% set default size and document class
\documentclass[12pt]{extarticle}

% handle multiple languages
\usepackage{polyglossia}

% set main language
\setmainlanguage{\mainlanguage}

% language commands

\newcommand{\ifstr}[4]{\expandafter\ifstrequal\expandafter{#1}{#2}{#3}{#4}}

\newcommand{\bi}[2]{%
\ifstr{\mainlanguage}{en}{#1}{%
\ifstrempty{#2}{TRANSLATE ME!}{#2}%
}%
}

\newcommand{\en}[1]{\textenglish{#1}}

\newcommand{\fr}[1]{\textfrench{#1}}