final: prev: {
cascade-installer = prev.writeShellApplication {
  name="cascade-installer";
  runtimeInputs = with final; [ bash git parted util-linux jq ];
  text=''
    usage() {
      1>&2 echo "usage: cascade-installer HOSTNAME BLOCKDEVTONUKE PROFILE"
    }
    if [ -z "$1" ] || [ -z "$2" ] || [ -z "$3" ];then
      usage
      exit 1
    fi
    
    HOSTNAME="$1"
    BLOCKDEVTONUKE="$2"
    PROFILE="$3"

    if ! [ -d /usr/src/cascade/profiles/"$PROFILE" ];then
      1>&2 echo "profile $PROFILE does not exist. possible options:"
      (cd /usr/src/cascade/profiles/ && 1>&2 printf "  %s\n" [a-zA-Z0-9]*)
      exit 1
    fi

    mkdir -p /mnt

    # if the block device has children...
    if lsblk -J "$BLOCKDEVTONUKE" | jq -e '.blockdevices[]|.children' > /dev/null ; then
        1>&2 echo "$BLOCKDEVTONUKE still has partitions.  please clear the block device before installing"
        exit 3
    fi

    parted "$BLOCKDEVTONUKE" -- mklabel gpt
    parted "$BLOCKDEVTONUKE" -- mkpart primary 512MiB -2GiB
    parted "$BLOCKDEVTONUKE" -- mkpart primary linux-swap -2GiB 100%
    parted "$BLOCKDEVTONUKE" -- mkpart ESP fat32 1MiB 512MiB
    parted "$BLOCKDEVTONUKE" -- set 3 esp on
    parted "$BLOCKDEVTONUKE" -- name 1 nixos
    parted "$BLOCKDEVTONUKE" -- name 2 nixos-swap
    parted "$BLOCKDEVTONUKE" -- name 3 ESP

    sync
    sleep 3

    BLK_NIXOS="$(lsblk -OJ "$BLOCKDEVTONUKE" | jq -r '.blockdevices[].children[]|select(.partlabel == "nixos")|.name')"
    BLK_SWAP="$(lsblk -OJ "$BLOCKDEVTONUKE" | jq -r '.blockdevices[].children[]|select(.partlabel == "nixos-swap")|.name')"
    BLK_ESP="$(lsblk -OJ "$BLOCKDEVTONUKE" | jq -r '.blockdevices[].children[]|select(.partlabel == "ESP")|.name')"
    mkfs.xfs -L nixos "$BLK_NIXOS"
    mkswap -L nixos-swap "$BLK_SWAP"
    mkfs.fat -F 32 -n BOOT "$BLK_ESP"

    mount "$BLK_NIXOS" /mnt
    mkdir -p /mnt/boot /mnt/etc/nixos
    sed -e '
      s#[(] *toString ../profiles/.*[)]#(toString /usr/src/cascade/profiles/'"$PROFILE"')#
      s#networking.hostName = "nixos";#networking.hostName = "'"$HOSTNAME"'";#
    ' < /usr/src/cascade/hosts/_basic.nix > /etc/nixos/configuration.nix

    swapon "$BLK_SWAP"
    nixos-install
  '';
  };
}