% xkeymask package by Ramkumar Ramachandra.
%%
%% --------------------------------------------
%% Copyright (C) 2022-2023 Ramkumar Ramachandra
%% --------------------------------------------
%%
%% This work may be distributed and/or modified under the
%% conditions of the LaTeX Project Public License, either
%% version 1.3c of this license or (at your option)
%% any later version. The latest version of this license
%% can be found at:
%%   https://www.latex-project.org/lppl.txt
%% and version 1.3c or later is part of all distributions
%% of LaTeX version 2008/05/04 or later.
%%
%% This work has the LPPL maintenance status "maintained".
%%
%% This Current Maintainer is Ramkumar Ramachandra.
%%
%% This work consists of the file xkeymask.sty.
%%
%% The following files constitute the xkeymask bundle and
%% must be distributed as a whole:
%%   README, xkeymask.sty, xkeymask.tex, xkeymask.pdf.
%%
\RequirePackage{kvoptions, xkeyval}
\ProvidesPackage{xkeymask}[v1.0 An extension of xkeyval with a mask]

% Option processing
\newif\ifxkeymask@prefix
\DeclareStringOption{prefix}
\AddToKeyvalOption*{prefix}{\xkeymask@prefixtrue}
\ProcessKeyvalOptions*

\ifxkeymask@prefix
  % We patch xkeyval's \setkeys to use a mask to ignore keys
  \makeatletter
  % Our global mask
  \def\XKM@mask{}

  % First we define \appendmask
  \long\def\XKM@appendmask[#1]{
    \XKV@for@o\XKV@fams\XKV@tfam{
      \xdef\XKM@hdr{\XKV@prefix\XKV@tfam @}
      \XKV@for@o{#1}\XKV@tempa{
        % Remove spaces around key name
        \expandafter\KV@@sp@def\expandafter\XKV@tempa\expandafter{\XKV@tempa}
        \XKV@addtolist@x\XKM@mask{\XKM@hdr\XKV@tempa}
      }
    }
  }
  \def\appendmask{\XKV@testopta{\XKV@testoptc\XKM@appendmask}}

  % Query the mask for a key
  \long\def\XKM@ifinmask[#1]#2#3{
    \XKV@checksanitizea{#1}\XKV@tempc
    \XKV@for@o\XKV@fams\XKV@tfam{
      \XKV@for@o\XKV@tempc\XKV@tempb{
        \xdef\XKM@hdr{\XKV@prefix\XKV@tfam @}
        \xdef\XKV@tempd{\XKV@prefix\XKV@tfam @\XKV@tempb}
        \@expandtwoargs\in@\XKV@tempd\XKM@mask
        \ifin@
          #2
        \else
          #3
        \fi
      }
    }
  }
  \def\ifinmask{\XKV@testopta{\XKV@testoptc\XKM@ifinmask}}

  % A quick way to clear the mask
  \def\clearmask{\global\let\XKM@mask\@empty}

  % Now we override the definition of \XKV@setkeys
  \long\def\XKM@setkeys[#1]#2{
    \XKV@checksanitizea{#2}\XKV@resb
    \let\XKV@resa\@empty
    \XKV@for@o\XKV@fams\XKV@tfam{
      \XKV@for@o\XKV@resb\XKV@tempb{
        \expandafter\XKV@g@tkeyname\XKV@tempb=\@nil\XKV@tempc
        % Remove spaces around key name
        \expandafter\KV@@sp@def\expandafter\XKV@tempc\expandafter{\XKV@tempc}
        \xdef\XKV@tempd{\XKV@prefix\XKV@tfam @\XKV@tempc}
        % If \XKV@tempd is in \XKM@mask,
        % remove the corresponding kv from \XKV@resb
        \@expandtwoargs\in@\XKV@tempd\XKM@mask
        \ifin@\else\XKV@addtolist@o\XKV@resa\XKV@tempb\fi
      }
    }
    \ifnum\XKV@depth=\z@\let\XKV@rm\@empty\fi
    \expandafter\XKV@s@tkeys\expandafter{\XKV@resa}{#1}
    \let\CurrentOption\@empty
  }

  % A dispatcher to \XKM@setkeys or \XKV@setkeys
  \long\def\XKM@setkeys@dispatch{
    \xdef\XKV@tempa{\xkeymask@prefix @}
    \ifx\XKV@prefix\XKV@tempa
      \expandafter\XKM@setkeys
    \else
      \expandafter\XKV@setkeys
    \fi
  }

  % Finally, override \setkeys itself to call the dispatcher
  \def\setkeys{\XKV@testopta{\XKV@testoptc\XKM@setkeys@dispatch}}
  \makeatother
\fi