ISTIO_ENVOY_RELEASE_URL="${ISTIO_ENVOY_RELEASE_URL:-${ISTIO_ENVOY_BASE_URL}/envoy-alpha-${ISTIO_ENVOY_VERSION}${ISTIO_ENVOY_ARCH_SUFFIX}.tar.gz}"

# Envoy Linux vars.
ISTIO_ENVOY_LINUX_VERSION="${ISTIO_ENVOY_LINUX_VERSION:-${ISTIO_ENVOY_VERSION}}"
ISTIO_ENVOY_LINUX_DEBUG_URL="${ISTIO_ENVOY_LINUX_DEBUG_URL:-${ISTIO_ENVOY_DEBUG_URL}}"

# Wait for the proxy to become available
ISTIO_ENVOY_VERSION=${ISTIO_ENVOY_VERSION:-$1}
ISTIO_ENVOY_LINUX_VERSION=${ISTIO_ENVOY_LINUX_VERSION:-${ISTIO_ENVOY_VERSION}}
ISTIO_ENVOY_BASE_URL=${ISTIO_ENVOY_BASE_URL:-https://storage.googleapis.com/istio-build/proxy}
ISTIO_ENVOY_RELEASE_URL=${ISTIO_ENVOY_RELEASE_URL:-${ISTIO_ENVOY_BASE_URL}/envoy-alpha-${ISTIO_ENVOY_LINUX_VERSION}.tar.gz}

    DOWNLOAD_COMMAND="wget -qO -"
    return
  fi
  echo wget is not installed.

  echo Error: curl is not installed or does not support https, wget is not installed. \
       Cannot download envoy. Please install wget or add support of https to curl.
  exit 1
}

# Params:
#   $1: The URL of the ztunnel binary to be downloaded.
#   $2: The full path of the output binary.
#   $3: Non-versioned name to use