#! /bin/bash

backupdir=/var/dbbackup
keeptime="5 day ago"
datestamp= # date +format.

MYSQL_USR=
MYSQL_PWD=
compress=none

umask 077
[ -r /etc/uls/dbbackups.conf ] && . /etc/uls/dbbackups.conf

bexten="sql"

case "${compress}" in
	none)
		ctool=(cat)
		;;
	gz)
		bexten+=".gz"
		ctool=(gzip -9)
		;;
	bz2)
		bexten+=".bz2"
		ctool=(bzip2 -9)
		;;
	xz)
		bexten+=".xz"
		ctool=(xz -9)
		;;
	*)
		echo "Unregocnised value for compress, one of none, gz, bz2 or xz is expected." >&2
		exit 1
		;;
esac

export MYSQL_PWD

if [ -z "${MYSQL_USR}" ] || ! databases=($(mysql -u"${MYSQL_USR}" -B -N -e "show databases")); then
	MYSQL_PWD=
fi

if [ -z "${MYSQL_PWD}" ]; then
	tty -s || exit 1

	if [ -n "${MYSQL_USR}" ]; then
		echo "Configured credentials failed for user ${MYSQL_USR}.  You can"
		echo "Enter the correct password, or blank to reconfigure from scratch."
		echo
		read -p "Updated password for ${MYSQL_USR}: " -s MYSQL_PWD; echo
		while [ -n "${MYSQL_PWD}" ] && ! databases=($(mysql -u"${MYSQL_USR}" -B -N -e "show databases")); do
			read -p "Updated password for ${MYSQL_USR}: " -s MYSQL_PWD; echo
		done
	fi

	if [ -z "${MYSQL_PWD}" ]; then
		echo "We will now create a new user for db backup purposes (We will generate a random password if possible)."
		read -p "Username to use: " MYSQL_USR

		if which pwgen &>/dev/null; then
			MYSQL_PWD=$(pwgen 16 1)
			echo "Selected password ${MYSQL_PWD}"
		else
			read -p "Unable to generate random password, please enter: " -s MYSQL_PWD; echo
		fi

		echo "When prompted enter the MySQL root password.  This will first drop the user if it exists, and then recreate it."
		(
			echo "DROP USER IF EXISTS '${MYSQL_USR}'@localhost;"
			echo "GRANT SELECT, LOCK TABLES, SHOW VIEW, EXECUTE, RELOAD ON *.* TO '${MYSQL_USR}'@localhost IDENTIFIED BY '${MYSQL_PWD}';"
		) | mysql -uroot -p
	fi

	[ -d /etc/uls ] || mkdir /etc/uls || exit 1
	[ -r /etc/uls/dbbackups.conf ] && sed -e '/^MYSQL_/ d' -i /etc/uls/dbbackups.conf
	printf "MYSQL_USR=%q\nMYSQL_PWD=%q\n" "${MYSQL_USR}" "${MYSQL_PWD}" >> /etc/uls/dbbackups.conf
fi

[ -n "${datestamp}" ] && datestamp="$(date "+-${datestamp}")"

for db in "${databases[@]}"; do
	[ "${db}" = "information_schema" ] && continue
	[ "${db}" = "performance_schema" ] && continue
	
	# Determine if we've got InnoDB only ...
	innodbonly=$(mysql -u"${MYSQL_USR}" -B -N "${db}" -e "show table status" | awk 'BEGIN{ innodbonly=1 } $2!="InnoDB" && $NF!="VIEW" && $2!="Memory" { innodbonly=0 } END { print innodbonly }')

	if [ "${innodbonly}" -eq 1 ]; then
		locktype="--single-transaction"
	else
		locktype="--lock-tables"
	fi

	mysqldump -u"${MYSQL_USR}" -R ${locktype} "${db}" | "${ctool[@]}" > "${backupdir}/${db}${datestamp}.${bexten}"
done

keepmins=$(( ( $(date +%s) - $(date +%s -d "${keeptime}") ) / 60  )) || exit 1
find "${backupdir}" \( -name "*.sql" -o -name "*.sql.{gz,bz2,xz}" \) -mmin +${keepmins} -delete