Move managed parser into its own project (test code coverage) (#774)

* Created New ManagedBatchParser project in .NetStandard

* Addressing PR Comments

* Resolve 'No Repository' warning.

* Move batch parser tests to integrations test project

* Fix SLN file

src/Microsoft.SqlTools.ManagedBatchParser/BatchParser/LexerInput.cs

@@ -0,0 +1,186 @@
+//
+// 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.IO;
+using System.Text;
+
+namespace Microsoft.SqlTools.ServiceLayer.BatchParser
+{
+    /// <summary>
+    /// Lexer input class used by lexer in SMO Batch Parser
+    /// </summary>
+    internal sealed class LexerInput : IDisposable
+    {
+        private readonly string filename;
+        private TextReader input;
+        private int currentLine;
+        private int currentColumn;
+        private int bufferStartOffset;
+        private int currentSbOffset;
+        private StringBuilder buffer;
+
+        /// <summary>
+        /// Constructor method for the LexerInput class
+        /// </summary>
+        public LexerInput(TextReader reader, string filename)
+        {
+            input = reader;
+            this.filename = filename;
+            currentLine = 1;
+            currentColumn = 1;
+            bufferStartOffset = 0;
+            currentSbOffset = 0;
+            buffer = new StringBuilder();
+            EnsureBytes(1);
+        }
+
+        /// <summary>
+        /// Get filename associated with lexer input
+        /// </summary>
+        public string Filename
+        {
+            get { return filename; }
+        }
+
+        /// <summary>
+        /// Get current line associated with lexer input
+        /// </summary>
+        public int CurrentLine 
+        {
+            get { return currentLine; }
+        }
+
+        /// <summary>
+        /// Get current column associated with lexer input
+        /// </summary>
+        public int CurrentColumn 
+        {
+            get { return currentColumn; }
+        }
+
+        /// <summary>
+        /// Consume token used by lexer input
+        /// </summary>
+        public void Consume()
+        {
+            bool newLineWithCR = false;
+
+            char? ch = Lookahead();
+            if (ch == null)
+            {
+                // end of stream
+                return;
+            }
+            else if (ch == '\r')
+            {
+                newLineWithCR = true;
+            }
+            else if (ch == '\n')
+            {
+                currentLine++;
+                currentColumn = 0;
+            }
+
+            int count = EnsureBytes(1);
+            if (count == 0)
+            {
+                // end of stream
+                return;
+            }
+            currentSbOffset++;
+
+            if (newLineWithCR && Lookahead() != '\n')
+            {
+                currentLine++;
+                currentColumn = 0;
+            }
+            currentColumn++;
+        }
+
+        public void Dispose()
+        {
+            if (input != null)
+            {
+                input.Dispose();
+                input = null;
+            }
+        }
+
+        /// <summary>
+        /// Get current offset for the lexer input
+        /// </summary>
+        public int CurrentOffset
+        {
+            get { return bufferStartOffset + currentSbOffset; }
+        }
+
+        /// <summary>
+        /// Ensure correct number of bytes to buffer
+        /// </summary>
+        public int EnsureBytes(int bytesToBuffer)
+        {
+            if (currentSbOffset + bytesToBuffer > buffer.Length)
+            {
+                if (input == null)
+                {
+                    return buffer.Length - currentSbOffset;
+                }
+                int chArrayLength = bytesToBuffer - (buffer.Length - currentSbOffset) + 128;
+                char[] chArray = new char[chArrayLength];
+                int count = input.ReadBlock(chArray, 0, chArrayLength);
+                buffer.Append(chArray, 0, count);
+                if (count < chArrayLength)
+                {
+                    input.Dispose();
+                    input = null;
+                }
+                return buffer.Length - currentSbOffset;
+            }
+            return bytesToBuffer;
+        }
+
+        /// <summary>
+        /// look ahead bytes in lexer input
+        /// </summary>
+        public char? Lookahead()
+        {
+            int count = EnsureBytes(1);
+            if (count == 0)
+            {
+                return null;
+            }
+            return buffer[currentSbOffset];
+        }
+
+        /// <summary>
+        /// look ahead bytes in lexer input
+        /// </summary>
+        public char? Lookahead(int lookahead)
+        {
+            int count = EnsureBytes(lookahead + 1);
+            if (count < lookahead + 1)
+            {
+                return null;
+            }
+            return buffer[currentSbOffset + lookahead];
+        }
+
+        /// <summary>
+        /// Flush buffered text in lexer input
+        /// </summary>
+        public string FlushBufferedText()
+        {
+            string text;
+
+            text = buffer.ToString(0, currentSbOffset);
+            bufferStartOffset += currentSbOffset;
+            buffer.Remove(0, currentSbOffset);
+            currentSbOffset = 0;
+
+            return text;
+        }
+    }
+}