% Feature module: index

\ifdefined\NextFeatureIndexLoaded
  \endinput
\fi
\def\NextFeatureIndexLoaded{1}

\RequirePackage[xindy]{imakeidx}

\providecommand{\IndexTitle}{}
\makeatletter
\ifx\IndexTitle\@empty
  \makeindex[intoc]
\else
  \makeindex[title={\IndexTitle}, intoc]
\fi
\makeatother

\indexsetup{
  othercode = {
    \setlength{\parindent}{0pt}
    \setlength{\parskip}{0pt}
    \linespread{1.10}\selectfont
  }
}

\DeclareRobustCommand{\NextIndexCjkDescription}[1]{（#1）}
\DeclareRobustCommand{\NextIndexWesternDescription}[1]{%
  \nobreakspace(#1)%
}
\DeclareRobustCommand{\NextIndexBareDescription}[1]{%
  \nobreakspace#1%
}

\ExplSyntaxOn

\prop_new:N \g__next_index_seen_prop
\int_new:N \g__next_index_target_int
\tl_new:N \l__next_index_parentheses_tl
\tl_new:N \l__next_index_description_tl
\tl_new:N \l__next_index_display_tl
\tl_new:N \l__next_index_sort_tl
\tl_new:N \l__next_index_key_tl
\tl_new:N \l__next_index_target_tl

\keys_define:nn { next/index/term }
  {
    sort .tl_set:N = \l__next_index_sort_tl,
    key .tl_set:N = \l__next_index_key_tl,
    parentheses .choice:,
    parentheses / auto .code:n =
      { \tl_set:Nn \l__next_index_parentheses_tl { auto } },
    parentheses / cjk .code:n =
      { \tl_set:Nn \l__next_index_parentheses_tl { cjk } },
    parentheses / western .code:n =
      { \tl_set:Nn \l__next_index_parentheses_tl { western } },
    parentheses / none .code:n =
      { \tl_set:Nn \l__next_index_parentheses_tl { none } },
    parentheses .value_required:n = true,
    parens .meta:n = { parentheses = #1 },
  }

\cs_new_protected:Npn \__next_index_resolve_parentheses:
  {
    \str_if_eq:VnT \l__next_index_parentheses_tl { auto }
      {
        \tl_set:Nn \l__next_index_parentheses_tl { western }
        \cs_if_exist:NT \NextSystemUiTag
          {
            \str_if_eq:eeT { \NextSystemUiTag } { zh }
              { \tl_set:Nn \l__next_index_parentheses_tl { cjk } }
          }
      }
  }

\cs_new_protected:Npn \__next_index_set_description:n #1
  {
    \tl_clear:N \l__next_index_description_tl
    \tl_if_blank:nF {#1}
      {
        \str_case:Vn \l__next_index_parentheses_tl
          {
            { cjk }
              {
                \tl_set:Nn \l__next_index_description_tl
                  { \NextIndexCjkDescription{#1} }
              }
            { western }
              {
                \tl_set:Nn \l__next_index_description_tl
                  { \NextIndexWesternDescription{#1} }
              }
            { none }
              {
                \tl_set:Nn \l__next_index_description_tl
                  { \NextIndexBareDescription{#1} }
              }
          }
      }
  }

\cs_new_protected:Npn \__next_index_emit_term:nnnn #1#2#3#4
  {
    \textbf{#3}#4\unskip\nobreak\hspace{0pt}
    \prop_if_in:NnF \g__next_index_seen_prop {#1}
      {
        \prop_gput:Nnn \g__next_index_seen_prop {#1} { indexed }
        \int_gincr:N \g__next_index_target_int
        \tl_set:Nx \l__next_index_target_tl
          { idx:\int_use:N \g__next_index_target_int }
        \cs_if_exist:NT \hypertarget
          { \hypertarget{\l__next_index_target_tl}{} }
        \cs_if_exist:NTF \hyperlink
          {
            \index
              {
                #2@\protect\hyperlink
                  {\l__next_index_target_tl}
                  {#3#4}
              }
          }
          { \index{#2@#3#4} }
      }
  }
\cs_generate_variant:Nn \__next_index_emit_term:nnnn { VVVV }

\NewDocumentCommand{\Term}{ O{} m o g g }
  {
    \group_begin:
      \tl_set:Nn \l__next_index_parentheses_tl { auto }
      \tl_set:Nn \l__next_index_display_tl {#2}
      \tl_set:Nn \l__next_index_sort_tl {#2}
      \tl_set:Nn \l__next_index_key_tl {#2}
      \tl_clear:N \l__next_index_description_tl
      \IfNoValueTF{#5}
        {
          \IfNoValueTF{#3}
            {
              % Also accept the recently introduced braced optional form.
              \IfNoValueF{#4}
                { \tl_set:Nn \l__next_index_description_tl {#4} }
            }
            { \tl_set:Nn \l__next_index_description_tl {#3} }
        }
        {
          % Legacy form: \Term{key}{display}{description}
          \tl_set:Nn \l__next_index_display_tl {#4}
          \tl_set:Nn \l__next_index_description_tl {#5}
        }
      \keys_set:nn { next/index/term } {#1}
      \__next_index_resolve_parentheses:
      \exp_args:NV \__next_index_set_description:n
        \l__next_index_description_tl
      \__next_index_emit_term:VVVV
        \l__next_index_key_tl
        \l__next_index_sort_tl
        \l__next_index_display_tl
        \l__next_index_description_tl
    \group_end:
  }

\ExplSyntaxOff