#!/bin/bash
#state variable that determines if the main loop is running
loop=true
#time of next update
nexttime=$(date +%s)
#intervals between updates in seconds
interval=60
#time before an starts before a notification pops up
remind=900
#calendar printout format
cformat="{start-time:.<8}→{end-time:.<10}{title:.<25}{location:.<30}"
#gets username and password
read -p  "username:" caluser
export caluser
read -s -p "password:" calpass
echo ""
export calpass
#This has to be done at the beginning of every run of the script now, don't know
#why, but if it isn't then vdirsyncer sync will refuse to run
vdirsyncer discover
#help message
echo "Beginning to sync up caledar files, type \"q\" + enter to quit,
\"s\" + enter to sync now,
\"k\" + enter to launch khal in interactive mode,
and \"a\" + enter to list agenda"
while [ "$loop" == true ]; do
	#w/ timeout of 1, read input 
	read  -t 1 input
	#handles quit, this is run at every loop and pretty much determines how
	#slow the loop runs
	if [ "$input" == "q" ]; then
		loop=false
	fi
	if [ "$input" == "k" ]; then
		khal interactive
		#in case anything was editted
		nexttime=$(date +%s)
	fi
	if [ "$input" == "a" ]; then
		khal calendar --format="$cformat"
	fi
	if [ "$input" == "s" ]; then
		nexttime=$(date +%s)
	fi
	#If the current time is greater than the next scheduled update, update
	if [ $(date +%s) -ge $nexttime ]; then
		echo starting sync at $(date +%s)
		#syncs with remote calDAV server
		vdirsyncer sync
		#stores the old list of upcoming events so that we can compare
		#after updating, this will create an error on the first run but
		#this doesn't matter
		mv ~/.vdirsyncer/events ~/.vdirsyncer/oldevents
		#updates khal and also list any upcoming events
		#determines in seconds the interval of time that khal limits
		#itself to when looking for events (their start times have have
		#to fall within this interval)
		window=$(( (interval) * 3 ))s
		#determines the time which khal is actually querying, this
		#should be now + remind before time, window does not matter
		#because we're testing for when an event passes out of the
		#interval
		testtime=$(( $(date +%s) + $remind ))
		#now get the properly formated string representing the above
		#time in a way khal understands
		#Note: The below only works if the time format is set to be the
		#same way in khal's config
		timestring=$(date --date="@$testtime" "+%m/%d/%Y %I:%M %p")
		echo Testing for upcoming events at $timestring
		#writes upcoming events to events file to be diffed later
		khal list $now $timestring --once --notstarted >> ~/.vdirsyncer/events
		#checks to see if any changes in the upcoming events queue
		#exists by diff'ing oldevents and events, then finding what was
		#removed
		difference=$(diff ~/.vdirsyncer/oldevents ~/.vdirsyncer/events | grep "<")
		#only when an event is exiting the test interval do we care, so
		#if $difference is "< No events" or empty, then we say that
		# an event entered the interval or no change occured
		#Schedules the next update, keeps adding $interval until we get
		#one that's actually in the future, since it's not guaranteed
		#that each update will take less than 1 $interval to run
		if [ "$difference" == "" ]; then
			echo No changes in upcoming events
		elif [ "$difference" == "< No events" ]; then
			echo an event entered the test interval
		else
			echo an event has exited the test interval
			notify-send "$difference"
		fi
		while [ $(date +%s) -ge $nexttime ]; do
			nexttime=$(( $nexttime + $interval))
		done
		echo next sync scheduled at $nexttime
	fi
done