%<*driver>
% \iffalse meta-comment
%
% Copyright (c) 2026 Aris Chatzichristos, PhD
%
% This work may be distributed and/or modified under the conditions of
% the LaTeX Project Public License, either version 1.3c of this license
% or, at your option, any later version.
%
% This work has the LPPL maintenance status "maintained".
%
% The Current Maintainer of this work is Aris Chatzichristos.
%
\documentclass{ltxdoc}
\usepackage[a4paper,margin=2.5cm]{geometry}
\usepackage{fontspec}
\IfFontExistsTF{Segoe UI}
  {\setmonofont{Segoe UI}[Scale=MatchLowercase]}
  {
    \IfFontExistsTF{DejaVu Sans Mono}
      {\setmonofont{DejaVu Sans Mono}[Scale=MatchLowercase]}
      {
        \IfFontExistsTF{Noto Sans Mono}
          {\setmonofont{Noto Sans Mono}[Scale=MatchLowercase]}
          {}
      }
  }
\EnableCrossrefs
\CodelineIndex
\RecordChanges
\begin{document}
  \DocInput{boustrophedon.dtx}
  \PrintIndex
\end{document}
% \fi
%</driver>
%
% \GetFileInfo{boustrophedon.sty}
%
% \title{The \textsf{boustrophedon} package}
% \author{Aris Chatzichristos, PhD}
% \date{Version 1.1.0, 2026-05-13}
% \maketitle
%
% \begin{abstract}
% \textsf{boustrophedon} typesets text in boustrophedon style, alternating
% writing direction line by line. It supports generic mirrored text, Archaic
% and Classical Greek glyph rendering, automatic wrapping, explicit line
% breaks, and inline bracketed spans.
% \end{abstract}
%
% \section{Overview}
%
% This package typesets text in \emph{boustrophedon} style, alternating the
% writing direction on each line.
%
% Have you ever wondered why most Western languages are written left-to-right,
% while many Middle Eastern languages are written right-to-left? Both
% conventions may seem arbitrary today---but this was not always the case.
%
% In one of the earliest fully developed alphabets, the Archaic Greek alphabet
% (from \emph{alpha} and \emph{beta}, hence ``alphabet''), writing was often
% performed \emph{boustrophedon}, meaning ``as the ox turns in ploughing.''
% Text was written left-to-right on one line, then right-to-left on the next,
% with both the direction of the text \emph{and the letterforms themselves}
% mirrored accordingly.
%
% This method creates a continuous flow of reading, as the reader does not need
% to jump back to the start of each new line, but instead follows the text in a
% natural back-and-forth motion.
%
% Reading takes some getting used to, but after a while it becomes surprisingly
% natural. One may also observe that:
%
% \begin{itemize}
%   \item Capital letters (both in the Latin alphabet and especially in the
%   Greek alphabet) are particularly well-suited to this type of writing, and
%   are much easier to read than lowercase letters (which were developed later
%   in both systems).
%   \item For example, pairs such as \emph{b} vs \emph{d}, or comparable
%   look-alikes in polytonic Greek, can make reading more difficult, as the
%   reader must keep mental track of the text direction.
%   \item In contrast, capital Greek letters---already in use during the
%   boustrophedon period---have the appropriate symmetry to be read in both
%   directions without ambiguity.
% \end{itemize}
%
% This package brings an ancient writing paradigm into modern digital
% typography.
%
% \section{Installation}
%
% To generate the package file from this documented source, run:
%
% \begin{verbatim}
% latex boustrophedon.ins
% \end{verbatim}
%
% This produces \texttt{boustrophedon.sty}. Place it beside your document or
% install it in a TeX tree searched by your distribution.
%
% \section{Requirements}
%
% XeLaTeX or LuaLaTeX is recommended, especially for Greek Unicode input. The
% package requires \texttt{xparse}, \texttt{expl3}, \texttt{graphicx},
% \texttt{iftex}, \texttt{greek6cbc}, and \texttt{greek4cbc}.
%
% \section{Usage}
%
% The main command is:
%
% \begin{verbatim}
% \boustrophedon[<keys>]{<text>}
% \end{verbatim}
%
% Important keys are:
% \begin{itemize}
%   \item \texttt{Type=Any}, \texttt{Type=Archaic}, or \texttt{Type=Classical}
%   \item \texttt{start=LTR} or \texttt{start=RTL}
%   \item \texttt{resetDirection=Page} or \texttt{resetDirection=Paragraph}
%   \item \texttt{LineWidth=Auto} or an explicit dimension
%   \item \texttt{ObscureLetters=On} or \texttt{ObscureLetters=Off}
%   \item \texttt{inLine=True} or \texttt{inLine=False}
% \end{itemize}
%
% Inline mode keeps surrounding text normal and transforms only bracketed spans:
%
% \begin{verbatim}
% \boustrophedon[inLine=True]{Normal text with [THIS PART] mirrored inline.}
% \boustrophedon[Type=Classical,inLine=True]{A sentence with [DHMOS ATHNAIWN].}
% \end{verbatim}
%
% The start/stop form is also available:
%
% \begin{verbatim}
% \startBoustrophedon[Type=Archaic]
% ANDRA MOI ENNEPE MOUSA POLYTROPON ...
% \stopBoustrophedon
% \end{verbatim}
%
% \section{Examples}
%
% See \texttt{examples/boustrophedon\_template.tex} for a minimal starter and
% \texttt{examples/boustrophedon\_demos.tex} for the full demonstration and
% regression document.
%
% \section{License and maintenance}
%
% This work is distributed under the LaTeX Project Public License, version 1.3c
% or later. The work has LPPL maintenance status ``maintained''. The Current
% Maintainer is Aris Chatzichristos.
%
% \StopEventually{\PrintChanges}
%
% \section{Implementation}
%
%    \begin{macrocode}
%<*package>
\NeedsTeXFormat{LaTeX2e}
\ProvidesPackage{boustrophedon}[2026/05/13 v1.1.0 Documented source distribution]

\RequirePackage{xparse}
\RequirePackage{expl3}
\RequirePackage{graphicx}
\RequirePackage{greek6cbc}
\RequirePackage{greek4cbc}
\RequirePackage{iftex}

\ExplSyntaxOn

% --------------------------------------------------------------------------
% Options
% --------------------------------------------------------------------------
\bool_new:N \g_boustro_start_ltr_bool
\bool_new:N \g_boustro_obscure_letters_bool
\bool_new:N \g_boustro_reset_page_bool
\bool_new:N \g_boustro_inline_bool
\int_new:N  \g_boustro_line_int
\tl_new:N   \g_boustro_type_tl
\dim_new:N  \g_boustro_linewidth_dim

\bool_set_true:N  \g_boustro_start_ltr_bool
\bool_set_true:N  \g_boustro_obscure_letters_bool
\bool_set_true:N  \g_boustro_reset_page_bool
\bool_set_false:N \g_boustro_inline_bool
\int_gzero:N      \g_boustro_line_int
\tl_set:Nn        \g_boustro_type_tl {any}
\dim_set:Nn       \g_boustro_linewidth_dim { 0pt }

\cs_new_protected:Npn \boustro_set_linewidth:n #1
  {
    \tl_set:Nn \l_tmpb_tl {#1}
    \tl_trim_spaces:N \l_tmpb_tl
    \tl_set:NV \l_tmpa_tl \l_tmpb_tl
    \tl_set:Nx \l_tmpa_tl { \tl_lower_case:n { \l_tmpa_tl } }
    \tl_if_blank:VTF \l_tmpa_tl
      { \dim_set:Nn \g_boustro_linewidth_dim { 0pt } }
      {
        \str_if_eq:VnTF \l_tmpa_tl { auto }
          { \dim_set:Nn \g_boustro_linewidth_dim { 0pt } }
          {
            \dim_set:Nn \g_boustro_linewidth_dim { \l_tmpb_tl }
          }
      }
  }

\keys_define:nn { boustro }
  {
    start .choice:,
    start / LTR .code:n = { \bool_set_true:N  \g_boustro_start_ltr_bool },
    start / RTL .code:n = { \bool_set_false:N \g_boustro_start_ltr_bool },
    Type .choice:,
    Type / Any .code:n      = { \tl_set:Nn \g_boustro_type_tl {any} },
    Type / Archaic .code:n  = { \tl_set:Nn \g_boustro_type_tl {archaic} },
    Type / Classical .code:n= { \tl_set:Nn \g_boustro_type_tl {classical} },
    LineWidth .code:n = { \boustro_set_linewidth:n {#1} },
    ObscureLetters .choice:,
    ObscureLetters / On  .code:n = { \bool_set_true:N  \g_boustro_obscure_letters_bool },
    ObscureLetters / Off .code:n = { \bool_set_false:N \g_boustro_obscure_letters_bool },
    % Backwards-compat alias (deprecated):
    digammaAndKoppa .choice:,
    digammaAndKoppa / On  .code:n = { \bool_set_true:N  \g_boustro_obscure_letters_bool },
    digammaAndKoppa / Off .code:n = { \bool_set_false:N \g_boustro_obscure_letters_bool },
    resetDirection .choice:,
    resetDirection / Page      .code:n = { \bool_set_true:N  \g_boustro_reset_page_bool },
    resetDirection / Paragraph .code:n = { \bool_set_false:N \g_boustro_reset_page_bool },
    % Backwards-compat alias (deprecated):
    reset .choice:,
    reset / page      .code:n = { \bool_set_true:N  \g_boustro_reset_page_bool },
    reset / paragraph .code:n = { \bool_set_false:N \g_boustro_reset_page_bool },
    inLine .choice:,
    inLine / True  .code:n = { \bool_set_true:N  \g_boustro_inline_bool },
    inLine / False .code:n = { \bool_set_false:N \g_boustro_inline_bool },
    inLine / true  .code:n = { \bool_set_true:N  \g_boustro_inline_bool },
    inLine / false .code:n = { \bool_set_false:N \g_boustro_inline_bool },
    inline .choice:,
    inline / True  .code:n = { \bool_set_true:N  \g_boustro_inline_bool },
    inline / False .code:n = { \bool_set_false:N \g_boustro_inline_bool },
    inline / true  .code:n = { \bool_set_true:N  \g_boustro_inline_bool },
    inline / false .code:n = { \bool_set_false:N \g_boustro_inline_bool },
  }
\ProcessKeyOptions [ boustro ]

\AddToHook{shipout/after}
  {
    \bool_if:NT \g_boustro_reset_page_bool
      { \int_gzero:N \g_boustro_line_int }
  }

% --------------------------------------------------------------------------
% Variables
% --------------------------------------------------------------------------
\seq_new:N \l__boustro_lines_seq
\seq_new:N \l__boustro_symbols_seq
\seq_new:N \l__boustro_tmp_seq
\seq_new:N \l__boustro_words_seq
\seq_new:N \l__boustro_pars_seq
\bool_new:N \l__boustro_input_has_greek_bool
\tl_new:N  \l__boustro_norm_tl
\tl_new:N  \l__boustro_scan_tl
\tl_new:N  \l__boustro_scan_tail_tl
\tl_new:N  \l__boustro_head_tl
\tl_new:N  \l__boustro_next_tl
\tl_new:N  \l__boustro_combined_tl
\tl_new:N  \l__boustro_current_line_tl
\tl_new:N  \l__boustro_candidate_tl
\tl_new:N  \l__boustro_words_tl
\tl_new:N  \l__boustro_input_tl
\tl_new:N  \l__boustro_inline_mode_tl
\box_new:N \l__boustro_measure_box
\dim_new:N \l__boustro_width_dim
\dim_new:N \l__boustro_target_dim

\cs_new_protected:Npn \boustro_set_target_width:n #1
  {
    \dim_compare:nNnTF { \g_boustro_linewidth_dim } > { 0pt }
      { \dim_set_eq:NN \l__boustro_target_dim \g_boustro_linewidth_dim }
      {
        \str_case:nnF {#1}
          {
            {any}{\dim_set:Nn \l__boustro_target_dim { .95\linewidth }}
            {archaic}{\dim_set:Nn \l__boustro_target_dim { .95\linewidth }}
            {classical}{\dim_set:Nn \l__boustro_target_dim { .95\linewidth }}
          }
          { \dim_set:Nn \l__boustro_target_dim { .95\linewidth } }
      }
    \dim_compare:nNnT { \l__boustro_target_dim } > { \linewidth }
      { \dim_set:Nn \l__boustro_target_dim { \linewidth } }
  }

\cs_new_protected:Npn \boustro_maybe_reset:
  {
    \bool_if:NF \g_boustro_reset_page_bool
      { \int_gzero:N \g_boustro_line_int }
  }

\cs_new:Npn \boustro_line_is_reverse:
  {
    \bool_if:NTF \g_boustro_start_ltr_bool
      { \int_if_even_p:n { \g_boustro_line_int } }
      { \int_if_odd_p:n  { \g_boustro_line_int } }
  }

\cs_new:Npn \boustro_line_is_reverse_n:n #1
  {
    \bool_if:NTF \g_boustro_start_ltr_bool
      { \int_if_even_p:n {#1} }
      { \int_if_odd_p:n  {#1} }
  }

% --------------------------------------------------------------------------
% Explicit line splitting and paragraph splitting
% --------------------------------------------------------------------------
\cs_new_protected:Npn \boustro_split_explicit_lines:n #1
  {
    \tl_set:Nn \l__boustro_input_tl {#1}
    \tl_replace_all:Nnn \l__boustro_input_tl {\\} { <BLINEBREAK> }
    \seq_clear:N \l__boustro_pars_seq
    \seq_set_split:NnV \l__boustro_tmp_seq { <BLINEBREAK> } \l__boustro_input_tl
    \seq_map_inline:Nn \l__boustro_tmp_seq
      {
        \tl_set:Nn \l_tmpa_tl {##1}
        \tl_trim_spaces:N \l_tmpa_tl
        \tl_if_blank:VF \l_tmpa_tl
          { \seq_put_right:NV \l__boustro_pars_seq \l_tmpa_tl }
      }
  }

% --------------------------------------------------------------------------
% Unicode Greek normalization to internal symbols.
% Sentinels: 1 theta, 2 phi, 3 chi, 4 psi, 5 xi, 6 omega, 7 koppa, 8 digamma
% --------------------------------------------------------------------------
\cs_new_protected:Npn \boustro_normalize_unicode_greek:
  {
    % remove common accent marks first
    \regex_replace_all:nnN { [άὰᾶἀἁἂἃἄἅἆἇᾳᾀᾁᾂᾃᾄᾅᾆᾇᾱᾰ] } { a } \l__boustro_norm_tl
    \regex_replace_all:nnN { [ΆᾺἈἉἊἋἌἍἎἏᾼ] } { A } \l__boustro_norm_tl
    \regex_replace_all:nnN { [έὲἐἑἒἓἔἕ] } { e } \l__boustro_norm_tl
    \regex_replace_all:nnN { [ΈῈἘἙἚἛἜἝ] } { E } \l__boustro_norm_tl
    \regex_replace_all:nnN { [ήὴῆἠἡἢἣἤἥἦἧῃᾐᾑᾒᾓᾔᾕᾖᾗ] } { h } \l__boustro_norm_tl
    \regex_replace_all:nnN { [ΉῊἨἩἪἫἬἭἮἯῌ] } { H } \l__boustro_norm_tl
    \regex_replace_all:nnN { [ίὶῖϊῒῗἰἱἲἳἴἵἶἷ] } { i } \l__boustro_norm_tl
    \regex_replace_all:nnN { [ΊῚΪἸἹἺἻἼἽἾἿ] } { I } \l__boustro_norm_tl
    \regex_replace_all:nnN { [όὸὀὁὂὃὄὅ] } { o } \l__boustro_norm_tl
    \regex_replace_all:nnN { [ΌῸὈὉὊὋὌὍ] } { O } \l__boustro_norm_tl
    \regex_replace_all:nnN { [ύὺῦϋῢῧὐὑὒὓὔὕὖὗ] } { u } \l__boustro_norm_tl
    \regex_replace_all:nnN { [ΎῪΫὙὛὝὟ] } { U } \l__boustro_norm_tl
    \regex_replace_all:nnN { [ώὼῶὠὡὢὣὤὥὦὧῳᾠᾡᾢᾣᾤᾥᾦᾧ] } { 6 } \l__boustro_norm_tl
    \regex_replace_all:nnN { [ΏῺὨὩὪὫὬὭὮὯῼ] } { 6 } \l__boustro_norm_tl

    \bool_if:NT \g_boustro_obscure_letters_bool
      {
        % Unicode koppa / digamma (if user inputs them directly)
        \regex_replace_all:nnN { Ϙ|ϙ } { 7 } \l__boustro_norm_tl
        \regex_replace_all:nnN { Ϝ|ϝ } { 8 } \l__boustro_norm_tl
      }

    % plain Greek letters
    \regex_replace_all:nnN { α } { a } \l__boustro_norm_tl
    \regex_replace_all:nnN { Α } { A } \l__boustro_norm_tl
    \regex_replace_all:nnN { β } { b } \l__boustro_norm_tl
    \regex_replace_all:nnN { Β } { B } \l__boustro_norm_tl
    \regex_replace_all:nnN { γ } { g } \l__boustro_norm_tl
    \regex_replace_all:nnN { Γ } { G } \l__boustro_norm_tl
    \regex_replace_all:nnN { δ } { d } \l__boustro_norm_tl
    \regex_replace_all:nnN { Δ } { D } \l__boustro_norm_tl
    \regex_replace_all:nnN { ε } { e } \l__boustro_norm_tl
    \regex_replace_all:nnN { Ε } { E } \l__boustro_norm_tl
    \regex_replace_all:nnN { ζ } { z } \l__boustro_norm_tl
    \regex_replace_all:nnN { Ζ } { Z } \l__boustro_norm_tl
    \regex_replace_all:nnN { η } { h } \l__boustro_norm_tl
    \regex_replace_all:nnN { Η } { H } \l__boustro_norm_tl
    \regex_replace_all:nnN { θ } { 1 } \l__boustro_norm_tl
    \regex_replace_all:nnN { Θ } { 1 } \l__boustro_norm_tl
    \regex_replace_all:nnN { ι|ϊ|ΐ } { i } \l__boustro_norm_tl
    \regex_replace_all:nnN { Ι|Ϊ } { I } \l__boustro_norm_tl
    \regex_replace_all:nnN { κ } { k } \l__boustro_norm_tl
    \regex_replace_all:nnN { Κ } { K } \l__boustro_norm_tl
    \regex_replace_all:nnN { λ } { l } \l__boustro_norm_tl
    \regex_replace_all:nnN { Λ } { L } \l__boustro_norm_tl
    \regex_replace_all:nnN { μ } { m } \l__boustro_norm_tl
    \regex_replace_all:nnN { Μ } { M } \l__boustro_norm_tl
    \regex_replace_all:nnN { ν } { n } \l__boustro_norm_tl
    \regex_replace_all:nnN { Ν } { N } \l__boustro_norm_tl
    \regex_replace_all:nnN { ξ } { 5 } \l__boustro_norm_tl
    \regex_replace_all:nnN { Ξ } { 5 } \l__boustro_norm_tl
    \regex_replace_all:nnN { ο } { o } \l__boustro_norm_tl
    \regex_replace_all:nnN { Ο } { O } \l__boustro_norm_tl
    \regex_replace_all:nnN { π } { p } \l__boustro_norm_tl
    \regex_replace_all:nnN { Π } { P } \l__boustro_norm_tl
    \regex_replace_all:nnN { ρ } { r } \l__boustro_norm_tl
    \regex_replace_all:nnN { Ρ } { R } \l__boustro_norm_tl
    \regex_replace_all:nnN { σ|ς } { s } \l__boustro_norm_tl
    \regex_replace_all:nnN { Σ } { S } \l__boustro_norm_tl
    \regex_replace_all:nnN { τ } { t } \l__boustro_norm_tl
    \regex_replace_all:nnN { Τ } { T } \l__boustro_norm_tl
    \regex_replace_all:nnN { υ|ϋ|ΰ } { u } \l__boustro_norm_tl
    \regex_replace_all:nnN { Υ|Ϋ } { U } \l__boustro_norm_tl
    \regex_replace_all:nnN { φ } { 2 } \l__boustro_norm_tl
    \regex_replace_all:nnN { Φ } { 2 } \l__boustro_norm_tl
    \regex_replace_all:nnN { χ } { 3 } \l__boustro_norm_tl
    \regex_replace_all:nnN { Χ } { 3 } \l__boustro_norm_tl
    \regex_replace_all:nnN { ψ } { 4 } \l__boustro_norm_tl
    \regex_replace_all:nnN { Ψ } { 4 } \l__boustro_norm_tl
    \regex_replace_all:nnN { ω } { 6 } \l__boustro_norm_tl
    \regex_replace_all:nnN { Ω } { 6 } \l__boustro_norm_tl
  }

\cs_new_protected:Npn \boustro_normalize_input:n #1
  {
    \tl_set:Nn \l__boustro_norm_tl {#1}
    \regex_match:nnTF { [\x{0370}-\x{03FF}\x{1F00}-\x{1FFF}] } {#1}
      { \bool_set_true:N \l__boustro_input_has_greek_bool }
      { \bool_set_false:N \l__boustro_input_has_greek_bool }
    \boustro_normalize_unicode_greek:

    \bool_if:NF \l__boustro_input_has_greek_bool
      {
        \regex_replace_all:nnN { J } { I } \l__boustro_norm_tl
        \regex_replace_all:nnN { j } { i } \l__boustro_norm_tl
        \regex_replace_all:nnN { Ō|ō|Ô|ô } { 6 } \l__boustro_norm_tl
        \bool_if:NT \g_boustro_obscure_letters_bool
          {
            \regex_replace_all:nnN { TH|Th|tH|th } { 1 } \l__boustro_norm_tl
            \regex_replace_all:nnN { PH|Ph|pH|ph } { 2 } \l__boustro_norm_tl
            \regex_replace_all:nnN { CH|Ch|cH|ch|KH|Kh|kH|kh } { 3 } \l__boustro_norm_tl
            \regex_replace_all:nnN { PS|Ps|pS|ps } { 4 } \l__boustro_norm_tl
            \regex_replace_all:nnN { KS|Ks|kS|ks } { 5 } \l__boustro_norm_tl
            \regex_replace_all:nnN { KA } { 7A } \l__boustro_norm_tl
            \regex_replace_all:nnN { Ka } { 7a } \l__boustro_norm_tl
            \regex_replace_all:nnN { kA } { 7A } \l__boustro_norm_tl
            \regex_replace_all:nnN { ka } { 7a } \l__boustro_norm_tl
            \regex_replace_all:nnN { KO } { 7O } \l__boustro_norm_tl
            \regex_replace_all:nnN { Ko } { 7o } \l__boustro_norm_tl
            \regex_replace_all:nnN { kO } { 7O } \l__boustro_norm_tl
            \regex_replace_all:nnN { ko } { 7o } \l__boustro_norm_tl
            \regex_replace_all:nnN { W } { 8 } \l__boustro_norm_tl
            \regex_replace_all:nnN { w } { 8 } \l__boustro_norm_tl
          }
      }

    \regex_replace_all:nnN { [.,;:!?] } { ~ } \l__boustro_norm_tl
    \regex_replace_all:nnN { [-()\[\]"'] } { ~ } \l__boustro_norm_tl
    \regex_replace_all:nnN { [^A-Za-z0-9~ ] } { } \l__boustro_norm_tl
    % Normalize any remaining whitespace to a visible/measureable separator.
    % Using `~` lets us map it to an explicit `\space` during rendering so it
    % isn't lost inside macro expansions (important for width-based wrapping).
    \regex_replace_all:nnN { \s+ } { ~ } \l__boustro_norm_tl
    \regex_replace_all:nnN { ~+ } { ~ } \l__boustro_norm_tl
  }

\cs_new_protected:Npn \boustro_line_to_seq:n #1
  {
    \seq_clear:N \l__boustro_symbols_seq
    \boustro_normalize_input:n {#1}
    % Treat certain digraph encodings as atomic tokens (e.g. 7A/7O for koppa+vowel)
    % so reversal doesn't split them into separate characters.
    \tl_set_eq:NN \l__boustro_scan_tl \l__boustro_norm_tl
    \boustro_scan_norm_into_symbols:
  }

\cs_new_protected:Npn \boustro_scan_norm_into_symbols:
  {
    \tl_if_empty:NTF \l__boustro_scan_tl
      { }
      {
        \tl_set:Nx \l__boustro_head_tl { \tl_head:N \l__boustro_scan_tl }
        \tl_set:Nx \l__boustro_scan_tail_tl { \tl_tail:N \l__boustro_scan_tl }

        \tl_if_empty:NTF \l__boustro_scan_tail_tl
          {
            \seq_put_right:NV \l__boustro_symbols_seq \l__boustro_head_tl
            \tl_clear:N \l__boustro_scan_tl
          }
          {
            \tl_set:Nx \l__boustro_next_tl { \tl_head:N \l__boustro_scan_tail_tl }
            \tl_if_eq:NnTF \l__boustro_head_tl { 7 }
              {
                \str_case:nnF { \l__boustro_next_tl }
                  {
                    {A}{ \tl_set:Nn \l__boustro_combined_tl { 7A } }
                    {a}{ \tl_set:Nn \l__boustro_combined_tl { 7a } }
                    {O}{ \tl_set:Nn \l__boustro_combined_tl { 7O } }
                    {o}{ \tl_set:Nn \l__boustro_combined_tl { 7o } }
                  }
                  { \tl_clear:N \l__boustro_combined_tl }

                \tl_if_blank:VTF \l__boustro_combined_tl
                  {
                    \seq_put_right:NV \l__boustro_symbols_seq \l__boustro_head_tl
                    \tl_set_eq:NN \l__boustro_scan_tl \l__boustro_scan_tail_tl
                  }
                  {
                    \seq_put_right:NV \l__boustro_symbols_seq \l__boustro_combined_tl
                    \tl_set:Nx \l__boustro_scan_tl { \tl_tail:N \l__boustro_scan_tail_tl }
                  }
              }
              {
                \seq_put_right:NV \l__boustro_symbols_seq \l__boustro_head_tl
                \tl_set_eq:NN \l__boustro_scan_tl \l__boustro_scan_tail_tl
              }
          }
        \boustro_scan_norm_into_symbols:
      }
  }

% --------------------------------------------------------------------------
% Glyph mapping helpers
% --------------------------------------------------------------------------
\cs_new:Npn \boustro_archaic_map:n #1
  {
    \str_case:nnF {#1}
      {
        {~}{\space}
        {A}{\Aalpha}{a}{\Aalpha}
        {B}{\Abeta}{b}{\Abeta}
        {G}{\Agamma}{g}{\Agamma}
        {D}{\Adelta}{d}{\Adelta}
        {E}{\Aepsilon}{e}{\Aepsilon}
        {Z}{\Azeta}{z}{\Azeta}
        {H}{\Aeta}{h}{\Aeta}
        {1}{\Atheta}
        {I}{\Aiota}{i}{\Aiota}
        {K}{\Akappa}{k}{\Akappa}
        {7}{\Akoppa}
        {7A}{\Akoppa\Aalpha}{7a}{\Akoppa\Aalpha}
        {7O}{\Akoppa\Aomicron}{7o}{\Akoppa\Aomicron}
        {L}{\Alambda}{l}{\Alambda}
        {M}{\Amu}{m}{\Amu}
        {N}{\Anu}{n}{\Anu}
        {X}{\Axi}{x}{\Axi}{5}{\Axi}
        {O}{\Aomicron}{o}{\Aomicron}
        {6}{\Aomega}
        {P}{\Api}{p}{\Api}
        {R}{\Arho}{r}{\Arho}
        {S}{\Asigma}{s}{\Asigma}
        {T}{\Atau}{t}{\Atau}
        {U}{\Aupsilon}{u}{\Aupsilon}
        {Y}{\Aupsilon}{y}{\Aupsilon}
        {3}{\Achi}
        {2}{\Aphi}
        {4}{\Apsi}
        {8}{\Adigamma}
      }
      {#1}
  }

\cs_new:Npn \boustro_classical_normal_map:n #1
  {
    \str_case:nnF {#1}
      {
        {~}{\space}
        {A}{\Aalpha}{a}{\Aalpha}
        {B}{\Abeta}{b}{\Abeta}
        {G}{\Agamma}{g}{\Agamma}
        {D}{\Adelta}{d}{\Adelta}
        {E}{\Aepsilon}{e}{\Aepsilon}
        {Z}{\Azeta}{z}{\Azeta}
        {H}{\Aeta}{h}{\Aeta}
        {1}{\Atheta}
        {I}{\Aiota}{i}{\Aiota}
        {K}{\Akappa}{k}{\Akappa}
        {L}{\Alambda}{l}{\Alambda}
        {M}{\Amu}{m}{\Amu}
        {N}{\Anu}{n}{\Anu}
        {X}{\Axi}{x}{\Axi}{5}{\Axi}
        {O}{\Aomicron}{o}{\Aomicron}
        {6}{\Aomega}
        {P}{\Api}{p}{\Api}
        {R}{\Arho}{r}{\Arho}
        {S}{\Asigma}{s}{\Asigma}
        {T}{\Atau}{t}{\Atau}
        {U}{\Aupsilon}{u}{\Aupsilon}
        {Y}{\Aupsilon}{y}{\Aupsilon}
        {3}{\Achi}
        {2}{\Aphi}
        {4}{\Apsi}
      }
      {
        \str_if_eq:nnTF {#1}{7A}
          { \textgvibc{\Akoppa}\Aalpha }
          {
            \str_if_eq:nnTF {#1}{7a}
              { \textgvibc{\Akoppa}\Aalpha }
              {
                \str_if_eq:nnTF {#1}{7O}
                  { \textgvibc{\Akoppa}\Aomicron }
                  {
                    \str_if_eq:nnTF {#1}{7o}
                      { \textgvibc{\Akoppa}\Aomicron }
                      {
        \str_if_eq:nnTF {#1}{7}
          {\textgvibc{\Akoppa}}
          {
            \str_if_eq:nnTF {#1}{8}
              {\textgvibc{\Adigamma}}
              {#1}
          }
                      }
                  }
              }
          }
      }
  }

\cs_new:Npn \boustro_classical_reverse_map:n #1
  {
    \str_case:nnF {#1}
      {
        {~}{\space}
        {A}{\ARalpha}{a}{\ARalpha}
        {B}{\ARbeta}{b}{\ARbeta}
        {G}{\ARgamma}{g}{\ARgamma}
        {D}{\ARdelta}{d}{\ARdelta}
        {E}{\ARepsilon}{e}{\ARepsilon}
        {Z}{\ARzeta}{z}{\ARzeta}
        {H}{\AReta}{h}{\AReta}
        {1}{\ARtheta}
        {I}{\ARiota}{i}{\ARiota}
        {K}{\ARkappa}{k}{\ARkappa}
        {L}{\ARlambda}{l}{\ARlambda}
        {M}{\ARmu}{m}{\ARmu}
        {N}{\ARnu}{n}{\ARnu}
        {X}{\ARxi}{x}{\ARxi}{5}{\ARxi}
        {O}{\ARomicron}{o}{\ARomicron}
        {6}{\ARomega}
        {P}{\ARpi}{p}{\ARpi}
        {R}{\ARrho}{r}{\ARrho}
        {S}{\ARsigma}{s}{\ARsigma}
        {T}{\ARtau}{t}{\ARtau}
        {U}{\ARupsilon}{u}{\ARupsilon}
        {Y}{\ARupsilon}{y}{\ARupsilon}
        {3}{\ARchi}
        {2}{\ARphi}
        {4}{\ARpsi}
      }
      {
        \str_if_eq:nnTF {#1}{7A}
          { \textgvibc{\Akoppa}\ARalpha }
          {
            \str_if_eq:nnTF {#1}{7a}
              { \textgvibc{\Akoppa}\ARalpha }
              {
                \str_if_eq:nnTF {#1}{7O}
                  { \textgvibc{\Akoppa}\ARomicron }
                  {
                    \str_if_eq:nnTF {#1}{7o}
                      { \textgvibc{\Akoppa}\ARomicron }
                      {
        \str_if_eq:nnTF {#1}{7}
          {\textgvibc{\Akoppa}}
          {
            \str_if_eq:nnTF {#1}{8}
              {\textgvibc{\Adigamma}}
              {#1}
          }
                      }
                  }
              }
          }
      }
  }

\cs_new_protected:Npn \boustro_render_archaic_forward:
  { {\textgvibc{\seq_map_inline:Nn \l__boustro_symbols_seq {\boustro_archaic_map:n{##1}}}} }
\cs_new_protected:Npn \boustro_render_archaic_reverse:
  {
    \seq_set_eq:NN \l__boustro_tmp_seq \l__boustro_symbols_seq
    \seq_reverse:N \l__boustro_tmp_seq
    {
      \textgvibc
        {
          \seq_map_inline:Nn \l__boustro_tmp_seq
            {
              \str_if_eq:nnTF {##1} {~}
                { \space }
                { \reflectbox { \boustro_archaic_map:n {##1} } }
            }
        }
    }
  }
\cs_new_protected:Npn \boustro_render_classical_forward:
  { {\textgivbc{\seq_map_inline:Nn \l__boustro_symbols_seq {\boustro_classical_normal_map:n{##1}}}} }
\cs_new_protected:Npn \boustro_render_classical_reverse:
  {
    \seq_set_eq:NN \l__boustro_tmp_seq \l__boustro_symbols_seq
    \seq_reverse:N \l__boustro_tmp_seq
    {
      \textgivbc
        {
          \seq_map_inline:Nn \l__boustro_tmp_seq
            {
              \str_if_eq:nnTF {##1} {~}
                { \space }
                { \reflectbox { \boustro_classical_normal_map:n {##1} } }
            }
        }
    }
  }

% --------------------------------------------------------------------------
% Width measurement and wrapping
% --------------------------------------------------------------------------
\cs_new_protected:Npn \boustro_measure_any:nN #1#2
  {
    \hbox_set:Nn \l__boustro_measure_box {#1}
    \dim_set:Nn #2 { \box_wd:N \l__boustro_measure_box }
  }

\cs_new_protected:Npn \boustro_measure_archaic:nN #1#2
  {
    \boustro_line_to_seq:n {#1}
    \hbox_set:Nn \l__boustro_measure_box { \boustro_render_archaic_forward: }
    \dim_set:Nn #2 { \box_wd:N \l__boustro_measure_box }
  }

\cs_new_protected:Npn \boustro_measure_classical:nN #1#2
  {
    \boustro_line_to_seq:n {#1}
    \hbox_set:Nn \l__boustro_measure_box { \boustro_render_classical_forward: }
    \dim_set:Nn #2 { \box_wd:N \l__boustro_measure_box }
  }
\cs_generate_variant:Nn \boustro_measure_any:nN { VN }
\cs_generate_variant:Nn \boustro_measure_archaic:nN { VN }
\cs_generate_variant:Nn \boustro_measure_classical:nN { VN }

\cs_new:Npn \boustro_map_string_archaic:n #1
  {
    \boustro_line_to_seq:n {#1}
    \seq_map_inline:Nn \l__boustro_symbols_seq { \boustro_archaic_map:n{##1} }
  }

\cs_new:Npn \boustro_map_string_classical:n #1
  {
    \boustro_line_to_seq:n {#1}
    \seq_map_inline:Nn \l__boustro_symbols_seq { \boustro_classical_normal_map:n{##1} }
  }

\cs_new_protected:Npn \boustro_wrap_text:nnN #1#2#3
  {
    \seq_clear:N #3
    \boustro_set_target_width:n {#1}
    \tl_set:Nx \l__boustro_words_tl { \tl_to_str:n {#2} }
    \regex_replace_all:nnN { \s+ } { <BSPACE> } \l__boustro_words_tl
    \seq_set_split:NnV \l__boustro_words_seq { <BSPACE> } \l__boustro_words_tl
    \seq_remove_all:Nn \l__boustro_words_seq { }
    \tl_clear:N \l__boustro_current_line_tl
    \seq_map_inline:Nn \l__boustro_words_seq
      {
        \tl_if_blank:VTF \l__boustro_current_line_tl
          { \tl_set:Nn \l__boustro_candidate_tl {##1} }
          { \tl_set:Ne \l__boustro_candidate_tl { \l__boustro_current_line_tl \c_space_tl ##1 } }
        \use:c { boustro_measure_#1:VN } \l__boustro_candidate_tl \l__boustro_width_dim
        \dim_compare:nNnTF { \l__boustro_width_dim } > { \l__boustro_target_dim }
          {
            \tl_if_blank:VTF \l__boustro_current_line_tl
              { \seq_put_right:Nn #3 {##1} }
              {
                \seq_put_right:NV #3 \l__boustro_current_line_tl
                \tl_set:Nn \l__boustro_current_line_tl {##1}
              }
          }
          { \tl_set:NV \l__boustro_current_line_tl \l__boustro_candidate_tl }
      }
    \tl_if_blank:VF \l__boustro_current_line_tl
      { \seq_put_right:NV #3 \l__boustro_current_line_tl }
  }

\cs_new_protected:Npn \boustro_wrap_epigraphic_text:nnN #1#2#3
  {
    \seq_clear:N #3
    \boustro_normalize_input:n {#2}
    \tl_set_eq:NN \l__boustro_words_tl \l__boustro_norm_tl
    \regex_replace_all:nnN { \s+ } { <BSPACE> } \l__boustro_words_tl
    \seq_set_split:NnV \l__boustro_words_seq { <BSPACE> } \l__boustro_words_tl
    \seq_remove_all:Nn \l__boustro_words_seq { }
    \boustro_set_target_width:n {#1}
    \tl_clear:N \l__boustro_current_line_tl
    \seq_map_inline:Nn \l__boustro_words_seq
      {
        \tl_if_blank:VTF \l__boustro_current_line_tl
          { \tl_set:Nn \l__boustro_candidate_tl {##1} }
          { \tl_set:Ne \l__boustro_candidate_tl { \l__boustro_current_line_tl \c_space_tl ##1 } }
        \use:c { boustro_measure_#1:VN } \l__boustro_candidate_tl \l__boustro_width_dim
        \dim_compare:nNnTF { \l__boustro_width_dim } > { \l__boustro_target_dim }
          {
            \tl_if_blank:VTF \l__boustro_current_line_tl
              { \seq_put_right:Nn #3 {##1} }
              {
                \seq_put_right:NV #3 \l__boustro_current_line_tl
                \tl_set:Nn \l__boustro_current_line_tl {##1}
              }
          }
          { \tl_set:NV \l__boustro_current_line_tl \l__boustro_candidate_tl }
      }
    \tl_if_blank:VF \l__boustro_current_line_tl
      { \seq_put_right:NV #3 \l__boustro_current_line_tl }
  }

\cs_new_protected:Npn \boustro_prepare_lines:nn #1#2
  {
    \seq_clear:N \l__boustro_lines_seq
    \tl_set:Nn \l__boustro_input_tl {#2}
    \tl_if_in:NnTF \l__boustro_input_tl {\\}
      {
        \boustro_split_explicit_lines:n {#2}
        \seq_map_inline:Nn \l__boustro_pars_seq
          {
            \boustro_wrap_text:nnN {#1} {##1} \l__boustro_tmp_seq
            \seq_map_inline:Nn \l__boustro_tmp_seq
              { \seq_put_right:Nn \l__boustro_lines_seq {####1} }
          }
      }
      {
        \str_case:nnF {#1}
          {
            {any}{\boustro_wrap_text:nnN {any} {#2} \l__boustro_lines_seq}
            {archaic}{\boustro_wrap_text:nnN {archaic} {#2} \l__boustro_lines_seq}
            {classical}{\boustro_wrap_text:nnN {classical} {#2} \l__boustro_lines_seq}
          }
          { \boustro_wrap_text:nnN {#1} {#2} \l__boustro_lines_seq }
      }
  }

% --------------------------------------------------------------------------
% Printing line by line
% --------------------------------------------------------------------------
\cs_new_protected:Npn \boustro_print_any_line:nn #1#2
  {
    \par\noindent
    \bool_if:nTF { \boustro_line_is_reverse_n:n {#1} }
      { \makebox[\linewidth][c]{\makebox[\l__boustro_target_dim][r]{\reflectbox{#2}}}\par }
      { \makebox[\linewidth][c]{\makebox[\l__boustro_target_dim][l]{#2}}\par }
  }

\cs_new_protected:Npn \boustro_print_archaic_line:nn #1#2
  {
    \par\noindent
    \boustro_line_to_seq:n {#2}
    \bool_if:nTF { \boustro_line_is_reverse_n:n {#1} }
      { \makebox[\linewidth][c]{\makebox[\l__boustro_target_dim][r]{\boustro_render_archaic_reverse:}}\par }
      { \makebox[\linewidth][c]{\makebox[\l__boustro_target_dim][l]{\boustro_render_archaic_forward:}}\par }
  }

\cs_new_protected:Npn \boustro_print_classical_line:nn #1#2
  {
    \par\noindent
    \boustro_line_to_seq:n {#2}
    \bool_if:nTF { \boustro_line_is_reverse_n:n {#1} }
      {
        \makebox[\linewidth][c]{\makebox[\l__boustro_target_dim][r]{\boustro_render_classical_reverse:}}\par
      }
      {
        \makebox[\linewidth][c]{\makebox[\l__boustro_target_dim][l]{\boustro_render_classical_forward:}}\par
      }
  }

% --------------------------------------------------------------------------
% Public typesetter (mode, text)
% --------------------------------------------------------------------------
\cs_new_protected:Npn \boustro_typeset_block:nn #1#2
  {
    \boustro_maybe_reset:
    \boustro_set_target_width:n {#1}
    \boustro_prepare_lines:nn {#1} {#2}
    \int_set:Nn \l_tmpa_int { \g_boustro_line_int }
    \str_case:nnF {#1}
      {
        {any}
          {
            \seq_map_indexed_inline:Nn \l__boustro_lines_seq
              { \boustro_print_any_line:nn { \int_eval:n { \l_tmpa_int + ##1 } } {##2} }
          }
        {archaic}
          {
            \seq_map_indexed_inline:Nn \l__boustro_lines_seq
              { \boustro_print_archaic_line:nn { \int_eval:n { \l_tmpa_int + ##1 } } {##2} }
          }
        {classical}
          {
            \seq_map_indexed_inline:Nn \l__boustro_lines_seq
              { \boustro_print_classical_line:nn { \int_eval:n { \l_tmpa_int + ##1 } } {##2} }
          }
      }{}
    \int_gadd:Nn \g_boustro_line_int { \seq_count:N \l__boustro_lines_seq }
    \par
  }

% --------------------------------------------------------------------------
% Inline markup: normal text outside [ ... ], boustrophedon only inside.
% The square brackets are markup delimiters and are not printed.
% --------------------------------------------------------------------------
\cs_new_protected:Npn \boustro_render_inline:nn #1#2
  {
    \group_begin:
      \str_case:VnF \l__boustro_inline_mode_tl
        {
          {any}{ \reflectbox {#2} }
          {archaic}
            {
              \boustro_line_to_seq:n {#2}
              \boustro_render_archaic_reverse:
            }
          {classical}
            {
              \boustro_line_to_seq:n {#2}
              \boustro_render_classical_reverse:
            }
        }
        { \reflectbox {#2} }
    \group_end:
  }

\cs_new_protected:Npn \boustro_typeset_inline:nn #1#2
  {
    \tl_set:Nn \l__boustro_inline_mode_tl {#1}
    \boustro_inline_parse:w #2 [ \q_no_value ] \q_stop
  }

\cs_new_protected:Npn \boustro_inline_parse:w #1[#2]#3 \q_stop
  {
    #1
    \quark_if_no_value:nF {#2}
      {
        \boustro_render_inline:nn { \l__boustro_inline_mode_tl } {#2}
        \boustro_inline_parse:w #3 \q_stop
      }
  }

% --------------------------------------------------------------------------
% Public API (single command)
% --------------------------------------------------------------------------
\NewDocumentCommand{\boustrophedon}{ O{} +m }
  {
    \group_begin:
      \keys_set:nn { boustro } {#1}
      \bool_if:NTF \g_boustro_inline_bool
        { \exp_args:Nx \boustro_typeset_inline:nn { \tl_use:N \g_boustro_type_tl } {#2} }
        { \exp_args:Nx \boustro_typeset_block:nn { \tl_use:N \g_boustro_type_tl } {#2} }
    \group_end:
  }

% Convenience aliases (v0.76 compatibility)
\NewDocumentCommand{\boustrophedonAny}{+m}
  { \boustrophedon[Type=Any]{#1} }
\NewDocumentCommand{\boustrophedonArchaic}{+m}
  { \boustrophedon[Type=Archaic]{#1} }
\NewDocumentCommand{\boustrophedonClassical}{+m}
  { \boustrophedon[Type=Classical]{#1} }

% Block style API with start/stop commands (single command, optional [keys])
\makeatletter
\def\startBoustrophedon{%
  \@ifnextchar[{\boustro_start_with_keys@}{\boustro_start_with_keys@[]}%
}
\long\def\boustro_start_with_keys@[#1]#2\stopBoustrophedon{%
  \boustrophedon[#1]{#2}%
}
\makeatother

% --------------------------------------------------------------------------
% Block style API with start/stop commands
% --------------------------------------------------------------------------
\long\def\startBoustrophedonAny#1\stopBoustrophedonAny{\boustrophedonAny{#1}}
\long\def\startBoustrophedonArchaic#1\stopBoustrophedonArchaic{\boustrophedonArchaic{#1}}
\long\def\startBoustrophedonClassical#1\stopBoustrophedonClassical{\boustrophedonClassical{#1}}

% --------------------------------------------------------------------------
% Engine notice
% --------------------------------------------------------------------------
\AtBeginDocument{
  \ifPDFTeX
    \PackageWarningNoLine{boustrophedon}{Greek Unicode input works best with XeLaTeX or LuaLaTeX; transliteration input is still fine in pdfLaTeX}
  \fi
}

\ExplSyntaxOff

%</package>
%    \end{macrocode}
% \Finale