lexer.cpp

#include "lexer.hpp"

#include <map>
#include <string>

#include "defaults.hpp"
#include "token.hpp"

using Type = Token::Type;

// Maps words to token types.
static const std::map<std::string, Type> str_to_type = {
	{"exit", Type::EXIT},
	{"cd", Type::CD},
	{"|", Type::PIPE},
};

// Attempts to convert a word to a token type by
// searching in the dictionary. Returns UNDEF token if
// it fails to find a known word.
static inline Token search_dict(std::string& word) {
	auto type = str_to_type.find(word);
	if (type != str_to_type.end()) return Token(type->second, type->first);
	return Token(Type::UNDEF);
}

// Returns the next token in the expression and pops if called with pop = true.
template <bool pop>
static inline Token next_token(CPPArgList& expr) {
	if (!expr.size()) return Token(Type::EOE);
	std::string word = expr.back();
	if constexpr (pop) expr.pop_back();
	Token attempt_dict = search_dict(word);
	if (attempt_dict.type != Type::UNDEF)
		return attempt_dict;
	else
		return Token(word);
}

// Returns next token.
Token lexer::peek(CPPArgList& expr) { return next_token<false>(expr); }

// Returns next token and pops.
Token lexer::pop(CPPArgList& expr) { return next_token<true>(expr); }