#!/bin/bash

# bluetooth device to check
DEVICE="00:00:00:00:00:00"

# seconds between each signal check in normal mode
NEAR_CHECK_INTERVAL=4
FAR_CHECK_INTERVAL=4

# seconds to wait to recheck near or far signal before running commands
NEAR_RECHECK_INTERVAL=0.5
FAR_RECHECK_INTERVAL=0.5

# times to run the recheck
NEAR_RECHECK_TIMES=1
FAR_RECHECK_TIMES=3

# rssi threshold between near and far
THRESHOLD=-16

# commands to run when state changes
FAR_COMMAND='/usr/bin/gnome-screensaver-command --activate' # command to run when device goes out of range
NEAR_COMMAND='/usr/bin/gnome-screensaver-command --deactivate' # command to run when device comes into range

connected=0

function connect {
    connected=0
    for s in `hcitool con`; do
        if [ "$s" == "$DEVICE" ]; then
            connected=1;
        fi
    done
    if [ $connected -eq 0 ]; then
        echo "Attempting connection..."
        if [ -z "`hcitool cc $DEVICE 2>&1`" ] || [ -z "`l2ping -c 2 $DEVICE 2>&1`" ]; then
            echo "Connected."
            connected=1
        else
            echo "ERROR: Cannot connect to device $DEVICE."
            connected=0
        fi
    fi
}

connect

while [ $connected -eq 0 ]; do
    connect
    sleep 3
done

echo "Monitoring proximity of device $DEVICE";


let prox=$NEAR_RECHECK_TIMES+1
while [ -z "" ]; do
    connect
    if [ $prox -gt 0 ]; then
        int=$NEAR_CHECK_INTERVAL
    else
        int=$FAR_CHECK_INTERVAL
    fi
    badsig=0
    if [ $connected -eq 1 ]; then
        str="RSSI return value: "
        rssi=`hcitool rssi $DEVICE | grep "$str" | sed -e "s/$str//g"`
        if [ $rssi -le $THRESHOLD ]; then
            badsig=1
        elif [ $rssi -ge $[$THRESHOLD+2] ] && [ $prox -le $NEAR_RECHECK_TIMES ]; then
            if [ $prox -eq $NEAR_RECHECK_TIMES ]; then
                $NEAR_COMMAND > /dev/null 2>&1
                let prox=$NEAR_RECHECK_TIMES+1
            else
                int=$NEAR_RECHECK_INTERVAL
                if [ $prox -le 0 ]; then
                    let prox=1
                else
                    let prox++
                fi
            fi
        fi
        if [ $prox -gt 0 ]; then
            echo "RSSI = $rssi, device is within proximity."
        else
            echo "RSSI = $rssi, device is out of proximity."
        fi
    else
        badsig=1
    fi
    if [ $badsig -eq 1 ] && [ $prox -ge -$FAR_RECHECK_TIMES ]; then
        if [ $prox -eq -$FAR_RECHECK_TIMES ]; then
            $FAR_COMMAND > /dev/null 2>&1
            let prox=-$FAR_RECHECK_TIMES-1
        else
            int=$FAR_RECHECK_INTERVAL
            if [ $prox -ge 0 ]; then
                let prox=-1
            else
                let prox--
            fi
        fi
    fi
    sleep $int
done