{
  pkgs,
  ...
}:
let
  inherit (builtins)
    genericClosure
    hasAttr
    length
    map
    ;
  inherit (pkgs) runCommandLocal writeText;
  inherit (pkgs.lib)
    concatLines
    concatLists
    concatMap
    filter
    isDerivation
    isList
    mapAttrsToList
    ;
in
rec {
  drvOutputs = drv: if hasAttr "outputs" drv then map (out: drv.${out}) drv.outputs else [ drv ];
  drvDeps =
    drv:
    mapAttrsToList (
      k: v:
      if isDerivation v then
        (drvOutputs v)
      else if isList v then
        concatMap drvOutputs (filter isDerivation v)
      else
        [ ]
    ) drv;
  drvClosure =
    let
      wrap = drv: {
        key = drv.outPath;
        inherit drv;
      };
    in
    drv:
    map (obj: obj.drv) (genericClosure {
      startSet = map wrap (drvOutputs drv);
      operator = obj: map wrap (concatLists (drvDeps obj.drv.drvAttrs));
    });
  drvMaintainers =
    drv:
    if !hasAttr "meta" drv then
      [ ]
    else if !hasAttr "maintainers" drv.meta then
      [ ]
    else
      drv.meta.maintainers;
  nobodyMaintains =
    drv: hasAttr "meta" drv && hasAttr "maintainers" drv.meta && (length drv.meta.maintainers) == 0;
  stringJoin = objToString: objs: writeText "txt" (concatLines (map objToString objs));

  allMaintainers =
    drv:
    let
      closure = drvClosure drv;
      maintainers = concatMap drvMaintainers closure;
      mainToString = m: "${m.name} (${m.email})";
    in
    runCommandLocal "uniq-maintainers.txt" { } ''
      <${stringJoin mainToString maintainers} sort | uniq -c > $out
    '';

  noMaintainers =
    drv:
    let
      closure = drvClosure drv;
      unmaintained = filter nobodyMaintains closure;
      drvToString = drv: "${drv.name} ${drv.meta.position}";
    in
    runCommandLocal "no-maintainers.txt" { } ''
      <${stringJoin drvToString unmaintained} sort -u \
        | sed 's/\/nix\/store\/[^/]*/https:\/\/github.com\/NixOS\/nixpkgs\/blob\/master/' \
        | sed 's/.nix:\(.*\)$/.nix#L\1/' \
        | ${pkgs.unixtools.column}/bin/column -t \
        > $out
    '';
}