%D \module
%D   [       file=node-par,
%D        version=2008.09.30,
%D          title=\CONTEXT\ Node Macros,
%D       subtitle=Paragraph Building,
%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 Node Macros / Paragraph Building}

%D This is very experimental, undocumented, subjected to changes, etc. just as
%D the underlying interfaces.

% \enableparbuilders
%
% \startparbuilder[default]
%     \input tufte \par
%     \startparbuilder[oneline]
%         \input tufte \par
%     \stopparbuilder
%     \input tufte \par
% \stopparbuilder

\unprotect

\registerctxluafile{node-par}{1.001}

\definesystemattribute[parbuilder][public]

% todo auto-enable

% management (enable/disable) is global and will move to lua

\installcorenamespace {parbuilder}

\newcount\c_node_paragraphs_n_of_builders

\let\m_node_paragraphs_current_builder\empty

\unexpanded\def\defineparbuilder[#1]%
  {\global\advance\c_node_paragraphs_n_of_builders\plusone
   \ctxlua{builders.paragraphs.constructors.register("#1",\number\c_node_paragraphs_n_of_builders)}%
   \setxvalue{\??parbuilder#1}{\attribute\parbuilderattribute\number\c_node_paragraphs_n_of_builders}}

\unexpanded\def\startparbuilder[#1]%
  {\edef\m_node_paragraphs_current_builder{\number\attribute\parbuilderattribute}%
   \globalpushmacro\m_node_paragraphs_current_builder
   \getvalue{\??parbuilder#1}\relax
   \node_paragraphs_builders_check}

\unexpanded\def\stopparbuilder
  {\ifhmode\par\fi
   \globalpopmacro\m_node_paragraphs_current_builder
   \attribute\parbuilderattribute\m_node_paragraphs_current_builder\relax
   \node_paragraphs_builders_check}

\unexpanded\def\setmainparbuilder[#1]%
  {\ctxlua{builders.paragraphs.constructors.set("#1")}}

% no high level interface, after all implementing a linebreaker is not something that
% the average user will do

\defineparbuilder[default] % just for testing
\defineparbuilder[oneline] % just for testing
\defineparbuilder[basic]   % just for testing

\def\enableparbuilders {\ctxlua{builders.paragraphs.constructors.enable ()}}
\def\disableparbuilders{\ctxlua{builders.paragraphs.constructors.disable()}}

\def\node_paragraphs_builders_check % can be made more efficient as we don't want to do this too often
  {\ifcase\attribute\parbuilderattribute
     \disableparbuilders
   \else
     \enableparbuilders
   \fi}

\protect \endinput