%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
% Module:    ZzTeX Cross-Referencing Facilities
%
% Synopsis:
%
% Author:    Paul C. Anagnostopoulos
% Created:   19 September 1989
%
% Copyright 1989--2020 by Paul C. Anagnostopoulos
% under The MIT License (opensource.org/licenses/MIT)
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%                       Data Structures
%                       ---- ----------


\definewrite{\zxrootfile}

\definewrite{\zxdivfile}
\setflag \zxdivopen = \false

\definewrite{\zxcompfile}
\setflag \zxcompavail = \false

\chardef \xrefbadmode       = 0         % Invalid mode.
\chardef \xrefrunmode       = 1         % Normal running environment.
\chardef \xrefsnapmode      = 2         % Taking a division snapshot.
\chardef \xrefcopymode      = 3         % Copying cross-reference files.
\chardef \xrefloadmodes     = 4         % Beginning of load modes:
\chardef \xrefloadtagmode   = 5         % Load tag definitions.
\chardef \xrefloadtocmode   = 6         % Load table of contents.
\chardef \xrefloadauxmode   = 7         % Create BibTeX auxiliary file.
\chardef \xrefloadendmode   = 8         % Load endnotes.
\chardef \xrefloadcitemode  = 9         % Load citation folios.

\let \xrefmode = \xrefbadmode           % Default mode.

%                       Comment Lines
%                       ------- -----


{\catcode`\%=\catother
\gdef \zcomment {%\space}
} % \catcode


\def \zxwritecomment #1#2#3{%                   {file}{keyword}{values}
  \immediate\write #1 {\zcomment #2: #3}}

%                       Initialization
%                       --------------


\def \zxrefinit {%
  \zxcompinit
  \zxopenroot
  \let \xrefmode = \xrefrunmode}

\def \zxcompinit {%
  \checkfile{\zxcompavail}{\jobname.zzc}%
  \if \zxcompavail
    \zxloadcomp{\xrefloadtagmode}%
  \else
    \checkfile{\zxcompavail}{\jobname.zzx}%
    \if \zxcompavail
      \zxgencomp
      \zxloadcomp{\xrefloadtagmode}%
    \else
      \remark{There is no cross-reference file available for this run.}% 
    \fi
  \fi}

\def \zxopenroot {%
  \immediate\openout \zxrootfile = \jobname.zzx\relax
  \zxwritecomment{\zxrootfile}{root}{\jobname}}

%                       Division Handling
%                       -------- --------


\def \zxdivinit #1#2{%                          {division-name}{setting-it?}
  \immediate\write \zxrootfile {\noexpand\zinputzzx{#1}}%
  \if #2%
    \immediate\openout \zxdivfile = #1.zzx\relax
    \global\setflag \zxdivopen = \true
    \zxwritecomment{\zxdivfile}{division}{#1}%
    \immediate\write \zxdivfile
      {\noexpand\xref{div}{}{}{}{\the\divisionname}\zcomment}%
  \fi}

% There is nothing to do with each entry in the cross-reference file.

\def \xrefdiv #1#2#3#4{}


\def \zxdivfinal #1{%
  \if \zxdivopen
    \ztakesnap
    \zxwritecomment{\zxdivfile}{end}{#1}%
    \immediate\closeout \zxdivfile
    \global\setflag \zxdivopen = \false
  \fi}

%                       Finalization
%                       ------------


\def \zxreffinal {%
  \zxwritecomment{\zxrootfile}{end}{\jobname}%
  \immediate\closeout \zxrootfile
  \zxgencomp}

%                       Generate Composite File
%                       -------- --------- ----


\def \zxgencomp {%
  \remark{Generating composite cross-reference file:}%
  \immediate\openout \zxcompfile = \jobname.zzc\relax
  \zxwriteinfo{\true}{jobname}{\jobname}{}%
  \zxwriteinfo{\true}{time}{\number\year.\number\month.\number\day}{\formattime}%
  \zxwriteinfo{\true}{version}{\ZzTeXversion}{}%
  \zxwriteinfo{\true}{author}{\bookauthor}{}%
  \zxwriteinfo{\true}{title}{\booktitle}{}%
  \zxwriteinfo{\true}{publisher}{\bookpublisher}{}%
  \zxwriteinfo{\true}{ISBN}{\bookISBN}{}%
  \zxwriteinfo{\true}{art-root}{\zartroot}{}%
  \zxwriteinfo{\true}{place-art}{\zplaceart}{}%
  \zxwriteinfo{\true}{PDF-hyperlinks}{\PDFhyperlinks}{}%
  \zxwriteinfo{\true}{proof}{\the\zproofid}{}%
  \zxwriteinfo{\true}{compositor}{\ininame}{\iniorganization}%
  \zxwriteinfo{\true}{trim}{\the\trimwidth}{\the\trimheight}%
  \zxwriteinfo{\true}{head-margin}{\the\headmargin}{}%
  \zxwriteinfo{\true}{inner-margin}{\the\eveninnermargin}{\the\oddinnermargin}%
  \let \zxmodesave = \xrefmode
  \let \xrefmode = \xrefcopymode
  \input \jobname.zzx\relax
  \let \xrefmode = \zxmodesave
  \zxwritecomment{\zxcompfile}{end}{\jobname}%
  \immediate\closeout \zxcompfile}

% This macro writes an information entry in the composite cross-reference
% file.

\def \zxwriteinfo #1#2#3#4{%            {composite?}{key}{value1}{value2}
  \if #1%
    \immediate\write \zxcompfile {\noexpand\xref{info}{}{#2}{#3}{#4}\zcomment}%
  \else
    \zbeginhidewrite
      \edef \znext {\noexpand\xref{info}{\noexpand\folio}%
                                        {#2}%
                                        {#3}
                                        {#4}}%
      \znext
    \zendhidewrite
  \fi}

%%%  \immediate\write #1{\noexpand\xref{info}{#2}{#3}{#4}{\noexpand\folio}\zcomment}}

% There is nothing to do when info entries are executed.

\def \xrefinfo #1#2#3#4{}

% This macro is used in the root cross-reference file to suck in the
% division cross-reference files.

\def \zinputzzx #1{%
  \checkfile{\znext}{#1.zzx}%
  \if \znext \input #1.zzx \fi}

%                       Load Composite File
%                       ---- --------- ----


\def \zxloadcomp #1{%                                   {xref-mode}
  \if \zxcompavail
    \let \zxmodesave = \xrefmode
    \let \xrefmode =#1%
    \input \jobname.zzc\relax
    \let \xrefmode = \zxmodesave
  \fi}

\def \zxloadothercomp #1#2{%                            {file}{xref-mode}
  \let \zxmodesave = \xrefmode
  \let \xrefmode = #2%
  \input #1\relax
  \let \xrefmode = \zxmodesave}

\def \loadrelatedxref #1{%                              {file}
  \zxloadothercomp{#1}{\xrefloadtagmode}}

%                       Cross-Reference Macro
%                       --------------- -----


% Here's how the arguments are treated in each of the modes:
%
%   Mode        type        page        arg3        title       arg5
%
%   load        expanded    --- passed to appropriate \xrefxxx macro ---
%   copy        expanded    expanded    expanded    unexpanded  expanded
%   run         expanded    unexpanded  expanded    unexpanded  expanded
%   snap        expanded    expanded    expanded    expanded    expanded

% This macro is written for speed.

\long\def \xref #1#2#3#4#5{%           {type}{page-number}{arg3}{title}{arg5}
  \ifnum \xrefmode>\xrefloadmodes
    \name{\xref#1}{#2}{#3}{#4}{#5}%
  \else\ifnum \xrefmode=\xrefcopymode
    {\def \zxtitle {#4}%
     \immediate\write \zxcompfile {\noexpand\xref{#1}{#2}{#3}%
               {\expandafter\zdefof \meaning\zxtitle\zmark}{#5}\zcomment}}%
    \name{\xref#1}{#2}{#3}{#4}{#5}% In case they want to do something.
  \else\ifnum \xrefmode=\xrefrunmode
    {\def \zxtitle {#4}%
     \edef \znext {\noexpand\noexpand\noexpand\xref
                     {#1}{\noexpand#2}{#3}%
                     {\expandafter\zdefof \meaning\zxtitle\zmark}{#5}}%
     \expandafter\zxwrite\expandafter{\znext\zcomment}}%
    \if \vmodep \repeatpenalty \fi % In case glue follows write.
  \else\ifnum \xrefmode=\xrefsnapmode
    \immediate\zxwrite{\noexpand\xref{#1}{#2}{#3}{#4}{#5}\zcomment}%
  \else
    \zxnomode
  \fi\fi\fi\fi}

\def \zxwrite {%
  \if \zxdivopen \write \zxdivfile \else \write \zxrootfile \fi}

\def \zxnomode {%
  \zzerror{No cross-reference mode is set}}

%                       Page Hints
%                       ---- -----


\def \pagehint #1{%
  \xref{hint}{\noexpand\folio}{}{#1}{}}

% There is nothing to do when hint entries are executed.

\def \xrefhint #1#2#3#4{}