#!/usr/bin/perl
# Playing with toys is much more fun than studying some boring exam...

# FIXME TODO:
# * detect handovers GPRS <-> UMTS?
# * detect handovers from cells??
# * other nice commands from gpsd?

use strict;
use Device::Modem;
use POSIX qw(strftime);
use Net::Telnet();

sub GetSignalQuality {
	my $modem = shift;
	my $rssi = "-";
	my $ber = "-";
	my $tmp = $modem->atsend( "AT+CSQ" . "\r\n" );
	split '\n', $modem->answer();
	$_=@_[0];
	split ' ';
	if ($_=="+CSQ") {
		(my $tmp, $_) = split ' ';
		($rssi, $ber) = split ',';
		$rssi = $rssi + 0;
		$ber = $ber + 0;
		if ($rssi==99) {
			$rssi = "-";
		} else {
			$rssi = $rssi+0;
			$rssi = -113 + 2*$rssi; # convert rssi to dBm
			if ($rssi == -113) {
				$rssi = "<= $rssi";
			} elsif ($rssi == -51) {
				$rssi = ">= $rssi";
			}
			$rssi = "$rssi dBm";
		}
		if ($ber==99) {
			$ber = "-";
		} else {
			# convert ber to % bit errors, according to
			# www.miccom.cc/handy/handytipps/umrechnungstabelle.html
			my $tmp = $ber;
			$ber = 0.2;
			while ($tmp>0) {
				$ber=$ber*2;
				$tmp=$tmp-1;
			}
			if ($ber==25.6) {
				$ber=">12.8%"
			} else {
				$ber="<$ber%"
			}
		}
	} elsif ($_=="+ERROR") {
		print STDERR "Error while trying AT+CSQ: @_\n";
	} else {
		print "Error: unkown response from AT+CSQ: @_\n";
	}
	return $rssi, $ber;
}

sub GetRegistrations {
	my $modem = shift;
	my $base = "-"; # base network registration
	my $psnet = "-"; # packet switched network registration
	$modem->atsend("AT+CREG?" . "\r\n");
	split '\n', $modem->answer();
	$_=@_[0];
	chomp;
	split ' ';
	if ($_=="+CREG") {
		(my $tmp1, $base) = split ',';
		$base=$base+0;
	} elsif ($_=="+ERROR") {
		print STDERR "Error while trying AT+CREG?: @_\n";
	} else {
		print STDERR "Error unknown response from AT+CREG?: @_\n";
	}
	$modem->atsend("AT+CGREG?" . "\r\n");
	split '\n', $modem->answer();
	$_=@_[0];
	chomp;
	split ' ';
	if ($_=="+CGREG") {
		(my $tmp1, $psnet) = split ',';
		$psnet=$psnet+0;
	} elsif ($_=="+ERROR") {
		print STDERR "Error while trying AT+CGREG?: @_\n";
	} else {
		print STDERR "Error unknown response from AT+CGREG?: @_\n";
	}
	return $base, $psnet
}

sub GetAccessTechnology {
	my $modem = shift;
	my $at = "-";
	my $prov = "-";
	$modem->atsend( "AT+COPS?" . "\r\n" );
	split '\n', $modem->answer();
	$_=@_[0];
	split ' ';
	if ($_=="+COPS") {
		(my $tmp1, $_)=split ' ';
		$_ = join ' ', @_;
		(my $tmp1, my $tmp2, $prov, $at) = split ',';
		if ($at == 0) {
			$at = "GSM";
		} elsif ($at == "1") {
			$at = "GSM Compact";
		} elsif ($at == "2") {
			$at = "UMTS";
		} else {
			print STDERR "Error: unkown access technology: $at\n";
		}
	} elsif ($_=="+ERROR") {
		print STDERR "Error while trying AT+COPS?: @_\n";
	} else {
		print "Error: unkown response from AT+COPS?: @_\n";
	}
	return $prov, $at;
}

sub GetGPSLocation {
	my $gps = shift;
	my $lat = "-";
	my $long = "-";
	my $status = "-";
	my $speed = "-";
	$gps->print("s");
	$_=$gps->getline;
	chomp;
	s/GPSD,S=//;
	$status=$_;
	$gps->print("v");
	$_=$gps->getline;
	chomp;
	($speed) = /V=(\d+\.\d*)/;
	$speed=0.514444444*$speed; # convert knots to m/s
	$speed="$speed m/s";
	$gps->print("p");
	$_=$gps->getline;
	chomp;
	s/GPSD,P=//;
	split;
	$lat = @_[0];
	$long = @_[1];
	if ($lat eq "") {
		print STDERR "Error: couldn't get current location from localhost:gps\n";
	}
	return $lat,$long,$speed,$status;
}

sub GpsErrorHandler {
	my $gps = shift;
	$_ = $gps->errmsg;
	if ($_ eq "write error: filehandle isn't open") {
		print STDERR "Error: couldn't communicate with gpsd! Check if gpsd is running.\n";
		# try to reopen gpsd connection... perhaps user has restarted
		# gpsd
		$gps->open(Host => "localhost", Port => "gps");
	} elsif (/problem connecting to/) {
		# open failed... do nothing
	} else {
		print STDERR "Error: $_.\n";
	}
}

my $port = '/dev/ttyUSB2';
my $delay = 1;
my $baud = 19200;

my $a=shift @ARGV;
while (! "$a" eq "") {
	$_=$a;
	if (/^-d/) {
		$delay = shift @ARGV;
		$delay = $delay + 0;
		if ($delay <= 0) {
			die "Error: delay time <= 0 is invalid!";
		}
	} elsif (/^-p/) {
		$port = shift @ARGV;
		if ($port eq "") {
			die "Error: no port specified!";
		}
	}
	$a=shift @ARGV;
}

my $modem = new Device::Modem(port => $port);
die "Could not connect to $port!\n" unless $modem->connect( baudrate => $baud );

my $gps = new Net::Telnet(Telnetmode => 0);
my @GpsArrayRef=(\&GpsErrorHandler,$gps);
$gps->errmode(\@GpsArrayRef);
$gps->open(Host => "localhost", Port => "gps");

# print header
print "date\tGPS: lat\tlong\tspeed\tstatus\tGSM rssi\tber\toperator\tbase registration\tpacket switched registration\taccess technology\n";
while() {
	my $t=time();
	$t=strftime "%Y-%m-%d %H:%M:%S", localtime;
	(my $lat, my $long, my $speed, my $gpsstatus) = GetGPSLocation($gps);
	(my $rssi, my $ber) = GetSignalQuality($modem);
	(my $operator, my $at) = GetAccessTechnology($modem);
	(my $basereg, my $psreg) = GetRegistrations($modem);
	print "$t\t$lat\t$long\t$speed\t$gpsstatus\t$rssi\t$ber\t$operator\t$basereg\t$psreg\t$at\n";
	sleep $delay;
}