Formatting Table of Contents so it has Chapter in front of every chapter and appendix in front of every appendix

Question

I've searched for days and unfortunately could not find the solution to my problem.

Consider the following minimal example, it produces a ToC as follows:

This is not the one I need. I need the following ToC:

Contents

   Chapter 1: Ch1   .............................. 3 
           1.1: Sec 1    .............................. 3 
           1.2: Sec 2    .............................. 4 
   Chapter 2: Ch2   .............................. 7 
           2.1: Sec 1    .............................. 7 
           2.2: Sec 2    .............................. 8
Appendix A: App1 .............................. 11
           A.1: Sec 1    .............................. 11
           A.2: Sec 2    .............................. 12
Appendix B: App2 .............................. 15
           B.1: Sec 1    .............................. 15
           B.2: Sec 2    .............................. 16

I have tried the following packages, but could not make them work: tocloft, titletoc and titlesec. I use TeXLive 2017 (XeLaTeX).

Minimal Code:

\documentclass[a4paper,10pt,twoside]{book}
\usepackage{lipsum} % for dummy text only

\begin{document}
    \tableofcontents

    \chapter{Ch1}
        \section{Sec1}
            \lipsum
        \section{Sec2}
            \lipsum
    \chapter{Ch2}
        \section{Sec1}
            \lipsum
        \section{Sec2}
            \lipsum
    \appendix
    \chapter{App1}
        \section{Sec1}
            \lipsum
        \section{Sec2}
            \lipsum
    \chapter{App2}
        \section{Sec1}
            \lipsum
        \section{Sec2}
            \lipsum 


\end{document}

Answer 1

This is based on this answer but adds \l@appendix for appendices. Specifically, it modifies the \@chapter macro from book to use \chapterhandler instead of chapter in \addcontentsline. One must reset it to appendix manually (unless you also want to modify the \appendix definition).

\documentclass[a4paper,10pt,twoside]{book}
\usepackage{lipsum} % for dummy text only
%\usepackage{appendix}

\makeatletter
    \renewcommand*\l@chapter[2]{%
  \ifnum \c@tocdepth >\m@ne
    \addpenalty{-\@highpenalty}%
    \vskip 1.0em \@plus\p@
    \setlength\@tempdima{1.5em}%
    \begingroup
      \settowidth{\@tempdimb}{\normalsize\bfseries \chaptername~}%
      \advance\leftskip by \@tempdimb
      \parindent \z@ \rightskip \@pnumwidth
      \parfillskip -\@tempdima
      \leavevmode \bfseries
      \advance\leftskip\@tempdima
      \hskip -\leftskip
      \chaptername~#1\nobreak\hfil \nobreak\hb@xt@\@pnumwidth{\hss #2}\par
      \penalty\@highpenalty
    \endgroup
  \fi}

\newcommand*\l@appendix[2]{%
  \ifnum \c@tocdepth >\m@ne
    \addpenalty{-\@highpenalty}%
    \vskip 1.0em \@plus\p@
    \setlength\@tempdima{1.5em}%
    \begingroup
      \settowidth{\@tempdimb}{\normalsize\bfseries \appendixname~}%
      \advance\leftskip by \@tempdimb
      \parindent \z@ \rightskip \@pnumwidth
      \parfillskip -\@tempdima
      \leavevmode \bfseries
      \advance\leftskip\@tempdima
      \hskip -\leftskip
      \appendixname~#1\nobreak\hfil \nobreak\hb@xt@\@pnumwidth{\hss #2}\par
      \penalty\@highpenalty
    \endgroup
  \fi}

\newcommand{\chapterhandler}{chapter}

\def\@chapter[#1]#2{\ifnum \c@secnumdepth >\m@ne
                       \if@mainmatter
                         \refstepcounter{chapter}%
                         \typeout{\@chapapp\space\thechapter.}%
                         \addcontentsline{toc}{\chapterhandler}%
                                   {\protect\numberline{\thechapter}#1}%
                       \else
                         \addcontentsline{toc}{\chapterhandler}{#1}%
                       \fi
                    \else
                      \addcontentsline{toc}{\chapterhandler}{#1}%
                    \fi
                    \chaptermark{#1}%
                    \addtocontents{lof}{\protect\addvspace{10\p@}}%
                    \addtocontents{lot}{\protect\addvspace{10\p@}}%
                    \if@twocolumn
                      \@topnewpage[\@makechapterhead{#2}]%
                    \else
                      \@makechapterhead{#2}%
                      \@afterheading
                    \fi}
\makeatother

\begin{document}
    \tableofcontents

    \chapter{A very long chapter title just to test the hanging indentation}
        \section{Sec1}
            \lipsum
        \section{Sec2}
            \lipsum
    \chapter{Ch2}
        \section{Sec1}
            \lipsum
        \section{Sec2}
            \lipsum
    \appendix
    \renewcommand{\chapterhandler}{appendix}
    \chapter{A very long appendix title just to test the hanging indentation}
        \section{Sec1}
            \lipsum
        \section{Sec2}
            \lipsum
    \chapter{App2}
        \section{Sec1}
            \lipsum
        \section{Sec2}
            \lipsum 

\end{document}