{ stdenv, fetchurl, perl, nettools, java, polyml, z3, rlwrap }:
# nettools needed for hostname

stdenv.mkDerivation rec {
  pname = "isabelle";
  version = "2020";

  dirname = "Isabelle${version}";

  src = if stdenv.isDarwin
    then fetchurl {
      url = "https://isabelle.in.tum.de/website-${dirname}/dist/${dirname}_macos.tar.gz";
      sha256 = "1sfr5filsaqj93g5y4p9n8g5652dhr4whj25x4lifdxr2pp560xx";
    }
    else fetchurl {
      url = "https://isabelle.in.tum.de/website-${dirname}/dist/${dirname}_linux.tar.gz";
      sha256 = "1bibabhlsvf6qsjjkgxcpq3cvl1z7r8yfcgqbhbvsiv69n3gyfk3";
    };

  buildInputs = [ perl polyml z3 ]
             ++ stdenv.lib.optionals (!stdenv.isDarwin) [ nettools java ];

  sourceRoot = dirname;

  postPatch = ''
    patchShebangs .

    cat >contrib/z3*/etc/settings <<EOF
      Z3_HOME=${z3}
      Z3_VERSION=${z3.version}
      Z3_SOLVER=${z3}/bin/z3
      Z3_INSTALLED=yes
    EOF

    cat >contrib/polyml-*/etc/settings <<EOF
      ML_SYSTEM_64=true
      ML_SYSTEM=${polyml.name}
      ML_PLATFORM=${stdenv.system}
      ML_HOME=${polyml}/bin
      ML_OPTIONS="--minheap 1000"
      POLYML_HOME="\$COMPONENT"
      ML_SOURCES="\$POLYML_HOME/src"
    EOF

    cat >contrib/jdk*/etc/settings <<EOF
      ISABELLE_JAVA_PLATFORM=${stdenv.system}
      ISABELLE_JDK_HOME=${java}
    EOF

    echo ISABELLE_LINE_EDITOR=${rlwrap}/bin/rlwrap >>etc/settings

    for comp in contrib/jdk* contrib/polyml-* contrib/z3-*; do
      rm -rf $comp/x86*
    done
    '' + (if ! stdenv.isLinux then "" else ''
    arch=${if stdenv.hostPlatform.system == "x86_64-linux" then "x86_64-linux" else "x86-linux"}
    for f in contrib/*/$arch/{bash_process,epclextract,eprover,nunchaku,SPASS}; do
      patchelf --set-interpreter $(cat ${stdenv.cc}/nix-support/dynamic-linker) "$f"
    done
    '');

  installPhase = ''
    mkdir -p $out/bin
    mv $TMP/$dirname $out
    cd $out/$dirname
    bin/isabelle install $out/bin
  '';

  meta = with stdenv.lib; {
    description = "A generic proof assistant";

    longDescription = ''
      Isabelle is a generic proof assistant.  It allows mathematical formulas
      to be expressed in a formal language and provides tools for proving those
      formulas in a logical calculus.
    '';
    homepage = "https://isabelle.in.tum.de/";
    license = licenses.bsd3;
    maintainers = [ maintainers.jwiegley ];
    platforms = platforms.linux;
  };
}