%
% Copyright (c) 2021-2025 Zeping Lee
% Released under the MIT License.
% Repository: https://github.com/zepinglee/citeproc-lua
%

% ## Bibliography commands

% The options like `notcategory` can be used multiple times and thus we save
% them into a seq instead of a prop.
\seq_new:N \l__csl_bib_filter_seq
\int_new:N \g__csl_bib_list_index_int
\tl_new:N \g__csl_bib_list_index_tl
\tl_new:N \l__csl_bibliography_tl
\seq_new:N \l__csl_bibliography_seq

\NewDocumentCommand \printbibliography { O { } }
  {
    \int_gincr:N \g__csl_bib_list_index_int
    \tl_gset:Ne \g__csl_bib_list_index_tl { \int_use:N \g__csl_bib_list_index_int }
    \__csl_set_categories:
    % Bibliography filter
    \group_begin:
      \seq_clear:N \l__csl_bib_filter_seq
      \seq_put_right:Ne \l__csl_bib_filter_seq
        { index = \g__csl_bib_list_index_tl }
      \keys_set:nn { csl / bibliography } {#1}
      \__csl_serialize_seq:NN \l__csl_bib_filter_seq \l__csl_bib_filter_tl
      % Collect the bibliography to token list
      \sys_if_engine_luatex:TF
        {
          \bool_if:NT \l__csl_engine_initialized_bool
            {
              \__csl_collect_bibliography:n
                {
                  \lua_now:e
                    { csl_citation_manager:bibliography("\l__csl_bib_filter_tl") }
                }
            }
        }
        {
          % Write to aux file
          \exp_args:NV \__csl_write_aux_bibliography:n \l__csl_bib_filter_tl
        }
      % Print the bibliography
      \prop_get:NVNTF \g__csl_bibliographies_prop \g__csl_bib_list_index_tl
          \l__csl_bibliography_tl
        {
          \bool_if:NT \l__csl_regression_test_bool
            {
              \seq_set_split:NnV \l__csl_bibliography_seq { \par } \l__csl_bibliography_tl
              \seq_show:N \l__csl_bibliography_seq
            }
          \tl_use:N \l__csl_bibliography_tl
        }
        { \msg_warning:nn { citation-style-language } { empty-bibliography } }
    \group_end:
  }

\msg_new:nnn { citation-style-language } { empty-bibliography }
  { The~ bibliography~ is~ empty.  }

\DeclareDocumentCommand \bibliography { m }
  {
    \clist_map_inline:nn {#1}
      {
        \exp_args:Ne \__csl_write_aux_bibdata:nn {##1} {}
      }
    \printbibliography \relax
  }


\tl_new:N \l__csl_bib_env_tl
\tl_new:N \l__csl_bib_head_name_tl
\tl_new:N \l__csl_bib_head_title_tl
\tl_new:N \l__csl_bib_head_label_tl
\tl_new:N \l__csl_bib_pre_note_tl
\tl_new:N \l__csl_bib_post_note_tl
\tl_new:N \l__csl_bib_filter_tl

\tl_set:Nn \l__csl_bib_env_tl { bibliography }
\tl_set:Nn \l__csl_bib_head_name_tl { bibliography }

\keys_define:nn { csl / bibliography }
  {
    % env         .tl_set:N = \l__csl_bib_env_name_tl ,
    heading     .tl_set:N = \l__csl_bib_head_name_tl ,
    title       .tl_set:N = \l__csl_bib_head_title_tl ,
    label       .tl_set:N = \l__csl_bib_head_label_tl ,
    % block
    prenote     .tl_set:N = \l__csl_bib_pre_note_tl ,
    postnote    .tl_set:N = \l__csl_bib_post_note_tl ,
    % section
    % segment
    type        .code:n = { \seq_put_right:Nn \l__csl_bib_filter_seq { type = {#1} } } ,
    nottype     .code:n = { \seq_put_right:Nn \l__csl_bib_filter_seq { nottype = {#1} } } ,
    % subtype     .code:n = { \seq_put_right:Nn \l__csl_bib_filter_seq { subtype = {#1} } } ,
    % notsubtype  .code:n = { \seq_put_right:Nn \l__csl_bib_filter_seq { notsubtype = {#1} } } ,
    keyword     .code:n = { \seq_put_right:Nn \l__csl_bib_filter_seq { keyword = {#1} } } ,
    notkeyword  .code:n = { \seq_put_right:Nn \l__csl_bib_filter_seq { notkeyword = {#1} } } ,
    category    .code:n = { \seq_put_right:Nn \l__csl_bib_filter_seq { category = {#1} } } ,
    notcategory .code:n = { \seq_put_right:Nn \l__csl_bib_filter_seq { notcategory = {#1} } } ,
    % filter .tl_set:N = \l__csl_bibliography_nottype_tl ,
  }


\cs_new:Npn \__csl_write_aux_bibliography:n #1
  {
    \if@filesw
      \iow_now:Ne \@auxout
        {
          \token_to_str:N \csl@aux@bibliography
          { \int_use:N \g__csl_ref_section_index_int }
          {#1}
        }
    \fi
  }

\cs_new:Npn \csl@aux@bibliography #1#2 { }


\tl_new:N \l__csl_bib_index_tl
\bool_new:N \l__csl_hanging_indent_bool
\bool_new:N \l__csl_second_field_align_flush_bool
\bool_new:N \l__csl_second_field_align_margin_bool
\tl_new:N \l__csl_line_spacing_tl
\tl_new:N \l__csl_entry_spacing_tl
\tl_new:N \l__csl_bib_widest_label_tl

\keys_define:nn { csl / bib-options }
  {
    index          .tl_set:N   = \l__csl_bib_index_tl ,
    second-field-align .choice:,
    second-field-align / flush  .code:n =
      {
        \bool_set_true:N  \l__csl_second_field_align_flush_bool
        \bool_set_false:N \l__csl_second_field_align_margin_bool
      } ,
    second-field-align / margin .code:n =
      {
        \bool_set_false:N \l__csl_second_field_align_flush_bool
        \bool_set_true:N  \l__csl_second_field_align_margin_bool
      } ,
    second-field-align / false  .code:n =
      {
        \bool_set_false:N \l__csl_second_field_align_flush_bool
        \bool_set_false:N \l__csl_second_field_align_margin_bool
      } ,
    hanging-indent .bool_set:N = \l__csl_hanging_indent_bool ,
    line-spacing   .tl_set:N   = \l__csl_line_spacing_tl ,
    entry-spacing  .tl_set:N   = \l__csl_entry_spacing_tl ,
    widest-label   .tl_set:N   = \l__csl_bib_widest_label_tl ,
  }

\keys_set:nn { csl / bib-options }
  {
    index          = 1 ,
    second-field-align = false ,
    hanging-indent = false ,
    line-spacing   = 1 ,
    entry-spacing  = 1 ,
    widest-label   = { } ,
  }

\RenewDocumentEnvironment { thebibliography } { m }
  {
    \exp_args:NVV \__csl_make_bib_heading:nn
      \l__csl_bib_head_name_tl \l__csl_bib_head_title_tl
    \exp_args:NV \__csl_print_bib_note:n \l__csl_bib_pre_note_tl
    \group_begin:
      \tl_set:Nn \l__csl_bib_index_tl { 1 }
      \keys_set:nn { csl / bib-options } {#1}
      \tl_if_eq:NnF \l__csl_line_spacing_tl { 1 }
        { \linespread { \l__csl_line_spacing_tl } \selectfont }
      \l__csl_bib_font_tl
      % The label is generated by CSL, so the first argument is empty
      \list { }
        {
          \__csl_set_bib_label_spacing:n { \l__csl_bib_widest_label_tl }
          \__csl_set_bib_item_sep:
        }
      \sloppy
      \__csl_set_bib_page_break:
      \frenchspacing
      \__csl_bib_url_setup:
  }
  {
      \tl_set:Nn \@noitemerr
        { \msg_warning:nn { citation-style-language } { empty-bibliography } }
      \endlist
    \group_end:
    \exp_args:NV \__csl_print_bib_note:n \l__csl_bib_post_note_tl
  }



% ### Bibliography spacing

\dim_new:N \l__csl_bib_hang_dim

\cs_new:Npn \__csl_set_bib_label_spacing:n #1
  {
    \bool_if:NTF \l__csl_hanging_indent_bool
      {
        \dim_set:Nn \l__csl_bib_hang_dim { \l__csl_bib_hang_tl }
        \dim_set_eq:NN \leftmargin \l__csl_bib_hang_dim
        \dim_set:Nn \itemindent { - \leftmargin }
      }
      {
        \bool_if:NTF \l__csl_second_field_align_flush_bool
          {
            \settowidth \labelwidth { \@biblabel {#1} }
            \dim_set_eq:NN \labelsep \l__csl_bib_label_sep_dim
            \dim_set_eq:NN \leftmargin \labelwidth
            \dim_add:Nn \leftmargin { \labelsep }
          }
          {
            \bool_if:NTF \l__csl_second_field_align_margin_bool
              {
                \settowidth \labelwidth { \@biblabel {#1} }
                \dim_set_eq:NN \labelsep \l__csl_bib_label_sep_dim
                \dim_zero:N \leftmargin
              }
              {
                \dim_zero:N \leftmargin
                \dim_set:Nn \itemindent { \l__csl_bib_par_indent_tl }
              }
          }
      }
  }

% In standard LaTeX classes (10pt), the vertical sep of bibliographic item is
% \itemsep (4\p@ \@plus2\p@ \@minus\p@) + \parsep (4\p@ \@plus2\p@ \@minus\p@)
% = 8pt plus 4pt minus 2pt
\cs_new:Npn \__csl_set_bib_item_sep:
  {
    \skip_zero:N \parsep
    \tl_if_empty:NTF \l__csl_bib_item_sep_tl
      {
        \skip_set:Nn \itemsep
          {
            8 pt plus 4 pt minus 2 pt * \dim_ratio:nn { 1 em } { 8 pt }
            * \l__csl_entry_spacing_tl
          }
      }
      { \skip_set:Nn \itemsep { \l__csl_bib_item_sep_tl } }
    \bool_set_true:N \l_csl_bib_first_block_bool
  }


% ### Bibliography label

% CSL outputs the whole label thus the brackets are removed from \@biblabel
% \def\@biblabel#1{[#1]}
\cs_set:Npn \@biblabel #1 {#1}

% For numeric or label-style bibliography: \bibitem[{[17]}]{entrykey}
% \@lbibitem is redefined in `babel` and `hyperref` and we need to override it
% in the patching code. Thus we define \__csl_lbibitem: here and reassign it to
% \@lbibitem in compatability code
\cs_new:Npn \__csl_lbibitem:
  {
    \bool_if:NTF \l__csl_back_ref_bool
      { \__csl_lbibitem_back_ref:nnn }
      { \__csl_lbibitem_plain:nn }
  }

\cs_set_eq:NN \@lbibitem \__csl_lbibitem:

\cs_new:Npn \__csl_lbibitem_plain:nn [#1]#2
  {
    \item [ \@biblabel {#1} \hfill ]
    \ignorespaces
  }

% This is the version for use with backref feature.
\cs_new:Npn \__csl_lbibitem_back_ref:nnn [#1]#2#3\par
  {
    \__csl_lbibitem_plain:nn [#1] {#2}
    #3
    \prop_get:NnNT \g__csl_back_ref_info_prop {#2} \l_tmpa_tl
      {
        \c_space_tl
        \exp_args:NV \__csl_print_back_refs:n \l_tmpa_tl
      }
    \par
  }

% Used for per-author publication listing
\bool_new:N \l_csl_bib_first_block_bool

\cs_new:Npn \cslblock #1
  {
    \bool_if:NF \l_csl_bib_first_block_bool
      {
        \skip_set:NV \l_tmpa_skip { \l__csl_bib_name_sep_tl }
        \addvspace { \l_tmpa_skip }
      }
    \bool_set_false:N \l_csl_bib_first_block_bool
    \item [ ]
    \skip_horizontal:n { - \leftmargin }
    % \hskip - \leftmargin \relax
    #1
    \par
    \skip_set:NV \l_tmpa_skip { \l__csl_bib_after_name_sep_tl }
    \addvspace { \l_tmpa_skip }
  }

\cs_new:Npn \__csl_print_back_refs:n #1
  % #1: list of {<page>}{<label>}{anchor}
  {
    \clist_set:Nn \l_tmpa_clist {#1}
    % To remove duplicates
    \prop_clear:N \l_tmpa_prop
    % Output seq
    \seq_clear:N \l_tmpa_seq
    \clist_map_inline:Nn \l_tmpa_clist { \__csl_print_back_ref_aux:nnn ##1 }
    \backref { \seq_use:Nn \l_tmpa_seq { ,~ } }
  }

\cs_new:Npn \__csl_print_back_ref_aux:nnn #1#2#3
  {
    \str_if_eq:VnTF \l__csl_back_ref_type_str { page }
      {
        \prop_if_in:NnF \l_tmpa_prop {#1}
          {
            \bool_if:NTF \l__csl_hyperref_loaded_bool
              { \seq_put_right:Nn \l_tmpa_seq { \hyperlink { page. #1 } {#1} } }
              { \seq_put_right:Nn \l_tmpa_seq {#1} }
            \prop_put:Nnn \l_tmpa_prop {#1} {#1}
          }
      }
      {
        % section
        \prop_if_in:NnF \l_tmpa_prop {#2}
          {
            \bool_if:NTF \l__csl_hyperref_loaded_bool
              { \seq_put_right:Nn \l_tmpa_seq { \hyperlink {#3} {#2} } }
              { \seq_put_right:Nn \l_tmpa_seq {#2} }
            \prop_put:Nnn \l_tmpa_prop {#2} {#2}
          }
      }
  }

% Hook
\cs_if_free:NT \backref
  { \cs_new:Npn \backref #1 {#1} }


% For author-date bibliography
% \def\@bibitem#1{\item\if@filesw \immediate\write\@auxout
%        {\string\bibcite{#1}{\the\value{\@listctr}}}\fi\ignorespaces}
\cs_new:Npn \__csl_bibitem:
  {
    \bool_if:NTF \l__csl_back_ref_bool
      { \__csl_bibitem_back_ref:nn }
      { \__csl_bibitem_plain:n }
  }

\cs_set_eq:NN \@bibitem \__csl_bibitem:

\cs_new:Npn \__csl_bibitem_plain:n #1
  {
    \item
    \ignorespaces
  }

\cs_new:Npn \__csl_bibitem_back_ref:nn #1#2\par
  {
    \__csl_bibitem_plain:n {#1}
    #2
    % \prop_show:N \g__csl_back_ref_info_prop
    \prop_get:NnNT \g__csl_back_ref_info_prop {#1} \l_tmpa_tl
      {
        \c_space_tl
        \exp_args:NV \__csl_print_back_refs:n \l_tmpa_tl
      }
    \par
  }


% ### Bibliography sections and segments


\int_new:N \g__csl_ref_section_index_int
\int_new:N \g__csl_max_ref_section_index_int
\int_gset:Nn \g__csl_ref_section_index_int { 0 }
\int_gset:Nn \g__csl_max_ref_section_index_int { 0 }

\keys_define:nn { csl / ref-section }
  {
    style .code:n =
      {
        \tl_set:Nn \l__csl_style_tl {#1}
        \renewcommand \csl@style {#1}
      } ,
    bib-resource .code:n =
      {
        \clist_clear:N \l__csl_bib_resources_clist
        \clist_map_inline:nn {#1}
          { \clist_put_right:Ne \l__csl_bib_resources_clist {##1} }
      } ,
    locale .tl_set:N = \l__csl_locale_tl ,
  }

\NewDocumentCommand \refsection { O { } }
  {
    \int_gincr:N \g__csl_max_ref_section_index_int
    \int_gset_eq:NN \g__csl_ref_section_index_int \g__csl_max_ref_section_index_int

    \tl_clear:N \l__csl_style_tl
    \clist_clear:N \l__csl_bib_resources_clist
    \tl_clear:N \l__csl_locale_tl
    \keys_set:nn { csl / ref-section } { #1 }
    \tl_if_empty:NTF \l__csl_style_tl
      {
        \tl_set_eq:NN \l__csl_style_tl \g__csl_global_style_tl
        \tl_set_eq:NN \csl@style \l__csl_style_tl
      }
      {
        \tl_set_eq:NN \csl@style \l__csl_style_tl
        \exp_args:NV \__csl_write_aux_bibstyle:n \l__csl_style_tl
      }
    \clist_if_empty:NF \l__csl_bib_resources_clist
      {
        \clist_map_inline:Nn \l__csl_bib_resources_clist
          { \exp_args:Ne \__csl_write_aux_bibdata:nn {##1} { } }
      }
    \tl_if_empty:NTF \l__csl_locale_tl
      { \tl_set_eq:NN \l__csl_locale_tl \g__csl_global_locale_tl }
      {
        \exp_args:Ne \__csl_write_aux_options:n
          { locale = \l__csl_locale_tl }
      }
    \sys_if_engine_luatex:TF
      {
        \lua_now:e
          {
            csl_citation_manager:begin_ref_section(
              "\l__csl_style_tl",
              "\clist_use:Nn \l__csl_bib_resources_clist { , }",
              "\l__csl_locale_tl"
            )
          }
        \str_if_eq:eeTF
          {
            \lua_now:n
              {
                tex.sprint(tostring(
                  csl_citation_manager.ref_section.initialized
                ))
              }
          }
          { true }
          { \bool_set_true:N \l__csl_engine_initialized_bool }
          { \bool_set_false:N \l__csl_engine_initialized_bool }
        \__csl_get_style_class_luatex:
      }
      {
        \__csl_get_style_class:
      }
    \__csl_read_entry_ids:
  }

\NewCommandCopy \newrefsection \refsection

\cs_new:Npn \endrefsection {
  \int_compare:nNnT { \g__csl_ref_section_index_int } > { 0 }
    {
      \int_gzero:N \g__csl_ref_section_index_int
      \sys_if_engine_luatex:T
        { \lua_now:n { csl_citation_manager:end_ref_section() } }
      \__csl_read_entry_ids:
    }
}


% ### Bibliography Headings and Environments

\prop_new:N \l__csl_bib_env_begin_prop
\prop_new:N \l__csl_bib_env_end_prop
\prop_new:N \l__csl_bib_item_prop

% \defbibenvironment{⟨name⟩}{⟨begin code⟩}{⟨end code⟩}{⟨item code⟩}
\NewDocumentCommand { \defbibenvironment } { m m m m }
  {
    \prop_put:Nnn \l__csl_bib_env_begin_prop {#1} {#2}
    \prop_put:Nnn \l__csl_bib_env_end_prop {#1} {#3}
    \prop_put:Nnn \l__csl_bib_item_prop {#1} {#4}
  }

% \defbibenvironment { bibliography }
%   { }


% #1: bib heading name
% #2: bib heading title
\cs_new:Npn \__csl_make_bib_heading:nn #1#2
  {
    \DeclareCommandCopy \newrefsection \relax
    \tl_if_empty:NTF \bibsection
      {
        \cs_if_exist:cF { __csl_head_ #1 :n }
          {
            \msg_error:nnn { citation-style-language } { undefined-bib-heading }
              {#1}
          }
        \tl_if_blank:nTF {#2}
          { \use:c { __csl_head_ #1 :n } }
          { \use:c { __csl_head_ #1 :n } [#2] }
      }
      { \bibsection }
    \tl_if_empty:NF \l__csl_bib_head_label_tl
      { \exp_args:NV \label \l__csl_bib_head_label_tl }
    \DeclareCommandCopy \newrefsection \refsection
  }

\msg_new:nnn { citation-style-language } { undefined-bib-heading }
  { Bibliography~ heading~ '#1'~ undefined. }

\keys_define:nn { csl / bib-heading }
  {
    heading .tl_set:N = \l__csl_bib_head_name_tl ,
    title   .tl_set:N = \l__csl_bib_head_title_tl ,
    % label
  }

\cs_new:Npn \__csl_reset_heading_options:
  {
    \tl_set:Nn \l__csl_bib_head_name_tl { bibliography }
    \tl_set:Nn \l__csl_bib_head_title_tl { }
  }

\NewDocumentCommand { \printbibheading } { O { } }
  {
    % We can't use a group here.
    % See <https://github.com/plk/biblatex/issues/1278>.
    \__csl_reset_heading_options:
    \keys_set:nn { csl / bib-heading } {#1}
    \exp_args:NVV \__csl_make_bib_heading:nn
      \l__csl_bib_head_name_tl \l__csl_bib_head_title_tl
    \__csl_reset_heading_options:
  }

% \defbibheading { ⟨name⟩}[⟨title⟩]{⟨code⟩}
\NewDocumentCommand { \defbibheading } { m O { \bibname } }
  {
    \expandafter \newcommand \csname __csl_head_ #1 :n \endcsname [1] [ {#2} ]
  }


\cs_if_exist:NF \refname
  { \cs_set:Npn \refname { References } }

\cs_if_exist:NTF \chapter
  {
    % `book` or `report`
    \defbibheading { bibliography } [ \bibname ]
      {
        \chapter* {#1}
        \@mkboth { \MakeUppercase {#1} } { \MakeUppercase {#1} }
      }
    \defbibheading { biblist } [ \biblistname ]
      {
        \chapter* {#1}
        \@mkboth { \MakeUppercase {#1} } { \MakeUppercase {#1} }
      }
    \defbibheading { bibintoc } [ \bibname ]
      {
        \chapter* {#1}
        \addcontentsline { toc } { chapter } {#1}
        \@mkboth { \MakeUppercase {#1} } { \MakeUppercase {#1} }
      }
    \defbibheading { biblistintoc } [ \biblistname ]
      {
        \chapter* {#1}
        \addcontentsline { toc } { chapter } {#1}
        \@mkboth { \MakeUppercase {#1} } { \MakeUppercase {#1} }
      }
    \defbibheading { bibnumbered } [ \bibname ]
      { \chapter {#1} }
    \defbibheading { biblistnumbered } [ \biblistname ]
      { \chapter {#1} }
    \defbibheading { subbibliography } [ \refname ]
      {
        \section* {#1}
        \if@twoside
          \markright { \MakeUppercase {#1} }
        \fi
      }
    \defbibheading { subbibintoc } [ \refname ]
      {
        \section* {#1}
          \addcontentsline { toc } { section } {#1}
          \if@twoside
            \markright { \MakeUppercase {#1} }
          \fi
      }
    \defbibheading { subbibnumbered } [ \refname ]
      { \section {#1} }
  }
  {
    % `article`
    \defbibheading { bibliography } [ \refname ]
      {
        \section* {#1}
        \@mkboth { \MakeUppercase {#1} } { \MakeUppercase {#1} }
      }
    \defbibheading { biblist } [ \biblistname ]
      {
        \section* {#1}
        \@mkboth { \MakeUppercase {#1} } { \MakeUppercase {#1} }
      }
    \defbibheading { bibintoc } [ \refname ]
      {
        \section* {#1}
        \addcontentsline { toc } { section } {#1}
        \@mkboth { \MakeUppercase {#1} } { \MakeUppercase {#1} }
      }
    \defbibheading { biblistintoc } [ \biblistname ]
      {
        \section* {#1}
        \addcontentsline { toc } { section } {#1}
        \@mkboth { \MakeUppercase {#1} } { \MakeUppercase {#1} }
      }
    \defbibheading { bibnumbered } [ \refname ]
      { \section {#1} }
    \defbibheading { biblistnumbered } [ \biblistname ]
      { \section {#1} }
    \defbibheading { subbibliography } [ \refname ]
      { \subsection* {#1} }
    \defbibheading { subbibintoc } [ \refname ]
      {
        \subsection* {#1}
        \addcontentsline { toc } { subsection } {#1}
      }
    \defbibheading { subbibnumbered } [ \refname ]
      { \subsection {#1} }
  }

\defbibheading { none } { }


% Bibliography notes

\prop_new:N \l__csl_bib_notes_prop

% #1: name
% #2: text
\NewDocumentCommand { \defbibnote } { m m }
  { \prop_put:Nnn \l__csl_bib_notes_prop {#1} {#2} }

% #1: note name
\cs_new:Npn \__csl_print_bib_note:n #1
  {
    \tl_if_empty:nF {#1}
      {
        \prop_get:NnNF \l__csl_bib_notes_prop {#1} \l_tmpa_tl
          {
            \msg_error:nnn { citation-style-language } { undefined-bib-note }
              {#1}
          }
        \tl_if_empty:NF \l_tmp_tl
          {
            \group_begin:
              % \cs_set_eq:NN \newrefsection \relax
              % \cs_set_eq:NN \newrefsegment \relax
              \noindent
              \tl_use:N \l_tmpa_tl
              \par \nobreak
            \group_end:
          }
      }
  }

\msg_new:nnn { citation-style-language } { undefined-bib-note }
  { Bibliography~ note~ '#1'~ undefined. }



% ### Bibliography Categories

\prop_new:N \l__csl_categories_prop

% \DeclareBibliographyCategory{⟨category⟩}
\NewDocumentCommand \DeclareBibliographyCategory { m }
  {
    \prop_put:Nnn \l__csl_categories_prop { #1 } { }
  }

% \addtocategory{⟨category⟩}{⟨keys⟩}
\NewDocumentCommand \addtocategory { m m }
  {
    \prop_get:NnNTF \l__csl_categories_prop {#1} \l_tmpa_tl
      {
        \tl_if_empty:NF \l_tmpa_tl
          { \tl_put_right:Nn \l_tmpa_tl { , } }
        \tl_put_right:Nn \l_tmpa_tl {#2}
        \prop_put:NnV \l__csl_categories_prop {#1} \l_tmpa_tl
      }
      {
        \msg_error:nnn { citation-style-language } { category-not-declared }
          {#1}
      }
  }

% Set categories in Lua module or write to aux file.
% This procesure is at `\printbibligoraphy` to allow \addtocategory in main text.
\cs_new:Npn \__csl_set_categories:
  {
    % Set categories
    \prop_if_empty:NF \l__csl_categories_prop
      {
        \tl_clear:N \l_tmpa_tl
        \prop_map_inline:Nn \l__csl_categories_prop
          {
            \tl_if_empty:NF \l_tmpa_tl
              { \tl_put_right:Nn \l_tmpa_tl { , } }
            \tl_put_right:Nn \l_tmpa_tl { ##1 = {##2} }
          }
        \sys_if_engine_luatex:T
          { \lua_now:e { csl_citation_manager:set_categories("\l_tmpa_tl") } }
          {
            \tl_put_left:Ne \l_tmpa_tl { categories = \c_left_brace_str }
            \tl_put_right:NV \l_tmpa_tl \c_right_brace_str
            \exp_args:NV \__csl_write_aux_options:n \l_tmpa_tl
          }
      }
  }

\msg_new:nnn { citation-style-language } { category-not-declared }
  { Category~ '#1'~ not~ declared. }


% ### Page break in bibliography

% See <https://github.com/plk/biblatex/blob/e16f4aaa5d9857c7b844bbcbe246f0535fd334e9/tex/latex/biblatex/biblatex.def#L219-L258>

\cs_new:Npn \__csl_set_bib_page_break:
  {
    \bool_if:NTF \l__csl_bib_entry_page_break_bool
      { \__csl_set_bib_allow_break: }
      { \__csl_set_bib_no_break: }
  }

% The following code allows linebreaks before numbers and letters.
% This is often the only way to break DOIs. It also allows breaks
% after hyphens and adjusts \Urlmuskip to add some stretchability
% to URLs.

\cs_new:Npn \__csl_set_bib_allow_break:
  {
    \sloppy
    \int_set:Nn \clubpenalty { 4000 }
    \int_set_eq:NN \@clubpenalty \clubpenalty
    \int_set:Nn \widowpenalty { 4000 }
    % \sfcode`\.\@m
    \frenchspacing
  }

\cs_new:Npn \__csl_set_bib_no_break:
  {
    \sloppy
    \int_set:Nn \interlinepenalty { 5000 }
    \int_set:Nn \widowpenalty { 10000 }
    \int_set:Nn \clubpenalty { 10000 }
    \int_set_eq:NN \@clubpenalty \clubpenalty
    \raggedbottom
    \frenchspacing
  }


% ### Urls in bibliography
% Taken from `biblatex`'s \biburlsetup
% https://github.com/plk/biblatex/blob/dev/tex/latex/biblatex/biblatex.def

\int_new:N \l__csl_url_big_break_penalty_int
\int_new:N \l__csl_url_break_penalty_int
\int_new:N \l__csl_url_num_penalty_int
\int_new:N \l__csl_url_uc_penalty_int
\int_new:N \l__csl_url_lc_penalty_int

\int_set:Nn \l__csl_url_big_break_penalty_int { 100 }
\int_set:Nn \l__csl_url_break_penalty_int { 200 }
% Allow linebreaks before numbers and letters.
% Taken from `xurl.sty`.
\int_set:Nn \l__csl_url_num_penalty_int { 9000 }
\int_set:Nn \l__csl_url_uc_penalty_int { 9000 }
\int_set:Nn \l__csl_url_lc_penalty_int { 8000 }

\muskip_new:N \l__csl_url_big_muskip
\muskip_new:N \l__csl_url_num_muskip
\muskip_new:N \l__csl_url_uc_muskip
\muskip_new:N \l__csl_url_lc_muskip

\muskip_set:Nn \l__csl_url_big_muskip { 0mu plus 3mu }
\muskip_set:Nn \l__csl_url_num_muskip { 0mu }
\muskip_set:Nn \l__csl_url_uc_muskip { 0mu }
\muskip_set:Nn \l__csl_url_lc_muskip { 0mu }

\cs_new:Npn \__csl_bib_url_setup:
  {
    \urlstyle { same }
    \muskip_set_eq:NN \Urlmuskip \l__csl_url_big_muskip
    \mathchardef \UrlBigBreakPenalty = \l__csl_url_big_break_penalty_int
    \mathchardef \UrlBreakPenalty = \l__csl_url_break_penalty_int
    % \int_set_eq:NN doesn't work here
    % \int_set_eq:NN \UrlBigBreakPenalty \l__csl_url_big_break_penalty_int
    % \int_set_eq:NN \UrlBreakPenalty \l__csl_url_break_penalty_int
    \tl_set:Nn \UrlBigBreaks { \do \: \do \- }
    \tl_set:Nn \UrlBreaks
      {
        \do \. \do \@ \do \/ \do \\ \do \! \do \_ \do \| \do \; \do \> \do \]
        \do \) \do \} \do \, \do \? \do \' \do \+ \do \= \do \# \do \$ \do \&
        \do \* \do \^ \do \"
      }
    \int_compare:nNnT { \l__csl_url_num_penalty_int } > { 0 }
      {
        \clist_map_inline:nn
          { \1 , \2 , \3 , \4 , \5 , \6 , \7 , \8 , \9 , \0 }
          {
            \tl_put_right:Nn \UrlSpecials
              {
                \do ##1
                  {
                    \mathchar`##1
                    \mskip \l__csl_url_num_muskip
                    \penalty \l__csl_url_num_penalty_int
                  }
              }
          }
      }
    \int_compare:nNnT { \l__csl_url_uc_penalty_int } > { 0 }
      {
        \clist_map_inline:nn
          {
            \A , \B , \C , \D , \E , \F , \G , \H , \I , \J ,
            \K , \L , \M , \N , \O , \P , \Q , \R , \S , \T ,
            \U , \V , \W , \X , \Y , \Z
          }
          {
            \tl_put_right:Nn \UrlSpecials
              {
                \do ##1
                  {
                    \mathchar`##1
                    \mskip \l__csl_url_uc_muskip
                    \penalty \l__csl_url_uc_penalty_int
                  }
              }
          }
      }
    \int_compare:nNnT { \l__csl_url_lc_penalty_int } > { 0 }
      {
        \clist_map_inline:nn
          {
            \a , \b , \c , \d , \e , \f , \g , \h , \i , \j ,
            \k , \l , \m , \n , \o , \p , \q , \r , \s , \t ,
            \u , \v , \w , \x , \y , \z
          }
          {
            \tl_put_right:Nn \UrlSpecials
              {
                \do ##1
                  {
                    \mathchar`##1
                    \mskip \l__csl_url_lc_muskip
                    \penalty \l__csl_url_lc_penalty_int
                  }
              }
          }
      }
    \cs_set_eq:NN \do \exp_not:N
  }
