bt-auto-lock

#!/bin/bash


. ~/lib/bluetooth-phone


SIGNAL_THRESHOLD=0	# received signal strength indication below which the display will blank/lock
POLL_FREQUENCY=5	# attempt to poll this frequently (in seconds)
FAIL_RETRIES=4		# lock screen on this many failures
SCRIPT_NAME=$(basename $0)
LOG_FILE="$HOME/.${SCRIPT_NAME}.log"


# Ensure only THIS instance of the script is running
for pid in $(pidof -xo $$ $SCRIPT_NAME 2>/dev/null); do
	other_pids+=" $(pstree -Apl $pid | sed -r 's/[^)]*\(//g; s/\)/ /g' | xargs echo)"
done
[[ $other_pids ]] && kill $other_pids &>/dev/null


log() { # input is a string // log input, rotating log daily
	[[ ! -e "$LOG_FILE" ]] && >"$LOG_FILE"
	day=$(date +%A)
	if [[ $day != $day_log ]]; then
		day_log=$day
		rm -f "$LOG_FILE.gz"
		gzip "$LOG_FILE"
	fi
	echo "$(date +%Y-%m-%d/%H:%M:%S) $@" >>"$LOG_FILE"
}


delay() { # no input // delay until seconds since epoch is a multiple of POLL_FREQUENCY
	local seconds=$(date +%s)
	local delay=$(( POLL_FREQUENCY - (seconds % POLL_FREQUENCY) ))
	sleep $delay
}


getSignal() { # no input // get signal strength
	hcitool con | grep -q $MAC || sudo hcitool cc $MAC 2>/dev/null
	signal=$(hcitool rssi $MAC 2>/dev/null)
	signal=${signal##* }
	signal=${signal:--1000}
	sudo hcitool dc $MAC 2>/dev/null
}


lock() { # no input // lock the screen
	gnome-screensaver-command --activate
}


unlock() { # no input // unlock the screen
	gnome-screensaver-command --deactivate
	xset dpms force on
	xset s reset
}


# Main loop
while delay; do

	getSignal

	action=wait
	if [[ $signal -lt $SIGNAL_THRESHOLD ]]; then
		((counter++))
		if [[ $counter -eq $FAIL_RETRIES ]]; then
			action=lock
		fi
	else
		if [[ $counter -ge $FAIL_RETRIES ]]; then
			action=unlock
		fi
		counter=0
	fi

	log "action=$action signal=$signal counter=$counter"

	case $action in
		lock|unlock) $action;;
	esac
done