% Book-specific authoring environments and shared box presentation.
% Copyright 2019, 2026 Adib Hasan. Part of BOOKbangla; LPPL 1.3c or later.

% Examples, reminders and DIY boxes share borders, padding and page breaking.
% Each environment defines its own title placement.
\tcbset{
  bookbangla/base/.style={enhanced,breakable,arc=1mm,boxrule=.7pt,
    colframe=bookbanglaboxframe,colback=bookbanglaboxbackground,
    colbacktitle=bookbanglaboxbackground,coltitle=bookbanglaboxframe,
    fonttitle=\bfseries,left=3pt,right=3pt,bottom=2pt,top=8pt,
    before skip=8pt plus 2pt minus 4pt},
  bookbangla/reminder/.style={bookbangla/base,
    attach boxed title to top center={yshift=-\tcboxedtitleheight/2},
    boxed title style={size=fbox,colback=bookbanglaboxbackground,
      boxrule=.7pt,colframe=bookbanglaboxframe,
      frame code={\path[tcb fill frame]
        ([xshift=-2mm]frame.west)--(frame.north west)--(frame.north east)--
        ([xshift=2mm]frame.east)--(frame.south east)--(frame.south west)--cycle;},
      interior code={\path[tcb fill interior]
        ([xshift=-2mm]interior.west)--(interior.north west)--(interior.north east)--
        ([xshift=2mm]interior.east)--(interior.south east)--(interior.south west)--cycle;}}}}
\newtcolorbox{diybox}{bookbangla/base,left=4pt,right=4pt,bottom=4pt,
  top=4pt,title={\bookbangla@diyname},
  attach boxed title to top center={yshift=-\tcboxedtitleheight/2},
  boxed title style={size=normal,colframe=bookbanglaboxbackground,boxrule=0pt}}
\newtcolorbox{reminder}[1][\bookbangla@remindername]{bookbangla/reminder,title={#1}}
% amsthm shapes its heading in a temporary box, then unpacks it into the
% paragraph. With LuaTeX/HarfBuzz, a hyphenated Bangla heading can carry PDF
% text-extraction nodes inside a discretionary that cannot be unpacked safely.
% Disable hyphenation only inside that heading box; spaces still allow breaks,
% and the theorem body keeps its ordinary language and hyphenation settings.
\ifLuaTeX
  \xpatchcmd{\deferred@thm@head}{\normalfont#1}%
    {\normalfont\language=\l@nohyphenation #1}{}{%
      \ClassError{bookbangla}{Unable to configure theorem heading hyphenation}%
        {Check the amsthm version.}}
\fi
% Formal theorems use amsthm's ordinary plain style and optional name.
% Their chapter-based counter is independent of examples and exercises.
\theoremstyle{plain}
\newtheorem{theorem}{\bookbangla@theoremname}[chapter]
\renewcommand*\theoremautorefname{\bookbangla@theoremname}

\newcounter{example}[chapter]
\renewcommand*\theexample{\thechapter.\arabic{example}}
\providecommand*\exampleautorefname{\bookbangla@examplename}
% The starred option preserves our chapter-based formatter instead of having
% tcolorbox replace it with its default decimal-only formatter.
\newtcolorbox[use counter*=example]{example}[1][]{bookbangla/base,
  before skip=8pt plus 2pt minus 2pt,after skip=4pt plus 2pt,
  attach boxed title to top left={yshift=-9pt,xshift=6pt},
  boxed title style={size=fbox,boxrule=.7pt,colframe=bookbanglaboxframe,arc=1mm},
  % tcolorbox creates the anchor in its phantom box. Restore the reference
  % value in the body too, so an ordinary \label agrees with its label key.
  before upper={\protected@edef\@currentlabel{\p@example\theexample}},
  title={\bookbangla@examplename~\theexample},#1}

% Use amsthm's proof/QED machinery; only its heading presentation changes.
% A failed patch is reported, rather than silently losing the promised style.
\xpatchcmd{\proof}{\itshape}{\normalfont\bfseries}{}{%
  \ClassError{bookbangla}{Unable to style the proof heading}{Check the amsthm version.}}
\xpatchcmd{\proof}{\@addpunct{.}}{\@addpunct{:}}{}{%
  \ClassError{bookbangla}{Unable to style proof punctuation}{Check the amsthm version.}}
\newenvironment{solution}[1][\bookbangla@solutionname]{\begin{proof}[#1]}{\end{proof}}
\newtheoremstyle{bookbangla}{3pt}{3pt}{\normalfont}{}%
  {\bfseries}{:}{.5em}{\thmname{#1}\thmnumber{ #2}\thmnote{ (#3)}}
\theoremstyle{bookbangla}
\newtheorem*{remark}{\bookbangla@remarkname}
% Do not make our remark style the default for authors' later declarations.
\theoremstyle{plain}

% Inset quotations with a right-aligned attribution. LaTeXbangla handles
% script switching, so quotations can mix Bangla and English.
\newcommand*\bookbanglaquotefont{\itshape}
\NewDocumentEnvironment{chapquote}{O{2em} m}
  {\begin{adjustwidth}{#1}{#1}\bookbanglaquotefont
   \def\bookbangla@quotationauthor{#2}\ignorespaces}
  {\par\nobreak\hfill{\normalfont—\ \bookbangla@quotationauthor}\par
   \end{adjustwidth}\bigskip\ignorespacesafterend}

% A normal enumitem list: callers can override labels, margins and spacing.
% Draw overlapping rounded diamonds. The explicit bounds reserve whitespace,
% and the baseline aligns the marker with the list text. Authors can replace
% the marker through enumitem's label option.
\newcommand*\bookbangla@listmarker{%
  \tikz[x=1pt,y=1pt,baseline=-1.12pt]{%
    \path[use as bounding box] (-5.53,-4.28) rectangle (5.65,6.90);
    \foreach \x/\y in {0/0,.13/2.625}{%
      \draw[black,line width=.86pt,rounded corners=.4pt,shift={(\x,\y)}]
        (0,3.67)--(3.67,0)--(0,-3.67)--(-3.67,0)--cycle;}}}
\newlist{smartlist}{itemize}{4}
\setlist[smartlist]{label={\bookbangla@listmarker\;\;},labelsep=0pt,labelwidth=2em,
  leftmargin=1.5em,itemindent=0pt}

% Each problem owns its reference anchor. Keep hints local to the environment,
% and typeset them after the body without capturing or reprocessing the body.
\newcounter{exercise}[chapter]
\renewcommand*\theexercise{\thechapter.\arabic{exercise}}
\providecommand*\exerciseautorefname{\bookbangla@exercisename}
\ExplSyntaxOn
\tl_new:N \l__bookbangla_exercise_hint_tl
\keys_define:nn {bookbangla/exercise}
  {hint .tl_set:N = \l__bookbangla_exercise_hint_tl}
\NewDocumentEnvironment{exercise}{O{}}
  {
    \tl_clear:N \l__bookbangla_exercise_hint_tl
    \keys_set:nn {bookbangla/exercise}{#1}
    \par\addvspace{\topsep}
    \refstepcounter{exercise}
    \noindent\textbf{\bookbangla@exercisename\nobreakspace\theexercise{}:}\enspace\ignorespaces
  }
  {
    \par
    \tl_if_blank:VF \l__bookbangla_exercise_hint_tl
      {\nobreak\smallskip\noindent\textbf{\bookbangla@hintname{}:}\enspace
       \tl_use:N \l__bookbangla_exercise_hint_tl\par}
    \addvspace{\topsep}\ignorespacesafterend
  }
\ExplSyntaxOff
\endinput