#!/bin/bash

# ============LICENSE_START=======================================================
#  Copyright (C) 2021 The Nordix Foundation. All rights reserved.
# ================================================================================
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#      http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#
# SPDX-License-Identifier: Apache-2.0
# ============LICENSE_END=========================================================

set -o errexit
set -o nounset
set -o pipefail

#-------------------------------------------------------------------------------
# Print the help message which includes the usage, the expected parameters
# and their default values if they are not specified
#-------------------------------------------------------------------------------
function usage() {

  # NOTE: shellcheck complains quoting in the example so SC2086 is disabled
  # shellcheck disable=SC2086
  cat <<EOF

Usage: $(basename ${0}) [-l <file with list of docker images>] [-c <container-tool>] [-o <output-path> ] [-v] [-h]

    -l: File with list of docker images. (Default /tmp/dockersave-list.tmp)
    -c: container command. (Default docker)
    -v: Increase verbosity and keep logs for troubleshooting. (Default false)
    -o: Path in which to save the images. (Default /tmp/images.tgz)
    -h: This message.

EOF
  exit 0

}

#-------------------------------------------------------------------------------
# Parse the arguments that are passed to the script
# If an argument is not specified, default values for those are set
#
# The priority order is
# - arguments: overrides the default values and values set as environment
#   values. highest prio.
# - env vars: overrides the default values but not the values set from command
#   line.
# - default values: only takes effect if the user doesn't specify the value
#   of an argument either as an env var or from command line. lowest prio.
#-------------------------------------------------------------------------------
function parse_cmdline_opts() {

  # set variables to the values set in env - otherwise, set them to defaults
  LISTOFDOCKERIMAGES=${LISTOFDOCKERIMAGES:-"/tmp/dockersave-list.tmp"}
  OUTPUT_PATH=${OUTPUT_PATH:-"/tmp/images.tgz"}
  VERBOSITY="false"
  CONTAINER_TOOL="docker"

  while getopts "hl:c:o:v" o; do
    case "${o}" in
      h) usage ;;
      l) LISTOFDOCKERIMAGES="${OPTARG}" ;;
      c) CONTAINER_TOOL="${OPTARG}" ;;
      o) OUTPUT_PATH="${OPTARG}" ;;
      v) VERBOSITY="true" ;;
      *) echo "ERROR: Invalid option '-${OPTARG}'"; usage ;;
    esac
  done

  # Do all the exports
  export LISTOFDOCKERIMAGES="${LISTOFDOCKERIMAGES}"
  export VERBOSITY="${VERBOSITY}"
  export CONTAINER_TOOL="${CONTAINER_TOOL}"
}

parse_cmdline_opts "$@"

mkdir -p "$(dirname "${OUTPUT_PATH}")"
xargs "${CONTAINER_TOOL}" save < "${LISTOFDOCKERIMAGES}" | gzip --rsyncable - > "${OUTPUT_PATH}"