# This function downloads and unpacks an archive file, such as a zip
# or tar file. This is primarily useful for dynamically generated
# archives, such as GitHub's /archive URLs, where the unpacked content
# of the zip file doesn't change, but the zip file itself may
# (e.g. due to minor changes in the compression algorithm, or changes
# in timestamps).

{ lib, fetchurl, unzip }:

{ # Optionally move the contents of the unpacked tree up one level.
  stripRoot ? true
, url
, ... } @ args:

fetchurl ({
  name = args.name or (baseNameOf url);

  recursiveHash = true;

  downloadToTemp = true;

  postFetch =
    ''
      export PATH=${unzip}/bin:$PATH
      mkdir $out
      cd $out
      renamed="$TMPDIR/${baseNameOf url}"
      mv "$downloadedFile" "$renamed"
      unpackFile "$renamed"
    ''
    # FIXME: handle zip files that contain a single regular file.
    + lib.optionalString stripRoot ''
      shopt -s dotglob
      if [ "$(ls -d $out/* | wc -l)" != 1 ]; then
        echo "error: zip file must contain a single directory."
        exit 1
      fi
      fn=$(cd "$out" && echo *)
      mv $out/$fn/* "$out/"
      rmdir "$out/$fn"
    '';
} // args)