% Counter presentation; arithmetic and reset relationships stay upstream.
% Part of latexbangla, LPPL 1.3c or later; copyright 2026 Adib Hasan.

% Use a written inventory, not Unicode arithmetic: the conventional order is
% not a contiguous Unicode range. Bengali has no uppercase/lowercase distinction.
\clist_const:Nn \c__latexbangla_alphabet_clist
  {ক,খ,গ,ঘ,ঙ,চ,ছ,জ,ঝ,ঞ,ট,ঠ,ড,ঢ,ণ,ত,থ,দ,ধ,ন,
   প,ফ,ব,ভ,ম,য,র,ল,শ,ষ,স,হ,ড়,ঢ়,য়,ৎ}

% Keep this formatter expandable: labels are written to .aux/.toc files and
% expanded in PDF strings. Match LaTeX's empty value for zero and its error for
% values beyond the alphabet instead of silently inventing multiple letters.
\cs_new:Npn \__latexbangla_format_alphabetic:n #1
  {
    \int_compare:nNnTF {#1} = {0}
      {}
      {
        \int_compare:nNnTF {#1} < {1}
          {\@ctrerr}
          {
            \int_compare:nNnTF {#1} > {\clist_count:N \c__latexbangla_alphabet_clist}
              {\@ctrerr}
              {\clist_item:Nn \c__latexbangla_alphabet_clist {#1}}
          }
      }
  }

% Polyglossia replaces \thefootnote on language activation even when the class
% chose Roman or symbolic marks. Its decimal formatter already localizes the
% ordinary \arabic-based definition, so that replacement is unnecessary here.
% Hook the specific upstream activation command, not begin-document: an author
% can change footnote formatting in a later hook or switch languages afterward.
% These two hooks are the isolated dependency on Polyglossia's implementation.
% Save immediately before activation and undo only its known footnote rewrite.
\AddToHook{cmd/bengali@globalnumbers/before}[latexbangla/footnotes]
  {\cs_set_eq:NN \__latexbangla_original_footnote: \thefootnote}
\cs_new_nopar:Npn \__latexbangla_upstream_footnote: {\localnumeral*{footnote}}

\AddToHook{cmd/bengali@globalnumbers/after}[latexbangla/numbering]
  {
    \bool_if:NT \g__latexbangla_convert_counters_bool
      {
        \cs_if_eq:NNT \thefootnote \__latexbangla_upstream_footnote:
          {\cs_set_eq:NN \thefootnote \__latexbangla_original_footnote:}
        % The tested upstream formatter accepts digits, not a leading minus.
        % Reuse the signed wrapper around its converter, only if the upstream
        % formatter is still installed. Explicit author formatters take priority.
        \cs_if_eq:NNT \@arabic \bengalinumber
          {\cs_set_eq:NN \@arabic \__latexbangla_format_integer:n}
      }
  }

\AddToHook{begindocument/end}[latexbangla/alphabet]
  {
    \bool_if:NT \g__latexbangla_convert_counters_bool
      {
        \cs_set_eq:NN \@alph \__latexbangla_format_alphabetic:n
        \cs_set_eq:NN \@Alph \__latexbangla_format_alphabetic:n
      }
  }

% Retained explicit converters always request Bengali digits, including when
% automatic counter conversion is disabled. Let Polyglossia supply the mapping.
% Counter values are signed TeX integers. Split off their sign because the
% upstream digit-only converter is not a general text filter.
\cs_new:Npn \__latexbangla_format_integer:n #1
  {
    \int_compare:nNnTF {#1} < {0}
      {-\exp_args:Ne \bengalidigits {\int_abs:n {#1}}}
      {\exp_args:Ne \bengalidigits {\int_eval:n {#1}}}
  }
\NewExpandableDocumentCommand \numtobangla {m}
  {\bengalidigits{#1}}
\NewExpandableDocumentCommand \tobangla {m}
  {\__latexbangla_format_integer:n {\value{#1}}}

\endinput