#include "Lexer.h"
#include <iostream>

namespace Parser
{
    using Parser::Lexer;
    std::list<Lexer::Token> Lexer::tokenize(const std::string_view &text)
    {
        tokens.clear();
        this->text = text;

        while (current != text.length())
        {
            if (text.at(current) == ' ')
            {
                advance();
                continue;
            }
            if (text.at(current) == '\n')
            {
                advance();
                line++;
                continue;
            }

            start = current;

            switch (Lexer::peek())
            {
            case '+':
                advance();
                token(Token::PLUS);
                break;
            case '-':
                advance();
                token(Token::MINUS);
                break;
            case '*':
                advance();
                token(Token::MULTIPLY);
                break;
            case '/':
                advance();
                token(Token::DIVIDE);
                break;
            case '=':
                advance();
                token(Token::ASSIGNMENT);
                break;
            case '(':
                advance();
                token(Token::BRACKET_LEFT);
                break;
            case ')':
                advance();
                token(Token::BRACKET_RIGHT);
                break;

            default:
                if (isDigit(peek()))
                {
                    advance();
                    number();
                }

                if (isAlpha(peek()))
                {
                    advance();
                    identifier();
                }
            }
        }

        return tokens;
    }
    void Lexer::advance()
    {
        current++;
    }

    char Lexer::peek()
    {
        if (current == text.length())
            return 0;
        return text.at(current);
    }

    void Lexer::token(const Token::TokenType type)
    {
        tokens.emplace_back(Token(type, line, text.substr(start, (current - start))));
    }

    bool Lexer::isDigit(const char &c)
    {
        return c >= '0' && c <= '9';
    }

    void Lexer::number()
    {
        while (isDigit(peek()))
        {
            advance();
        }

        token(Token::INT);
    }

    bool Lexer::isAlpha(const char &c)
    {
        return ((c >= 'a') && (c <= 'z')) || ((c >= 'A') && (c <= 'Z'));
    }

    void Lexer::identifier()
    {
        while (isAlpha(peek()) || isDigit(peek()))
        {
            advance();
        }

        token(Token::IDENTIFIER);
    }
}