#! /bin/bash

set -e

file_owner="nagios"
rrd_file="$1"
required_ds="$2"

if [[ -z ${rrd_file} ]] || [[ -z ${required_ds} ]]; then
    echo "Usage: $0 <rrd file> <no required data sources>"
    exit 1
fi

rm -f ${rrd_file}.chg

current_ds=$(rrdtool info ${rrd_file} | grep ^ds | cut -d "[" -f 2 | cut -d "]" -f 1 | sort -n | tail -n 1)

additional_ds=$((required_ds - current_ds))
new_ds=$((current_ds + additional_ds))

if [[ ${additional_ds} -lt 1 ]]; then
    echo "Error: RRD file already has ${current_ds} data sources"
    exit 1
fi

start_ds=$((current_ds + 1))

echo "Increasing data sources from ${current_ds} to ${new_ds} data sources"

cp -p ${rrd_file} ${rrd_file}.bak

/usr/lib/pnp4nagios/libexec/rrd_modify.pl ${rrd_file} insert ${start_ds},${additional_ds} && chown ${file_owner}: ${rrd_file} && mv ${rrd_file}.chg ${rrd_file}

if [[ $(rrdtool info ${rrd_file} | grep ^ds | cut -d "[" -f 2 | cut -d "]" -f 1 | tail -n 1) != ${new_ds} ]]; then
    echo "Error: Last data source index in RRD file does not match expected data source index! Reverting..."
    mv ${rrd_file}.bak ${rrd_file}
    exit 1
fi

echo "RRD file successfully updated"