#pragma once
#ifndef LEXER_InputLexer_H
#define LEXER_InputLexer_H

#include <exception>
#include <istream>
#include <string>

class InputLexer {
    public:
        class NoMoreTokens : public std::exception {};
        class NoMatch : public std::exception {};

        enum TokenType {
            nonmatching,
            ARROW,
            COLON,
            GRAMMAR,
            LEFT,
            LEXESIS,
            LEXESISNAME,
            NONASSOC,
            NUM,
            PARSER,
            PARSERTYPE,
            PIPE,
            PRECEDENCE,
            RIGHT,
            SEMICOLON,
            START,
            TERMINAL,
            TERMINALS,
            VARIABLE,
            ignore,
        };

        struct Token {
            TokenType type;
            std::string content;
        };
        
        InputLexer(std::istream& in);
        ~InputLexer();

        /**
         * Get the next token
         *
         * @throws NoMoreTokens if no more tokens are available
         * @throws NoMatch if no match was found
         */
        Token nextToken();

        /**
         * Skip the following `n` bytes.
         *
         * @param n The number of bytes to skip
         */
        void skip(std::size_t n);

        /**
         * Peek at the current head of the input stream, useful in error reporting when a character mismatches for example
         *
         * @throws NoMoreTokens if the input stream is at an end
         */
        char peek();

        /**
         * Get the current byte offset
         */
        std::size_t getByteOffset();

    private:
        std::size_t m_offset;
        std::istream& m_input;
};

#endif //LEXER_InputLexer_H