%D \module
%D   [       file=spac-lin,
%D        version=2012.01.08, % 2009.10.16 (core-ver) 1997.03.31 (core-spa)
%D          title=\CONTEXT\ Spacing Macros,
%D       subtitle=Vertical,
%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.

\writestatus{loading}{ConTeXt Spacing Macros / Lines}

\unprotect

%D When spacing is active we need to handle commands in
%D a special way:
%D
%D \starttyping
%D \setuplines[space=on]
%D
%D \startlines
%D Let's talk about this{\ttsl\gobbleoneargument or}that.
%D \stoplines
%D
%D \startlines
%D Let's talk about this{\getvalue{ttsl}or}that.
%D \stoplines
%D \stoptyping
%D
%D One can indent in several ways:
%D
%D \starttyping
%D \setupindenting[medium] \setuplines[indenting=odd] % no yes odd even
%D
%D \startlines
%D first
%D second
%D third
%D fourth
%D \stoplines
%D \stoptyping

%D Contrary to \MKII\ we can now define classes of lines (generalized by
%D Wolfgang). I will probably rewrite bits in \LUA.

\installcorenamespace{lines}

\installcommandhandler \??lines {lines} \??lines

\setuplines
  [\c!option=,
   \c!command=,
   \c!before=\blank,
   \c!after=\blank,
   \c!inbetween=\blank,
   \c!indenting=\v!no,
   \c!space=\v!default]

\appendtoks
   \setuevalue{\e!start\currentlines}{\spac_lines_start[\currentlines]}%
   \letvalue  {\e!stop \currentlines }\spac_lines_stop
\to \everydefinelines

\unexpanded\def\spac_lines_start[#1]%
  {\bgroup
   \edef\currentlines{#1}%
   \obeylines
   \dosingleempty\spac_lines_start_indeed}

\let\p_lines_option\empty

\let\spac_lines_break            \relax
\let\spac_after_first_obeyed_line\relax

\def\spac_lines_start_indeed[#1]% new: optional second argument (WS)
  {\iffirstargument
     \setupcurrentlines[#1]%
   \fi
   \edef\p_lines_option{\linesparameter\c!option}%
   \ifx\p_lines_option\v!packed
     \let\spac_lines_break\nobreak
   \else
     \let\spac_lines_break\relax
   \fi
   \linesparameter\c!before
   \push_macro_checkindentation
   \whitespace
   \dostarttaggedchained\t!lines\currentlines\??lines
   \begingroup
   \uselinesstyleandcolor\c!style\c!color
   \useindentingparameter\linesparameter
   \usealignparameter\linesparameter
   \typesettinglinestrue
   \setupwhitespace[\v!none]% todo use fast variant
   %\obeylines % move upwards to keep spaces in the first line due to optional argument
   \ignorespaces
   \glet\spac_after_first_obeyed_line\spac_lines_after_first_obeyed_line_a
   \let\obeyedline\spac_lines_obeyed_line
   \activatespacehandler{\linesparameter\c!space}%
   \dostarttagged\t!line\empty
   \ignorepars} % this will become a nice lowercased helper

% we could have states instead and handle option in there

\def\spac_lines_after_first_obeyed_line_a % tzt two pass, like itemize
  {\linesparameter\c!command
   \linesparameter\c!left
   \glet\spac_after_first_obeyed_line\spac_lines_after_first_obeyed_line_b}

\def\spac_lines_after_first_obeyed_line_b
  {\spac_lines_break
   \linesparameter\c!command
   \linesparameter\c!left}

\def\spac_lines_obeyed_line
  {\ifdone\linesparameter\c!right\fi
   \dostoptagged % can be a dummy one as we don't look ahead
   \par
   \dostarttagged\t!line\empty
   \futurelet\next\spac_lines_between}

\unexpanded\def\spac_lines_stop
  {\dostoptagged
   \endgroup
   \dostoptagged
   \pop_macro_checkindentation
   \linesparameter\c!after
   \egroup}

\def\spac_lines_between
  {\ifx\next\spac_lines_stop
     \donefalse
   \else
     \doifelsemeaning\next\obeyedline % brrr
       {\donefalse\linesparameter\c!inbetween}
       {\donetrue\spac_after_first_obeyed_line}%
   \fi}

\definelines[\v!lines]

\unexpanded\def\emptylines
  {\dosingleempty\spac_lines_empty}

% \def\spac_lines_empty[#1]%
%   {\endgraf
%    \dorecurse{\iffirstargument#1\else3\fi}\crlf}

\def\spac_lines_empty[#1]%
  {\endgraf
   \begingroup
  %\forgetall % debatable
   \ifhmode
      \crlf % finish the current line
   \fi
   \dorecurse{\iffirstargument#1\else3\fi}{\strut\crlf}%
   \endgroup}

\ifdefined\startlines \else
    \expandafter\let\expandafter\startlines\csname\e!start\v!lines\endcsname
    \expandafter\let\expandafter\stoplines \csname\e!stop \v!lines\endcsname
\fi

\protect \endinput