Tokenizing input

Lexer.h

@@ -2,16 +2,28 @@
 #define LEXER_H
 
 #include <vector>
-
-class Token;
+#include "Token.h"
 
 class Lexer {
 private:
     std::string source;
+    int currentIndex = 0;
+    int currentLine = 0;
+
+    Token nextToken();
+    Token matchEnd();
+    Token matchNewLine();
+    Token matchInvalid();
+    Token matchSymbol(char symbol, Token::Kind kind);
+    Token matchInteger();
+
+    bool isWhiteSpace(int index);
+    bool isNewLine(int index);
+    bool isDigit(int index);
 
 public:
     Lexer(std::string source);
-    std::vector<Token> tokens();
+    std::vector<Token> getTokens();
 };
 
 #endif