note-verbale.cls

\NeedsTeXFormat{LaTeX2e}
\RequirePackage{expl3}
\ProvidesExplClass
  {note-verbale}
  {2015/02/10}
  {1}
  {Class for enbassy notes}

\LoadClass[12pt]{article}

\RequirePackage{xparse}

\RequirePackage [ margin = 1in ] { geometry }
\RequirePackage { graphicx }
\RequirePackage { textcomp }
\RequirePackage { datetime }
\RequirePackage { fancyhdr }
\pagestyle{fancy}
\renewcommand\headrulewidth{0pt}

\fancyhf{}
\rhead{
  Continuation~ of~ Note~ \textnumero\nobreakspace

  \int_use:N \g_noteverbale_date_day_int
  \slash
  \int_use:N \g_noteverbale_date_month_int
  \slash
  \int_use:N \g_noteverbale_date_year_int
}

\cs_new:Npn \noteverbale_parse_date:nNNN
  #1 #2 #3 #4
 {
  \noteverbale_parse_date_internal:nnnNNN
  #1 \q_stop: #2 #3 #4
 }

\cs_new:Npn \noteverbale_parse_date_internal:nnnNNN
 #1-#2-#3 \q_stop: #4 #5 #6
 {
   \int_set:Nn #4 {#1}
   \int_set:Nn #5 {#2}
   \int_set:Nn #6 {#3}
 }

\tl_new:N  \g_noteverbale_city_tl
\tl_new:N  \g_noteverbale_country_tl
\int_new:N \g_noteverbale_date_month_int
\int_new:N \g_noteverbale_date_day_int
\int_new:N \g_noteverbale_date_year_int
\tl_new:N  \g_noteverbale_seal_tl

\keys_define:nn { note-verbale } {
  city    .tl_set:N  = \g_noteverbale_city_tl,
  country .tl_set:N  = \g_noteverbale_country_tl,
  date    .code:n    = {
    \noteverbale_parse_date:nNNN
      {#1}
      \g_noteverbale_date_year_int
      \g_noteverbale_date_month_int
      \g_noteverbale_date_day_int
  },
  seal    .tl_set:N  = \g_noteverbale_seal_tl,

  city    .value_required:,
  country .value_required:,
  month   .value_required:,
  day     .value_required:,
  seal    .default:n = { example-image-a },
  % Customize the above to provide a reasonable default
}

\NewDocumentCommand \Information { m } {
  \keys_set:nn { note-verbale } { #1 }
}

\RenewDocumentCommand \maketitle { } {
  \thispagestyle{empty}
  \begin{minipage}{.25\textwidth}
    \includegraphics [
      width = \textwidth,
    ] {
      \g_noteverbale_seal_tl
    }
  \end{minipage}
  \hfill
  \begin{minipage}{.6\textwidth}
    \color{blue}
    \sffamily
    \centering

    EMBAIXADA~ DO~ BRASIL~ --~ EMBASSY~ OF~ BRAZIL
    \par\vspace{1ex}
    \tl_use:N \g_noteverbale_city_tl
    \par\vspace{1ex}
    NOME~ DO~ PA\'IS~ --~
    \tl_use:N \g_noteverbale_country_tl
  \end{minipage}
  \par\vspace*{1cm}
  Note~ \textnumero\nobreakspace

  \int_use:N \g_noteverbale_date_day_int
  \slash
  \int_use:N \g_noteverbale_date_month_int
  \slash
  \int_use:N \g_noteverbale_date_year_int

  \par\vspace*{1cm}

  The~ Embassy~ of~ Brazil~ in~

  \tl_use:N \g_noteverbale_city_tl {}~

  presents~ its~ compliments~ to~ the~ Ministry~ of~ Foreign~ Affairs~
  and~ has~ the~ honour~ to

  \par
}

\setlength\parskip{2ex}
\setlength\parindent{.5in}

\AtEndDocument{

  \par

  The~ Embassy~ of~ Brazil~ avails~ itself~ of~ this~ opportunity~ to~
  renew~ to~ the~ Ministry~ of~ Foreign~ Affaris~ the~ assurances~ of~
  its~ highest~ consideration.

  \par

  \tl_use:N \g_noteverbale_city_tl,~
  \shortmonthname [
    \int_use:N \g_noteverbale_date_month_int
  ]
  \nobreakspace
  \int_use:N \g_noteverbale_date_day_int,~
  \int_use:N \g_noteverbale_date_year_int
}

note.tex

\documentclass{note-verbale}

\Information{
  seal = example-image-a,
  city = City of Sans Seriffe,
  country = Denmark,
  date = 2015-02-10,
}

\usepackage{mwe}
\begin{document}
\maketitle
\lipsum
\end{document}