% ========================================================================
% Progress Navigation Bar for Beamer
% ========================================================================
% Usage: \input{progress-navbar.tex} in the preamble (after \usetheme)
%
% Features:
%   - Dynamic equal-width boxes: each box = (paperwidth - 50pt) / total frames
%   - Three-level symbols: ≡ (home), 1/2/3 (section), ◆ (subsection), - (slide)
%   - Teal progress coloring: visited = teal!60 fill, unvisited = hollow
%   - Clickable hyperlinks on every box
%   - Automatic section/subsection title pages
%   - Requires --runs 2 for correct width calculation
%
% Customization:
%   - Change "teal!60" to any color (e.g. myblue!60) for different themes
%   - Change "teal" in \color{teal}\hrule for the top separator line
% ========================================================================

\makeatletter

% ── Auto section/subsection title pages ─────────────────────────────────
\AtBeginSection[]{\frame{\sectionpage}}
\AtBeginSubsection[]{\frame{\subsectionpage}}

% ── Lengths and counters ────────────────────────────────────────────────
\newlength{\my@unitwidth}
\newlength{\my@tempsize}
\newcounter{my@sectnum}

% ── Helper: extract last digit of section number ────────────────────────
\newcommand{\my@lastdigit}[1]{%
  \loop\ifnum\value{#1}>9\addtocounter{#1}{-10}\repeat
  {\normalfont\arabic{#1}}%
}

% ── Box primitives ──────────────────────────────────────────────────────
\newcommand\my@fixedbox[2]{%
  \makebox[#1]{\rule[-1ex]{0pt}{3.25ex}#2}%
}

\newcommand\my@colorbox[3]{%
  {\setlength{\fboxsep}{0pt}\colorbox{#1}{\my@fixedbox{#2}{#3}}}%
}

% ── Level marker: b=section, m=subsection, s=slide ─────────────────────
\def\my@temptext{}
\def\my@level{s}

\newcommand{\my@navbox}[1][]{%
  \if\relax\detokenize{#1}\relax
    \def\my@tempbox{\my@fixedbox}%
  \else
    \def\my@tempbox{\my@colorbox{#1}}%
  \fi
  \if b\my@level
    \def\my@temptext{\my@lastdigit{my@sectnum}}%
  \fi
  \if m\my@level
    \def\my@temptext{$\diamond$}%
  \fi
  \if s\my@level
    \def\my@temptext{$-$}%
  \fi
  \my@tempbox{\my@unitwidth}{\my@temptext}%
}

% ── Navigation box templates (home / done / todo) ──────────────────────
\defbeamertemplate{navigation box}{home}{%
  \my@colorbox{teal!60}{\my@unitwidth}{$\equiv$}%
}

\defbeamertemplate{navigation box}{done}{%
  \my@navbox[teal!60]%
}

\defbeamertemplate{navigation box}{todo}{%
  \my@navbox
}

% ── Box dispatch commands ──────────────────────────────────────────────
\newcommand{\my@bigbox}{\gdef\my@level{b}\usebeamertemplate{navigation box}}
\newcommand{\my@medbox}{\gdef\my@level{m}\usebeamertemplate{navigation box}}
\newcommand{\my@smallbox}{\gdef\my@level{s}\usebeamertemplate{navigation box}}

% ── Hook into Beamer's navigation infrastructure ──────────────────────
\renewcommand{\sectionentry}[5]{\gdef\my@currentbox{big}\setcounter{my@sectnum}{#1}}
\renewcommand{\beamer@subsectionentry}[5]{\gdef\my@currentbox{med}}

\renewcommand{\slideentry}[6]{%
  \def\my@temp@i{1/1}%
  \def\my@temp@ii{#4}%
  % Default: assume done
  \ifx\my@temp@i\my@temp@ii
    \setbeamertemplate{navigation box}[home]%
  \else
    \setbeamertemplate{navigation box}[done]%
  \fi
  % Override to todo if this slide is ahead of current position
  \ifnum\c@section<#1%
    \setbeamertemplate{navigation box}[todo]%
  \else
    \ifnum\c@section=#1\ifnum\c@subsection<#2%
      \setbeamertemplate{navigation box}[todo]%
    \else
      \ifnum\c@subsection=#2\ifnum\c@subsectionslide<#3%
        \setbeamertemplate{navigation box}[todo]%
      \fi\fi
    \fi\fi
  \fi
  % Dispatch to correct level box
  \def\my@test@big{big}%
  \def\my@test@med{med}%
  \ifx\my@temp@i\my@temp@ii
    \beamer@link(#4){\my@bigbox}%
  \else
    \ifx\my@currentbox\my@test@big
      \beamer@link(#4){\my@bigbox}%
    \else\ifx\my@currentbox\my@test@med
      \beamer@link(#4){\my@medbox}%
    \else
      \beamer@link(#4){\my@smallbox}%
    \fi\fi
  \fi
  \gdef\my@currentbox{small}%
}

% ── Footline template ─────────────────────────────────────────────────
\defbeamertemplate{footline}{progress}
{%
  % Dynamic width: divide available space equally among all frames
  \ifnum\inserttotalframenumber>0
    \setlength{\my@unitwidth}{\dimexpr(\paperwidth - 50pt)/\inserttotalframenumber\relax}%
  \else
    \setlength{\my@unitwidth}{20pt}%
  \fi
  {\color{teal}\hrule}%
  \hbox to \paperwidth{%
    \hbox to \dimexpr\paperwidth - 50pt\relax{%
      \kern2pt{\normalfont\dohead}\hfill
    }%
    \hbox to 50pt{%
      \hfill{\normalfont\insertframenumber{}/\inserttotalframenumber}\kern4pt
    }%
  }%
}

% ── Activate ──────────────────────────────────────────────────────────
\setbeamertemplate{navigation symbols}{}
\setbeamertemplate{footline}[progress]

\makeatother