根据页面长度具有不同页眉和页脚外观的正式信函

Question

我正在尝试写一封正式信函。我遇到的问题是如何fancyhdr正确使用。我希望实现以下目标：

---

• 如果只有一页：
  • 仅页眉和页脚 - 没有页码。

---

• 如果超过一页：
  • 第一页的特定页眉
  • 最后一页的特定页脚
  • 所有页面的页码

---

代码已包含在内。

 % !TEX TS-program = lualatex
\documentclass{letter}
\usepackage{geometry}
\geometry{letterpaper}
\usepackage{setspace}
\usepackage[ddmmmyyyy]{datetime} 
\usepackage{fancyhdr}
\usepackage{fontspec}
\usepackage{lipsum}

\fancypagestyle{first-page}{
      \fancyhf{}% No header/footer
    \fancyhead[C]{ABC}
    \fancyfoot[R]{\thepage}% Right footer
    \renewcommand{\headrulewidth}{0.4pt}% No header rule
        \renewcommand{\footrulewidth}{0.4pt}% A footer rule
    }
}

\fancypagestyle{default}{
    \fancyhf{}% No header/footer
    \fancyfoot[R]{\thepage}% Right footer
    \renewcommand{\footrulewidth}{0.4pt}% A footer rule
}

\fancypagestyle{last-page}{
      \fancyhf{}% No header/footer
    \fancyfoot[C]{ABC}% Centre footer
    \fancyfoot[R]{\thepage}% Right footer
    \renewcommand{\footrulewidth}{0.4pt}% A footer rule
}

\AtBeginDocument{\thispagestyle{first-page}}
\AtEndDocument{\thispagestyle{last-page}}
\begin{document}

\raggedleft
\today

\normalsize Receiver\leavevmode \\ \small Address \leavevmode \\ \small Etc \leavevmode%

\raggedright        

        \normalsize Dear Receiver,

\lipsum[1-6]



        \normalsize Sender \leavevmode \\

        \small  Sender Address \leavevmode \\ \small

        Sender address etc \leavevmode \\ \small


\end{document}

2020.01.27 更新

我能够使用以下代码解决我的问题：

% !TEX TS-program = lualatex
\documentclass{letter}
\usepackage{lastpage}
\usepackage{refcount}
\usepackage{zref-lastpage}
\usepackage{hyperref}
\usepackage{etoolbox}
\usepackage{ifthen}
\usepackage{lipsum,fancyhdr}
\usepackage{geometry}
\geometry{letterpaper}
\usepackage{setspace}
\usepackage[ddmmmyyyy]{datetime} 


\pagestyle{fancy}

\makeatletter
\newcommand{\LastPageNumber}{\zref@extractdefault{LastPage}{page}{0}}
\makeatother

\begin{document}
    \ifnumcomp{\getpagerefnumber{LastPage}}{>}{1}
    %for multiple pages header
    {{\fancyhead[C]{\ifthenelse{\value{page}=1}{First Page of Multiples}{Other pages of Multiples}}}}
    %for only one page
    {\fancyhead[C]{Single Page Header}
    } 
    \ifnumcomp{\getpagerefnumber{LastPage}}{>}{1}
    %for multiple pages header
    {{
            \fancyfoot[R]{\thepage}
            \fancyfoot[C]{\ifnum\value{page}<\LastPageNumber
                \textit{Continue Multiple Pages}%
                \else
                \textit{Final Page End}
                \fi
             }}}
    %for only one page
    {\fancyfoot[C]{Single Page End}} 
    % If document is longer than 2 pages there will be page numeration, if not there will     not be.
    \lipsum[1-10] % automatically remove page number in a document with this line
\end{document}