use path to identify edit target (#1292)

* use path to identify edit target

* async action

* revert RequestContext change

* comments

* address comments

* fix test

src/Microsoft.SqlTools.ServiceLayer/TableDesigner/DesignerPathUtils.cs

@@ -0,0 +1,80 @@
+//
+// 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;
+using System.Linq;
+using Microsoft.SqlTools.ServiceLayer.TableDesigner.Contracts;
+
+namespace Microsoft.SqlTools.ServiceLayer.TableDesigner
+{
+    public static class DesignerPathUtils
+    {
+        ///<summary>
+        /// validate the path in the table designer change information.
+        /// Below are the 3 scenarios and their expected path.
+        /// Note: 'index-{x}' in the description below are numbers represent the index of the object in the list.
+		/// 1. 'Add' scenario
+		///     a. ['propertyName1']. Example: add a column to the columns property: ['columns'].
+		///     b. ['propertyName1',index-1,'propertyName2']. Example: add a column mapping to the first foreign key: ['foreignKeys',0,'mappings'].
+		/// 2. 'Update' scenario
+		///     a. ['propertyName1']. Example: update the name of the table: ['name'].
+		///     b. ['propertyName1',index-1,'propertyName2']. Example: update the name of a column: ['columns',0,'name'].
+		///     c. ['propertyName1',index-1,'propertyName2',index-2,'propertyName3']. Example: update the source column of an entry in a foreign key's column mapping table: ['foreignKeys',0,'mappings',0,'source'].
+		/// 3. 'Remove' scenario
+        ///     a. ['propertyName1',index-1]. Example: remove a column from the columns property: ['columns',0'].
+		///     b. ['propertyName1',index-1,'propertyName2',index-2]. Example: remove a column mapping from a foreign key's column mapping table: ['foreignKeys',0,'mappings',0].
+        ///<summary>
+        public static void Validate(object[] path, DesignerEditType editType)
+        {
+            if (path == null || path.Length == 0)
+            {
+                throw new ArgumentException(SR.TableEditPathNotProvidedException);
+            }
+
+            // Length validation
+            int[] validLengthList;
+            if (editType == DesignerEditType.Add)
+            {
+                validLengthList = new int[] { 1, 3 };
+            }
+            else if (editType == DesignerEditType.Update)
+            {
+                validLengthList = new int[] { 1, 3, 5 };
+            }
+            else
+            {
+                validLengthList = new int[] { 2, 4 };
+            }
+
+            bool isValid = validLengthList.ToList<int>().Contains(path.Length);
+            if (isValid)
+            {
+                for (int i = 0; i < path.Length; i++)
+                {
+                    // On odd number positions, the value must be a number.
+                    if (i % 2 != 0)
+                    {
+                        int val;
+                        isValid = Int32.TryParse(path[i]?.ToString(), out val);
+                    }
+                    else
+                    {
+                        isValid = path[i] is string;
+                    }
+                    if (!isValid)
+                    {
+                        break;
+                    }
+                }
+            }
+
+            if (!isValid)
+            {
+                throw new ArgumentException(SR.InvalidTableEditPathException(string.Join(',', path), editType.ToString()));
+            }
+        }
+    }
+}