Object Explorer Service (#311)

* moving OE service from an old branch

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

@@ -0,0 +1,161 @@
+//
+// 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 System.Collections.Generic;
+using System.Diagnostics;
+using System.Linq;
+using System.Reflection;
+using Microsoft.SqlServer.Management.Smo;
+using Microsoft.SqlTools.ServiceLayer.ObjectExplorer.Nodes;
+using Microsoft.SqlTools.ServiceLayer.Utility;
+using Microsoft.SqlTools.Utility;
+
+namespace Microsoft.SqlTools.ServiceLayer.ObjectExplorer.SmoModel
+{
+    public class SmoChildFactoryBase : ChildFactory
+    {
+        public override IEnumerable<string> ApplicableParents()
+        {
+            return null;
+        }
+        
+        public override IEnumerable<TreeNode> Expand(TreeNode parent)
+        {
+            //parent.BeginChildrenInit();
+            try
+            {
+                List<TreeNode> allChildren = new List<TreeNode>();
+                OnExpandPopulateFolders(allChildren, parent);
+                RemoveFoldersFromInvalidSqlServerVersions(allChildren, parent);
+                OnExpandPopulateNonFolders(allChildren, parent);
+                OnBeginAsyncOperations(parent);
+                return allChildren;
+            }
+            finally
+            {
+                //parent.EndChildrenInit();
+            }
+        }
+        
+        /// <summary>
+        /// Populates any folders for a given parent node 
+        /// </summary>
+        /// <param name="allChildren">List to which nodes should be added</param>
+        /// <param name="parent">Parent the nodes are being added to</param>
+        protected virtual void OnExpandPopulateFolders(IList<TreeNode> allChildren, TreeNode parent)
+        {
+        }
+
+        /// <summary>
+        /// Populates any non-folder nodes such as specific items in the tree.
+        /// </summary>
+        /// <param name="allChildren">List to which nodes should be added</param>
+        /// <param name="parent">Parent the nodes are being added to</param>
+        protected virtual void OnExpandPopulateNonFolders(IList<TreeNode> allChildren, TreeNode parent)
+        {
+            if (ChildQuerierTypes == null)
+            {
+                // This node does not support non-folder children
+                return;
+            }
+            SmoQueryContext context = parent.GetContextAs<SmoQueryContext>();
+            Validate.IsNotNull(nameof(context), context);
+            IEnumerable<SmoQuerier> queriers = context.ServiceProvider.GetServices<SmoQuerier>(q => IsCompatibleQuerier(q));
+            foreach (var querier in queriers)
+            {
+                foreach(var smoObject in querier.Query(context))
+                {
+                    if (smoObject == null)
+                    {
+                        Console.WriteLine("smoObject should not be null");
+                    }
+                    TreeNode childNode = CreateChild(parent, smoObject);
+                    if (childNode != null)
+                    {
+                        allChildren.Add(childNode);
+                    }
+                }
+            }
+        }
+
+        private bool IsCompatibleQuerier(SmoQuerier querier)
+        {
+            if (ChildQuerierTypes == null)
+            {
+                return false;
+            }
+
+            Type actualType = querier.GetType();
+            foreach (Type childType in ChildQuerierTypes)
+            {
+                // We will accept any querier that is compatible with the listed querier type
+                if (childType.IsAssignableFrom(actualType))
+                {
+                    return true;
+                }
+            }
+            return false;
+
+        }
+        
+        /// <summary>
+        /// Filters out invalid folders if they cannot be displayed for the current server version
+        /// </summary>
+        /// <param name="allChildren">List to which nodes should be added</param>
+        /// <param name="parent">Parent the nodes are being added to</param>
+        protected virtual void RemoveFoldersFromInvalidSqlServerVersions(IList<TreeNode> allChildren, TreeNode parent)
+        {
+        }
+
+        // TODO Assess whether async operations node is required
+        protected virtual void OnBeginAsyncOperations(TreeNode parent)
+        {
+        }
+
+        public override bool CanCreateChild(TreeNode parent, object context)
+        {
+            return false;
+        }
+
+        public override TreeNode CreateChild(TreeNode parent, object context)
+        {
+            throw new NotImplementedException();
+        }
+
+        protected virtual void InitializeChild(TreeNode child, object context)
+        {
+            NamedSmoObject smoObj = context as NamedSmoObject;
+            if (smoObj == null)
+            {
+                Debug.WriteLine("context is not a NamedSmoObject. type: " + context.GetType());
+            }
+            else
+            {
+                SmoTreeNode childAsMeItem = (SmoTreeNode)child;
+                childAsMeItem.CacheInfoFromModel(smoObj);
+            }
+        }
+
+        internal virtual Type[] ChildQuerierTypes { 
+            get
+            {
+                return null;
+            }
+        }
+
+        /// <summary>
+        /// Returns true if any final validation of the object to be added passes, and false
+        /// if validation fails. This provides a chance to filter specific items out of a list 
+        /// </summary>
+        /// <param name="parent"></param>
+        /// <param name="contextObject"></param>
+        /// <returns>boolean</returns>
+        public virtual bool PassesFinalFilters(TreeNode parent, object context)
+        {
+            return true;
+        }
+    }
+}