% Copyright 2020 by Christian Feuersaenger
%
% 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.
%
% In addition to the above licenses, this particular file may also be
% directly inlined into other documents and this copyright notice may
% be removed. Additionally, when you inline this file, you may modify
% it as needed and you may remove comments.
%
% This file is intended to be distributed or even inlined into a file
% when a document needs to be typeset on a system that does not have
% pgf/TikZ installed.
%
% It replaces \tikzpicture/ \endtikzpicture and \tikz and invokes the
% \includegraphics with the correct file name instead.

\RequirePackage{graphicx}

\toksdef\t@tikzexternal@tmpa=0
\toksdef\t@tikzexternal@tmpb=1

\def\tikzexternalize{\@ifnextchar[{\tikzexternalize@opt}{\tikzexternalize@opt[]}}%
\def\tikzexternalize@opt[#1]{\@ifnextchar\bgroup{\def\tikzexternal@realjob}{\let\tikzexternal@realjob=\jobname}}%

\def\tikzsetnextfilename#1{\gdef\tikzexternal@nextfile{#1}}
\def\tikzsetexternalprefix#1{\def\tikzexternal@filenameprefix{#1}}
\def\tikzsetfigurename#1{\def\tikzexternal@figurename{#1}}%
\def\tikzappendtofigurename#1{\expandafter\def\expandafter\tikzexternal@figurename\expandafter{\tikzexternal@figurename #1}}%
\tikzsetnextfilename{}
\tikzsetexternalprefix{}
\tikzsetfigurename{\tikzexternal@realjob-figure}%

\long\def\tikzpicture#1\end#2{% collect every thing up to \end{tikzpicture}
    \def\tikzexternal@laTeX@collectpicture@@{#2}%
    \ifx\tikzexternal@laTeX@collectpicture@@\tikzexternal@laTeX@tikzpicturestring
        \tikzexternal@image
        \end{tikzpicture}%
    \else
        \expandafter
        \tikzpicture
    \fi
}%
\def\endtikzpicture{}
\def\tikzexternal@laTeX@tikzpicturestring{tikzpicture}%

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Replacement for \tikz short command:
\def\tikz{\@ifnextchar[{\tikz@opt}{\tikz@opt[]}}
\def\tikz@opt[#1]{\@ifnextchar\bgroup{\tikz@opt@{#1}}{\tikz@opt@@{#1}}}
\def\tikz@opt@#1#2{\tikz@opt@process{#1}{#2}}
\def\tikz@opt@@#1{%
  \def\tikz@next{\tikz@collectnormalsemicolon{#1}}%
  \ifnum\the\catcode`\;=\active\relax%
    \def\tikz@next{\tikz@collectactivesemicolon{#1}}%
  \fi%
  \tikz@next}
\def\tikz@collectnormalsemicolon#1#2;{\tikz@opt@process{#1}{#2;}}
{
  \catcode`\;=\active
  \gdef\tikz@collectactivesemicolon#1#2;{%
    \tikz@opt@process{#1}{#2;}%
  }
}
\def\tikz@opt@process#1#2{\tikzexternal@image}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\def\tikzexternal@image{%
    \leavevmode
    \begingroup
    \t@tikzexternal@tmpa=\expandafter{\tikzexternal@filenameprefix}%
    \ifx\tikzexternal@nextfile\empty
        \expandafter\ifx\csname c@tikzext@no@\tikzexternal@figurename\endcsname\relax
            \expandafter\gdef\csname c@tikzext@no@\tikzexternal@figurename\endcsname{0}%
        \fi
        \t@tikzexternal@tmpb=\expandafter{\tikzexternal@figurename}%
        \count0=\csname c@tikzext@no@\tikzexternal@figurename\endcsname
        \xdef\tikzexternal@curfilename{\the\t@tikzexternal@tmpa\the\t@tikzexternal@tmpb\the\count0 }%
        \advance\count0 by1\relax
        \expandafter\xdef\csname c@tikzext@no@\tikzexternal@figurename\endcsname{\the\count0 }%
    \else
        \t@tikzexternal@tmpb=\expandafter{\tikzexternal@nextfile}%
        \xdef\tikzexternal@curfilename{\the\t@tikzexternal@tmpa\the\t@tikzexternal@tmpb}%
    \fi
    \endgroup
    \global\let\tikzexternal@nextfile=\empty
    \pgfincludeexternalgraphics\tikzexternal@curfilename
}%
\def\tikzset#1{}\def\pgfkeys#1{}\def\pgfqkeys#1#2{}
\long\def\beginpgfgraphicnamed#1#2\endpgfgraphicnamed{\pgfincludeexternalgraphics{#1}}
\def\tikzifinpicture#1#2{#2}
\def\pgfincludeexternalgraphics#1{%
    \begingroup
    \pgfexternalreaddpth{#1}%
    \setbox1=\hbox{\includegraphics{#1}}%
    \ifdim\pgfretval=0pt
        \box1
    \else
        \dimen0=\pgfretval\relax
        \hbox{\lower\dimen0 \box1 }%
    \fi
    \endgroup
}
\newread\r@pgf@reada
\def\pgfexternalreaddpth#1{%
    \edef\pgfexternalreaddpth@restore{%
        \noexpand\endlinechar=\the\endlinechar\space
        \noexpand\catcode`\noexpand\@=\the\catcode`\@\space
    }%
    \def\pgfretval{0pt}%
    \endlinechar=-1 % suppress white space at end
    \catcode`\@=11
    \openin\r@pgf@reada=#1.dpth
    \pgfincludeexternalgraphics@read@dpth
    \pgfexternalreaddpth@restore
}%
\def\pgfincludeexternalgraphics@read@dpth{%
    \ifeof\r@pgf@reada
        \closein\r@pgf@reada
    \else
        \read\r@pgf@reada to\pgfincludeexternalgraphics@auxline
        \ifx\pgfincludeexternalgraphics@auxline\empty
        \else
            \expandafter\pgfincludeexternalgraphics@read@dpth@line\pgfincludeexternalgraphics@auxline\pgfincludeexternalgraphics@read@dpth@line@EOI
        \fi
        \expandafter\pgfincludeexternalgraphics@read@dpth
    \fi
}%
\long\def\pgfincludeexternalgraphics@read@dpth@line#1#2\pgfincludeexternalgraphics@read@dpth@line@EOI{%
    \ifcat\noexpand#1\relax
        \if@filesw
            {\toks0={#1#2}%
            \immediate\write\@auxout{\noexpand\def\noexpand\dpthimport{\the\toks0 }\noexpand\dpthimport }%
            }%
        \fi
    \else%
        \def\pgfretval{#1#2}%
    \fi
}%
