% Copyright 2003--2007 by Till Tantau
% Copyright 2010 by Vedran Mileti\'c
% Copyright 2015 by Vedran Mileti\'c, Joseph Wright
% Copyright 2017,2018 by Louis Stuart, Joseph Wright
%
% 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 LICENSE.md for more details.

% To track which slide we are on in a frame
\newcount\beamer@slideinframe
\newcount\beamer@minimum

% Indicate whether another slide needs to be processed in this frame
\newif\ifbeamer@anotherslide
\newif\ifbeamer@localanotherslide

% Used to know that beamerpauses needs to be used in substitution
\newif\ifbeamer@plusencountered

% The main decoding macro tolerates a range of active characters, which
% require a little set up. In particular, as an active space is allowed
% all of the lines here have to be terminated with "%". The two-step
% setup for \beamer@@@temp makes sure everything is expanded and removes
% all of the spaces at this stage.
\newbox\beamer@decode@box
\begingroup
  \catcode`\|=\active
  \catcode`\:=\active
  \catcode`\,=\active
  \catcode`\.=\active
  \catcode`\+=\active
  \catcode`\-=\active
  \catcode`\(=\active
  \catcode`\)=\active
  \catcode`\ =\active
\xdef\beamer@masterdecode#1{%
\noexpand\beamer@localanotherslidefalse%
\setbox\beamer@decode@box=\hbox{%
\unexpanded{%
\ifnum\catcode`\|=\active\edef|{\string|}\fi%
\ifnum\catcode`\:=\active\edef:{\string:}\fi%
\ifnum\catcode`\,=\active\edef,{\string,}\fi%
\ifnum\catcode`\.=\active\edef.{\string.}\fi%
\ifnum\catcode`\+=\active\edef+{\string+}\fi%
\ifnum\catcode`\-=\active\edef-{\string-}\fi%
\ifnum\catcode`\(=\active\edef({\string(}\fi%
\ifnum\catcode`\)=\active\edef){\string)}\fi%
\ifnum\catcode`\ =\active\edef {\string }\fi}%
\edef\noexpand\beamer@@@temp{#1\string|stop\string:0\string|}%
\edef\noexpand\beamer@@@temp{\unexpanded{\expandafter\zap@space\beamer@@@temp}%
\space\noexpand\@empty}%
\unexpanded{\expandafter\beamer@decode\beamer@@@temp%
\ifbeamer@localanotherslide\aftergroup\beamer@localanotherslidetrue\fi}%
}%
}%
\endgroup

% Sets dowhat to doif, if \beamer@slideinframe is in the specified
% interval. Example: 5-7,-3,9,11,13- would mean pages
% 1,2,3,5,6,7,9,11,13,14,15,16,...
%
% As a side effect, \@another is called whenever the there is a number
% in the list that is larger than the current serialnumber

\def\beamer@allsign{*}

% The main decoding routine starts by initialising the starting a search
% for everything up to "|": to allow for the simple case of overlays in
% slides for presentations there is a need to insert "beamer:". Notice
% that \beamer@@decodefind may be called multiple times, hence being set
% up as an auxiliary.
\def\beamer@decode{%
  \beamer@plusencounteredfalse
  \global\beamer@minimum=10000\relax
  \gdef\beamer@decaction{}%
  \global\let\beamer@decodefound=\beamer@allsign
  \beamer@@decodefind}
\def\beamer@@decodefind#1|{\beamer@@@decodefind#1:|}
\def\beamer@@@decodefind#1:#2|{%
  \ifblank{#2}%
    {\beamer@decodefind beamer:#1:}%
    {\beamer@decodefind #1:#2}}

% A list of possible overlay modes
\def\beamer@default{default}
\def\beamer@articlemode{article}
\def\beamer@secondmode{second}
\def\beamer@beamermode{beamer}
\def\beamer@presentationmode{presentation}
\def\beamer@modeall{all}
\def\beamer@ovmodestop{stop}

% The main parsing function for each sub-part starts by splitting at any
% "@" and then checking the spec for various cases: keywords, "+", ".".
% After that, there is some cleanup to do before potentially looping.
\def\beamer@decodefind#1:#2:{%
  \def\beamer@ovmode{#1}%
  \beamer@decodeaction{#2}%
  \expandafter\futurelet\expandafter\next\expandafter
    \beamer@checkcat\beamer@spec:%
  \expandafter\beamer@decodeplus\beamer@spec+:%
  \expandafter\beamer@decodedot\beamer@spec.:%
  \ifx\beamer@ovmode\beamer@ovmodestop
    \expandafter\beamer@@decode\beamer@decodefound,!%
    \let\beamer@next=\relax
    \ifbeamer@plusencountered\stepcounter{beamerpauses}\fi
  \else
    \ifx\beamer@ovmode\beamer@currentmode
      \beamer@@decodefound
    \else
      \ifx\beamer@ovmode\beamer@modeall
        \beamer@@decodefound
      \else
        \ifx\beamer@ovmode\beamer@presentationmode
          \ifx\beamer@currentmode\beamer@articlemode
          \else
            \beamer@@decodefound
          \fi
        \else
          \ifx\beamer@ovmode\beamer@beamermode
            \ifx\beamer@currentmode\beamer@secondmode
              \beamer@@decodefound
            \fi
          \fi
        \fi
      \fi
    \fi
    \let\beamer@next=\beamer@@decodefind
  \fi
 \beamer@next}

% The aim here is to find any "<action>@" spec, and to split it off the
% action from the rest. That uses a pretty stand search approach.
\edef\beamer@decodeaction#1{%
  \noexpand\beamer@@decodeaction#1\string @\string @:}
\begingroup
\edef\beamer@@@temp{%
  \endgroup
  \def\noexpand\beamer@@decodeaction##1\string @##2\string @##3:{%
    \noexpand\ifblank{##2}%
      {%
        \def\noexpand\beamer@action{default}%
        \def\noexpand\beamer@spec{##1}%
      }%
      {%
        \def\noexpand\beamer@action{##1}%
        \def\noexpand\beamer@spec{##2}%
      }%
  }%
}%
\beamer@@@temp

% Search for the case where the specification is a keyword, and if it
% is set the overlay mode and spec.
\def\beamer@checkcat#1:{%
  \ifcat\next a%
    \gdef\beamer@ovmode{#1}%
    \ifx\beamer@decodefound\beamer@allsign
      \gdef\beamer@decodefound{0}%
    \fi
    \def\beamer@spec{1-}%
  \fi}

\def\beamer@decodeplus{%
  \def\beamer@spec{}\beamer@@decodeplus}
\def\beamer@@decodeplus#1+#2:{%
  \edef\beamer@spec{\beamer@spec#1}% everything up to a +
  \ifblank{#2}{}
  {% ok, check if followed by number:
    \beamer@plusencounteredtrue
    \beamer@@@decodeplus#2:}}
\def\beamer@@@decodeplus{%
  \kernel@ifnextchar(%)
    {\beamer@relnumber}{\beamer@relnumber(0)}}
\def\beamer@relnumber(#1){%
  \beamer@plusencounteredtrue
  \@tempcnta=\numexpr #1 + \value{beamerpauses}\relax%
  \ifnum\@tempcnta<0\@tempcnta=0\fi%
  \edef\beamer@spec
    {\beamer@spec\number\@tempcnta}%
  \beamer@@decodeplus}

\def\beamer@decodedot{%
  \def\beamer@spec{}\beamer@@decodedot}
\def\beamer@@decodedot#1.#2:{%
  \edef\beamer@spec{\beamer@spec#1}% everything up to first .
  \ifblank{#2}{}{\beamer@@@decodedot#2:}}
\def\beamer@@@decodedot{%
  \kernel@ifnextchar(%)
    {\beamer@relnumberdot}{\beamer@relnumberdot(0)}}
\def\beamer@relnumberdot(#1){%
  \@tempcnta=\numexpr #1 + \value{beamerpauses} -1\relax%
  \ifnum\@tempcnta<0\@tempcnta=0\fi%
  \edef\beamer@spec
    {\beamer@spec\number\@tempcnta}%
  \beamer@@decodedot}

\def\beamer@@decodefound{%
  \ifx\beamer@action\beamer@default
    \xdef\beamer@decodefound{\beamer@spec}%
  \else
    \xdef\beamer@decaction{\beamer@decaction{\beamer@action<\beamer@spec>}}%
  \fi}
\def\beamer@currentaction{default}

\def\beamer@doifnotinframe{}

% A set of macros to deal with what can form the basis of an action
% spec once we know the basic shape: the key concepts are whether there
% are more slides to do and how many there are in total.
\def\beamer@@decode{%
  \kernel@ifnextchar!%
  {\beamer@decodeend}%
  {%
    \kernel@ifnextchar*%
    {\beamer@decodeall}{%
      \kernel@ifnextchar-%
      {\beamer@decodeuntil}%
      {\beamer@decodenumber}}}}
\def\beamer@decodeend!{}
\def\beamer@decodeall*,{%
  \ifnum1<\beamer@minimum
    \global\beamer@minimum=1\relax
  \fi
  \ifnum1>\beamer@slideinframe
    \global\beamer@anotherslidetrue\beamer@localanotherslidetrue
  \fi
  \gdef\beamer@doifnotinframe{\beamer@doifinframe}%
  \beamer@@decode}
\def\beamer@decodeuntil-#1,{%
  \ifnum1<\beamer@minimum
    \global\beamer@minimum=1\relax
  \fi
  \ifnum#1>\beamer@slideinframe
    \global\beamer@anotherslidetrue\beamer@localanotherslidetrue
  \fi
  \ifnum\beamer@slideinframe>#1\relax
  \else
    \gdef\beamer@doifnotinframe{\beamer@doifinframe}%
  \fi
  \beamer@@decode}
\def\beamer@decodenumber#1{%
  \kernel@ifnextchar,%
  {\beamer@decodeone{#1}}%
  {\kernel@ifnextchar-%
    {\beamer@decodenumberto{#1}}%
    {\beamer@decodegobble{#1}}}}
\def\beamer@decodegobble#1#2{%
  \beamer@decodenumber{#1#2}}
\def\beamer@decodenumberto#1-{%
  \kernel@ifnextchar,%
  {\beamer@decodeto{#1}}%
  {\beamer@decodebetween{#1}}}
\def\beamer@decodeto#1,{%
  \ifnum#1<\beamer@minimum
    \global\beamer@minimum=#1\relax
  \fi
  \ifnum#1>\beamer@slideinframe
    \global\beamer@anotherslidetrue\beamer@localanotherslidetrue
  \fi
  \ifnum#1>\beamer@slideinframe
  \else
    \gdef\beamer@doifnotinframe{\beamer@doifinframe}%
  \fi
  \beamer@@decode}
\def\beamer@decodebetween#1#2,{%
  \ifnum#1<\beamer@minimum
    \global\beamer@minimum=#1\relax
  \fi
  \ifnum#1>\beamer@slideinframe
    \global\beamer@anotherslidetrue\beamer@localanotherslidetrue
  \fi
  \ifnum#2>\beamer@slideinframe
    \global\beamer@anotherslidetrue\beamer@localanotherslidetrue
  \fi
  \ifnum#1>\beamer@slideinframe
  \else
    \ifnum#2<\beamer@slideinframe
    \else
      \gdef\beamer@doifnotinframe{\beamer@doifinframe}%
    \fi
  \fi
  \beamer@@decode}
\def\beamer@decodeone#1,{%
  \ifnum#1<\beamer@minimum
    \global\beamer@minimum=#1\relax
  \fi
  \ifnum#1>\beamer@slideinframe
    \global\beamer@anotherslidetrue\beamer@localanotherslidetrue
  \fi
  \ifnum#1=\beamer@slideinframe
    \gdef\beamer@doifnotinframe{\beamer@doifinframe}%
  \fi
  \beamer@@decode}

\def\beamer@donow{\beamer@doifnotinframe}
