#!/usr/bin/env bash

#
# nagios-downtime(1) -- Shortcut to scheduling fixed downtime in Nagios,
# because it's annoying to do with the web interface for large sets of hosts
# or services.
#
#     $ ndt <host>[/<service>] <start> <end> [optional comment]
#
# Good for for/while loops:
#
#   for hostname in hosta hostb hostc; do ndt "$hostname" ... ; done
#   while read -r hostname; do ndt "$hostname" ... ; done < downtime-hosts
#
# Assumes date(1) with +%s format and --date option (probably only GNU date).
#
# Author: Tom Ryder <tom@sanctum.geek.nz>
# Copyright: 2014 Sanctum
#

# Name self
self=nagios-downtime

# Usage printing function
usage() {
    printf 'USAGE: %s <host[/service]> <start> <end> [comment]\n' "$self"
}

# Process options (just help at the moment)
OPTIND=1
while getopts 'h' opt ; do
    case "$opt" in
        h)
            usage
            exit 0
            ;;
        '?')
            usage >&2
            exit 1
            ;;
    esac
done
shift "$((OPTIND-1))"

# Bail if too few arguments left; we need at least the hostname, the start date, and the end date
if (($# < 3)) ; then
    usage >&2
    exit 1
fi

# Define relatively fixed/guaranteed fields for Nagios command; note that the
# comment has a default of 'no comment given'
now=$(date +%s)
spec=$1
fixed=1
trigger=0
duration=0
author=${SUDO_USER:-$USER}
comment=${4:-'no comment given'}
cmdfile=${NAGCMD_FILE:-/usr/local/nagios/var/rw/nagios.cmd}

# If a service name is specified after a slash, figure that out
if [[ $spec == */* ]] ; then
    host=${spec%/*}
    service=${spec##*/}
else
    host=$spec
    service=
fi

# Quietly replace semicolons in comment with commas
comment=${comment//;/,}

# Attempt to parse start and end dates; fail usefully if the call doesn't work
if ! dtstart=$(date +%s --date "$2") ; then
    printf '%s: Could not parse start date %s' "$self" "$2" >&2
    exit 1
fi
if ! dtend=$(date +%s --date "$3") ; then
    printf '%s: Could not parse end date %s' "$self" "$3" >&2
    exit 1
fi

# Write command and print message if it fails; succeed silently
if [[ $service ]] ; then
    cmd=$(printf '[%lu] SCHEDULE_SVC_DOWNTIME;%s;%s;%s;%s;%u;%u;%u;%s;%s' \
        "$now" "$host" "$service" "$dtstart" "$dtend" \
        "$fixed" "$trigger" "$duration" "$author" "$comment")
else
    cmd=$(printf '[%lu] SCHEDULE_HOST_DOWNTIME;%s;%s;%s;%u;%u;%u;%s;%s' \
        "$now" "$host" "$dtstart" "$dtend" \
        "$fixed" "$trigger" "$duration" "$author" "$comment")
fi

# Attempt to write command to file
if ! printf '%s\n' "$cmd" > "$cmdfile" ; then
    printf '%s: Failed to write command to file\n' "$self" >&2
    exit 1
fi