#!/bin/bash

# Copyright (c) 2016 The CoreOS Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

SCRIPT_ROOT=$(dirname $(readlink -f "$0"))
. "${SCRIPT_ROOT}/common.sh" || exit 1

USAGE="USAGE: $0 [-v] [date flags]

This script calculates the date given the CoreOS major version or calculates
the version given a date.

Examples:

  $0 -v 1000
  Sun Mar 27 00:00:00 UTC 2016

  $0 -v 1000 --iso-8601
  2016-03-27

  $0 --date 'Jun 1, 2016'
  1066
"

case "$1" in
    "-h")
        echo "$USAGE"
        ;;

    "-v")
        shift
        if [[ $# -ge 1 ]] && [[ "$1" != [-+]* ]]; then
            v="$1"
            shift
        else
            v="${FLATCAR_VERSION}"
        fi

        # strip of a v prefix or .0.0 suffix
        v="${v#v}"
        v="${v%%.*}"

        export TZ=${TZ:=UTC}
        date -d @$(( (v * 86400) + COREOS_EPOCH )) "$@"
        ;;

    *)
        t=$(date +%s "$@")
        echo $(( (t - COREOS_EPOCH) / 86400 ))
        ;;
esac