% \iffalse meta-comment
%
% File: datestamp.dtx
% ----------------------------------------------------------
% Package:     datestamp
% Version:     v0.3 (14 December, 2021)
% Author:      निरंजन
% Description: Fixed date-stamps with LuaLaTeX.
% Repository:  http://puszcza.gnu.org.ua/projects/datestamp
% License:     GPLv3+, GFDLv1.3+
% ----------------------------------------------------------
%
% LaTeX Package datestamp v0.3
% Copyright © 2021 निरंजन
%
% This program is free software: you can redistribute it
% and/or modify it under the terms of the GNU General Public
% License as published by the Free Software Foundation,
% either version 3 of the License, or (at your option) any
% later version.
%
% This program is distributed in the hope that it will be
% useful, but WITHOUT ANY WARRANTY; without even the implied
% warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
% PURPOSE. See the GNU General Public License for more
% details.
%
% You should have received a copy of the GNU General Public
% License along with this program. If not, see
% <https://www.gnu.org/licenses/>.
%
% The current maintainer of this work is निरंजन.
%
% This work consists of the files datestamp.dtx
%                                 datestamp.ins
% and the derived file            datestamp.sty.
% \fi
% \iffalse
%<*internal>
\iffalse
%</internal>
%<*readme>
-----------------------------------------------------------
Package:     datestamp
Version:     v0.3 (14 December, 2021)
Author:      निरंजन
Description: Fixed date-stamps with LuaLaTeX
Repository:  http://puszcza.gnu.org.ua/projects/datestamp
License:     GPLv3+, GFDLv1.3+
-----------------------------------------------------------
%</readme> 
%<*internal>
\fi
%</internal>
%<*driver|package>
\def\datestampname{datestamp}
\def\datestampversion{0.3}
\def\datestampdate{2021-12-14}
\def\datestampdescription{%
  Fixed date-stamps with LuaLaTeX.%
}
%</driver|package>
%<*driver>
\documentclass{l3doc}
\usepackage{xcolor}
\usepackage{fontawesome5}
\usepackage{fancyvrb}
\usepackage{hyperref}
\hypersetup{%
  unicode,%
  colorlinks,%
  urlcolor=blue!60!black,%
  linkcolor=blue!60!black,%
  citecolor=green!60!black,%
  pdftitle={The datestamp package},%
  pdfauthor={निरंजन},%
  pdfsubject={\datestampdescription}
}%
\usepackage{fontspec}
\newfontfamily\devanagari[%
  Script=Devanagari,%
  Scale=0.8%
]%
{Shobhika}
\newcommand\textcode[1]{\Verb|#1|}

\begin{document}
    \DocInput{\datestampname.dtx}
\end{document}
%</driver>
% \fi
% \title{The \pkg{\datestampname} package}
% \author{{\devanagari निरंजन}}
% \date
% {^^A
%   Version \datestampversion\ --- \datestampdate\\[1ex]^^A
%   {^^A
%     \small\faIcon{link}\quad
%     \url{https://ctan.org/pkg/datestamp}^^A
%   }\\^^A
%   {^^A
%     \small\faIcon{bug}\quad
%     \url{http://puszcza.gnu.org/bugs/?group=datestamp}^^A
%   }^^A
% }
%
% \maketitle
% 
% \begin{documentation}
%   \begin{abstract}
%     \href{https://tex.stackexchange.com/q/611721/174620}%
%     {This} question on SE inspired me to write a code
%     which can store and recall dates whenever needed.
%     Lua\LaTeX\ provided a smooth interface for achieving
%     this and thus this package was developed.
%   \end{abstract}
%   \section{Documentation}
%   \begin{function}{\adddatestamp}
%     \begin{syntax}
%       \cs{adddatestamp} \marg{key}
%     \end{syntax}
%     This command takes one mandatory argument which is the
%     key that we set for printing the date. The key is
%     printed in the auxiliary file with extension
%     \verb|.ds|. If in case one loses their auto-generated
%     \verb|.ds| file, they can simply write one with
%     whichever dates of their choice. e.g.\ A sample
%     \verb|.ds| file might look like the following.
% \begin{verbatim}
% firstdate = "August 21, 2021"
% seconddate = "September 21, 2021"
% thirddate = "October 22, 2021"
% \end{verbatim}
%     One can fool the program by writing a file like this
%     themselves!
%   \end{function}
%   \begin{function}{\addmonthstamp}
%     \begin{syntax}
%       \cs{addmonthstamp} \marg{key}
%     \end{syntax}
%     Similar to \cs{adddatestamp}, this command prints a
%     fixed month-stamp.
%   \end{function}
%   \begin{function}{\addyearstamp}
%     \begin{syntax}
%       \cs{addyearstamp} \marg{key}
%     \end{syntax}
%     This command prints a fixed year-stamp.
%   \end{function}
%   \vfill
%
%   \hrule
%
%   \medskip
%   {^^A
%     \setlength{\parindent}{0pt}
%     \LaTeX\ package \pkg{datestamp}
%     
%     Copyright © 2021 {\devanagari निरंजन}
%   
%     Permission is granted to copy, distribute and/or
%     modify this document under the terms of the GNU Free
%     Documentation License, Version 1.3 or any later
%     version published by the Free Software Foundation;
%     with no Invariant Sections, no Front-Cover Texts, and
%     no Back-Cover Texts. A copy of the license is included
%     in the section entitled ``GNU Free Documentation
%     License''.
%   }%
% \end{documentation}
% \newpage
% \begin{implementation}
% \section{Implementation}
% Provide package with its basic information.
%    \begin{macrocode}
%<@@=datestamp>
%<*package>
\ProvidesPackage{datestamp}[2021/12/14 v0.3
Fixed date-stamps with LuaLaTeX.]
%    \end{macrocode}
% Load package \pkg{xparse} for declaring the robust command
% \cs{luacodefordatestamp}. This is a generic \& internal
% command. We will Call \cs{directlua} \& open a file in
% append mode so that it will be created if doesn't exist \&
% just appended if exists. The following code creates a file
% with the extension \verb|.ds| \& the name of the root
% file. Note that using \verb|a+| mode also enables the
% \verb|read| mode.
%    \begin{macrocode}
\RequirePackage{xparse}
\NewDocumentCommand{\luacodefordatestamp}{ m m }{%
  \directlua{%
    dsfile = io.open("\jobname.ds", "a+")
%    \end{macrocode}
% Now we store the content of the \verb|.ds| file in a
% variable named \verb|dscontent|.
%    \begin{macrocode}
    dscontent = dsfile:read "*a"
%    \end{macrocode}
% We first check if the key used in the argument of
% \cs{adddatestamp} is already present in our aux file and
% if it is present, our code does nothing. It adds the key
% followed by the \verb|=| sign and the date to the
% \verb|.ds| file if the key is absent. We close the file
% when this job is done \& we end the if-conditional.
%    \begin{macrocode}
    if string.find(dscontent, "#1") then
    else
      dsfile:write("#1 = \string\"#2\string\"\string\n")
      io.close(dsfile)
    end
%    \end{macrocode}
% With \verb|dofile| command we execute the \verb|.ds| file
% as a Lua code. With this our keys automatically become Lua
% variables which store the dates.
%    \begin{macrocode}
    dofile("\jobname.ds")
%    \end{macrocode}
% Finally we print the date by calling the key as a Lua
% variable (which is by the way our \TeX-argument XD).
%    \begin{macrocode}
    tex.sprint(#1)
  }%
}
%    \end{macrocode}
% After creating this generic internal command, we use it
% for producing various stamps. i.e.\ date, month \& year. I
% am using the default \TeX-commands for producing them as
% these commands have great localization-support.
%    \begin{macrocode}
\NewDocumentCommand{\adddatestamp}{ m }{%
  \luacodefordatestamp{#1}{\today}%
}%
\NewDocumentCommand{\addyearstamp}{ m }{%
  \luacodefordatestamp{#1}{\the\year}%
}%
\NewDocumentCommand{\addmonthstamp}{ m }{%
  \luacodefordatestamp{#1}{\the\month}%
}%
\NewDocumentCommand{\adddaystamp}{ m }{%
  \luacodefordatestamp{#1}{\the\day}%
}%
%    \end{macrocode}
% End of the package.
%    \begin{macrocode}
%</package>
%    \end{macrocode}
% \end{implementation}
% \newpage
% \phantomsection
% \addcontentsline{toc}{section}{GNU Free Documentation License}
% \include{gfdl-tex.tex}
% \Finale