#!/bin/sh
STAG=cbackup:
# lock wait time max 15mn * 60 = 900 secs (sufficient time to update)
LOCKWAIT=900
# this is a protection to make sure a backup is not currently created while checking
bname=mbackup
BAKPATH=""
_curr_dir=""
BAKEXT=".tar.gz"
BAKMD5EXT=".md5"
mybasename=""

readonly LOCKFILE_DIR=/var/lock
readonly LOCK_FD=980

lock() {
    local prefix=$1
    local fd=${2:-$LOCK_FD}
    local lock_file=$LOCKFILE_DIR/$prefix.lock

    # still allow to run unlocked if the lock dir does not exist
    if [ ! -d "${LOCKFILE_DIR}" ]; then
        return 0
    fi

    # create lock file
    eval "exec $fd>$lock_file"
    # still allow to run unlocked if the lock file cannot be created
    if [ $? -ne 0 ]; then
        return 0
    fi

    # acquier the lock
    flock -w ${LOCKWAIT} $fd \
        && return 0 \
        || return 1
}

unlock() {
    local prefix=$1
    local fd=${2:-$LOCK_FD}
    local lock_file=$LOCKFILE_DIR/$prefix.lock

    # release the lock
    flock -u $fd
    sync
}

function my_exit()
{
    cd "$_curr_dir"
    unlock $bname
    exit $*
}

function __sig_int {
    log_write " "
    log_write "$STAG WARNING: SIGINT caught"
    my_exit 110
}

function __sig_quit {
    log_write " "
    log_write "$STAG WARNING: SIGQUIT caught"
    my_exit 111
}

function __sig_term {
    log_write " "
    log_write "$STAG WARNING: SIGTERM caught"
    my_exit 112
}

function __sig_hup {
    log_write " "
    log_write "$STAG WARNING: SIGHUP caught"
    my_exit 113
}

function log_write()
{
	echo "$*"
}

function log_write_nr()
{
	echo -n "$*"
}

function show_help {
    log_write "cbackup help information:"
    log_write "checks integrity of backup created with mbackup, exit with 0 when valid"
    log_write "Usage: cbackup [ --help ] <bfile>"
    log_write " where: <bfile>     # source backup base file name (without .tar.gz)"
    log_write "                    #  same base file name as provided with mbackup -f option"
    log_write "          --help    # displays this help information"
    log_write "example: cbackup /mnt/storage/.sysbackup/bk-mnt-rom-user # checks backup"
}

function check_path()
{
	local retval=0
    local slen=${#1}
    local mystr
    if ! [ -d $1 ] ; then
        log_write "$STAG directory does not exist ($1)!"
        retval=80
    else
        if [ "${1:$slen - 1:1}" == "/" ] ; then
            mystr=${1:0:$slen - 1}
            slen=$((slen-1))
        else
            mystr=$1
        fi
        BAKPATH=$mystr"/"
    fi
    return $retval
}

_curr_dir=`pwd`

# Lock to test a single instance is running, and exit if wait timeout
log_write "$STAG Checking if allowed to run..."
lock $bname || ( log_write "$STAG Checking if allowed to run... failed"; exit 100 )
log_write "$STAG Checking if allowed to run... done"

# Set TRAPs to release lock if forced to exit
trap __sig_int SIGINT
trap __sig_quit SIGQUIT
trap __sig_term SIGTERM
trap __sig_hup SIGHUP

TOTALARG=$#
while getopts :- FLAG; do
    case $FLAG in
        '-')
        show_help
        my_exit 0;;
        \?)
        log_write "Invalid option: -$OPTARG" && my_exit 1;;
        \:)
        log_write "Required argument not found for option: -$OPTARG" && my_exit 2;;
  esac
done

# removes processed option(s) from the cmd line args
shift $((OPTIND-1))

if [ "$#" -ne 1 ]; then
    show_help
    my_exit 3
fi

check_path `dirname "$1"`
valret=$?
if [ $valret -ne 0 ]; then
    my_exit $valret
fi
mybasename=`basename "$1"`

log_write "$STAG Checking backup: "$BAKPATH$mybasename
if ! [ -f $BAKPATH$mybasename$BAKEXT ] ; then
    log_write "$STAG Source backup does not exist ($BAKPATH$mybasename$BAKEXT)!"
    my_exit 4
fi
if ! [ -f $BAKPATH$mybasename$BAKMD5EXT ] ; then
    log_write "$STAG Source backup MD5 does not exist ($BAKPATH$mybasename$BAKMD5EXT)!"
    my_exit 5
fi
# verify if backup is valid
cd $BAKPATH
if [ $? != 0 ]; then
    log_write "$STAG change dir to ($BAKPATH) failed."
    my_exit 6
fi
# verifies if md5 is for the expected backup file
md5file=`cat $BAKPATH$mybasename$BAKMD5EXT | awk '{ print $2 }'`
if ! [ "./"$mybasename$BAKEXT == "$md5file" ]; then
    log_write "$STAG MD5 ref file is not backup file ($md5file)!"
    my_exit 7
fi
# verifies if md5 is correct
myresult=$(md5sum -c $BAKPATH$mybasename$BAKMD5EXT 2>&1)
myres=$?
if [ $myres != 0 ]; then
    log_write "$STAG Checksum invalid"
    my_exit 8
fi
log_write "$STAG Checksum Ok."
my_exit 0