% Font behavior selection and application logic.
% This layer owns inline/block behavior strategies, starting with RTL.

\RequirePackage{iftex}
\ifXeTeX
  \RequirePackage{bidi}
\else
  \providecommand\RL[1]{#1}
  \expandafter\ifx\csname RTL\endcsname\relax
    \expandafter\def\csname RTL\endcsname{}
  \fi
  \expandafter\ifx\csname endRTL\endcsname\relax
    \expandafter\def\csname endRTL\endcsname{}
  \fi
\fi

\ExplSyntaxOn

\tl_new:N \l__font_inline_behavior_tl
\tl_new:N \l__font_vertical_strategy_tl

\clist_const:Nn \c__font_tibetan_non_tsheg_punctuation_codepoints_clist
  {
    "0F04, "0F05, "0F06, "0F07, "0F08, "0F09, "0F0A,
    "0F0D, "0F0E, "0F0F, "0F10, "0F11, "0F12, "0F14,
    "0F3A, "0F3B, "0F3C, "0F3D,
    "0F85,
    "0FD0, "0FD1, "0FD2, "0FD3, "0FD4,
    "0FD9, "0FDA
  }

\cs_new_protected:Npn \__font_behavior_tibetan_breaks:n #1
  {
    \tl_set:Nn \l_tmpa_tl {#1}
    \regex_replace_all:nnN { ་ ([ཀ-ཬྈ-ྌ]) } { ་ \c{allowbreak} \1 } \l_tmpa_tl
    \tl_use:N \l_tmpa_tl
  }

\prg_new_conditional:Npnn \__font_should_infer_rtl: { TF }
  {
    \__font_tl_if_in_set:NnTF \l__font_decl_family_id_tl
      {
        arabic,urdu,aramaic,nabataean,hebrew,syriac,syriac_eastern,
        kharosthi,pahlavi_parthian,pahlavi_inscriptional,pahlavi_psalter,
        avestan,manichaean,phoenician,samaritan,sogdian,sogdian_old,
        hungarian,turkic,uyghur
      }
      { \prg_return_true: }
      {
        \__font_tl_if_in_set:NnTF \l__font_script_tl
          {
            Arabic,Hebrew,Syriac,Avestan,Nabataean,Phoenician,Samaritan,
            PsalterPahlavi,ImperialAramaic,Kharoshthi,OldHungarian,
            OldTurkic,OldUyghur,Sogdian,OldSogdian,Manichaean
          }
          { \prg_return_true: }
          {
            \tl_if_in:VnTF \l__font_features_tl { script=arab }
              { \prg_return_true: }
              {
                \tl_if_in:VnTF \l__font_features_tl { script=hebr }
                  { \prg_return_true: }
                  {
                    \tl_if_in:VnTF \l__font_features_tl { script=syrc }
                      { \prg_return_true: }
                      {
                        \tl_if_in:VnTF \l__font_features_tl { script=armi }
                          { \prg_return_true: }
                          {
                            \tl_if_in:VnTF \l__font_features_tl { script=mani }
                              { \prg_return_true: }
                              {
                                \tl_if_in:VnTF \l__font_features_tl { script=phli }
                                  { \prg_return_true: }
                                  {
                                    \tl_if_in:VnTF \l__font_features_tl { script=prti }
                                      { \prg_return_true: }
                                      {
                                        \tl_if_in:VnTF \l__font_features_tl { script=sogd }
                                          { \prg_return_true: }
                                          {
                                            \tl_if_in:VnTF \l__font_features_tl { script=ougr }
                                              { \prg_return_true: }
                                              {
                                                \tl_if_in:VnTF \l__font_features_tl { script=khar }
                                                  { \prg_return_true: }
                                                  { \prg_return_false: }
                                              }
                                          }
                                      }
                                  }
                              }
                          }
                      }
                  }
              }
          }
      }
  }

\cs_new_protected:Npn \__font_apply_behavior_defaults:
  {
    \tl_if_blank:VTF \l__font_inline_behavior_tl
      {
        \__font_should_infer_rtl:TF
          { \tl_set:Nn \l__font_inline_behavior_tl { rtl } }
          { \tl_set:NV \l__font_inline_behavior_tl \FontDefaultInlineBehavior }
      }
      { }
    \tl_if_blank:VTF \l__font_vertical_strategy_tl
      { \tl_set:NV \l__font_vertical_strategy_tl \FontDefaultVerticalStrategy }
      { }
  }

\cs_new_protected:Npn \__font_validate_behavior_state:
  {
    \__font_tl_if_in_set:NnTF \l__font_inline_behavior_tl
      { normal,rtl,tibetan,vertical-fallen,vertical-boxed }
      { }
      {
        \PackageError{font-defaults}
          {Invalid~inline~behavior~`\tl_use:N \l__font_inline_behavior_tl`}
          {Use~normal,~rtl,~tibetan,~vertical-fallen,~or~vertical-boxed.}
      }
  }

\cs_new_protected:Npn \__font_apply_script_line_breaking:
  {
    \str_if_eq:VnT \l__font_decl_family_id_tl { thai }
      {
        \sys_if_engine_xetex:T
          {
            \XeTeXlinebreaklocale "th_TH"
            \global\XeTeXlinebreakskip = 0pt plus 1pt\relax
            \global\XeTeXlinebreakpenalty = 100\relax
          }
      }
  }

\cs_new_protected:Npn \__font_define_behavior_hooks:n #1
  {
    \str_if_eq:VnTF \l__font_inline_behavior_tl { rtl }
      {
        \cs_set_protected:cpn { __font_behavior_inline_#1:n } ##1
          { \RL{##1} }
        \cs_set_protected:cpn { __font_behavior_block_#1:n } ##1
          {
            \begingroup
            \RTL
            \leftskip=0pt plus 1fil\relax
            \rightskip=0pt\relax
            \parfillskip=0pt\relax
            \noindent ##1
            \endRTL
            \endgroup
          }
      }
      {
        \str_if_eq:VnTF \l__font_inline_behavior_tl { tibetan }
          {
            \cs_set_protected:cpn { __font_behavior_inline_#1:n } ##1
              { \__font_behavior_tibetan_breaks:n {##1} }
            \cs_set_protected:cpn { __font_behavior_block_#1:n } ##1
              { \__font_behavior_tibetan_breaks:n {##1} }
          }
          {
            \cs_set_protected:cpn { __font_behavior_inline_#1:n } ##1
              { ##1 }
            \cs_set_protected:cpn { __font_behavior_block_#1:n } ##1
              { ##1 }
          }
      }
  }

\cs_new_protected:Npn \__font_apply_behavior:nn #1#2
  {
    \tl_set:Nn \l_tmpa_tl {#2}
    \tl_if_in:NnTF \l_tmpa_tl { \par }
      { \use:c { __font_behavior_block_#1:n } {#2} }
      {
        \mode_if_horizontal:TF
          { \use:c { __font_behavior_inline_#1:n } {#2} }
          { \use:c { __font_behavior_block_#1:n } {#2} }
      }
  }

\ExplSyntaxOff