#!/bin/bash
#                       /usr/local/bin/triweekly
#  http://crystalfaeries.net/posix/bin/triweekly
# celeste:crystalfaery 2016-10-27 21:29:00+00:00

# We maintain event timestamps, for which,
# if our timestamp is 21 days old,
# we notify, and reset the timestamp
# option -l displays all timestamps,
# which are displayed anyway if any new event added

# Crontab is a wonderful facility but unable to choose an "every 3 weeks" schedule...
# therefore, we assist cron with this script, which is executed nightly by cron.
# 00	00	 *	 *	*	/usr/local/bin/triweekly

# manual invocation to list timestamps being tracked:
# triweekly -l

# manual invocation to initiate a new, or reset timer of, existing item(s):
# triweely alpha beta

temporary=`mktemp` || exit -1
cd	# there's no place like home, where the user timestamps live
#	if called with arguments, those are the names of the events we are timing
if [ "$1" == "-v" ]
then
	echo	"`ls -Flad $0`"
	head		   $0
	exit	0
fi
if [ "$1" == "--version" ]
then
	echo	"`ls -Flad $0`"
	head		   $0
	exit	0
fi
if [ "$1" == "-h" ]
then
	echo	"$0 accepts as arguments the names of events for which you are requesting a 3 week timer."
	echo	"If the event already existed, its timer is reset to 3 weeks."
	echo	"If any event was specified, all events are listed."
	echo	"Optional -l flag forces listing of timestamps."
	exit	0
fi
if [ "$1" == "--help" ]
then
	echo	"$0 accepts as arguments the names of events for which you are requesting a 3 week timer."
	echo	"If the event already existed, its timer is reset to 3 weeks."
	echo	"If any event was specified, all events are listed."
	echo	"Optional -l flag forces listing of timestamps."
	exit	0
fi
let	list=1	# false
if [ "$1" == "-l" ]
then
	let	list=0	# true
	shift
fi
while [[ $# -gt 0 ]] ;
do
	/usr/local/bin/now	 >>	 ."$1".triweekly.txt	# UTC Timestamp inside file
	shift	# we time-stamped our named event, will notify in 3 weeks
	let	list=0	# true
done
if [[ $list -eq 0 ]]
then
	ls -Flart .*.triweekly.txt	# all my triweekly events are stored in my home directory
fi

# now find any timestamp three weeks old and notify
find . -maxdepth 1 -iname '.*.triweekly.txt' -daystart -mtime +20 | sed 's/^\.\/\.//' | sed 's/.triweekly.txt$//' > \
				$temporary

cat			       "$temporary" 1>&2
if [ -s				$temporary ]
then	# a 3 week timer expired, therefore notify in multiple ways
	#	delete old TriWeekly events from Calendar
	grep -v TriWeekly			~/.calendar/calendar								>  /tmp/$$
	for item in `cat	$temporary`;
	do
	#	append new TriWeekly events onto Calendar
		echo "`date -u --rfc-3339=date | sed 's/^[0-9][0-9][0-9][0-9]-//g;s/-/ /g'`		TriWeekly $item"	>> /tmp/$$
		/usr/local/bin/now				 >>	.$item.triweekly.txt && \
		mail -s "TriWeekly $item" `/usr/bin/whoami`	 <	.$item.triweekly.txt || \
		exit -1	# if notify was successful then reset the timer else error exit
	done
	#	install new Calendar file
	mv	/tmp/$$				~/.calendar/calendar
fi
rm		/tmp/$$		$temporary	2>/dev/null
exit	0	# pau