%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
% Module:    ZzTeX I/O Facilities
%
% Synopsis:
%
% Author:    Paul C. Anagnostopoulos
% Created:   9 September 1989
%
% Copyright 1989--2020 by Paul C. Anagnostopoulos
% under The MIT License (opensource.org/licenses/MIT)
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%                       Terminal & Log I/O
%                       -------- - --- ---

% \message writes to the terminal and the log file, without newlines.
% This macro adds a newline feature:

\def \messagenl #1{%                                    {text}
  {\newlinechar = `\_%
   \message{#1}}}

% This macro writes a line to the log file, with a newline at the end.

\def \writelog {\immediate\write -1}

% \ask combines a prompt using \messagenl with a read from the terminal.

\def \ask #1#2{%                                {\result-macro}{question}
  {\messagenl{_#2}%
   \endlinechar = -1
   \global\read 16 to #1}}

%                       Including Files
%                       --------- -----


\def \include #1{%                                      {file}
  {\checkfile{\zifile}{#1}%
   \if \zifile
     \gdef \znext {\input #1\relax}%
   \else
     \warning{noinclfile}{File `#1' does not exist}%
     \ask{\newfile}{Enter a new file name, or a period (.) to skip it.}%
     \stringeql{\znext}{\newfile}{.}%
     \if \znext
       \xdef \znext {}%
     \else
       \xdef \znext {\noexpand\include{\newfile}}%
     \fi
   \fi}%
  \znext
  \endgraf}

\def \zportionid {}

\def \includeportion #1#2{%                             {file}{portion-id}
  \gdef \zportionid {#2}%
  \include{#1}%
  \gdef \zportionid {}}

\def \portion #1{%                                      {portion-id}
  \stringeql{\znext}{#1}{\zportionid}%
  \if \znext}

\let \endportion = \fi

\def \includeifexists #1{%                              {file}
  \checkfile{\zifile}{#1}%
  \if \zifile
    \input #1\relax
    \endgraf
  \fi}

%                       Utilities
%                       ---------


\def \checkfile #1#2{%                          {\result-flag}{file}
  \openin \zreada #2\relax
  \setflag #1= {\notp{\eofp{\zreada}}}%
  \closein \zreada}