#ifndef CAMELLYA_LEXER_H
#define CAMELLYA_LEXER_H

#include <string>
#include <vector>
#include <optional>
#include <variant>

namespace camellya {

enum class TokenType {
    // Keywords
    CLASS, FUNC, NUMBER, STRING, BOOL, LIST, MAP,
    IF, ELSE, WHILE, FOR, RETURN, VAR,
    TRUE, FALSE, NIL, THIS,
    
    // Operators
    PLUS, MINUS, STAR, SLASH, PERCENT,
    EQUAL, EQUAL_EQUAL, BANG_EQUAL,
    LESS, LESS_EQUAL, GREATER, GREATER_EQUAL,
    AND, OR, BANG,
    
    // Delimiters
    LEFT_PAREN, RIGHT_PAREN,
    LEFT_BRACE, RIGHT_BRACE,
    LEFT_BRACKET, RIGHT_BRACKET,
    COMMA, DOT, SEMICOLON, COLON,
    ARROW,
    
    // Literals
    IDENTIFIER, NUMBER_LITERAL, STRING_LITERAL,
    
    // Special
    END_OF_FILE, INVALID
};

struct Token {
    TokenType type;
    std::string lexeme;
    std::variant<std::monostate, double, std::string> literal;
    int line;
    int column;
    
    Token(TokenType type, std::string lexeme, int line, int column)
        : type(type), lexeme(std::move(lexeme)), line(line), column(column) {}
    
    template<typename T>
    Token(TokenType type, std::string lexeme, T literal, int line, int column)
        : type(type), lexeme(std::move(lexeme)), literal(std::move(literal)), line(line), column(column) {}
};

class Lexer {
public:
    explicit Lexer(std::string source);
    
    std::vector<Token> tokenize();
    
private:
    std::string source_;
    size_t start_ = 0;
    size_t current_ = 0;
    int line_ = 1;
    int column_ = 1;
    std::vector<Token> tokens_;
    
    bool is_at_end() const { return current_ >= source_.length(); }
    char advance();
    char peek() const;
    char peek_next() const;
    bool match(char expected);
    
    void skip_whitespace();
    void skip_comment();
    
    void scan_token();
    void add_token(TokenType type);
    void add_token(TokenType type, std::variant<std::monostate, double, std::string> literal);
    
    void scan_string();
    void scan_number();
    void scan_identifier();
    
    TokenType get_keyword_type(const std::string& text) const;
};

} // namespace camellya

#endif // CAMELLYA_LEXER_H