%D \module
%D   [       file=mult-aux,
%D        version=2010.08.2,
%D          title=\CONTEXT\ Multilingual Macros,
%D       subtitle=Helpers,
%D         author=Hans Hagen,
%D           date=\currentdate,
%D      copyright={PRAGMA ADE \& \CONTEXT\ Development Team}]
%C
%C This module is part of the \CONTEXT\ macro||package and is
%C therefore copyrighted by \PRAGMA. See mreadme.pdf for
%C details.

% todo: setupxxx and setupxxxs (so a plural for the root setup and
% we can consider blocking the root)

% todo (e.g for columnsets and registers): \definexxx[parent][1]
%

%D A generalization of \MKIV-like inheritance. Just something to play
%D with (interface might change). The code here evolved in an email
%D exchange between me and Wolgang Schuster.

% todo: doifelse<whatever>

\writestatus{loading}{ConTeXt Multilingual Macros / Helpers}

\registerctxluafile{mult-aux}{}

\unprotect

\edef\??empty{\Uchar25}  \letvalue{\Uchar25}\empty % cancel: dec:24 hex:18

%edef\s!parent{\Uchar29} \letvalue{\Uchar29}\empty % + inlining  is ugly, a tiny bit faster, but neglectable on a run

%D \starttyping
%D \unprotect
%D     \def\????aa{@@@@aa}
%D
%D     \installparameterhandler   \????aa {whatever}
%D     \installsetuphandler       \????aa {whatever}
%D     \installdefinehandler      \????aa {whatever} \????aa % #3 == defaultroot
%D     \installfontandcolorhandler\????aa {whatever}
%D
%D   % \installcommandhandler     \????aa {whatever} \????aa
%D \protect
%D
%D % \whateverparameter \c!test
%D % \whateverparameterhash \c!test
%D % \namedwhateverparameter \mycurrentwhatever \c!test
%D % \usewhateverstyleandcolor \c!style \c!color
%D % \everydefinewhatever (sets \currentwhatever)
%D % \everypresetwhatever (can be used to reset parameters as we can redefine)
%D % \everysetupwhatever (sets \currentwhatever)
%D
%D \starttext
%D     \definewhatever[first] \definewhatever[second][first]
%D                                           test: \def\currentwhatever{first}  \whateverparameter{method} \par
%D     \setupwhatever        [method=unset]  test: \def\currentwhatever{first}  \whateverparameter{method} \par
%D     \setupwhatever[first] [method=first]  test: \def\currentwhatever{first}  \whateverparameter{method} \par
%D                                           test: \def\currentwhatever{second} \whateverparameter{method} \par
%D     \setupwhatever[second][method=second] test: \def\currentwhatever{second} \whateverparameter{method} \par
%D \stoptext
%D \stoptyping

% problem: every* could clash
%
% There can be less {} in the following definitions if we assume \??aa and \c!somecs
%
% todo: \def\detokenized...parameter#1{\detokenize\expandafter\expandafter\expandafter{\csname#1#2\endcsname}} % always root
%
% it might be more efficient to do this at the lua and
%
% watch the push/pop and predefinition of current .. this is needed for nested
% definitions and overloaded defines using the predefined one

% todo: add (relaxed) postsetup and postdefine hooks, just after the everys

% Start of experimental code: especially tables can have many assignments
% and although most time is spent in the typesetting anyway, we can squeeze
% out a little bit. Of course having 500 rows of 50 columns each with some
% setting does not happen that often. One should keep in mind that in the
% average document having some 500 assignments is no exception but there we're
% talking of neglectable runtime for them. Of course in the definitions below
% there is no real gain, only in the generated \setup* commands. Another
% situation with many assignments is \XML\ where we can pass attributes
% and normally don't do testing of them making sense.
%
% \testfeatureonce{100000}{\getparameters[bla][a=111,b=222,c=333]}% 1.669s
% \testfeatureonce{100000}{\mult_interfaces_get_parameters{bla} [a=111,b=222,c=333]}% 1.529s
% \testfeatureonce{100000}{\def\m_mult_interfaces_namespace{bla}\mult_interfaces_get_parameters_indeed[a=111,b=222,c=333]}% 1.466s

\let\m_mult_interfaces_namespace\empty

\def\mult_interfaces_get_parameters#1[#2%
  {\if\noexpand#2]%
     \expandafter\gobbleoneargument
   \else
     \def\m_mult_interfaces_namespace{#1}%
     \expandafter\mult_interfaces_get_parameters_indeed
   \fi#2}

\def\mult_interfaces_get_parameters_indeed#1]% namespace already set
  {\mult_interfaces_get_parameters_item#1,],\_e_o_p_}

\def\mult_interfaces_get_parameters_item#1,#2% #2 takes space before ,
  {\if,#1,% dirty trick for testing #1=empty
     \expandafter\mult_interfaces_get_parameters_item
   \else\if]#1%
     \doubleexpandafter\gobbleoneargument
   \else
     \mult_interfaces_get_parameters_assign#1==\empty\_e_o_p_
   % \doubleexpandafter\mult_interfaces_get_parameters_item % saves skipping when at end
   \fi\fi#2}

\def\mult_interfaces_get_parameters_error#1#2% #3%
  {\mult_interfaces_get_parameters_error_indeed{#1}{#2}%
   \gobbleoneargument}

\def\mult_interfaces_get_parameters_error_indeed#1#2%
  {\showassignerror{#2}{\the\inputlineno\space(#1)}}

\def\mult_interfaces_get_parameters_assign#1=#2=#3#4\_e_o_p_
  {\ifx\empty#1\empty
     \expandafter\mult_interfaces_get_parameters_error
   \else\ifx#3\empty
     \doubleexpandafter\mult_interfaces_get_parameters_error
   \else
     \doubleexpandafter\mult_interfaces_def
   \fi\fi
   \m_mult_interfaces_namespace{#1}{#2}%
   \doubleexpandafter\mult_interfaces_get_parameters_item}

\startinterface english

    % some 10% faster

    \let\mult_interfaces_get_parameters_error\undefined

    \def\mult_interfaces_get_parameters_error_one#1\csname#2#3\endcsname#4%
      {\mult_interfaces_get_parameters_error_indeed{#2}{#3}\iftrue}

    \def\mult_interfaces_get_parameters_error_two#1\csname#2#3\endcsname#4%
      {\mult_interfaces_get_parameters_error_indeed{#2}{#3}}

    \def\mult_interfaces_get_parameters_assign#1=#2=#3#4\_e_o_p_
      {\ifx\empty#1\empty
         \mult_interfaces_get_parameters_error_one
       \else\ifx#3\empty
         \mult_interfaces_get_parameters_error_two
       \else
         \expandafter\def\csname\m_mult_interfaces_namespace#1\endcsname{#2}%
       \fi\fi
       \doubleexpandafter\mult_interfaces_get_parameters_item}

    % interesting but not faster
    %
    % \def\mult_interfaces_get_parameters_error_one#1\m_mult_interfaces_namespace#2\fi\fi%
    %   {\mult_interfaces_get_parameters_error_indeed\m_mult_interfaces_namespace{#2}\m_mult_interfaces_namespace\s!dummy\fi}
    %
    % \def\mult_interfaces_get_parameters_error_two#1\m_mult_interfaces_namespace#2\fi\fi%
    %   {\mult_interfaces_get_parameters_error_indeed\m_mult_interfaces_namespace{#2}\m_mult_interfaces_namespace\s!dummy\fi\fi}
    %
    % \def\mult_interfaces_get_parameters_assign#1=#2=#3#4\_e_o_p_
    %   {\expandafter\def\csname
    %      \ifx\empty#1\empty
    %        \mult_interfaces_get_parameters_error_one
    %      \else\ifx#3\empty
    %        \mult_interfaces_get_parameters_error_two
    %      \else
    %        \m_mult_interfaces_namespace#1%
    %      \fi\fi
    %    \endcsname{#2}
    %    \doubleexpandafter\mult_interfaces_get_parameters_item}

\stopinterface

\newif\ifassignment

\def\mult_check_for_assignment_indeed#1=#2#3\_end_
  {\if#2@\assignmentfalse\else\assignmenttrue\fi}

\def\mult_check_for_assignment_indeed_begin_#1=#2#3\_end_
  {\if#2@}


\def\mult_check_for_assignment#1%
  {\expandafter\mult_check_for_assignment_indeed\detokenize{#1}=@@\_end_}

% End of experimental code.

\unexpanded\def\mult_interfaces_let #1#2{\expandafter\let \csname#1\ifcsname\k!prefix!#2\endcsname\csname\k!prefix!#2\endcsname\else#2\fi\endcsname}
\unexpanded\def\mult_interfaces_lete#1#2{\expandafter\let \csname#1\ifcsname\k!prefix!#2\endcsname\csname\k!prefix!#2\endcsname\else#2\fi\endcsname\empty}
\unexpanded\def\mult_interfaces_def #1#2{\expandafter\def \csname#1\ifcsname\k!prefix!#2\endcsname\csname\k!prefix!#2\endcsname\else#2\fi\endcsname}
\unexpanded\def\mult_interfaces_edef#1#2{\expandafter\edef\csname#1\ifcsname\k!prefix!#2\endcsname\csname\k!prefix!#2\endcsname\else#2\fi\endcsname}
\unexpanded\def\mult_interfaces_gdef#1#2{\expandafter\gdef\csname#1\ifcsname\k!prefix!#2\endcsname\csname\k!prefix!#2\endcsname\else#2\fi\endcsname}
\unexpanded\def\mult_interfaces_xdef#1#2{\expandafter\xdef\csname#1\ifcsname\k!prefix!#2\endcsname\csname\k!prefix!#2\endcsname\else#2\fi\endcsname}

\startinterface english

    \unexpanded\def\mult_interfaces_let #1#2{\expandafter \let\csname#1#2\endcsname}
    \unexpanded\def\mult_interfaces_lete#1#2{\expandafter \let\csname#1#2\endcsname\empty}
    \unexpanded\def\mult_interfaces_def #1#2{\expandafter \def\csname#1#2\endcsname}
    \unexpanded\def\mult_interfaces_edef#1#2{\expandafter\edef\csname#1#2\endcsname}
    \unexpanded\def\mult_interfaces_gdef#1#2{\expandafter\gdef\csname#1#2\endcsname}
    \unexpanded\def\mult_interfaces_xdef#1#2{\expandafter\xdef\csname#1#2\endcsname}

\stopinterface

% the commented detokenized variant that backtracks ... needs testing usage first
%
% \let\whatever\relax
%
% \definetest[oeps][bagger=\whatever]
%
% \def\currenttest{oeps} \edef\hans{\detokenizedtestparameter{bagger}}\meaning\hans\par
% \def\currenttest{oeps} \edef\hans{\detokenizedtestparameter{reggab}}\meaning\hans\par
%
% slower: \def#3##1{\csname\ifcsname#1#2:##1\endcsname\expandafter\csstring\lastnamedcs\else\expandafter#5\csname#1#2:\s!parent\endcsname{##1}\fi\endcsname}%
%
% pre-expansion can be a bit faster but handly any effect on a normal run so let's go for
% saving some memory

\def\mult_interfaces_detokenize{\expandafter\expandafter\expandafter\detokenize\expandafter\expandafter\expandafter}

\unexpanded\def\mult_interfaces_install_parameter_handler#1#2#3#4#5#6#7#8% inlining \csname*\endcsname is more efficient (#3 and #6 only)
  {\ifx#2\relax\let#2\empty\fi                                           % it is hardly faster but produces less expansion tracing
   \def#3##1{\csname\ifcsname#1#2:##1\endcsname#1#2:##1\else\expandafter#5\csname#1#2:\s!parent\endcsname{##1}\fi\endcsname}%
   \def#4##1##2{\ifcsname##1:##2\endcsname##1:##2\else\expandafter#5\csname##1:\s!parent\endcsname{##2}\fi}%
  %\def#5##1##2{\ifx##1\relax\??empty\else#4{##1}{##2}\fi}% is {} needed around ##1 ?
   \def#5##1##2{\ifx##1\relax\??empty\else#4##1{##2}\fi}% is {} needed around ##1 ?
   \def#6##1##2{\csname\ifcsname#1##1:##2\endcsname#1##1:##2\else\expandafter#5\csname#1##1:\s!parent\endcsname{##2}\fi\endcsname}%
   \def#7##1{\detokenize\expandafter\expandafter\expandafter{\csname#1#2:##1\endcsname}}% always root, no backtrack
   \def#8##1{\begincsname#1#2:##1\endcsname}}

\unexpanded\def\installparameterhandler#1#2%
  {\normalexpanded
     {\mult_interfaces_install_parameter_handler
        {\noexpand#1}% \??aa
        \expandafter\noexpand\csname current#2\endcsname
        \expandafter\noexpand\csname #2parameter\endcsname
        \expandafter\noexpand\csname do#2parameter\endcsname           % or : #2_parameter
        \expandafter\noexpand\csname do#2parentparameter\endcsname     % or : #2_parent_parameter
        \expandafter\noexpand\csname named#2parameter\endcsname
        \expandafter\noexpand\csname detokenized#2parameter\endcsname
        \expandafter\noexpand\csname direct#2parameter\endcsname}} % strict#2parameter is gone

\unexpanded\def\mult_interfaces_install_root_parameter_handler#1#2#3%
  {\def#2##1{\detokenize\expandafter\expandafter\expandafter{\csname#1:##1\endcsname}}% always root
   \def#3##1{\begincsname#1:##1\endcsname}}

\unexpanded\def\installrootparameterhandler#1#2%
  {\normalexpanded
     {\mult_interfaces_install_root_parameter_handler
        {\noexpand#1}% \??aa
        \expandafter\noexpand\csname detokenizedroot#2parameter\endcsname
        \expandafter\noexpand\csname root#2parameter\endcsname}}

\unexpanded\def\mult_interfaces_install_parameter_hash_handler#1#2#3#4#5#6#7#8#9%
  {\ifx#2\relax\let#2\empty\fi
   \def#3##1{#1#4{#1#2}{##1}:}% leading #1 was missing .. is this one used?
   \def#4##1##2{\ifcsname##1:##2\endcsname##1\else\expandafter#5\csname##1:\s!parent\endcsname{##2}\fi}%
  %\def#5##1##2{\ifx##1\relax\else#4{##1}{##2}\fi}%
   \def#5##1##2{\ifx##1\relax\else#4##1{##2}\fi}%
   \def#6{#1#2:}%
   \def#7##1{#1##1:}%
   \def#8{\ifx#2\empty\else\ifcsname#1#2:\s!parent\endcsname\else\expandafter\let\csname#1#2:\s!parent\endcsname#1\fi\fi}%
   \unexpanded\def#9##1{\expandafter\edef\csname#1##1:\s!parent\endcsname{#1#2}}}

\unexpanded\def\installparameterhashhandler#1#2%
  {\expandafter\let\csname#2namespace\endcsname#1%
   \normalexpanded
     {\mult_interfaces_install_parameter_hash_handler
        {\noexpand#1}% \??aa
        \expandafter\noexpand\csname current#2\endcsname
        \expandafter\noexpand\csname #2parameterhash\endcsname
        \expandafter\noexpand\csname do#2parameterhash\endcsname         % or : #2_parameter_hash
        \expandafter\noexpand\csname do#2parentparameterhash\endcsname   % or : #2_parent_parameter_hash
        \expandafter\noexpand\csname current#2hash\endcsname
        \expandafter\noexpand\csname named#2hash\endcsname
        \expandafter\noexpand\csname check#2parent\endcsname
        \expandafter\noexpand\csname chaintocurrent#2\endcsname}}

% In \MKIV\ we can probably use the english variant for all other
% languages too.

% todo: inline the def/let

\unexpanded\def\mult_interfaces_install_parameter_set_handler#1#2#3#4#5#6%
  {\ifx#2\relax\let#2\empty\fi
   \unexpanded\def#3{\mult_interfaces_def {#1#2:}}%              ##1 {##2} (braces are mandate)
   \unexpanded\def#4{\mult_interfaces_edef{#1#2:}}%              ##1 {##2} (braces are mandate)
   \unexpanded\def#5{\mult_interfaces_let {#1#2:}}%              ##1 ##2
   \unexpanded\def#6{\mult_interfaces_lete{#1#2:}}}% ##1

\startinterface english

    \unexpanded\def\mult_interfaces_install_parameter_set_handler#1#2#3#4#5#6%
      {\ifx#2\relax\let#2\empty\fi
       \unexpanded\def#3##1{\expandafter \def\csname#1#2:##1\endcsname}%        ##1 {##2} (braces are mandate)
       \unexpanded\def#4##1{\expandafter\edef\csname#1#2:##1\endcsname}%        ##1 {##2} (braces are mandate)
       \unexpanded\def#5##1{\expandafter \let\csname#1#2:##1\endcsname}%        ##1 ##2
       \unexpanded\def#6##1{\expandafter \let\csname#1#2:##1\endcsname\empty}}% ##1

\stopinterface

\unexpanded\def\installparametersethandler#1#2%
  {\normalexpanded
     {\mult_interfaces_install_parameter_set_handler
        {\noexpand#1}% \??aa
        \expandafter\noexpand\csname current#2\endcsname
        \expandafter\noexpand\csname set#2parameter\endcsname
        \expandafter\noexpand\csname setexpanded#2parameter\endcsname
        \expandafter\noexpand\csname let#2parameter\endcsname
        \expandafter\noexpand\csname reset#2parameter\endcsname}}

\let\dousecurrentstyleparameter\relax
\let\dousecurrentcolorparameter\relax

\let\currentstyleparameter\empty
\let\currentcolorparameter\empty

\unexpanded\def\mult_interfaces_install_style_and_color_handler#1#2#3#4%
  {\unexpanded\def#2##1##2% style color
     {\edef\currentstyleparameter{#1{##1}}% this name is public (can also set color e.g. in underline)
      \ifx\currentstyleparameter\empty\else\dousecurrentstyleparameter\fi
      \edef\currentcolorparameter{#1{##2}}% this name is public (so we do this after the style switch)
      \ifx\currentcolorparameter\empty\else\dousecurrentcolorparameter\fi}%
   \unexpanded\def#3##1% style
     {\edef\currentstyleparameter{#1{##1}}% this name is public
      \ifx\currentstyleparameter\empty\else\dousecurrentstyleparameter\fi}%
   \unexpanded\def#4##1% color
     {\edef\currentcolorparameter{#1{##1}}% this name is public
      \ifx\currentcolorparameter\empty\else\dousecurrentcolorparameter\fi}}

\unexpanded\def\installstyleandcolorhandler#1#2%
  {\normalexpanded
     {\mult_interfaces_install_style_and_color_handler
        \expandafter\noexpand\csname #2parameter\endcsname
        \expandafter\noexpand\csname use#2styleandcolor\endcsname % maybe an alias use#2styleandcolorparameters
        \expandafter\noexpand\csname use#2styleparameter\endcsname
        \expandafter\noexpand\csname use#2colorparameter\endcsname}}

\let\definehandlerparent\empty

\def\mult_check_for_parent#1#2#3#4%
  {\ifcsname#1#4:\s!parent\endcsname \else \ifx#4\empty \else
     \writestatus\m!system{error: invalid parent #4 for #3, #4 defined too (best check it)}%
     \expandafter\edef\csname#1#4:\s!parent\endcsname{#2}%
   \fi \fi}

%def\mult_interfaces_chain#1#2{\ifcsname#1#2:\s!chain\endcsname\csname#1#2:\s!chain\endcsname\space\fi}
%def\getparentchain       #1#2{\ifcsname#1#2:\s!chain\endcsname\csname#1#2:\s!chain\endcsname\fi}
%def\getcurrentparentchain#1#2{\ifcsname#1#2:\s!chain\endcsname\csname#1#2:\s!chain\endcsname\fi}

\def\mult_interfaces_chain#1#2{\ifcsname#1#2:\s!chain\endcsname\lastnamedcs\space\fi}
\def\getparentchain       #1#2{\begincsname#1#2:\s!chain\endcsname}
\def\getcurrentparentchain#1#2{\begincsname#1#2:\s!chain\endcsname}

\unexpanded\def\mult_interfaces_install_define_handler#1#2#3#4#5#6#7#8#9% why is \expanded still needed in clones
  {\ifx#4\relax\let#4\empty\fi                                          % see \defineregister
   \unexpanded\def#2{\dotripleempty#5}%
   \newtoks#6%
   \newtoks#7%
   \unexpanded\def#5[##1][##2][##3]% [child][parent][settings] | [child][settings] | [child][parent] | [child]
     {\let#9#4%
      \edef#4{##1}%
      \ifthirdargument
        \the#6% predefine
        \edef#8{##2}%
        \mult_check_for_parent{#1}{#3}#4#8%
        \expandafter\edef\csname#1#4:\s!chain\endcsname{\mult_interfaces_chain#1{##2}##1}%
        \expandafter\edef\csname#1#4:\s!parent\endcsname{#1##2}%
        \mult_interfaces_get_parameters{#1#4:}[##3]%
      \else\ifsecondargument
        \the#6% predefine
        \expandafter\mult_check_for_assignment_indeed\detokenize{##2}=@@\_end_
        \ifassignment
          \let#8\empty
          \expandafter\edef\csname#1#4:\s!chain\endcsname{##1}%
          \expandafter\edef\csname#1#4:\s!parent\endcsname{#3}%
          \mult_interfaces_get_parameters{#1#4:}[##2]%
        \else
          \edef#8{##2}%
          \mult_check_for_parent{#1}{#3}#4#8%
          \expandafter\edef\csname#1#4:\s!chain\endcsname{\mult_interfaces_chain#1{##2}##1}%
          \expandafter\edef\csname#1#4:\s!parent\endcsname{#1##2}%
        \fi
      \else
        \the#6% predefine
        \let#8\empty
        \expandafter\edef\csname#1#4:\s!chain\endcsname{##1}%
        \expandafter\edef\csname#1#4:\s!parent\endcsname{#3}%
      \fi\fi
      \the#7%
      \let#4#9}}

% \unexpanded\def\mult_interfaces_install_define_handler#1#2#3#4#5#6#7#8#9% why is \expanded still needed in clones
%   {\ifx#4\relax\let#4\empty\fi                                          % see \defineregister
%    \unexpanded\def#2{\dotripleempty#5}%
%    \newtoks#6%
%    \newtoks#7%
%    \unexpanded\def#5[##1][##2][##3]% [child][parent][settings] | [child][settings] | [child][parent] | [child]
%      {\let#9#4%
%       \edef#4{##1}%
%       \ifthirdargument
%         \the#6% predefine
%         \edef#8{##2}%
%         \mult_check_for_parent{#1}{#3}#4#8%
%         \expandafter\edef\csname#1#4:\s!chain\endcsname{\mult_interfaces_chain#1{##2}##1}%
%         \expandafter\edef\csname#1#4:\s!parent\endcsname{#1##2}%
%         \mult_interfaces_get_parameters{#1#4:}[##3]%
%       \else\ifsecondargument
%         \the#6% predefine
%         \ifcondition\expandafter\mult_check_for_assignment_indeed_begin_\detokenize{##2}=@@\_end_
%           \edef#8{##2}%
%           \mult_check_for_parent{#1}{#3}#4#8%
%           \expandafter\edef\csname#1#4:\s!chain\endcsname{\mult_interfaces_chain#1{##2}##1}%
%           \expandafter\edef\csname#1#4:\s!parent\endcsname{#1##2}%
%         \else
%           \let#8\empty
%           \expandafter\edef\csname#1#4:\s!chain\endcsname{##1}%
%           \expandafter\edef\csname#1#4:\s!parent\endcsname{#3}%
%           \mult_interfaces_get_parameters{#1#4:}[##2]%
%         \fi
%       \else
%         \the#6% predefine
%         \let#8\empty
%         \expandafter\edef\csname#1#4:\s!chain\endcsname{##1}%
%         \expandafter\edef\csname#1#4:\s!parent\endcsname{#3}%
%       \fi\fi
%       \the#7%
%       \let#4#9}}

\unexpanded\def\installdefinehandler#1#2#3%
  {\normalexpanded
     {\mult_interfaces_install_define_handler
        {\noexpand#1}% \??aa
        \expandafter\noexpand\csname define#2\endcsname
        {\noexpand#3}% root
        \expandafter\noexpand\csname current#2\endcsname
        \expandafter\noexpand\csname define_#2\endcsname % semi-public
        \expandafter\noexpand\csname everypreset#2\endcsname
        \expandafter\noexpand\csname everydefine#2\endcsname
        \expandafter\noexpand\csname current#2parent\endcsname
        \expandafter\noexpand\csname saved_defined_#2\endcsname}}

\unexpanded\def\mult_interfaces_install_setup_handler#1#2#3#4#5#6#7#8#9%
  {\ifx#3\relax\let#3\empty\fi
   \unexpanded\def#2{\dodoubleempty#4}%
   \unexpanded\def#6{\mult_interfaces_get_parameters{#1#3:}}% no every ! don't change it
   \newtoks#5%
   \newtoks#8%
   \unexpanded\def#4[##1][##2]% maybe helper
     {\let#7#3%
      \ifsecondargument
        \def#9####1% we will have a simple one as well
          {\edef#3{####1}%
           \mult_interfaces_get_parameters{#1#3:}[##2]%
           \the#5}%
        \processcommalist[##1]#9%
      \else
        \let#3\empty
        \mult_interfaces_get_parameters{#1:}[##1]%
        \the#5%
      \fi
      \let#3#7%
      \the#8}}

\unexpanded\def\installsetuphandler#1#2%
  {\normalexpanded
     {\mult_interfaces_install_setup_handler
        {\noexpand#1}% \??aa
        \expandafter\noexpand\csname setup#2\endcsname
        \expandafter\noexpand\csname current#2\endcsname
        \expandafter\noexpand\csname setup_#2\endcsname % semi-public
        \expandafter\noexpand\csname everysetup#2\endcsname
        \expandafter\noexpand\csname setupcurrent#2\endcsname
        \expandafter\noexpand\csname saved_setup_current#2\endcsname
        \expandafter\noexpand\csname everysetup#2root\endcsname
        \expandafter\noexpand\csname nested_setup_current#2\endcsname}}

\let\doingrootsetupnamed\plusone    % \setuplayout[name][key=value]
\let\doingrootsetuproot \plustwo    % \setuplayout      [key=value]
\let\doingrootsetnamed  \plusthree  % \setuplayout[name]
\let\doingrootsetroot   \plusfour   % \setuplayout

\unexpanded\def\mult_interfaces_install_switch_setup_handler_a#1#2#3#4#5%
  {\ifx#3\relax\let#3\empty\fi
   \unexpanded\def#2{\dodoubleempty#4}%
   \unexpanded\def#5{\mult_interfaces_get_parameters{#1#3:}}}

\unexpanded\def\mult_interfaces_install_switch_setup_handler_b#1#2#3#4#5#6#7#8#9%
  {\newtoks#5%
   \newconstant#2%
   \newtoks#8%
   \newtoks#9%
   \ifx#6\relax\let#6\empty\fi
   \unexpanded\def#4[##1][##2]% maybe helper
     {\ifsecondargument % no commalist here
        % \setuplayout[whatever][key=value]
        \let#7#3%
        \let#6#3%
        \edef#3{##1}%
        #2\doingrootsetupnamed
        \mult_interfaces_get_parameters{#1#3:}[##2]%
        \the#5%
        \ifx#3#6\the#8\fi % only switchsetups if previous == current
        \let#3#7%
      \else\iffirstargument
        % \mult_check_for_assignment{##1}%
        \expandafter\mult_check_for_assignment_indeed\detokenize{##1}=@@\_end_
        \ifassignment
          % \setuplayout[key=value]
          \let#7#3%
          \let#6#3%
          \let#3\empty
          #2\doingrootsetuproot
          \mult_interfaces_get_parameters{#1:}[##1]%
          \the#5%
          \the#8% switchsetups
          \let#3#7%
        \else
          % \setuplayout[whatever]
          \let#6#3%   % previous becomes current
          \edef#3{##1}% this will catch reset so one needs to test for it
          #2\doingrootsetnamed
          \the#5%     % we can check for previous vs current
          \the#8% switchsetups
        \fi
      \else
        % \setuplayout
        \let#6#3%      % previous becomes current
        \let#3\empty   % current becomes empty
        #2\doingrootsetroot
        \the#5%
        \the#8% switchsetups
      \fi\fi
      #2\zerocount % mode is always zero at the end
      \the#9}}

% \unexpanded\def\mult_interfaces_install_switch_setup_handler_b#1#2#3#4#5#6#7#8#9%
%   {\newtoks#5%
%    \newconstant#2%
%    \newtoks#8%
%    \newtoks#9%
%    \ifx#6\relax\let#6\empty\fi
%    \unexpanded\def#4[##1][##2]% maybe helper
%      {\ifsecondargument % no commalist here
%         % \setuplayout[whatever][key=value]
%         \let#7#3%
%         \let#6#3%
%         \edef#3{##1}%
%         #2\doingrootsetupnamed
%         \mult_interfaces_get_parameters{#1#3:}[##2]%
%         \the#5%
%         \ifx#3#6\the#8\fi % only switchsetups if previous == current
%         \let#3#7%
%       \else\iffirstargument
%         % \mult_check_for_assignment{##1}%
%         \ifcondition\expandafter\mult_check_for_assignment_indeed_begin_\detokenize{##1}=@@\_end_
%           % \setuplayout[whatever]
%           \let#6#3%   % previous becomes current
%           \edef#3{##1}% this will catch reset so one needs to test for it
%           #2\doingrootsetnamed
%           \the#5%     % we can check for previous vs current
%           \the#8% switchsetups
%         \else
%           % \setuplayout[key=value]
%           \let#7#3%
%           \let#6#3%
%           \let#3\empty
%           #2\doingrootsetuproot
%           \mult_interfaces_get_parameters{#1:}[##1]%
%           \the#5%
%           \the#8% switchsetups
%           \let#3#7%
%         \fi
%       \else
%         % \setuplayout
%         \let#6#3%      % previous becomes current
%         \let#3\empty   % current becomes empty
%         #2\doingrootsetroot
%         \the#5%
%         \the#8% switchsetups
%       \fi\fi
%       #2\zerocount % mode is always zero at the end
%       \the#9}}

\unexpanded\def\installswitchsetuphandler#1#2%
  {\normalexpanded
     {\mult_interfaces_install_switch_setup_handler_a
        {\noexpand#1}% \??aa
        \expandafter\noexpand\csname setup#2\endcsname
        \expandafter\noexpand\csname current#2\endcsname
        \expandafter\noexpand\csname setup_#2\endcsname % semi-public
        \expandafter\noexpand\csname setupcurrent#2\endcsname
      \mult_interfaces_install_switch_setup_handler_b
        {\noexpand#1}% \??aa
        \expandafter\noexpand\csname #2setupmode\endcsname
        \expandafter\noexpand\csname current#2\endcsname
        \expandafter\noexpand\csname setup_#2\endcsname % semi-public
        \expandafter\noexpand\csname everysetup#2\endcsname
        \expandafter\noexpand\csname previous#2\endcsname
        \expandafter\noexpand\csname saved_setup_current#2\endcsname
        \expandafter\noexpand\csname everyswitch#2\endcsname
        \expandafter\noexpand\csname everysetup#2root\endcsname}}

\unexpanded\def\mult_interfaces_install_auto_setup_handler#1#2#3#4#5#6#7#8#9%
  {\ifx#3\relax\let#3\empty\fi
   \unexpanded\def#2{\dotripleempty#4}%
   \unexpanded\def#6{\mult_interfaces_get_parameters{#1#3:}}%
   \newtoks#5%
   \def#4[##1][##2][##3]%
     {\let#8#3%
      \ifthirdargument
        \def#9####1%
          {\edef#3{####1}%
           \expandafter\def\csname#1#3:\s!parent\endcsname{#1##2}%
           \mult_interfaces_get_parameters{#1#3:}[##3]% always sets parent
           \the#5}%
        \processcommalist[##1]#9%
      \else\ifsecondargument
        \def#9####1%
          {\edef#3{####1}%
           #7% checks parent and sets if needed
           \mult_interfaces_get_parameters{#1#3:}[##2]%
           \the#5}%
        \processcommalist[##1]#9%
      \else
        \let#3\empty
        \mult_interfaces_get_parameters{#1:}[##1]%
        \the#5%
      \fi\fi
      \let#3#8}}

\unexpanded\def\installautosetuphandler#1#2%
  {\normalexpanded
     {\mult_interfaces_install_auto_setup_handler
        {\noexpand#1}% \??aa
        \expandafter\noexpand\csname setup#2\endcsname
        \expandafter\noexpand\csname current#2\endcsname
        \expandafter\noexpand\csname setup_#2\endcsname % semi-public
        \expandafter\noexpand\csname everysetup#2\endcsname
        \expandafter\noexpand\csname setupcurrent#2\endcsname
        \expandafter\noexpand\csname check#2parent\endcsname
        \expandafter\noexpand\csname saved_setup_current#2\endcsname
        \expandafter\noexpand\csname nested_setup_current#2\endcsname}}

\unexpanded\def\installbasicparameterhandler#1#2%
  {\installparameterhandler    {#1}{#2}%
   \installparameterhashhandler{#1}{#2}%
   \installparametersethandler {#1}{#2}%
   \installrootparameterhandler{#1}{#2}}

\unexpanded\def\installbasicautosetuphandler#1#2#3% \??self name \??parent (can be \??self)
  {\installbasicparameterhandler{#1}{#2}%
   \installautosetuphandler     {#1}{#2}}

\unexpanded\def\installstylisticautosetuphandler#1#2#3% \??self name \??parent (can be \??self)
  {\installbasicparameterhandler{#1}{#2}%
   \installautosetuphandler     {#1}{#2}%
   \installstyleandcolorhandler {#1}{#2}}

\unexpanded\def\installcommandhandler#1#2#3% \??self name \??parent (can be \??self)
  {\installbasicparameterhandler{#1}{#2}%
   \installdefinehandler        {#1}{#2}{#3}%
   \installsetuphandler         {#1}{#2}%
   \installstyleandcolorhandler {#1}{#2}}

\unexpanded\def\installswitchcommandhandler#1#2#3% \??self name \??parent (can be \??self)
  {\installbasicparameterhandler{#1}{#2}%
   \installdefinehandler        {#1}{#2}{#3}%
   \installswitchsetuphandler   {#1}{#2}%
   \installstyleandcolorhandler {#1}{#2}}

\unexpanded\def\installautocommandhandler#1#2#3% automatically defined cloned setups
  {\installbasicparameterhandler{#1}{#2}%
   \installdefinehandler        {#1}{#2}{#3}%
   \installautosetuphandler     {#1}{#2}%
   \installstyleandcolorhandler {#1}{#2}}

\unexpanded\def\installsimplecommandhandler#1#2#3% no define (experiment) - use \check*parent when defining
  {\installbasicparameterhandler{#1}{#2}%
   \installsetuphandler         {#1}{#2}%
   \installstyleandcolorhandler {#1}{#2}}

%D Many mechanisms have some kind of inheritance in place, and these are
%D the speed||critical ones. Therefore there is no reason to stick to
%D \type {\@@xxkey} for the sake of performance. For this reason we also
%D provide a direct variant. This permits a more consistent treatment of
%D namespaces. A \type {\whateverparameter} call is three times slower
%D and a \type {\directwhateverparameter} call two times but for some
%D 100K expansions we only loose some .1 second which is neglectable
%D given the small amount of expansions in real runs.

%D We don't need colons for such simple cases.

\unexpanded\def\mult_interfaces_install_direct_parameter_handler#1#2#3#4#5%
%%{\def#3##1{\csname\ifcsname#1##1\endcsname#1##1\else\s!empty\fi\endcsname}%
  {\def#3##1{\begincsname#1##1\endcsname}%
   \def#4##1{\detokenize\expandafter\expandafter\expandafter{\csname#1##1\endcsname}}%
 % \def#4##1{\mult_interfaces_detokenize{\csname\ifcsname#1#2:##1\endcsname#1#2:##1\else\expandafter#5\csname#1#2:\s!parent\endcsname{##1}\fi\endcsname}}%
   \def#5##1{\begincsname#1##1\endcsname}}

\unexpanded\def\installdirectparameterhandler#1#2%
  {\normalexpanded
     {\mult_interfaces_install_direct_parameter_handler
        {\noexpand#1}%
        \expandafter\noexpand\csname current#2\endcsname
        \expandafter\noexpand\csname #2parameter\endcsname
        \expandafter\noexpand\csname detokenized#2parameter\endcsname
        \expandafter\noexpand\csname direct#2parameter\endcsname}}

\unexpanded\def\mult_interfaces_install_direct_setup_handler#1#2#3#4#5%
  {\unexpanded\def#2{\dosingleempty#3}%
   \newtoks#5%
   \def#3[##1]{\mult_interfaces_get_parameters#1[##1]\the#5}%
   \def#4{\mult_interfaces_get_parameters#1}}

\unexpanded\def\installdirectsetuphandler#1#2%
  {\normalexpanded
     {\mult_interfaces_install_direct_setup_handler
        {\noexpand#1}% \??aa
        \expandafter\noexpand\csname setup#2\endcsname
        \expandafter\noexpand\csname setup_#2\endcsname % semi-public
        \expandafter\noexpand\csname setupcurrent#2\endcsname % no \every (we use 'current' for consistency)
        \expandafter\noexpand\csname everysetup#2\endcsname}}

\unexpanded\def\mult_interfaces_install_direct_parameter_set_handler#1#2#3#4#5%
  {\unexpanded\def#2{\mult_interfaces_def #1}%
   \unexpanded\def#3{\mult_interfaces_edef#1}%
   \unexpanded\def#4{\mult_interfaces_let #1}%
   \unexpanded\def#5{\mult_interfaces_let #1\empty}}%

\startinterface english

    \unexpanded\def\mult_interfaces_install_direct_parameter_set_handler#1#2#3#4#5%
      {\unexpanded\def#2##1{\expandafter \def\csname#1##1\endcsname}%
       \unexpanded\def#3##1{\expandafter\edef\csname#1##1\endcsname}%
       \unexpanded\def#4##1{\expandafter \let\csname#1##1\endcsname}%
       \unexpanded\def#5##1{\expandafter \let\csname#1##1\endcsname\empty}}%

\stopinterface

\unexpanded\def\installdirectparametersethandler#1#2%
  {\normalexpanded
     {\mult_interfaces_install_direct_parameter_set_handler
        {\noexpand#1}% \??aa
        \expandafter\noexpand\csname set#2parameter\endcsname
        \expandafter\noexpand\csname setexpanded#2parameter\endcsname
        \expandafter\noexpand\csname let#2parameter\endcsname
        \expandafter\noexpand\csname reset#2parameter\endcsname}}

\let\installdirectstyleandcolorhandler\installstyleandcolorhandler

\unexpanded\def\installdirectcommandhandler#1#2%
  {\installdirectparameterhandler    {#1}{#2}%
   \installdirectsetuphandler        {#1}{#2}%
   \installdirectparametersethandler {#1}{#2}%
   \installdirectstyleandcolorhandler{#1}{#2}}

\unexpanded\def\installsetuponlycommandhandler#1#2%
  {\installdirectparameterhandler{#1}{#2}%
   \installdirectsetuphandler    {#1}{#2}%
  }% maybe \installdirectparametersethandler {#1}{#2}%

% Experiment:

% \installcorenamespace {one}
% \installcorenamespace {two}
%
% \installcommandhandler \??one {one} \??one
% \installcommandhandler \??two {two} \??two
%
% \defineone[test] \setupone[test][alpha=first]
% \definetwo[test] \setuptwo[test][beta=second]
%
% \protect
%
% \def\currentone{test}
% \def\currenttwo{test}
%
% \relateparameterhandlers {two} {test} {one} {test}
%
% yes:\oneparameter{alpha}\par
% nop:\oneparameter{beta}\par
% yes:\twoparameter{alpha}\par
% yes:\twoparameter{beta}\par

\unexpanded\def\relateparameterhandlers#1#2#3#4% {from} {instance} {to} {instance}
  {\expandafter\edef\csname\csname#1namespace\endcsname#2:\s!parent\endcsname{\csname#3namespace\endcsname#4}}

\unexpanded\def\relateparameterhandlersbyns#1#2#3#4% {from} {instance} {to} {instance}
  {\expandafter\edef\csname#1#2:\s!parent\endcsname{#3#4}}

%D Here is another experiment:

\unexpanded\def\installactionhandler#1%
  {\normalexpanded
     {\mult_interfaces_install_action_handler
        {#1}%
        \expandafter\noexpand\csname current#1\endcsname
        \expandafter\noexpand\csname setupcurrent#1\endcsname
        \expandafter\noexpand\csname #1_action\endcsname}}

\unexpanded\def\mult_interfaces_install_action_handler#1#2#3#4%
  {\unexpanded\expandafter\def\csname#1\endcsname{\dodoubleempty#4}%
   \unexpanded\def#4[##1][##2]%
     {\begingroup
      \ifsecondargument
        \edef#2{##1}%
        #3[##2]%
      \else\iffirstargument
        \doifelseassignment{##1}
          {\let#2\empty
           #3[##1]}%
          {\edef#2{##1}}%
      \else
        \let#2\empty
      \fi\fi
      \directsetup{handler:action:#1}%
      \endgroup}}

% First we had, in tune with the regular system variables:
%
% \starttyping
% \unexpanded\def\installnamespace#1{\setvalue{????#1}{@@@@#1}}
% \stoptyping
%
% The following variant is nicer and in principle faster but that gets
% unnoticed unless lots of expansion happens. Also, we can use long tags
% but the internal expansion will be relatively small (and unlikely more
% than 4 characters). For instance, \??xx used to expand to @@xx but now
% becomes for instance 123::. This is one character more but in quite some
% cases we had : after such a tag in the old situation. In the new situation
% we create more namespaces and don't need that : any more, so we end up
% with on the average the same amount of tokens and definitely less when
% we consider cases like \??xx:\c!align: which now is just \??somealign and
% therefore has length 5 now (instead of 4+1+5+1=10).
%
% Eventualy we will have a verbose \blablanamespace and the difference between
% core and regular can go ... after all, \xxxparameter can already clash between
% the two prefix groups .. if users use this mechanism a lot they should use
% verbose names anyway (the old two character names were mostly an optimization
% as they also expanded to these characters).

% todo: register namespaces at lua end for logging and reverse resolve
% todo: move this to syst-ini so that we can use it real early

\newcount\c_mult_interfaces_n_of_namespaces

%def\v_interfaces_prefix_template{\number    \c_mult_interfaces_n_of_namespaces>}
%def\v_interfaces_prefix_template{\characters\c_mult_interfaces_n_of_namespaces>}

%def\v_interfaces_prefix_template % consistently %03i>
% {\ifnum\c_mult_interfaces_n_of_namespaces<\plusten00\else\ifnum\c_mult_interfaces_n_of_namespaces<\plushundred0\fi\fi
%  \number\c_mult_interfaces_n_of_namespaces>}

\def\v_interfaces_prefix_template
  {\number\c_mult_interfaces_n_of_namespaces>}

\unexpanded\def\installnamespace#1% for modules and users
  {\ifcsname ????#1\endcsname
     \writestatus\m!system{duplicate user namespace '#1'}\wait
   \else
     \global\advance\c_mult_interfaces_n_of_namespaces\plusone
     \expandafter\edef\csname ????#1\endcsname{\v_interfaces_prefix_template}%
   \fi}

\unexpanded\def\installcorenamespace#1%
  {\ifcsname ??#1\endcsname
     \writestatus\m!system{duplicate core namespace '#1'}\wait
   \else
     \global\advance\c_mult_interfaces_n_of_namespaces\plusone
     \expandafter\edef\csname ??#1\endcsname{\v_interfaces_prefix_template}%
     \clf_registernamespace\c_mult_interfaces_n_of_namespaces{#1}%
   \fi}

\def\mult_interfaces_get_parameters_error_indeed#1#2%
  {\clf_showassignerror{#1}{#2}\inputlineno} % no longer \waitonfatalerror

% We install two core namespaces here, as we want nice error messages. Maybe
% we will reserve the first 9.

\installcorenamespace{fontinstanceready}
\installcorenamespace{fontinstancebasic}
\installcorenamespace{fontinstanceclass}

%D The next one is handy for local assignments.

\installcorenamespace{dummy}

\letvalue\??dummy\empty

           \def\dummyparameter           #1{\begincsname\??dummy#1\endcsname}
           \def\directdummyparameter     #1{\begincsname\??dummy#1\endcsname}
\unexpanded\def\setdummyparameter        #1{\expandafter\def\csname\??dummy#1\endcsname}
\unexpanded\def\setexpandeddummyparameter#1{\expandafter\edef\csname\??dummy#1\endcsname}
\unexpanded\def\letdummyparameter        #1{\expandafter\let\csname\??dummy#1\endcsname}

% \unexpanded\def\getdummyparameters
%   {\mult_interfaces_get_parameters\??dummy}

\unexpanded\def\getdummyparameters[#1%
  {\if\noexpand#1]%
     \expandafter\gobbleoneargument
   \else
     \let\m_mult_interfaces_namespace\??dummy
     \expandafter\mult_interfaces_get_parameters_indeed
   \fi#1}

\mult_interfaces_install_style_and_color_handler
  \directdummyparameter
  \usedummystyleandcolor
  \usedummystyleparameter
  \usedummycolorparameter

% Maybe a \definecorenamespace[name][directparameter,directsetup][parent]
% but we don't gain much. Actually we might just inline all definitions.

% \enabletrackers[interfaces.namespaces,context.flush]
%
% \definenamespace
%   [xy]
%   [type=module,
%    comment=test module,
%    version=1,
%    name=test,
%    style=yes,
%    command=yes,
%    setup=list,
%    set=yes,
%    parent=xy]
%
% \unprotect
% \getparameters
%   [\????xy]
%   [text=]
% \protect
%
% \definetest[one]
%
% \starttext
%
%   “\testparameter{text}”
%
%   \setuptest[text=foo]
%
%   “\testparameter{text}”
%
%   \setuptest[one][text=bar]
%
%   “\testparameter{text}”
%
% \stoptext
%
% This is a user (module) command:

\unexpanded\def\definenamespace
  {\dodoubleargument\mult_interfaces_define_name_space}

\def\mult_interfaces_define_name_space[#1][#2]% namespace settings
  {\clf_definenamespace{#1}{#2}}

\def\listnamespaces
  {\clf_listnamespaces}

%D Helper:
%D
%D \starttyping
%D \showparentchain{@@am}{left}
%D \stoptyping

\unexpanded\def\showparentchain#1#2%
  {\writestatus\m!system{chain: [ \mult_interfaces_show_parent_chain{#1#2}]}}

% \def\mult_interfaces_show_parent_chain#1%
%   {#1 => %
%    \ifcsname#1:\s!parent\endcsname
%       \expandafter\mult_interfaces_show_parent_chain\csname#1:\s!parent\endcsname
%    \fi}

\def\mult_interfaces_show_parent_chain#1%
  {#1 => %
   \ifcsname#1:\s!parent\endcsname
     %\expandafter\mult_interfaces_show_parent_chain\csname#1:\s!parent\endcsname
      \expandafter\mult_interfaces_show_parent_chain\lastnamedcs
   \fi}

%D Another helper (needs to be applied):

\unexpanded\def\doifelsecommandhandler#1#2% namespace name
  {\ifcsname#1#2:\s!parent\endcsname
     \expandafter\firstoftwoarguments
   \else
     \expandafter\secondoftwoarguments
   \fi}

\let\doifcommandhandlerelse\doifelsecommandhandler

\unexpanded\def\doifcommandhandler#1#2% namespace name
  {\ifcsname#1#2:\s!parent\endcsname
     \expandafter\firstofoneargument
   \else
     \expandafter\gobbleoneargument
   \fi}

\unexpanded\def\doifnotcommandhandler#1#2% namespace name
  {\ifcsname#1#2:\s!parent\endcsname
     \expandafter\gobbleoneargument
   \else
     \expandafter\firstofoneargument
   \fi}

\let\doifcommandhandlerelse\doifelsecommandhandler

% another set of (fast) helpers (grep for usage):

\def\expandnamespaceparameter#1#2#3% \??xx \getp \c!xx \v!yy
  {\csname#1\ifcsname#1\expandafter\expandafter\expandafter\mult_aux_expand_namespace_parameter#2#3}

\def\mult_aux_expand_namespace_parameter#1#2% \cs \v!yy
  {#1\endcsname#1\else#2\fi\endcsname}

\def\expandnamespacemacro#1#2#3% \??xx \some_edefed_cs \c!yy
  {\csname#1\ifcsname#1#2\endcsname#2\else#3\fi\endcsname}

\def\expandnamespacevalue#1#2% \??xx {...} \c!yy == optimized \expandcheckedcsname
  {\csname#1\ifcsname#1\normalexpanded{\noexpand\syst_helpers_expand_checked_value{#2}}}

\def\syst_helpers_expand_checked_value#1#2%
  {#1\endcsname#1\else#2\fi\endcsname}

%D Conventions:
%D
%D \starttyping
%D \newcount       \c_class_whatever
%D \newconditional \c_class_whatever
%D \newconstant    \c_class_whatever
%D \newdimen       \d_class_whatever
%D \newskip        \s_class_whatever
%D \newmuskip      \s_class_whatever
%D \newbox         \b_class_whatever
%D \newtoks        \t_class_whatever
%D
%D \edef\p_class_whatever{\classparameter\c!whatever}
%D \edef\m_class_whatever{whatever}
%D \stoptyping

% experiment: in principle this is faster but not that noticeable as we don't do that
% many assignments and mechanism that do are also slow; the advantage is mostly nicer
% in tracing

\def\s!simple{simple}
\def\s!single{single}
\def\s!double{double}
\def\s!triple{triple}

% \unexpanded\def\syst_helpers_double_empty#1#2#3%
%   {\syst_helpers_argument_reset
%    \doifelsenextoptional
%      {\syst_helpers_double_empty_one_yes_mult#2#3}%
%      {\syst_helpers_double_empty_one_nop_mult#1}}
%
% \def\syst_helpers_double_empty_one_yes_mult#1#2[#3]%
%   {\firstargumenttrue
%    \doifelsenextoptional
%      {\secondargumenttrue#2[{#3}]}%
%      {\syst_helpers_double_empty_two_nop_mult#1{#3}}}
%
% \def\syst_helpers_double_empty_one_nop_mult% #1%
%   {\firstargumentfalse
%    \secondargumentfalse
%    }% #1}
%
% \def\syst_helpers_double_empty_two_nop_mult
%   {\secondargumentfalse
%    \if_next_blank_space_token
%      \expandafter\syst_helpers_double_empty_one_spaced_mult
%    \else
%      \expandafter\syst_helpers_double_empty_one_normal_mult
%    \fi}
%
% \def\syst_helpers_double_empty_one_spaced_mult#1#2{#1[{#2}] }
% \def\syst_helpers_double_empty_one_normal_mult#1#2{#1[{#2}]}
%
% \unexpanded\def\mult_interfaces_install_setup_handler#1#2#3#4#5#6#7#8%
%   {\ifx#3\relax\let#3\empty\fi
%    \unexpanded\def#5{\mult_interfaces_get_parameters{#1#3:}}% no every ! don't change it
%    \newtoks#4%
%    \newtoks#7%
%    \edef\m_mult_interface_setup{\csstring#2_}%
%    \unexpanded\edef#2{\syst_helpers_double_empty
%      \csname\m_mult_interface_setup\s!simple\endcsname
%      \csname\m_mult_interface_setup\s!single\endcsname
%      \csname\m_mult_interface_setup\s!double\endcsname}%
%    \unexpanded\expandafter\def\csname\m_mult_interface_setup\s!double\endcsname[##1][##2]%
%      {\let#6#3%
%       \def#8####1% we will have a simple one as well
%         {\edef#3{####1}%
%          \mult_interfaces_get_parameters{#1#3:}[##2]%
%          \the#4}%
%       \processcommalist[##1]#8%
%       \let#3#6%
%       \the#7}%
%    \unexpanded\expandafter\def\csname\m_mult_interface_setup\s!single\endcsname[##1]%
%      {\let#6#3%
%       \let#3\empty
%       \mult_interfaces_get_parameters{#1:}[##1]%
%       \the#4%
%       \let#3#6%
%       \the#7}%
%    \unexpanded\expandafter\def\csname\m_mult_interface_setup\s!simple\endcsname%
%      {\let#6#3%
%       \let#3\empty
%       \the#4%
%       \let#3#6%
%       \the#7}}

% \unexpanded\def\installsetuphandler#1#2%
%   {\normalexpanded
%      {\mult_interfaces_install_setup_handler
%         {\noexpand#1}% \??aa
%         \expandafter\noexpand\csname setup#2\endcsname
%         \expandafter\noexpand\csname current#2\endcsname
%         \expandafter\noexpand\csname everysetup#2\endcsname
%         \expandafter\noexpand\csname setupcurrent#2\endcsname
%         \expandafter\noexpand\csname saved_setup_current#2\endcsname
%         \expandafter\noexpand\csname everysetup#2root\endcsname
%         \expandafter\noexpand\csname nested_setup_current#2\endcsname}}
%
% \unexpanded\def\syst_helpers_triple_empty#1#2#3#4%
%   {\syst_helpers_argument_reset
%    \doifelsenextoptional
%      {\syst_helpers_triple_empty_one_yes_mult#2#3#4}%
%      {\syst_helpers_triple_empty_one_nop_mult#1}}
%
% \def\syst_helpers_triple_empty_one_yes_mult#1#2#3[#4]%
%   {\firstargumenttrue
%    \doifelsenextoptional
%      {\syst_helpers_triple_empty_two_yes_mult#2#3{#4}}%
%      {\syst_helpers_triple_empty_two_nop_mult#1{#4}}}
%
% \def\syst_helpers_triple_empty_two_yes_mult#1#2#3[#4]%
%   {\secondargumenttrue
%    \doifelsenextoptional
%      {\thirdargumenttrue#2[{#3}][{#4}]}%
%      {\syst_helpers_triple_empty_three_nop_mult#1{#3}{#4}}}
%
% \def\syst_helpers_triple_empty_one_nop_mult % #1%
%   {\firstargumentfalse
%    \secondargumentfalse
%    \thirdargumentfalse
%    } % #1
%
% \def\syst_helpers_triple_empty_two_nop_mult
%   {\secondargumentfalse
%    \thirdargumentfalse
%    \if_next_blank_space_token
%      \expandafter\syst_helpers_triple_empty_two_spaced_mult
%    \else
%      \expandafter\syst_helpers_triple_empty_two_normal_mult
%    \fi}
%
% \def\syst_helpers_triple_empty_three_nop_mult
%   {\thirdargumentfalse
%    \if_next_blank_space_token
%      \expandafter\syst_helpers_triple_empty_three_spaced_mult
%    \else
%      \expandafter\syst_helpers_triple_empty_three_normal_mult
%    \fi}
%
% \def\syst_helpers_triple_empty_two_spaced_mult    #1#2{#1[{#2}] }
% \def\syst_helpers_triple_empty_two_normal_mult    #1#2{#1[{#2}]}
% \def\syst_helpers_triple_empty_three_spaced_mult#1#2#3{#1[{#2}][{#3}] }
% \def\syst_helpers_triple_empty_three_normal_mult#1#2#3{#1[{#2}][{#3}]}
%
% \unexpanded\def\mult_interfaces_install_auto_setup_handler#1#2#3#4#5#6#7#8%
%   {\ifx#3\relax\let#3\empty\fi
%    \unexpanded\def#5{\mult_interfaces_get_parameters{#1#3:}}%
%    \newtoks#4%
%    \edef\m_mult_interface_setup{\csstring#2_}%
%    \unexpanded\edef#2{\syst_helpers_triple_empty
%      \csname\m_mult_interface_setup\s!simple\endcsname
%      \csname\m_mult_interface_setup\s!single\endcsname
%      \csname\m_mult_interface_setup\s!double\endcsname
%      \csname\m_mult_interface_setup\s!triple\endcsname}%
%    \unexpanded\expandafter\def\csname\m_mult_interface_setup\s!triple\endcsname[##1][##2][##3]%
%      {\let#7#3%
%       \def#8####1%
%         {\edef#3{####1}%
%          \expandafter\def\csname#1#3:\s!parent\endcsname{#1##2}%
%          \mult_interfaces_get_parameters{#1#3:}[##3]% always sets parent
%          \the#4}%
%       \processcommalist[##1]#8%
%       \let#3#7}%
%    \unexpanded\expandafter\def\csname\m_mult_interface_setup\s!double\endcsname[##1][##2]%
%      {\let#7#3%
%       \def#8####1%
%         {\edef#3{####1}%
%          #6% checks parent and sets if needed
%          \mult_interfaces_get_parameters{#1#3:}[##2]%
%          \the#4}%
%       \processcommalist[##1]#8%
%       \let#3#7}%
%    \unexpanded\expandafter\def\csname\m_mult_interface_setup\s!single\endcsname[##1]%
%      {\let#7#3%
%       \let#3\empty
%       \mult_interfaces_get_parameters{#1:}[##1]%
%       \the#4%
%       \let#3#7}%
%    \unexpanded\expandafter\def\csname\m_mult_interface_setup\s!simple\endcsname%
%      {\let#7#3%
%       \let#3\empty
%       \the#4%
%       \let#3#7}}
%
% \unexpanded\def\installautosetuphandler#1#2%
%   {\normalexpanded
%      {\mult_interfaces_install_auto_setup_handler
%         {\noexpand#1}% \??aa
%         \expandafter\noexpand\csname setup#2\endcsname
%         \expandafter\noexpand\csname current#2\endcsname
%         \expandafter\noexpand\csname everysetup#2\endcsname
%         \expandafter\noexpand\csname setupcurrent#2\endcsname
%         \expandafter\noexpand\csname check#2parent\endcsname
%         \expandafter\noexpand\csname saved_setup_current#2\endcsname
%         \expandafter\noexpand\csname nested_setup_current#2\endcsname}}

% okay, we can also get rid of the #9, but this code looks pretty bad, while the previous is
% still okay given that we can also use #6 as setup (so in fact we can save some cs again and
% only use one extra)
%
% \global\advance\commalevel \plusone
% \expandafter\def\csname\??nextcommalevel\the\commalevel\endcsname####1,%
%   {\edef#3{####1}%
%    \mult_interfaces_get_parameters{#1#3:}[##2]%
%    \the#5%
%    \syst_helpers_do_process_comma_item}%
% \expandafter\syst_helpers_do_do_process_comma_item\gobbleoneargument\relax##1,]\relax
%   % \syst_helpers_do_do_process_comma_item##1,]\relax
% \global\advance\commalevel \minusone

% The next one is experimental (and used in publications):

\let\c_mult_set\relax

\unexpanded\def\mult_interfaces_install_definition_set#1#2#3#4#5#6#7%
  {\newcount#3%
   \let#6\empty
   \unexpanded\def#2%
     {\expandafter\let\expandafter\c_mult_set\csname #1_t_#6\endcsname
      \ifx\c_mult_set\relax
        \expandafter\newtoks\c_mult_set
        \expandafter\let\csname #1_t_#6\endcsname\c_mult_set
      \fi}
   \unexpanded\def#4##1%
     {\pushmacro#6%
      \advance#3\plusone
      \edef#6{##1}%
      \unprotect}%
   \unexpanded\def#5%
     {\protect
      \advance#3\minusone
      \popmacro#6}%
   \unexpanded\def#7##1%
     {\edef#6{##1}%
      #2%
      \the\c_mult_set\relax}}

\unexpanded\def\installdefinitionset#1#2%
  {\normalexpanded
     {\mult_interfaces_install_definition_set
        {\noexpand#1}% \??aa
        \expandafter\noexpand\csname set_#2_toks\endcsname
        \expandafter\noexpand\csname #2_nesting_depth\endcsname
        \expandafter\noexpand\csname push#2\endcsname
        \expandafter\noexpand\csname pop#2\endcsname
        \expandafter\noexpand\csname current#2\endcsname
        \expandafter\noexpand\csname use#2\endcsname}}

\unexpanded\def\mult_interfaces_install_definition_set_member#1#2#3#4#5#6#7#8#9% no everysetups etc
  {\let#5#2%
   \unexpanded\def#2%
     {\ifcase#4\relax\expandafter#5\else\expandafter#6\fi}%
   \unexpanded\def#6%
     {\dodoubleempty#7}%
   \unexpanded\def#7[##1][##2]%
     {\ifsecondargument
       %#3\c_mult_set\expandafter{\the\c_mult_set#9[##1][##2]}%
        #3\toksapp\c_mult_set{#9[##1][##2]}%
      \else\iffirstargument
       %#3\c_mult_set\expandafter{\the\c_mult_set#8[##1]}%
        #3\toksapp\c_mult_set{#8[##1]}%
      \fi\fi}}

\unexpanded\def\installdefinitionsetmember#1#2#3#4%
  {\normalexpanded
     {\mult_interfaces_install_definition_set_member
        {\noexpand#3}% \??aa
        \expandafter\noexpand\csname setup#4\endcsname
        \expandafter\noexpand\csname set_#2_toks\endcsname
        \expandafter\noexpand\csname #2_nesting_depth\endcsname
        \expandafter\noexpand\csname normal_setup_#4\endcsname
        \expandafter\noexpand\csname delayed_setup_#4\endcsname
        \expandafter\noexpand\csname do_delayed_setup_#4\endcsname
        \expandafter\noexpand\csname setup#4_\s!single\endcsname
        \expandafter\noexpand\csname setup#4_\s!double\endcsname}}

%D Another experiment:

\unexpanded\def\mult_interfaces_install_parent_injector#1#2#3#4%
  {\unexpanded\def#4##1%
     {\ifx#3\empty
        \expandafter\def\csname#1#2:\s!parent\endcsname{#1##1}%
      \fi}}

\unexpanded\def\installparentinjector#1#2%
  {\normalexpanded{\mult_interfaces_install_parent_injector
     {\noexpand#1}%
     \expandafter\noexpand\csname current#2\endcsname
     \expandafter\noexpand\csname current#2parent\endcsname
     \expandafter\noexpand\csname inject#2parent\endcsname}}

% Faster but not used that much to make a dent in performance. But, because it's
% cleaner anyway and also gives less tracing, we apply it a few times.

\unexpanded\def\syst_helpers_install_macro_stack#1#2#3%
  {\xdef\m_syst_helpers_push_macro{\csstring#1}%
   \expandafter\newcount\csname#3\m_syst_helpers_push_macro\endcsname
   \expandafter\edef\csname push_macro_\m_syst_helpers_push_macro\endcsname
     {\noexpand\expandafter\glet
         \noexpand\csname\m_syst_helpers_push_macro\noexpand\the\csname#3\m_syst_helpers_push_macro\endcsname\endcsname
         \noexpand#1%
       \global\advance\csname#3\m_syst_helpers_push_macro\endcsname\plusone}%
   \expandafter\edef\csname pop_macro_\m_syst_helpers_push_macro\endcsname
     {\global\advance\csname#3\m_syst_helpers_push_macro\endcsname\minusone
      \noexpand\expandafter#2%
         \noexpand\expandafter\noexpand#1%
         \noexpand\csname\m_syst_helpers_push_macro\noexpand\the\csname#3\m_syst_helpers_push_macro\endcsname\endcsname}}

\unexpanded\def\installmacrostack      #1{\syst_helpers_install_macro_stack#1\let \??localpushedmacro }
\unexpanded\def\installglobalmacrostack#1{\syst_helpers_install_macro_stack#1\glet\??globalpushedmacro}

\protect

%  \unprotect
%
%  \installcorenamespace {test} \installcommandhandler \??test {test} \??test
%  \unexpanded\def\TestMeA[#1]%
%    {\edef\currenttest{#1}
%     \edef\p_before{\testparameter\c!before}%
%     \ifx\p_before\empty \relax \else \relax \fi}
%  \unexpanded\def\TestMeB[#1]%
%    {\edef\currenttest{#1}
%     \doifelsenothing{\testparameter\c!before}\relax\relax}
%  \unexpanded\def\TestMeC[#1]%
%    {\edef\currenttest{#1}
%     \expandafter\expandafter\expandafter\ifx\testparameter\c!before\empty \relax \else \relax \fi}
%  \unexpanded\def\TestMeD[#1]%
%    {\edef\currenttest{#1}
%     \doubleexpandafter\ifx\testparameter\c!before\empty \relax \else \relax \fi}
%
%  \protect
%
%  \starttext
%    \definetest[foo] \definetest[bar][foo] \setuptest[bar][before=indeed]
%    \resettimer \dorecurse{100000}{\TestMeA[bar]} A:\elapsedtime \par % 0.502
%    \resettimer \dorecurse{100000}{\TestMeB[bar]} B:\elapsedtime \par % 0.530
%    \resettimer \dorecurse{100000}{\TestMeC[bar]} C:\elapsedtime \par % 0.487
%    \resettimer \dorecurse{100000}{\TestMeD[bar]} D:\elapsedtime \par % 0.493
%  \stoptext

% There is no real demand for this ... even if this is twice as fast we only gain
% a few milliseconds:
%
%   \unexpanded\def\foo#1{[foo:#1]}
%
%   \installcommalistprocessor                        {foo} \foo
%   \installcommalistprocessorcommand \processfoolist {foo} \foo
%
%   \commalistprocessor{foo}[a,b,c,d]
%   \processfoolist         [a, b, c, d]
%
%   \testfeatureonce{30000}{}                                           \elapsedtime\par % 0.01 -> 0.00
%   \testfeatureonce{30000}{\processfoolist         [fixed,middle]}     \elapsedtime\par % 0.07 -> 0.06
%   \testfeatureonce{30000}{\commalistprocessor{foo}[fixed,middle]}     \elapsedtime\par % 0.09 -> 0.08
%   \testfeatureonce{30000}{\processcommalist       [fixed,middle]\foo} \elapsedtime\par % 0.13 -> 0.12
%
% For instance the luatex manual only has some 3000 calls. But I keep this around as one
% never knows when we might need it.
%
%  \installcorenamespace{commalistprocessor}
%  \installcorenamespace{commalistprocessorcheck}
%  \installcorenamespace{commalistprocessorwrap}
%  \installcorenamespace{commalistprocessorfirst}
%  \installcorenamespace{commalistprocessorcheckspace}
%  \installcorenamespace{commalistprocessorcheckfinish}
%  \installcorenamespace{commalistprocessoraction}
%  \installcorenamespace{commalistprocessorgobblespace}
%
%  \unexpanded\def\installcommalistprocessor#1#2% 7 macro names overhead
%    {\let\nexttoken\relax
%     %
%     \unexpanded\expandafter\edef\csname\??commalistprocessor#1\endcsname[%
%       {\futurelet\nexttoken\csname\??commalistprocessorcheck#1\endcsname}%
%     %
%     \unexpanded\expandafter\edef\csname\??commalistprocessorcheck#1\endcsname
%       {\noexpand\ifx\nexttoken]%
%          \noexpand\expandafter\noexpand\gobblethreearguments
%        \noexpand\else
%          \noexpand\expandafter\csname\??commalistprocessorwrap#1\endcsname
%        \noexpand\fi
%        \relax}% this one preserved the next {}
%     %
%     \unexpanded\expandafter\edef\csname\??commalistprocessorwrap#1\endcsname##1]%
%       {\csname\??commalistprocessorfirst#1\endcsname##1,]\relax}%
%     %
%     \unexpanded\expandafter\edef\csname\??commalistprocessorfirst#1\endcsname##1% picks up \relax
%       {\csname\??commalistprocessorcheckspace#1\endcsname}%
%     %
%     \unexpanded\expandafter\edef\csname\??commalistprocessorcheckspace#1\endcsname
%       {\noexpand\ifx\nexttoken\noexpand\blankspace
%          \noexpand\expandafter\csname\??commalistprocessorgobblespace#1\endcsname
%        \noexpand\else
%          \noexpand\expandafter\csname\??commalistprocessorcheckfinish#1\endcsname
%        \noexpand\fi}%
%     %
%     \unexpanded\expandafter\edef\csname\??commalistprocessorcheckfinish#1\endcsname
%       {\noexpand\ifx\nexttoken]%
%          \noexpand\expandafter\noexpand\gobbleoneargument
%        \noexpand\else
%          \noexpand\expandafter\csname\??commalistprocessoraction#1\endcsname
%        \noexpand\fi}%
%     %
%     \unexpanded\expandafter\edef\csname\??commalistprocessoraction#1\endcsname##1,%
%       {\noexpand#2{##1}%
%        \futurelet\nexttoken\csname\??commalistprocessorcheckspace#1\endcsname}%
%     %
%     \let\next\:%
%     \unexpanded\edef            \:{\csname\??commalistprocessorgobblespace#1\endcsname}%
%     \unexpanded\expandafter\edef\: {\futurelet\nexttoken\csname\??commalistprocessorcheckspace#1\endcsname}%
%     \let\:\next
%     %
%     }
%
%  \unexpanded\def\installcommalistprocessorcommand#1#2#3%
%    {\installcommalistprocessor{#2}{#3}%
%     \expandafter\let\expandafter#1\csname\??commalistprocessor#2\endcsname}
%
%  \unexpanded\def\commalistprocessor#1{\csname\??commalistprocessor#1\endcsname}
