param name="node">node to start traversing at</param>
+        /// <param name="condition">Predicate function that accesses the tree and
+        /// determines whether to stop going further up the tree</param>
+        /// <param name="filter">Predicate function to filter the children when traversing</param>
+        /// <returns>A Tree Node that matches the condition</returns>
+        public static TreeNode FindNode(TreeNode node, Predicate<TreeNode> condition, Predicate<TreeNode> filter)
+        {
+            if(node == null)
+            {
+                return null;
+            }
+
+            if (condition(node))
+            {
+                return node;
+            }
+            foreach (var child in node.GetChildren())
+            {
+                if (filter != null && filter(child))
+                {
+                    TreeNode childNode = FindNode(child, condition, filter);
+                    if (childNode != null)
+                    {
+                        return childNode;
+                    }
+                }
+            }
+            return null;
+        }
+    }
+}