Tikz matrix with array below and braces

Question

I am trying to achieve a table similar to the picture below. I have almost made it, but I can't figure out how to put the row with "a_{1n} ..." below the matrix so that it matches to rows.

\documentclass{article}
\usepackage{amsmath}
\usepackage{tikz}
\usetikzlibrary{decorations.pathreplacing,matrix}
\tikzset{ 
table/.style={
  matrix of math nodes,
  row sep=-\pgflinewidth,
  column sep=-\pgflinewidth,
  nodes={rectangle,text width=3em,align=center},
  text depth=1.25ex,
  text height=2.5ex,
  nodes in empty cells,
  left delimiter=[,
  right delimiter={]},
  ampersand replacement=&
}
}
\begin{document}
[
A=
\begin{tikzpicture}[baseline,decoration=brace]
\matrix (m) [table] {
    1 & 0 & \cdots & 0 & \lvert & 1 & 1 & \cdots & 1 \
    0 & 1 & \cdots & 0 & \lvert  & 0 & 0 & \cdots & 0 \
    \vdots & \vdots &  \ddots & 0 & \lvert & \vdots & \vdots &\ddots& \vdots \
    0 & 0 & \cdots & 1 & \lvert & 0 & 0 & \cdots & 0 \
    \textrm{--} & \textrm{--} & \textrm{--} & \textrm{--} & \textrm{--}& \textrm{--} & \textrm{--} & \textrm{--} & \textrm{--} \
    0 & 0 & \cdots & 0 & \lvert & 1 & 0 & \cdots & 1 \
    0 & 0 & \cdots & 0 & \lvert  & 0 & 1 & \cdots & 0 \
    \vdots & \vdots &  \ddots & 0 & \lvert & \vdots & \vdots &\ddots& \vdots \
    1 & 1 & \cdots & 1 & \lvert & 0 & 0 & \cdots & 1 \
};
    \draw[decorate,transform canvas={xshift=-1.4em},thick] (m-4-1.south west) -- node[left=2pt] {$m$} (m-1-1.north west);

    \draw[decorate,transform canvas={xshift=-1.4em},thick] (m-9-1.south west) -- node[left=2pt] {$n$} (m-6-1.north west);
    \draw[decorate,transform canvas={yshift=0.5em},thick] (m-1-1.north west) -- node[above=2pt] {$m$} (m-1-4.north east);
    \draw[decorate,transform canvas={yshift=0.5em},thick] (m-1-6.north west) -- node[above=2pt] {$n-1$} (m-1-9.north east);
\end{tikzpicture}
]
\end{document}

Answer 1

Here are two solutions:

1. First one completing your code (full tikz matrix)
2. Second one with both nicematrix and tikz

Code

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{decorations.pathreplacing,matrix,calc,positioning}
\usepackage{nicematrix}
\tikzset{ 
    table/.style={
        matrix of math nodes,
        row sep=-\pgflinewidth,
        column sep=-\pgflinewidth,
        nodes={rectangle,text width=3em,align=center},
        text depth=1.25ex,
        text height=2.5ex,
        nodes in empty cells,
        left delimiter=[,
        right delimiter={]},
        ampersand replacement=\&
    }
}
\begin{document}
    [
    A=
    \begin{tikzpicture}[baseline,decoration=brace]
    \matrix (m) [table] {
        1 & 0 & \cdots & 0 & & 1 & 1 & \cdots & 1 \
        0 & 1 & \cdots & 0 & & 0 & 0 & \cdots & 0 \
        \vdots & \vdots &  \ddots & 0 & & \vdots & \vdots &\ddots& \vdots \
        0 & 0 & \cdots & 1 & & 0 & 0 & \cdots & 0 \
        0 & 0 & \cdots & 0 & & 1 & 0 & \cdots & 1 \
        0 & 0 & \cdots & 0 &  & 0 & 1 & \cdots & 0 \
        \vdots & \vdots &  \ddots & 0 & & \vdots & \vdots &\ddots& \vdots \
        1 & 1 & \cdots & 1 & & 0 & 0 & \cdots & 1 \
    };
    \node [above=.5em of m-1-1.north, anchor=south] {$a_{1n}$};
    \node [above=.5em of m-1-2.north, anchor=south] {$a_{2n}$};
    \node [above=.5em of m-1-3.north, anchor=south] {$\ldots$};
    \node [above=.5em of m-1-4.north, anchor=south] {$a_{mn}$};
    \node [above=.5em of m-1-6.north, anchor=south] {$a_{11}$};
    \node [above=.5em of m-1-7.north, anchor=south] {$a_{12}$};
    \node [above=.5em of m-1-8.north, anchor=south] {$\ldots$};
    \node [above=.5em of m-1-9.north, anchor=south] {$a_{1n-1}$};
    \draw[decorate,transform canvas={xshift=1.4em},thick] (m-1-9.north east) -- node[right=2pt] {$m$} (m-4-9.south east); % right
    \draw[decorate,transform canvas={xshift=1.4em},thick] (m-5-9.north east) -- node[right=2pt] {$n$} (m-8-9.south east); % right
    \draw[decorate,transform canvas={yshift=-.5em},thick] (m-8-4.south east) -- node[below=2pt] {$m$} (m-8-1.south west); % below
    \draw[decorate,transform canvas={yshift=-.5em},thick] (m-8-9.south east) -- node[below=2pt] {$n-1$} (m-8-6.south west); % below
    \draw [dotted] (m-1-5.north) -- (m-8-5.south);
    \draw [dotted] (m-4-1.south west) -- (m-4-9.south east);
    \end{tikzpicture}
    ]
$A''=\begin{pNiceMatrix}[first-row,%
code-before =
{
    \tikz \draw[decorate, decoration=brace,transform canvas={xshift=1.4em},thick] (row-1-|col-10) -- node[right=2pt] {$m$} (row-5-|col-10); % right
    \tikz \draw[decorate, decoration=brace,transform canvas={xshift=1.4em},thick] (row-5-|col-10) -- node[right=2pt] {$n$} (row-9-|col-10); % right
    \tikz \draw[decorate, decoration=brace,transform canvas={yshift=-.5em},thick] (row-9-|col-5) -- node[below=2pt] {$m$} (row-9-|col-1); % below
    \tikz \draw[decorate, decoration=brace,transform canvas={yshift=-.5em},thick] (row-9-|col-10) -- node[below=2pt] {$n-1$} (row-9-|col-6); % below
}
]
    a_{1n} & a_{2n} & \Cdots & a_{mn} && a_{11} & a_{12} & \Cdots & a_{1n-1}\\
    1 & 0 & \Cdots & 0 & \Vdotsfor{8} & 1 & 1 & \Cdots & 1\\
    0 & 1 & \Cdots & 0 &              & 0 & 0 & \Cdots & 0\\
    \Vdots & \Vdots & \Ddots & \Vdots & & \Vdots & \Vdots & \Ddots & \Vdots\\
    0 & 0 & \Cdots & 1 & & 0 & 0 & \Cdots & 0\\
    \hdottedline
    0 & 0 & \Cdots & 0 & & 1 & 0 & \Cdots & 0\\
    0 & 0 & \Cdots & 0 & & 0 & 1 & \Cdots & 0\\
    \Vdots & \Vdots & \Ddots & \Vdots & & \Vdots & \Vdots & \Ddots & \Vdots\\
    1 & 1 & \Cdots & 1 & & 0 & 0 & \Cdots & 1
\end{pNiceMatrix}$


\end{document}

Result

Answer 2

Here is what you can do with the latest version of nicematrix.

\documentclass{article}
\usepackage{nicematrix,tikz}
\begin{document}
$A=\begin{pNiceArray} [first-row,last-col,xdots/line-style=loosely dotted] {cccc:cccc}
a_{1n} & a_{2n} & \Cdots & a_{mn} & a_{11} & a_{12} & \Cdots & a_{1n-1} \hspace*{-6pt}\
1      & 0      & \Cdots & 0      & 1      & 1      & \Cdots & 1        & \Block{4-1}{\quad m}\
0      & 1      & \Cdots & 0      & 0      & 0      & \Cdots & 0 \
\Vdots & \Vdots & \Ddots & \Vdots & \Vdots & \Vdots & \Ddots & \Vdots \
0      & 0      & \Cdots & 1      & 0      & 0      & \Cdots & 0 \
\hdottedline
0      & 0      & \Cdots & 0      & 1      & 0      & \Cdots & 0        & \Block{4-1}{\quad n}\
0      & 0      & \Cdots & 0      & 0      & 1      & \Cdots & 0 \
\Vdots & \Vdots & \Ddots & \Vdots & \Vdots & \Vdots & \Ddots & \Vdots \
1      & 1      & \Cdots & 1      & 0      & 0      & \Cdots & 1
\CodeAfter
  \UnderBrace{last-1}{last-4}{m\vphantom{1}}[shorten,yshift=1.1mm]
  \UnderBrace{last-5}{last-8}{n-1}[shorten,yshift=1.1mm]
  \SubMatrix{.}{1-1}{4-last}{}}[xshift=2mm]
  \SubMatrix{.}{5-1}{last-last}{}}[xshift=2mm]
\end{pNiceArray}$
\end{document}