%% Copyright(C) 2002, 2004  Behdad Esfahbod <behdad@farsitex.org>
%% 
%% It may be distributed and/or modified under the
%% conditions of the LaTeX Project Public License, either version 1.2
%% of this license or (at your option) any later version.
%% The latest version of this license is in
%%    http://www.latex-project.org/lppl.txt
%% and version 1.2 or later is part of all distributions of LaTeX
%% version 1999/12/01 or later.
%% 
%% TODO: Add some penalties and whistles to newpoem
%%
\ifx\fmtname{LaTeX2e}
\NeedsTeXFormat{LaTeX2e}
\ProvidesPackage{persianpoem}%
	[2004/09/27 Environments for Setting Persian Poetry]
\else
	\typeout{2004/09/27 Environments for Setting Persian Poetry}
\fi

\def\poemcolsepskip{.1\versewidth plus .1\versewidth minus .05\versewidth}
\def\poemmarginskip{1em plus 1fil minus 1em}
\def\poemextrabaselineskip{0\baselineskip}
\def\poemskip{\medskip}
\def\poemblocksep{\quad$\Box$}

%% oldpoem environment

\newdimen\versewidth

\def\poem@verse#1{%
	\ifdim\wd#1>\new@poem@width
		\xdef\new@poem@width{\the\wd#1}%
		\ifdim\new@poem@width>\poem@width
			\xdef\poem@width{\new@poem@width}%
			\global\let\poem@needrun\relax
		\fi
	\fi
	\hbox to\poem@width{\unhbox#1}%
}
\def\poem@linebegin{\vadjust{}\hskip\@flushglue\hskip\poemmarginskip\relax}
\def\poem@lineend{\nobreak\hskip\poemmarginskip\hskip\@flushglue\vadjust{}}
\def\poem@lineversesep{%
	\nobreak
	\hskip\z@ plus 1filll%
	\penalty600%
	\hskip\poemcolsepskip
	\hskip\z@ plus -2filll%
	\vadjust{}%
	\nobreak
	\hskip\z@ plus 1filll%
}

\def\poem@lineparsebegin{%
	\halign\bgroup
		\global\setbox\verse@i=\hbox{\ignorespaces##\unskip}&&
		\global\setbox\verse@ii=\hbox{\ignorespaces##\unskip}
		\cr
}
\def\poem@lineparseend{%
	\crcr\egroup
	\vskip-\baselineskip
}
\def\oldpoem@cr{%
  \cr\poem@line
}

\newbox\verse@i
\newbox\verse@ii
\newif\ifpoem@started

\def\poem@line{%
	\poem@lineparseend
%
	\ifdim\wd\verse@i>\z@\global\poem@startedtrue\fi
	\ifdim\wd\verse@ii>\z@\global\poem@startedtrue\fi
	\ifpoem@started
	  \ifdim\wd\verse@ii>\z@\else
		  \nopagebreak[3]
	  \fi
	  \leavevmode
	  \poem@linebegin
	  \poem@verse\verse@i
	  \ifdim\wd\verse@ii>\z@
		  \poem@lineversesep
		  \poem@verse\verse@ii
	  \fi
	  \poem@lineend
	  \nopagebreak
	  \endgraf
	  \vskip\poemextrabaselineskip
	\fi
%
	\poem@lineparsebegin
}
\def\@oldpoem{%
	\stepcounter{poem@no}
        \ifnum\max@poem@no<\number\c@poem@no%
		\xdef\poem@width{\z@}%
        \else
		\xdef\poem@width{\poem@prop{poem@width}}%
	\fi
	\xdef\new@poem@width{\z@}%
	\global\versewidth=\poem@width
	\poemskip\leavevmode\par
	\begingroup
	\tabskip=\z@
	\parskip=\z@
	\parindent=\z@
	\parfillskip=\z@
	\rightskip=\z@
	\leftskip=\z@
	\widowpenalty=10000%	No break between verses of the same line.
	\clubpenalty=10000%	Same as above.  Not really needed.
	\def\newblock{\hfil\poemblocksep\hfil\null}%
	\def\par{\oldpoem@cr}% Redefine \par for possible \obeylines
	\def\\{\global\poem@startedtrue\oldpoem@cr}%
	\global\poem@startedfalse
	\csname poem@obeylines\endcsname
	\let\poem@obeylines\relax
	\poem@lineparsebegin
}
\def\@endoldpoem{%
	\cr
	\ifdim\wd\verse@i>\z@\poem@line\else\ifdim\wd\verse@ii>\z@\poem@line\else
		\noalign{%
			\skip0=\poemextrabaselineskip
			\vskip-\skip0
			\vskip-\baselineskip
		}%
	\fi\fi
	\poem@lineparseend
	\endgroup
	\par
	\vskip\baselineskip
	\poemskip
	\ifdim\new@poem@width<\poem@width
		\global\let\poem@needrun\relax
	\fi
        \poem@write@aux{poem@width@\romannumeral\c@poem@no}{\new@poem@width}%
	\ifx\AtEndDocument\undefined\poem@finish\fi
}
\newenvironment{oldpoem}{\@oldpoem}{\@endoldpoem}

\expandafter\def\csname oldpoem*\endcsname{\let\poem@obeylines=\obeylines\oldpoem}
\expandafter\def\csname endoldpoem*\endcsname{\endoldpoem}


\def\poem@finish{%
	\poem@write@aux{max@poem@no}{\number\c@poem@no}%
	\ifx\poem@needrun\relax
		\@@warning{Unjustified poetry.  Rerun to get poems right}%
		\global\let\poem@needrun\undefined
	\fi
}
\ifx\AtEndDocument\undefined\else\AtEndDocument\poem@finish\fi

\newcounter{poem@no}\setcounter{poem@no}{\z@}
\ifx\max@poem@no\undefined
        \def\max@poem@no{0}%
\fi

\newcommand{\poem@prop}[1]{\@nameuse{#1@\romannumeral\c@poem@no}}

\newcommand{\poem@write@aux}[2]{%
        \def\@x{\immediate\write\@auxout{\global\noexpand\@namedef{#1}{#2}}}%
        \@x
}

%% newpoem environment

\def\@newpoem{%
	\par
	\begingroup
	\parskip=\z@
	\parindent=\z@
	\def\[{\@settab\@tabplus\ignorespaces}%
	\def\]{\@tabminus\ignorespaces}%
	\def\newblock{\poemblocksep}%
	\let\newpoem@tabcr\@tabcr
	\def\par{% Redefine \par for possible \obeylines
	  \ifpoem@started\else
	    \ifdim\wd\@curline>\z@\global\poem@startedtrue\else
	      \@stopfield
	      \ifdim\wd\@curfield>\z@\global\poem@startedtrue\fi
	      \@contfield
	    \fi
	  \fi
	  \ifpoem@started\newpoem@tabcr\fi}%
	\def\@tabcr{\global\poem@startedtrue\newpoem@tabcr}%
	\global\poem@startedfalse
	\csname poem@obeylines\endcsname
	\let\poem@obeylines\relax
	\begin{tabbing}%
}
\def\@endnewpoem{%
	\global\poem@startedfalse
	\ifdim\wd\@curline>\z@\global\poem@startedtrue\else
	  \@stopfield
	  \ifdim\wd\@curfield>\z@\global\poem@startedtrue\fi
	  \@contfield
	\fi
	\ifpoem@started\else\let\@stopline\@stopfield\fi
	\end{tabbing}%
	\endgroup
	\par
}

\newenvironment{newpoem}{\@newpoem}{\@endnewpoem}

\expandafter\def\csname newpoem*\endcsname{\let\poem@obeylines=\obeylines\newpoem}
\expandafter\def\csname endnewpoem*\endcsname{\endnewpoem}


\endinput