How to remove trailing space from the argument in this href-url_encode

Question

The \percentifier in the code below makes sure that we can input e.g. Chinese characters into the first argument of e.g. \href, by converting strings into their percent-encoding using url_encode (for further reference, see also this answer to the OP "How to append a Chinese-character string argument from an environment to first argument of \href").

\percentifier:

\makeatletter
\directlua{function url_encode(str)
  if (str) then
    str = string.gsub (str, "\string\n", "\string\r\string\n")
    str = string.gsub (str, "([^\@percentchar w \@percentchar -\@percentchar _\@percentchar .\@percentchar \string~])",
        function (c) return string.format ("\@percentchar \@percentchar \@percentchar 02X", string.byte(c)) end)
    str = string.gsub (str, " ", "+")
  end
  return str    
end}
\makeatother
%
\def\percentifier#1{\directlua{
tex.print(url_encode('\detokenize{#1}'))
}}

\href:

  \href{http://a.beautiful.url/?searchid=\percentifier{#1}}{Link}%

Another component of our code is the mainentry-environment. Let's assume we need such an environment in our answer. In reality, this environment will have multiple arguments, but of course I minimized/simplified it for the purpose of a MWE. Its first argument will always be used to complete an URL:

mainentry-environment:

\newenvironment {mainentry}
  {\mainentryA}
%
  {\clearpage}
%
\def\mainentryA#1{%
     #1 \href{http://a.beautiful.url/?searchid=\percentifier{#1}}{Link}%
    }{
 }

In the MWE below, notice that the code works perfect for Test1 (since it is presented as Test1%. However, the code does not work well for Test2 (because Tex interprets a trailing space after it, which due to the url_encode adds a +).

Now, my intend is not to change the behavior of changing a space into a +, which should be done to have a properly functioning url_encode. Nevertheless, I do not want Tex to interpret the instance of Test2 as having a trailing space. So, perhaps the solution could be solved in the definition of \percentifier, or if not: in the definition of \mainentryA.

Please note I do NOT want to use Solution 1 or Solution 2 from this answer to another OP entitled "Why is this code outputting clickable URLs for some users, yet not for others?".

I would rather have a solution similar to this answer. Something using \cs_set_eq:NN\Trim\tl_trim_spaces:n or a similar construct. Somehow, I have not been able to do so.

MWE

\documentclass[a4paper]{article}

\usepackage{hyperref}

%%%%%%%
% \percentifier
\makeatletter
\directlua{function url_encode(str)
  if (str) then
    str = string.gsub (str, "\string\n", "\string\r\string\n")
    str = string.gsub (str, "([^\@percentchar w \@percentchar -\@percentchar _\@percentchar .\@percentchar \string~])",
        function (c) return string.format ("\@percentchar \@percentchar \@percentchar 02X", string.byte(c)) end)
    str = string.gsub (str, " ", "+")
  end
  return str    
end}
\makeatother
%
\def\percentifier#1{\directlua{
tex.print(url_encode('\detokenize{#1}'))
}}
%
%%%%%%%

%%%%%%%
% \mainentry
\newenvironment {mainentry}
  {\mainentryA}
%
  {\clearpage}
%
\def\mainentryA#1{%
     #1 \href{http://a.beautiful.url/?searchid=\percentifier{#1}}{Link}%
    }{
 }
%
%%%%%%%

\begin{document}

\begin{mainentry}{%
Test1%
}
\end{mainentry}

\begin{mainentry}{%
Test2
}
\end{mainentry}

\end{document}

Answer 1

For stripping trailing space from an argument you can use the \stripspace macro defined by following two lines:

\def\stripspace#1#2{\stripspaceA#2\end/ \end/\relax#1{#2}}
\def\stripspaceA#1 \end/#2\relax#3#4{\if\relax#2\relax#3{#4}\else#3{#1}\fi}

\def\percentifier#1{[#1]} % just for testing

\stripspace\percentifier {text1 and text}
\stripspace\percentifier {text2 and text }
without stripping: \percentifier{text3 and text }

\bye

This is full expandable solution.

In your application you can replace

\href{http://a.beautiful.url/?searchid=\percentifier{#1}}{Link}%

by

\href{http://a.beautiful.url/?searchid=\stripspace\percentifier{#1}}{Link}%