util::download_file() {
  local -r url=$1
  local -r destination_file=$2

  rm "${destination_file}" 2&> /dev/null || true

  for i in $(seq 5)
  do
    if ! curl -fsSL --retry 3 --keepalive-time 2 "${url}" -o "${destination_file}"; then
      echo "Downloading ${url} failed. $((5-i)) retries left."
      sleep 1
    else
      echo "Downloading ${url} succeed"
      return 0
    fi
  done
  return 1
}


# Example:  util::wait_for_success 120 5 "kubectl get nodes|grep localhost"
# arguments: wait time, sleep time, shell command
# returns 0 if the shell command get output, 1 otherwise.
util::wait_for_success(){
  local wait_time="$1"
  local sleep_time="$2"
  local cmd="$3"
  while [ "$wait_time" -gt 0 ]; do
    if eval "$cmd"; then
      return 0
    else
      sleep "$sleep_time"
      wait_time=$((wait_time-sleep_time))
    fi
  done
  return 1
}

util::host_os() {
  local host_os
  case "$(uname -s)" in
    Darwin)
      host_os=darwin
      ;;
    Linux)
      host_os=linux
      ;;
    *)
      echo "Unsupported host OS.  Must be Linux or Mac OS X."
      exit 1
      ;;
  esac
  echo "${host_os}"
}

util::host_arch() {
  local host_arch
  case "$(uname -m)" in
    x86_64*)
      host_arch=amd64
      ;;
    i?86_64*)
      host_arch=amd64
      ;;
    amd64*)
      host_arch=amd64
      ;;
    aarch64*)
      host_arch=arm64
      ;;
    arm64*)
      host_arch=arm64
      ;;
    arm*)
      host_arch=arm
      ;;
    i?86*)
      host_arch=x86
      ;;
    s390x*)
      host_arch=s390x
      ;;
    ppc64le*)
      host_arch=ppc64le
      ;;
    *)
      echo "Unsupported host arch. Must be x86_64, 386, arm, arm64, s390x or ppc64le."
      exit 1
      ;;
  esac
  echo "${host_arch}"
}

util::md5() {
  if which md5 >/dev/null 2>&1; then
    md5 -q "$1"
  else
    md5sum "$1" | awk '{ print $1 }'
  fi
}