#!/bin/sh
set -eu

usage() {
	cat <<-'EOF'
		Usage:
		  cronjob COMMAND...
		  cronjob -h
	EOF
}

help() {
	cat <<-'EOF'


		Options:
		  -h, --help    show this message

		  COMMAND       the command to be executed


		Execute the given command, and send the output to email, with
		special treatment to the status code.  It kills the job it it
		lasts more than one hour.

		It load the appropriate files, so that the actual cron
		declaration is smaller.


		Examples:

		  Run a backup:

		    $ cronjob backup -q cron
	EOF
}


for flag in "$@"; do
	case "$flag" in
		--)
			break
			;;
		--help)
			usage
			help
			exit
			;;
		*)
			;;
	esac
done

while getopts 'h' flag; do
	case "$flag" in
		h)
			usage
			help
			exit
			;;
		*)
			usage >&2
			exit 2
			;;
	esac
done
shift $((OPTIND - 1))

if [ -z "${1:-}" ]; then
	printf 'Missing COMMAND.\n\n' >&2
	usage >&2
	exit 2
fi

if [ "$(id -un)" != 'root' ]; then
	printf 'This script must be run as root.\n\n' >&2
	usage >&2
	exit 2
fi


set +eu
# shellcheck source=/dev/null
. /etc/rc
set -eu



epoch() {
	awk 'BEGIN { srand(); print(srand()); }'
}

now() {
	date '+%Y-%m-%dT%H:%M:%S%:z'
}


uuid() {
	od -xN20 /dev/random |
		head -n1 |
		awk '{OFS="-"; print $2$3,$4,$5,$6,$7$8$9}'
}

mkstemp() {
	name="${TMPDIR:-/tmp}/uuid-tmpname with spaces.$(uuid)"
	touch "$name"
	printf '%s' "$name"
}

pre() {
	# Same as:
	# sed -u "s|^|[$CMD]: |"
	# but the "-u" option is not POSIX
	IFS=''
	while read -r line; do
		printf '[%s]: %s\n' "$CMD" "$line"
	done
}

duration() {
	minutes=$((${1} / 60))
	seconds=$((${1} % 60))
	printf '%sm%ss' "$minutes" "$seconds"
}


CMD="$*"
HOSTNAME="$(hostname)"
FROM="cronjob@$HOSTNAME"
TIMEOUT='14400' # four hours
STATUS_F="$(mkstemp)"
OUT="$(mkstemp)"

email() {
	{
		cat <<-EOF
			Content-Type: text/plain; charset=UTF-8
			Content-Transfer-Encoding: 8bit
			From: $FROM
			To: root@localhost
			Subject: (exit status: $(cat "$STATUS_F")) - $HOSTNAME: $CMD

		EOF
		cat "$OUT"
	} | sendmail -t -f "$FROM"
	rm -f "$OUT" "$STATUS_F"
}
trap email EXIT

{
	cat <<-EOF
		Running commad: $CMD
		Starting at: $(now)

	EOF

	START="$(epoch)"
	STATUS=0
	timeout "$TIMEOUT" "$@" || STATUS=$?
	printf '%s' "$STATUS" > "$STATUS_F"
	END="$(epoch)"
	DURATION_SECONDS=$((END - START))

	cat <<-EOF

		Finished at: $(now)
		Duration: $(duration "$DURATION_SECONDS")
	EOF
} 2>&1 | pre | ts '%Y-%m-%dT%H:%M:%S' | tee "$OUT" >> /var/log/cronjobs.log