BibLaTeX automatic textcite/footcite

Question

I would like BibLaTeX to automatically change the citation style. If the whatever called cite command (in my case, I only use \citet[]{} [w/ or w/o optional argument]) is located inside a footnote, the result should look like this

\citet[20]{Doe:2018}: Doe (2018) 20.

To achieve this, I have already set up a boolean variable

\newif\ifinfootnote  
\let\svfootnote\footnote  
\renewcommand{\footnote}[2][\thefootnote]{%  
    \stepcounter{footnote}%  
    \gdef\infootnote{T}%  
    \svfootnote[#1]{\infootnotetrue#2}%  
}

that checks if you are inside a footnote environment. -- Thanks to @moewe for pointing that out (previous question).

The in text citation is already satisfying my needs

\citet[20]{Doe:2018}: Doe (2018, 20).

Please seethe attached cbx file.

As far as I can see, the solution would look nearly like this

\renewcommand{\citet}[2][]{%
    \if T\infootnote%
        % code for footnote citation
    \else%
        % code for in text citation
    \fi%
}

My cbx file (epicstructure.cbx):

\ProvidesFile{epicstructure.cbx}
[\abx@cbxid]

\ExecuteBibliographyOptions{labeldateparts,uniquename,uniquelist,autocite=inline}

\renewcommand*{\iffinalcitedelim}{\iflastcitekey}

\newbool{cbx:parens}

\newbibmacro*{cite}{%
  \iffieldundef{shorthand}
    {\ifthenelse{\ifnameundef{labelname}\OR\iffieldundef{labelyear}}
       {\usebibmacro{cite:label}%
        \setunit{\printdelim{nonameyeardelim}}}
       {\printnames[bibhyperref]{labelname}%
        \setunit{\printdelim{nameyeardelim}}}%
     \usebibmacro{cite:labeldate+extradate}}
    {\usebibmacro{cite:shorthand}}}

\newbibmacro*{citeyear}{%
  \iffieldundef{shorthand}
    {\iffieldundef{labelyear}
       {\usebibmacro{cite:label}}
       {\usebibmacro{cite:labeldate+extradate}}}
    {\usebibmacro{cite:shorthand}}}

\newbibmacro*{textcite}{%
  \ifnameundef{labelname}
    {\iffieldundef{shorthand}
       {\usebibmacro{cite:label}%
        \setunit{%
          \global\booltrue{cbx:parens}%
          \printdelim{nonameyeardelim}\bibopenparen}%
        \ifnumequal{\value{citecount}}{1}
          {\usebibmacro{prenote}}
          {}%
        \usebibmacro{cite:labeldate+extradate}}
       {\usebibmacro{cite:shorthand}}}
    {\printnames[bibhyperref]{labelname}%
     \setunit{%
       \global\booltrue{cbx:parens}%
       \printdelim{nameyeardelim}\bibopenparen}%
     \ifnumequal{\value{citecount}}{1}
       {\usebibmacro{prenote}}
       {}%
     \usebibmacro{citeyear}}%
}

\newbibmacro*{cite:shorthand}{%
  \printtext[bibhyperref]{\printfield{shorthand}}}

\newbibmacro*{cite:label}{%
  \iffieldundef{label}
    {\printtext[bibhyperref]{\printfield[citetitle]{labeltitle}}}
    {\printtext[bibhyperref]{\printfield{label}}}}

\newbibmacro*{cite:labeldate+extradate}{%
  \iffieldundef{labelyear}
    {}
    {\printtext[bibhyperref]{\usebibmacro{editionsupscr}\printlabeldateextra}}}

\newbibmacro{cite:labelyear+extrayear}{%
  \blx@warning{bibmacro 'cite:labelyear+extrayear' is deprecated.\MessageBreak
    Please use 'cite:labeldate+extradate'.\MessageBreak
    Using 'cite:labeldate+extradate' instead}%
  \usebibmacro{cite:labeldate+extradate}}

\newbibmacro*{textcite:postnote}{%
  \iffieldundef{postnote}
    {\ifbool{cbx:parens}
       {\bibcloseparen}
       {}}
    {\ifbool{cbx:parens}
       {\setunit{\postnotedelim}}
       {\setunit{\extpostnotedelim\bibopenparen}}%
     \printfield{postnote}\bibcloseparen}}

\DeclareCiteCommand{\cite}
  {\usebibmacro{prenote}}%
  {\usebibmacro{citeindex}%
   \usebibmacro{cite}}
  {\multicitedelim}
  {\usebibmacro{postnote}}

\DeclareCiteCommand*{\cite}
  {\usebibmacro{prenote}}%
  {\usebibmacro{citeindex}%
   \usebibmacro{citeyear}}
  {\multicitedelim}
  {\usebibmacro{postnote}}

\DeclareCiteCommand{\parencite}[\mkbibparens]
  {\usebibmacro{prenote}}%
  {\usebibmacro{citeindex}%
   \usebibmacro{cite}}
  {\multicitedelim}
  {\usebibmacro{postnote}}

\DeclareCiteCommand*{\parencite}[\mkbibparens]
  {\usebibmacro{prenote}}
  {\usebibmacro{citeindex}%
   \usebibmacro{citeyear}}
  {\multicitedelim}
  {\usebibmacro{postnote}}

\DeclareCiteCommand{\footcite}%[\mkbibfootnote]
  {\usebibmacro{prenote}}
  {\usebibmacro{citeindex}%
   \usebibmacro{cite}}
  {\multicitedelim}
  {\usebibmacro{postnote}}

\DeclareCiteCommand{\footcitetext}[\mkbibfootnotetext]
  {\usebibmacro{prenote}}
  {\usebibmacro{citeindex}%
   \usebibmacro{cite}}
  {\multicitedelim}
  {\usebibmacro{postnote}}

\DeclareCiteCommand{\smartcite}[\iffootnote\mkbibparens\mkbibfootnote]
  {\usebibmacro{prenote}}
  {\usebibmacro{citeindex}%
   \usebibmacro{cite}}
  {\multicitedelim}
  {\usebibmacro{postnote}}

\DeclareCiteCommand{\textcite}
  {\boolfalse{cbx:parens}}
  {\usebibmacro{citeindex}%
   \iffirstcitekey
     {\setcounter{textcitetotal}{1}}
     {\stepcounter{textcitetotal}%
      \textcitedelim}%
   \usebibmacro{textcite}}
  {\ifbool{cbx:parens}
     {\bibcloseparen\global\boolfalse{cbx:parens}}
     {}}
  {\usebibmacro{textcite:postnote}}

\DeclareCiteCommand{\citeauthor}
  {\boolfalse{citetracker}%
   \boolfalse{pagetracker}%
   \usebibmacro{prenote}}
  {\ifciteindex
     {\indexnames{labelname}}
     {}%
   \printnames[bibhyperref]{labelname}}
  {\multicitedelim}
  {\usebibmacro{postnote}}

\DeclareCiteCommand*{\citeauthor}
  {\boolfalse{citetracker}%
   \boolfalse{pagetracker}%
   \usebibmacro{prenote}}
  {\ifciteindex
     {\indexnames{labelname}}
     {}%
   \printnames[bibhyperref][1-1]{labelname}}
  {\multicitedelim}
  {\usebibmacro{postnote}}

\DeclareCiteCommand{\citeyear}
  {\boolfalse{citetracker}%
   \boolfalse{pagetracker}%
   \usebibmacro{prenote}}
  {\printfield[bibhyperref]{year}}
  {\multicitedelim}
  {\usebibmacro{postnote}}

\DeclareCiteCommand*{\citeyear}
  {\boolfalse{citetracker}%
   \boolfalse{pagetracker}%
   \usebibmacro{prenote}}
  {\printfield[bibhyperref]{\usebibmacro{editionsupscr}year}\printfield{extradate}}
  {\multicitedelim}
  {\usebibmacro{postnote}}

\DeclareMultiCiteCommand{\textcites}{\textcite}{}

\endinput