Autocomplete bug fixes (#43)

Fix-up the autocomplete support to better handle binding timeouts.
Also provide a default keyword suggestion list.

src/Microsoft.SqlTools.ServiceLayer/Utility/TextUtilities.cs

@@ -0,0 +1,62 @@
+//
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+//
+
+namespace Microsoft.SqlTools.EditorServices.Utility
+{
+    public static class TextUtilities
+    {
+        /// <summary>
+        /// Find the position of the previous delimeter for autocomplete token replacement.
+        /// SQL Parser may have similar functionality in which case we'll delete this method.
+        /// </summary>
+        /// <param name="sql"></param>
+        /// <param name="startRow"></param>
+        /// <param name="startColumn"></param>
+        /// <returns></returns>
+        public static int PositionOfPrevDelimeter(string sql, int startRow, int startColumn)
+        {
+            if (string.IsNullOrWhiteSpace(sql))
+            {
+                return 1;
+            }
+
+            int prevLineColumns = 0;
+            for (int i = 0; i < startRow; ++i)
+            {
+                while (sql[prevLineColumns] != '\n' && prevLineColumns < sql.Length)
+                {
+                    ++prevLineColumns;
+                }
+                ++prevLineColumns;
+            }
+
+            startColumn += prevLineColumns;
+
+            if (startColumn - 1 < sql.Length)
+            {
+                while (--startColumn >= prevLineColumns)
+                {
+                    if (sql[startColumn] == ' ' 
+                        || sql[startColumn] == '\t'
+                        || sql[startColumn] == '\n'
+                        || sql[startColumn] == '.'
+                        || sql[startColumn] == '+'
+                        || sql[startColumn] == '-'
+                        || sql[startColumn] == '*'
+                        || sql[startColumn] == '>'
+                        || sql[startColumn] == '<'
+                        || sql[startColumn] == '='
+                        || sql[startColumn] == '/'
+                        || sql[startColumn] == '%')
+                    {
+                        break;
+                    }
+                }
+            }
+
+            return startColumn + 1 - prevLineColumns;
+        }
+    }
+}