Fixing issues as per suggestions from @kevcunnane

src/Microsoft.SqlTools.ServiceLayer/Workspace/Contracts/FilePosition.cs

@@ -0,0 +1,110 @@
+//
+// 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.ServiceLayer.Workspace.Contracts
+{
+    /// <summary>
+    /// Provides details and operations for a buffer position in a
+    /// specific file.
+    /// </summary>
+    public class FilePosition : BufferPosition
+    {
+        #region Private Fields
+
+        private ScriptFile scriptFile;
+
+        #endregion
+
+        #region Constructors
+
+        /// <summary>
+        /// Creates a new FilePosition instance for the 1-based line and
+        /// column numbers in the specified file.
+        /// </summary>
+        /// <param name="scriptFile">The ScriptFile in which the position is located.</param>
+        /// <param name="line">The 1-based line number in the file.</param>
+        /// <param name="column">The 1-based column number in the file.</param>
+        public FilePosition(
+            ScriptFile scriptFile,
+            int line,
+            int column)
+                : base(line, column)
+        {
+            this.scriptFile = scriptFile;
+        }
+
+        /// <summary>
+        /// Creates a new FilePosition instance for the specified file by
+        /// copying the specified BufferPosition
+        /// </summary>
+        /// <param name="scriptFile">The ScriptFile in which the position is located.</param>
+        /// <param name="copiedPosition">The original BufferPosition from which the line and column will be copied.</param>
+        public FilePosition(
+            ScriptFile scriptFile,
+            BufferPosition copiedPosition)
+                 : this(scriptFile, copiedPosition.Line, copiedPosition.Column)
+        {
+            scriptFile.ValidatePosition(copiedPosition);
+        }
+
+        #endregion
+
+        #region Public Methods
+
+        /// <summary>
+        /// Gets a FilePosition relative to this position by adding the
+        /// provided line and column offset relative to the contents of
+        /// the current file.
+        /// </summary>
+        /// <param name="lineOffset">The line offset to add to this position.</param>
+        /// <param name="columnOffset">The column offset to add to this position.</param>
+        /// <returns>A new FilePosition instance for the calculated position.</returns>
+        public FilePosition AddOffset(int lineOffset, int columnOffset)
+        {
+            return this.scriptFile.CalculatePosition(
+                this,
+                lineOffset,
+                columnOffset);
+        }
+
+        /// <summary>
+        /// Gets a FilePosition for the line and column position
+        /// of the beginning of the current line after any initial
+        /// whitespace for indentation.
+        /// </summary>
+        /// <returns>A new FilePosition instance for the calculated position.</returns>
+        public FilePosition GetLineStart()
+        {
+            string scriptLine = scriptFile.FileLines[this.Line - 1];
+
+            int lineStartColumn = 1;
+            for (int i = 0; i < scriptLine.Length; i++)
+            {
+                if (!char.IsWhiteSpace(scriptLine[i]))
+                {
+                    lineStartColumn = i + 1;
+                    break;
+                }
+            }
+
+            return new FilePosition(this.scriptFile, this.Line, lineStartColumn);
+        }
+
+        /// <summary>
+        /// Gets a FilePosition for the line and column position
+        /// of the end of the current line.
+        /// </summary>
+        /// <returns>A new FilePosition instance for the calculated position.</returns>
+        public FilePosition GetLineEnd()
+        {
+            string scriptLine = scriptFile.FileLines[this.Line - 1];
+            return new FilePosition(this.scriptFile, this.Line, scriptLine.Length + 1);
+        }
+
+        #endregion
+   
+    }
+}
+