#!/usr/bin/perl -w
# -*- perl -*-

use Getopt::Long;
use vars qw($opt_verbose $opt_help);


sub initialize {
    
    GetOptions("verbose",
	       "help");
    
    if (defined $opt_verbose) {
	$verbose=1;
    } else {
	$verbose=0;
    }
    
    if (defined $opt_help) {
	print "usage: gpsd [-verbose] [-help]\n";
	exit;
    }

    $gps = "/dev/gps";

    open (LOC, ">>/tmp/location_log") || die "Couldn't open /tmp/location_log: $!\n";
    select LOC ; $|=1; select STDOUT;

    $status = system("stty speed 4800 < $gps"); 
    print "error: couldn't initialize $gps $! $status\n" if $status;

    $status = system("echo ASTRAL > $gps");
    print "error: couldn't send magic word ASTRAL $! $status\n" if $status;

    print "starting gps daemon\n";
    open (GPS, "<$gps");
    $time = time;

    $time = 
	$birds = 
	    $hdop = 
		$lat = 
		    $latdir = 
			$lon = 
			    $londir = 
				$speed = 
				    $dir = 
					$date = 
					    $mag = 
						$magvar = ""
						    
}


sub monitor {

    $oldt = time;
    while(<GPS>) {
	
	@Sentence = split(',', $_);
	
	if ($Sentence[0] eq "\$GPGGA" && $Sentence[2] ne '') {
	    
	    $time = $Sentence[1];
	    $lat = $Sentence[2]/100;
	    $latdir = $Sentence[3];
	    $lon = $Sentence[4]/100;
	    $londir = $Sentence[5];
	    $birds = $Sentence[7];
	    $hdop = $Sentence[8];



	    if ($birds > 2) {
		$valid = 1;
	    } else {
		$valid = 0;
	    }
	    
	} elsif ($Sentence[0] eq "\$GPRMC" && $Sentence[3] ne '') {
	    
	    $time = $Sentence[1];
	    $lat = $Sentence[3]/100;
	    $latdir = $Sentence[4];
	    $lon = $Sentence[5]/100;
	    $londir = $Sentence[6];
	    $speed = $Sentence[7];
	    $dir = $Sentence[8];
	    $date = $Sentence[9];
	    $mag = $Sentence[10];
	    $magvar = $Sentence[11];
	    
	    if ($Sentence[2] eq 'A') {
		$valid = 1;
	    } else {
		$valid = 0;
	    }

	} 

	
	if (time - $oldt > 9 && $lat ne '') {
	    
	    # convert to decimal degrees
	    # the raw gps output format is in degreesminutes.decimalseconds

	    $lonmin = $latmin = "";

	    ($latdeg, $latmin, $latsec) = ($1, $2, $3) if $lat =~ m/(\d\d)\.(\d\d)(.*)/;
	    ($londeg, $lonmin, $lonsec) = ($1, $2, $3) if $lon =~ m/(\d\d)\.(\d\d)(.*)/;
	    
	    $latmin .= "." . "$latsec";
	    $lonmin .= "." . "$lonsec";
	    
	    $latitude = $latdeg + $latmin/60;
	    $longitude = $londeg + $lonmin/60;
	    
	    $latitude *= -1 if $latdir eq 'S';
	    $longitude *= -1 if $londir eq 'W';
	    
	    spew();
	    $oldt = time;
	}
    }
}

sub spew {
    $ts = time;
    print LOC "$ts,$latitude,$longitude,$birds,$hdop,$date,$time,$speed,$dir\n";
    
}
    


initialize();
monitor();