__HEADER__(Automatic references to theorems in proofs. Claim counters within proofs)

\RequirePackage{xkeyval}

__LANGUAGE_OPTIONS_X__

__END_OPTIONS_X__

\RequirePackage{amssymb}
\RequirePackage{amsthm}
\RequirePackage{etoolbox}
\RequirePackage{xparse}

%%Give claim an own counter and let it reset at each proof
%See also at:
%https://tex.stackexchange.com/questions/283502/reset-counter-at-beginning-of-proof
\newtheorem{claim}{__IF__(english) Claim\else Behauptung\fi}
\newtheorem*{claim*}{__IF__(english) Claim\else Behauptung\fi}
\AtBeginDocument{\def\claimautorefname{__IF__(english) Claim\else Behauptung\fi}}

__NEW_IF__(hyperref,false)
\AtBeginDocument{
    \@ifpackageloaded{hyperref}{
        __SET_IF__(hyperref,true)
        \def\grab#1{\expandafter\@firstoffive#1}
        \def__PACKAGE_MACRO__(blankref)#1{\expandafter\grab\csname r@#1\endcsname}
        \let__PACKAGE_MACRO__(autoref)\autoref
    }{
        __SET_IF__(hyperref,true)
        \let__PACKAGE_MACRO__(blankref)\ref
        \let__PACKAGE_MACRO__(autoref)\ref
    }
}

\NewDocumentEnvironment{rproof}{m O{}}{\def__PACKAGE_MACRO__(aster){\relax}\begin{__PACKAGE_PREFIX__rproof@impl}{#1}[#2]}{\end{__PACKAGE_PREFIX__rproof@impl}}
\NewDocumentEnvironment{rproof*}{m O{}}{\def__PACKAGE_MACRO__(aster){*}\begin{__PACKAGE_PREFIX__rproof@impl}{#1}[#2]}{\end{__PACKAGE_PREFIX__rproof@impl}}

\NewDocumentEnvironment{__PACKAGE_PREFIX__rproof@impl}{m O{}}
{
    % Restore correct counter for claim
    \ifcsdef{the__PACKAGE_PREFIX__#1@save@claim}{
        \setcounter{claim}{\value{__PACKAGE_PREFIX__#1@save@claim}}
        \def__PACKAGE_MACRO__(proofprefix){__IF__(english) Continuation of proof__PACKAGE_MACRO__(aster)\space of\else Fortsetzung des Beweises__PACKAGE_MACRO__(aster)\space zu\fi}
        \edef\haha{\value{__PACKAGE_PREFIX__#1@part}}
    }{
        \newcounter{__PACKAGE_PREFIX__#1@save@claim}
        \setcounter{claim}{0}
        \def__PACKAGE_MACRO__(proofprefix){__IF__(english) Proof__PACKAGE_MACRO__(aster)\space of\else Beweis__PACKAGE_MACRO__(aster)\space von\fi}
    }
    % Set up counter number printing as subindexed by numbering of the reference
    \let__PACKAGE_MACRO__(theoldclaim)\theclaim
    \def\theclaim{__PACKAGE_MACRO__(blankref){#1}.__PACKAGE_MACRO__(theoldclaim)}
    % Now, start the actual proof
    \begin{proof}[__PACKAGE_MACRO__(proofprefix)\space__PACKAGE_MACRO__(autoref){#1}\if\relax\detokenize{#2}\relax\else\space(#2)\fi]
}
{
    \end{proof} % End proof
    % Save current claim counter for later restoration
    \setcounter{__PACKAGE_PREFIX__#1@save@claim}{\value{claim}}
}

% Proof (with asterisk)
\NewDocumentEnvironment{proof*}{O{}}
{
    \if\relax\detokenize{#1}\relax\begin{proof}[__IF__(english) Proof\emph{*}\else Beweis\emph{*}\fi]\else\begin{proof}[#1\emph{*}]\fi
}
{
    \end{proof}
}


%%subproof environment - essentially copied proof environment from amsthm and modified its name + symbol
\DeclareRobustCommand{\blackqed}{%
  \ifmmode \mathqed
  \else
    \leavevmode\unskip\penalty9999 \hbox{}\nobreak\hfill
    \quad\hbox{$\blacksquare$}%
  \fi
}

\newenvironment{subproof}[1][__IF__(english) Subproof\else Unterbeweis\fi]{\par
  \pushQED{\blackqed}%
  \normalfont \topsep6\p@\@plus6\p@\relax
  \trivlist
  \item[\hskip\labelsep
        \itshape
    #1\@addpunct{.}]\ignorespaces
}{%
  \popQED\endtrivlist\@endpefalse
}


%%%% This might be dropped, but for now is collected here

%%Solution (for exercises)
\newenvironment{solution}[1][]{\begin{proof}[__IF__(english){}Solution\else{}Lösung\fi{}#1]}{\end{proof}}