\NeedsTeXFormat{LaTeX2e}
\ProvidesPackage{mkessler-vocab}[2021-09-06 - Package for emphasizing vocabulary]
%%%%%%%%%%%%%%%%%%
%%Provides a \vocab<[name in index]>{vocabulary} command to print vocabulary in bold blue and automatically index it.

\newif\ifmkessler@vocab@english\mkessler@vocab@englishtrue
\DeclareOption{german}{\mkessler@vocab@englishfalse}
\DeclareOption{english}{\mkessler@vocab@englishtrue}

\newif\ifmkessler@vocab@index\mkessler@vocab@indexfalse
\DeclareOption{index}{\mkessler@vocab@indextrue}
\DeclareOption{noindex}{\mkessler@vocab@indexfalse}

\DeclareOption*{\PackageWarning{mkessler-vocab}{Unknown '\CurrentOption'}}
\ProcessOptions\relax

%%%%Management of vocabulary and corresponding index
\RequirePackage{xparse}
\RequirePackage{xcolor}
\ifmkessler@vocab@index
    \RequirePackage{imakeidx}
    \makeindex[name=mkessler@vocab@indexname, columns=2, title=\ifmkessler@vocab@english Index\else Stichwortverzeichnis\fi, intoc]

    %Emphasize \vocabulary
    \RequirePackage{expl3}
    \ExplSyntaxOn
    \NewDocumentCommand{\vocab}{O{} m}{
        \textbf{\color{blue} #2}%
        \if\relax\detokenize{#1}\relax%
        \index[mkessler@vocab@indexname]{\text_titlecase_first:n{#2}} % true branch: #1 was empty
        \else
        \index[mkessler@vocab@indexname]{#1} % false branch: #1 was supplied
        \fi
    }
    \ExplSyntaxOff
    \newcommand\printvocabindex{
        \printindex[mkessler@vocab@indexname]
    }
\else
    \NewDocumentCommand{\vocab}{O{} m }{
        \textbf{\color{blue} #2}
    }
\fi