% Copyright 2026 Adi Edelhaus
%
% terminaltrees is licensed under the LaTeX Project Public
% License, version 1.3c or any later version.
%
% Maintenance status: maintained
% Current maintainer: Adi Edelhaus
% Issue reports: https://github.com/edel67/terminaltrees/issues
%
% The files comprising this work are listed in manifest.txt.
% See LICENSE for the full license terms.

\NeedsTeXFormat{LaTeX2e}
\ProvidesPackage{terminaltrees}[2026/10/28 v1.0.2 Child-centered terminal trees]
\RequirePackage[edges]{forest}
\RequirePackage{needspace}

\forestset{
  declare count register={terminaltrees leaf index},
  declare dimen register={leaf pitch},
  declare dimen register={terminaltrees fork distance},
  declare dimen register={terminaltrees bend radius},
  declare dimen register={terminaltrees arrow inset},
  declare toks register={roundness},
  declare dimen={terminaltrees edge radius}{0pt},
  %
  terminal tree/.style={
    baseline=(current bounding box.north),
    leaf pitch=0pt,
    roundness=1,
    for tree={
      anchor=center,
      align=center,
      parent anchor=south,
      child anchor=north,
      edge={thin, ->, >=stealth},
      forked edge',
    },
    where n children=0{tier=terminal}{},
    %
    before drawing tree={
      % Leave room for the arrow tip so the shaft does not reverse direction.
      TeX={% Discard whitespace emitted when PGF first instantiates the arrow.
        \setbox0=\hbox\bgroup
          \tikzset{thin}\pgfarrowtotallength{stealth}%
          % Anchors extend beyond the label boxes at both ends.
          \edef\pgfmathresult{\the\csname pgf@xa\endcsname}%
          \pgfmathparse{\pgfmathresult+2*\pgfkeysvalueof{/pgf/outer ysep}}%
          \edef\pgfmathresult{\egroup
            \noexpand\forestset{terminaltrees arrow inset=\pgfmathresult pt}}%
          \pgfmathresult
      },
      %
      % Number leaf columns before centering parents over their children.
      terminaltrees leaf index=0,
      for leaves={
        x/.pgfmath={terminaltrees_leaf_index()},
        terminaltrees leaf index+=1,
      },
      %
      % Process children first so each midpoint uses their final positions.
      for tree children-first={
        if n children=0{}{
          x/.pgfmath={(x("!1")+x("!l"))/2},
        },
      },
      %
      % Column boundaries lie half a pitch beyond the outer leaf centers.
      % Fit each label and half the sibling gap within its nearer boundary.
      for tree={
        leaf pitch/.pgfmath={
          max(leaf_pitch(),
            (max(abs(min_x()),abs(max_x()))+s_sep()/2) /
            min(
              x()-x("!{first leaf'}")+0.5,
              x("!{last leaf'}")-x()+0.5
            )
          )
        },
      },
      for tree={x/.pgfmath={x()*leaf_pitch()}},
      %
      % Place each fork halfway through the clearance above the child labels.
      for tree={
        if n children=0{}{%
          terminaltrees fork distance/.pgfmath={
            (y()+min_y()-aggregate_max("y()+max_y()","children"))/2},
          %
          % Siblings use one radius so same-side branches share a departure curve.
          terminaltrees bend radius/.pgfmath={
            max(0,min(
              roundness()*terminaltrees_fork_distance(),
              terminaltrees_fork_distance()-terminaltrees_arrow_inset()
            ))
          },
          %
          % The two bends must fit within the horizontal parent-child distance.
          for children={
            if={x()!=x("!u")}{
              terminaltrees bend radius/.pgfmath={
                min(terminaltrees_bend_radius(),abs(x()-x("!u"))/2)
              },
            }{},
          },
          %
          for children={
            fork sep/.register=terminaltrees fork distance,
            terminaltrees edge radius/.pgfmath={
              ifthenelse(x()==x("!u"),0,terminaltrees_bend_radius())
            },
            edge+={rounded corners=\forestoption{terminaltrees edge radius}},
          },
        },
      },
    },
  },
}

\ExplSyntaxOn

\msg_new:nnn { terminaltrees } { invalid-roundness }
  { roundness~must~be~a~unitless~number~from~0~to~1. }

\forestset{
  roundness/.code={
    \pgfmathparse{#1}
    \ifpgfmathunitsdeclared
      \msg_fatal:nn { terminaltrees } { invalid-roundness }
    \fi
    \fp_compare:nTF {\pgfmathresult >= 0 && \pgfmathresult <= 1}
      { \forestrlet{roundness}\pgfmathresult }
      { \msg_fatal:nn { terminaltrees } { invalid-roundness } }
  },
}

\box_new:N \l__terminaltrees_tree_box
\dim_new:N \g__terminaltrees_smallest_font_dim
\dim_new:N \l__terminaltrees_minimum_font_dim
\dim_new:N \l__terminaltrees_available_height_dim
\fp_new:N \l__terminaltrees_scale_fp

% TeX quantizes dimension multipliers to one scaled point per point.
\int_const:Nn \c__terminaltrees_scale_steps_int { \dim_to_decimal_in_sp:n {1pt} }

\keys_define:nn { terminaltrees / fit }
  { minimum~label~size .dim_set:N = \l__terminaltrees_minimum_font_dim }

\msg_new:nnn { terminaltrees } { too-small }
  { Fitting~requires~#1pt~node~text,~below~the~#2~minimum.~
    Increase~an~undersized~node~font,~wrap~labels,~or~split~the~tree~manually;~
    automatic~pagination~is~not~implemented. }
\msg_new:nnn { terminaltrees } { invalid-context }
  { fittedterminaltree~requires~normal~document~flow,~not~a~box~or~float. }
\msg_new:nnn { terminaltrees } { invalid-size }
  { The~minimum~label~size~and~available~page~dimensions~must~be~positive. }

\cs_new_protected:Npn \__terminaltrees_record_smallest_font:
  { \dim_gset:Nn \g__terminaltrees_smallest_font_dim
      { \dim_min:nn { \g__terminaltrees_smallest_font_dim } { \f@size pt } } }

\cs_new_protected:Npn \__terminaltrees_fit:nn #1#2
  {
    \mode_if_inner:TF
      { \msg_fatal:nn { terminaltrees } { invalid-context } }
      {
        \par
        \group_begin:
          \footnotesize
          \dim_gset:Nn \g__terminaltrees_smallest_font_dim { \f@size pt }
        \group_end:
        %
        \dim_set_eq:NN \l__terminaltrees_minimum_font_dim \g__terminaltrees_smallest_font_dim
        \keys_set:nn { terminaltrees / fit } {#1}
        \dim_set:Nn \l__terminaltrees_available_height_dim { \textheight - \baselineskip }
        %
        \bool_lazy_or:nnTF
          { \dim_compare_p:n { \l__terminaltrees_minimum_font_dim <= 0pt } }
          { \dim_compare_p:n { \dim_min:nn {\linewidth}
                {\l__terminaltrees_available_height_dim} <= 0pt } }
          { \msg_fatal:nn { terminaltrees } { invalid-size } }
          {
            % Typeset labels once so fitting does not repeat their side effects.
            % The node hook runs after TikZ selects its font.
            \dim_gset:Nn \g__terminaltrees_smallest_font_dim { \maxdimen }
            \hbox_set:Nn \l__terminaltrees_tree_box
              { \begin{forest}
                  terminal~tree,
                  for~tree={execute~at~begin~node={\__terminaltrees_record_smallest_font:}},
                  #2
                \end{forest} }
            %
            % Round down so TeX cannot enlarge the fitted box beyond its limits.
            \fp_set:Nn \l__terminaltrees_scale_fp
              {
                floor(
                  \c__terminaltrees_scale_steps_int * min(
                    1,
                    \dim_to_fp:n {\linewidth} /
                      \dim_to_fp:n {\box_wd:N \l__terminaltrees_tree_box},
                    \dim_to_fp:n {\l__terminaltrees_available_height_dim} /
                      \dim_to_fp:n {
                        \box_ht:N \l__terminaltrees_tree_box +
                        \box_dp:N \l__terminaltrees_tree_box
                      }
                  )
                ) / \c__terminaltrees_scale_steps_int
              }
            %
            \fp_compare:nTF
              { \l__terminaltrees_scale_fp * \dim_to_fp:n {\g__terminaltrees_smallest_font_dim}
                  < \dim_to_fp:n {\l__terminaltrees_minimum_font_dim} }
              { \msg_fatal:nnxx { terminaltrees } { too-small }
                  % Round only the reported font size to two decimal places.
                  { \fp_eval:n { round(\l__terminaltrees_scale_fp *
                      \dim_to_fp:n {\g__terminaltrees_smallest_font_dim},2) } }
                  { \dim_use:N \l__terminaltrees_minimum_font_dim } }
              {
                \box_scale:Nnn \l__terminaltrees_tree_box
                  {\fp_use:N \l__terminaltrees_scale_fp}
                  {\fp_use:N \l__terminaltrees_scale_fp}
                %
                % Keep the chosen scale when moving the tree to the next page.
                \Needspace*{\dim_eval:n {\box_ht:N \l__terminaltrees_tree_box +
                  \box_dp:N \l__terminaltrees_tree_box + \baselineskip}}
                \noindent\makebox[\linewidth][c]{\box_use:N \l__terminaltrees_tree_box}\par
              }
          }
      }
  }

% Parenthesized options cannot consume Forest's opening root bracket.
\NewDocumentEnvironment{fittedterminaltree}{ D(){} +b }
  { \__terminaltrees_fit:nn {#1}{#2} } {}
\ExplSyntaxOff
\endinput