How does one organize each chapter's endnotes at the end of every part?

Question

Let's say I have endnotes running with alpha structure: a, b, c, d, e, ...

Normally, I can run endnotes at every chapter, and reset the counter...

\documentclass{report}
\usepackage{endnotes}
\renewcommand*{\theendnote}{\alph{endnote}}
\begin{document}

\chapter{First}
Testing.\endnote{First test.}
\theendnotes

\setcounter{endnote}{0}

\chapter{Next}
Again.\endnote{Second test.}
\theendnotes

\end{document}

How would I run 1+ chapters within a part and then have \theendnotes print the endnotes, by chapter?

Would this require a more sophisticated counter ... an array counter \newcounter{endnotecounter}[chapter] ???

Maybe something like this?

\documentclass{report}
\usepackage{endnotes}
\renewcommand*{\theendnote}{\alph{endnote}}
\begin{document}
\part{Part I}

\chapter{First}
Testing.\endnote{First test.}


\setcounter{endnote}{0} % this needs to be cached so next chapter isn't purged

\chapter{Next}
Again.\endnote{Second test.}


NOTES for Part I:

\theendnotesbychapterinpart

\end{document}

Answer 1

This seems a fully functional implementation of your requirements.

\documentclass{book}
\usepackage{endnotes}
\usepackage{alphalph}

\renewcommand{\theendnote}{\alphalph{\value{endnote}}}
\newcommand{\resetendnotes}{%
  \setcounter{endnote}{0}%
  \addtoendnotes{%
    \par\protect\addvspace{\topsep}%
    \noindent\textbf{Chapter \thechapter}\par\nobreak
    \protect\addvspace{\topsep}%
  }%
}
\renewcommand{\notesname}{Notes for part \thepart}

\begin{document}

\part{First part}

\chapter{First chapter}
\resetendnotes

\count255=0
\loop\ifnum\count255<50
\advance\count255 by 1
x\endnote{x}
\repeat

\chapter{First chapter}
\resetendnotes

\count255=0
\loop\ifnum\count255<50
\advance\count255 by 1
y\endnote{y}
\repeat

\clearpage
\theendnotes

\part{Second part}

\chapter{Third chapter}
\resetendnotes

\count255=0
\loop\ifnum\count255<50
\advance\count255 by 1
a\endnote{a}
\repeat

\chapter{Fourth chapter}
\resetendnotes

\count255=0
\loop\ifnum\count255<50
\advance\count255 by 1
b\endnote{b}
\repeat

\clearpage
\theendnotes

\end{document}

Answer 2

The end notes only get purged if you use \theendnotes. Note: You can include \thechapter as part of \theendnote, but it looks better without.

\documentclass{report}
\usepackage{endnotes}
\renewcommand*{\theendnote}{\alph{endnote}}
\begin{document}
\part{Part I}

\chapter{First}
\addtoendnotes{\medskip\noindent\textbf{\normalsize\chaptername~\thechapter}\par\medskip}%

Testing.\endnote{First test.}

\setcounter{endnote}{0}%
\chapter{Next}
\addtoendnotes{\medskip\noindent\textbf{\normalsize\chaptername~\thechapter}\par\medskip}%

Again.\endnote{Second test.}

\clearpage
NOTES for Part I:
\theendnotes

\end{document}