#!/bin/bash
# This script edits the file:
# /etc/mysql/mariadb.conf.d/50-server.cnf
# The config file will set
# the server-id to
# the server-id of
# the running MariaDB server.
# The config file is assumed to look like
# the default Debian configuration file
# approximately.
# MariaDB will break if the user
# has set the server-id in another file.
set -o pipefail
set -e
PATH=$(dirname "$0"):$PATH
source rpc.bash

use_real_config()
{
	MARIADB_CONFIG_FILE=/etc/mysql/mariadb.conf.d/50-server.cnf
}

use_fake_config()
{
	use_real_config
	OUR_RUNTIME_DIR=/run/hosting-tools
	mkdir -p "$OUR_RUNTIME_DIR"
	REAL_MARIADB_CONFIG_FILE=$MARIADB_CONFIG_FILE
	FAKE_MARIADB_CONFIG_FILE=$OUR_RUNTIME_DIR/50-server.cnf
	cp -i -a -T -- "$REAL_MARIADB_CONFIG_FILE" "$FAKE_MARIADB_CONFIG_FILE"
	MARIADB_CONFIG_FILE=$FAKE_MARIADB_CONFIG_FILE
}

remove_fake_config()
{
	rm -f /run/hosting-tools/50-server.cnf
}

get_mariadb_server_id_from_config()
{
	set -- 's/^ *server-id *= *([^ ]+) *$/\1/p'
	sed -n -E -e "$1" < "${MARIADB_CONFIG_FILE}"
}

valid_server_id()
{
	case "$newid" in
		'' | *[^0-9]* ) false ;;
		*             ) [ "$newid" -ge 1 ] ;;
	esac
}

set_mariadb_server_id_config()
{
	OUR_SUFFIX='.~hosting-tools~'
	MARIADB_CONFIG_FILE_BACKUP=$MARIADB_CONFIG_FILE$OUR_SUFFIX
	newid=$1
	if ! valid_server_id "$newid"
	then
		echo "Error: Invalid server-id: $newid" >&2
		return 9
	fi
	if grep -q '^ *server-id *=' "$MARIADB_CONFIG_FILE"
	then
		set -- s/'^( *server-id *= *)[^ ]+ *$'/'\1'"$newid"/
	else
		set -- s/'^#( *server-id *= *)1 *$'/'\1'"$newid"/
	fi
	set -- sed -E -i"${OUR_SUFFIX}" -e "$1"
	"$@" "$MARIADB_CONFIG_FILE"
}

run_server()
{
	local BASH_RPC_REMOTE_DEST="$1"
	shift
	remote_run_function "$@"
}

main()
{
	set -e
	set -o pipefail
	runtime_server_id=$(mariadb -s <<< 'select @@server_id')
	if false
	then
		use_fake_config
	else
		use_real_config
	fi
	config_server_id=$(get_mariadb_server_id_from_config)
	if [ "$runtime_server_id" = "$config_server_id" ]
	then
		printf 'Warning: %s\n' \
			"server-id is already correct. Doing nothing." >&2
		remove_fake_config
		return
	fi
	set_mariadb_server_id_config "$runtime_server_id"
	set +e
	validate_new_server_id "$runtime_server_id"
	r=$?
	interactive_show_config_change
	if [ "$r" = 0 ]
	then
		remove_fake_config
	fi
	return $r
}

interactive_show_config_change()
{
	(
		set +e
		diff -u --color \
			"$MARIADB_CONFIG_FILE_BACKUP" \
			"$MARIADB_CONFIG_FILE"
		[ $? = 1 ]
	)
}

validate_new_server_id()
{
	expected=$1
	received=$(get_mariadb_server_id_from_config)
	if [ "$expected" = "$received" ]
	then
		printf 'Success: %s: server-id = %s\n' \
			"wrote MariaDB config" \
			"$received" >&2
	else
		printf 'Error: %s: server-id = %s\n' \
			"failed to write MariaDB config" \
			"$received" >&2
		false
	fi
}

run_server "${1:-root@localhost}" main