Nice footnote cite

ffcite.tex

\ExecuteBiblatexOptions{citestyle=numeric-comp}

\makeatletter
\let\ffcitepre\empty
\let\ffcitepost\empty
\DeclareCiteCommand{\cite}[\mkbibbrackets]
	{%
		\usebibmacro{cite:init}%
		\usebibmacro{prenote}%
	}
	{%
		\usebibmacro{citeindex}%
		\usebibmacro{cite:comp}%
		\ifciteseen{}{%
			\csnumgdef{cbx@instcount\thefield{entrykey}}{-100}%
		}%
	}
	{}
	{%
		\usebibmacro{cite:dump}%
		\usebibmacro{postnote}%
	}

\DeclareCiteCommand{\@ffcite}[\cbx@ff]
	{%	% precode start
		\usebibmacro{cite:init}%
		%precode end
	}
	{%	% loop code
		\usebibmacro{citeindex}%
		\gdef\cbx@citekey{\thefield{entrykey}}%
		\ifciteseen
			{}% if true, empty
			{%	% if false
				% if cite for the first time
				% the the fakecount to -100
				% this will only run at first cite?
%				\BibliographyWarning{\cbx@citekey is unseen, ignoring ffcite }%
				\csnumgdef{cbx@instcount\cbx@citekey}{-100}%
			}%
		% end ifciteseen
		% when meet a cite within the same page...
		% compare two item defined by instcount and the fakecount
		\ifsamepage%
			{\value{instcount}} % first value
			{\number\csuse{cbx@instcount\cbx@citekey}}% the value previously set
			{}% do nothing if they are the same 
			{% write a footnote if not
				\xappto{\cbx@citehook}{%
					\noexpand\footnotetext[\thefield{labelnumber}]{%
						\fullcite{\thefield{entrykey}}%
					}%
				}%
%				\gdef\@makefnmark\old@makefnmark
			}%
		\csnumgdef{cbx@instcount\cbx@citekey}{\value{instcount}}%
%		\usebibmacro{cite:comp}%
	 	% end loop code
	}
	{}
	{\usebibmacro{cite:dump}}

\newrobustcmd{\cbx@ff}[1]{%
	\mkbibsuperscript{#1}%
	\cbx@citehook%
	\global\let\cbx@citehook=\empty%
}
\let\cbx@citehook=\empty

\newcommand{\ffcite}[1]{%
	\let\old@makefnmark\@makefnmark%
	\let\oldthefootnote\thefootnote
	\renewcommand{\thefootnote}{[\arabic{footnote}]}
	\renewcommand{\@makefnmark}{\makebox{\normalfont\@thefnmark}}%
	\@ffcite{#1}%
	\renewcommand{\thefootnote}{\oldthefootnote}
	\renewcommand{\@makefnmark}{\old@makefnmark}%
}

\makeatother