Object Explorer Service (#311)

* moving OE service from an old branch

src/Microsoft.SqlTools.ServiceLayer/ObjectExplorer/SmoModel/SmoTreeNode.cs

@@ -0,0 +1,90 @@
+//
+// 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.SqlServer.Management.Smo;
+using Microsoft.SqlTools.ServiceLayer.ObjectExplorer.Nodes;
+
+namespace Microsoft.SqlTools.ServiceLayer.ObjectExplorer.SmoModel
+{
+    /// <summary>
+    /// A Node in the tree representing a SMO-based object
+    /// </summary>
+    public class SmoTreeNode : TreeNode
+    {
+        public static int FolderSortPriority = 0;
+        private static int _nextSortPriority = FolderSortPriority + 1; // 0 is reserved for folders
+
+        protected SmoQueryContext context;
+
+        public SmoTreeNode() : base()
+        {
+        }
+
+        protected virtual void OnInitialize()
+        {
+            // TODO setup initialization
+        }
+        
+        /// <summary>
+        /// Is this a system (MSShipped) object?
+        /// </summary>
+        public bool IsMsShippedOwned { get; set; }
+
+        /// <summary>
+        /// Indicates which platforms a node is valid for
+        /// </summary>
+        public ValidForFlag ValidFor { get; set; }
+        
+        /// <summary>
+        /// Gets an incrementing sort priority value to assist in automatically sorting
+        /// elements in a tree
+        /// </summary>
+        public static int NextSortPriority
+        {
+            get
+            {
+                return System.Threading.Interlocked.Increment(ref _nextSortPriority);
+            }
+        }
+
+        public NamedSmoObject SmoObject { get; private set; }
+
+        public virtual void CacheInfoFromModel(NamedSmoObject smoObject)
+        {
+            SmoObject = smoObject;
+            NodeValue = smoObject.Name;
+        }
+        
+        public virtual NamedSmoObject GetParentSmoObject()
+        {
+            if (SmoObject != null)
+            {
+                return SmoObject;
+            }
+            // Return the parent's object, or null if it's not set / not a SmoTreeNode
+            return ParentAs<SmoTreeNode>()?.GetParentSmoObject();
+        }
+
+        public override object GetContext()
+        {
+            EnsureContextInitialized();
+            return context;
+        }
+
+        protected virtual void EnsureContextInitialized()
+        {
+            if (context == null)
+            {
+                SmoObjectBase smoParent = GetParentSmoObject();
+                SmoQueryContext parentContext = Parent?.GetContextAs<SmoQueryContext>();
+                if (smoParent != null && parentContext != null)
+                {
+                    context = parentContext.CopyWithParent(smoParent);
+                }
+            }
+        }
+    }
+}