% Copyright 2018 by Mark Wibrow
%
% This file may be distributed and/or modified
%
% 1. under the LaTeX Project Public License and/or
% 2. under the GNU Public License.
%
% See the file doc/generic/pgf/licenses/LICENSE for more details.

\newdimen\pgflsystemstep
\newcount\c@pgf@lsystem@iteration

\newif\ifpgf@lsystem@randomize@step
\newif\ifpgf@lsystem@randomize@angle

\pgfkeys{/pgf/lindenmayer system/.cd,%
    step/.code={\pgfmathsetlength\pgflsystemstep{#1}},%
    randomize step percent/.code={%
        \pgfmathparse{#1}%
        \let\pgflsystemrandomizesteppercent=\pgfmathresult%
        \ifdim\pgfmathresult pt=0pt\relax%
            \pgf@lsystem@randomize@stepfalse%
        \else%
            \pgf@lsystem@randomize@steptrue%
        \fi%
    },%
    left angle/.code={\pgfmathparse{#1}\let\pgflsystemleftangle=\pgfmathresult},%
    right angle/.code={\pgfmathparse{#1}\let\pgflsystemrightangle=\pgfmathresult},%
    angle/.style={/pgf/lindenmayer system/left angle=#1, /pgf/lindenmayer system/right angle=#1},%
    randomize angle percent/.code={%
        \pgfmathparse{#1}%
        \let\pgflsystemrandomizeanglepercent=\pgfmathresult%
        \ifdim\pgfmathresult pt=0pt\relax%
            \pgf@lsystem@randomize@anglefalse%
        \else%
            \pgf@lsystem@randomize@angletrue%
        \fi%
    }%
}%

\pgfkeys{/pgf/lindenmayer system/.cd,
    step=5pt,%
    randomize step percent=0,%
    angle=90,%
    randomize angle percent=0%
}%

\long\def\pgfdeclarelindenmayersystem#1#2{%
    \pgfutil@ifundefined{pgf@lsystem@#1}%
        {%
            \begingroup%
                \edef\pgf@lsystem@name{#1}%
                \expandafter\global\expandafter\let\csname pgf@lsystem@#1\endcsname=\pgf@lsystem@name%
                \let\symbol=\pgf@lsystem@symbol%
                \let\rule=\pgf@lsystem@rule%
                #2%
            \endgroup%
        }%
        {\pgferror{Lindenmayer system `#1' is already defined}}%
}%

\def\pgf@lsystem@symbol#1#2{%
    \expandafter\gdef\csname pgf@lsystem@\pgf@lsystem@name @symbol@#1\endcsname{#2}%
}%

\def\pgf@lsystem@rule#1{\expandafter\pgf@lsystem@rule@#1\pgf@stop}%
\def\pgf@lsystem@rule@#1{\def\pgf@lsystem@rule@head{#1}\pgf@lsystem@rule@@}%
\def\pgf@lsystem@rule@@#1->{% Now some `fooling around' to deal with unwanted spaces.
    \let\pgf@lsystem@rule@body=\pgfutil@empty%
    \pgfutil@ifnextchar x{\pgf@lsystem@rule@@@}{\pgf@lsystem@rule@@@}}%
\def\pgf@lsystem@rule@@@#1{%
    \ifx#1\pgf@stop%
        \expandafter\global\expandafter\let%
            \csname pgf@lsystem@\pgf@lsystem@name @rule@\pgf@lsystem@rule@head\endcsname=\pgf@lsystem@rule@body%
    \else%
        \edef\pgf@lsystem@rule@body{\pgf@lsystem@rule@body#1}%
        \expandafter\pgf@lsystem@rule@@@%
    \fi%
}%

\def\pgflindenmayersystem#1#2#3{%
    \begingroup%
        \edef\pgf@lsystem@name{#1}%
        \edef\pgf@lsystem@axiom{#2}%
        \pgfmathtruncatemacro\pgf@lsystem@order{#3}%
        %
        \let\pgf@lsystem@current@symbol=\relax%
        %
        \c@pgf@lsystem@iteration=0\relax%
        %
        \ifnum\pgf@lsystem@order=0\relax%
            \expandafter\pgf@lsystem@draw\pgf@lsystem@axiom\pgf@stop
            \let\pgf@lsystem@next=\pgf@lsystem@end%
        \else%
            \let\pgf@lsystem@next=\pgf@lsystem@run%
        \fi%
        \expandafter\pgf@lsystem@next\pgf@lsystem@axiom\pgf@lsystem@stop%
}%

\def\pgf@lsystem@run#1{%
    \ifx#1\pgf@lsystem@stop%
        \def\pgf@lsystem@token{\pgf@lsystem@stop}%
        \let\pgf@lsystem@next=\pgf@lsystem@end%
    \else%
        \ifx#1\pgf@stop%
            \advance\c@pgf@lsystem@iteration by-1\relax%
            \let\pgf@system@token=\pgfutil@empty%
            \let\pgf@lsystem@next=\pgf@lsystem@run%
        \else%
            % Does #1 appear on the RHS of a rule...?
            \expandafter\let\expandafter\pgf@lsystem@token\expandafter=%
                \csname pgf@lsystem@\pgf@lsystem@name @rule@#1\endcsname%
            \ifx\pgf@lsystem@token\relax%
                % ...nope. So draw it straight away.
                \pgf@lsystem@draw#1\pgf@stop%
                \let\pgf@lsystem@token=\pgfutil@empty%
            \else%
                % ...yep. So, if the order has been reached draw the LHS
                % immediately. Otherwise add the LHS to the token stream
                % and continue.
                \advance\c@pgf@lsystem@iteration by1\relax%
                \ifnum\c@pgf@lsystem@iteration=\pgf@lsystem@order%
                    \expandafter\pgf@lsystem@draw\pgf@lsystem@token \pgf@stop%
                    \advance\c@pgf@lsystem@iteration by-1\relax%
                    \let\pgf@lsystem@token=\pgfutil@empty%
                \else%
                    \expandafter\def\expandafter\pgf@lsystem@token\expandafter{\pgf@lsystem@token \pgf@stop}%
                \fi%
            \fi%
            \let\pgf@lsystem@next=\pgf@lsystem@run%
        \fi%
    \fi%
    \expandafter\pgf@lsystem@next\pgf@lsystem@token}%

\def\pgf@lsystem@end#1\pgf@lsystem@stop{\endgroup}%

\def\pgf@lsystem@draw#1{%
    \ifx#1\pgf@stop%
        \let\pgf@lsystem@next=\relax%
    \else%
        \expandafter\let\expandafter\pgf@lsystem@current@symbol\expandafter=%
            \csname pgf@lsystem@\pgf@lsystem@name @symbol@#1\endcsname%
        \ifx\pgf@lsystem@current@symbol\relax% Try a default symbol.
            \expandafter\let\expandafter\pgf@lsystem@current@symbol\expandafter=%
                \csname pgf@lsystem@symbol@default@#1\endcsname%
        \fi%
        \let\pgf@lsystem@next=\pgf@lsystem@@draw%
    \fi%
    \pgf@lsystem@next}%

\def\pgf@lsystem@@draw{%
    \edef\pgflsystemcurrentstep{\the\pgflsystemstep}%
    \let\pgflsystemcurrentrightangle=\pgflsystemrightangle%
    \let\pgflsystemcurrentrightangle=\pgflsystemleftangle%
    \pgf@lsystem@current@symbol%
    \pgf@lsystem@draw}%

\expandafter\def\csname
pgf@lsystem@symbol@default@F\endcsname{\pgflsystemdrawforward}%
\expandafter\def\csname
pgf@lsystem@symbol@default@f\endcsname{\pgflsystemmoveforward}%
\expandafter\def\csname
pgf@lsystem@symbol@default@+\endcsname{\pgflsystemturnleft}%
\expandafter\def\csname
pgf@lsystem@symbol@default@-\endcsname{\pgflsystemturnright}%
\expandafter\def\csname
pgf@lsystem@symbol@default@[\endcsname{\pgflsystemsavestate}%
\expandafter\def\csname
pgf@lsystem@symbol@default@]\endcsname{\pgflsystemrestorestate}%

\def\pgflsystemradonmizestep{%
    \ifpgf@lsystem@randomize@step%
        \pgfmathrand%
        \pgf@x=\pgflsystemrandomizesteppercent pt\relax%
        \pgf@x=\pgfmathresult\pgf@x%
        \divide\pgf@x by20\relax%
        \advance\pgf@x by\pgflsystemstep\relax%
        \edef\pgflsystemcurrentstep{\the\pgf@x}%
    \else%
        \edef\pgflsystemcurrentstep{\the\pgflsystemstep}%
    \fi%
}%

\def\pgflsystemdrawforward{%
    \pgflsystemradonmizestep
    \pgftransformxshift{+\pgflsystemcurrentstep}%
    \pgfpathlineto{\pgfpointorigin}}%

\def\pgflsystemmoveforward{%
    \pgflsystemradonmizestep
    \pgftransformxshift{+\pgflsystemcurrentstep}%
    \pgfpathmoveto{\pgfpointorigin}}%

\def\pgflsystemranomizerightangle{%
    \ifpgf@lsystem@randomize@angle%
        \pgf@x=\pgflsystemrandomizeanglepercent pt\relax%
        \divide\pgf@x by20\relax%
        \pgfmathrand%
        \pgf@x=\pgfmathresult\pgf@x%
        \advance\pgf@x by\pgflsystemrightangle pt\relax%
        \edef\pgflsystemcurrentrightangle{\pgfmath@tonumber{\pgf@x}}%
    \else%
        \let\pgflsystemcurrentrightangle=\pgflsystemrightangle%
    \fi%
}%

\def\pgflsystemranomizeleftangle{%
    \ifpgf@lsystem@randomize@angle%
        \pgf@x=\pgflsystemrandomizeanglepercent pt\relax%
        \divide\pgf@x by20\relax%
        \pgfmathrand%
        \pgf@x=\pgfmathresult\pgf@x%
        \advance\pgf@x by\pgflsystemleftangle pt\relax%
        \edef\pgflsystemcurrentleftangle{\pgfmath@tonumber{\pgf@x}}%
    \else%
        \let\pgflsystemcurrentleftangle=\pgflsystemleftangle%
    \fi%
}%

\def\pgflsystemturnright{%
    \pgflsystemranomizerightangle
    \pgftransformrotate{-\pgflsystemcurrentrightangle}}%

\def\pgflsystemturnleft{%
    \pgflsystemranomizeleftangle
    \pgftransformrotate{\pgflsystemcurrentleftangle}}%

\def\pgflsystemsavestate{\begingroup}%
\def\pgflsystemrestorestate{\endgroup\pgfpathmoveto{\pgfpointorigin}}%
