Parse multi-line comments

Lexer.Tests/MLexerShould.cs

@@ -234,5 +234,22 @@ namespace Lexer.Tests
             Assert.AreEqual(2, tokens.Count);
             Assert.AreEqual(TokenKind.NumberLiteral, tokens[0].Kind);
         }
+
+        [TestCase("%{\nabc\n%}", true)]
+        [TestCase("%{ a\nabc\n%}", false)]
+        [TestCase("if %{\nabc\n%}", false)]
+        public void ParseMultilineComments(string text, bool isMultiline)
+        {
+            var sut = CreateLexer(text);
+            var tokens = sut.ParseAll();
+            if (isMultiline)
+            {
+                Assert.AreEqual(1, tokens.Count);
+            }
+            else
+            {
+                Assert.Less(1, tokens.Count);
+            }
+        }
     }
 }

Lexer/MLexer.cs

@@ -27,6 +27,10 @@ namespace Lexer
 
         private Trivia LexComment()
         {
+            if (TokensSinceNewLine == 0 && Window.PeekChar(1) == '{')
+            {
+                return LexMultilineComment();
+            } 
             var n = 1;
             while (!IsEolOrEof(Window.PeekChar(n)))
             {
@@ -36,6 +40,52 @@ namespace Lexer
             return new Trivia(TriviaType.Comment, Window.GetAndConsumeChars(n));
         }
 
+        private Trivia LexMultilineComment()
+        {
+            var n = 2;
+            var metPercentSign = false;
+            var atFirstLine = true;
+            while (true)
+            {
+                var c = Window.PeekChar(n);
+                if (c == '\0')
+                {
+                    throw new ParsingException($"Unexpected end of file while parsing multi-line comment.");
+                }
+
+                if (c == '\n')
+                {
+                    atFirstLine = false;
+                }
+
+                if (atFirstLine && !IsWhitespace(c)) // this is a one-line comment
+                {
+                    while (!IsEolOrEof(Window.PeekChar(n)))
+                    {
+                        n++;
+                    }
+
+                    return new Trivia(TriviaType.Comment, Window.GetAndConsumeChars(n));
+                }
+
+                if (metPercentSign && c == '}')
+                {
+                    return new Trivia(TriviaType.MultiLineComment, Window.GetAndConsumeChars(n+1));
+                }
+
+                if (c == '%')
+                {
+                    metPercentSign = true;
+                }
+                else
+                {
+                    metPercentSign = false;
+                }
+
+                n++;
+            }
+        }
+
         private List<Trivia> LexCommentAfterDotDotDot()
         {
             var n = 0;

Lexer/TextWindow.cs

@@ -52,8 +52,19 @@
 
         public void ConsumeChars(int n)
         {
+            for (var i = 0; i < n; i++)
+            {
+                if (PeekChar(i) == '\n' || PeekChar(i) == '\r')
+                {
+                    _position.Line++;
+                    _position.Column = 0;
+                }
+                else
+                {
+                    _position.Column++;
+                }
+            }
             Offset += n;
-            _position.Column += n;
         }
 
         public char GetAndConsumeChar()

Lexer/TriviaType.cs

@@ -4,6 +4,7 @@
     {
         Whitespace,
         NewLine,
-        Comment
+        Comment,
+        MultiLineComment
     }
 }