{ lib
, runCommand
, findutils
, badown
, mediafire-dl
, gdown
}:
let

  mkFetcher = mkCmd: {
    name ? "source",
    assert_exists ? [],
    url,
    hash ? lib.fakeHash,
    preferLocalBuild ? true,
  }: runCommand name {
    outputHash = if hash == "" || hash == null then lib.fakeHash else hash;
    outputHashAlgo = null;
    outputHashMode = "recursive";
    inherit preferLocalBuild;
    passthru = { inherit url; };
  } ''
    cd $(mktemp -d)
    ${mkCmd url}
    ${lib.concatMapStringsSep "\n" (fname: ''
      if ! test -s ${lib.escapeShellArg fname}; then
        echo ERROR: file not found: ${lib.escapeShellArg fname}
        echo Files found:
        ${findutils}/bin/find .
        false
      fi
    '') assert_exists}
    if test $(ls | wc -l) -gt 1; then
      mkdir $out
    fi
    cp -v * $out
  '';

in {

  fetchFromDrive = mkFetcher (url:
    "HOME=$(mktemp -d) ${gdown}/bin/gdown ${lib.escapeShellArg url}"
  );

  fetchFromMediafire = mkFetcher (url:
    # TODO: why doesn't this work inside a FOD?
    #"${badown}/bin/badown ${lib.escapeShellArg url}"
    "${mediafire-dl}/bin/mediafire-dl ${lib.escapeShellArg url}"
  );

}