#!/usr/bin/env perl
# 
# Copyright: Markus Benning <me@w3r3wolf.de>
# License: GNU GPL, http://www.gnu.org/licenses/gpl.html

use strict;
use warnings;

use IO::File;
use Geo::Gpx;
use LWP::UserAgent;

my $infile = shift();
my $infh = IO::File->new("<".$infile);
my $gpx = Geo::Gpx->new( input => $infh );
my $ua = LWP::UserAgent->new();
$infh->close();

my $tracks = $gpx->tracks();

foreach my $track (@$tracks) {
	my $segments = $track->{'segments'};
	foreach my $segment (@$segments) {
		my $points = $segment->{'points'};
		my $last_ele;
		foreach my $point (@$points) {
			if(my $ele = get_ele($point)) {
				if($ele < 0 && defined $last_ele) {
					$ele = $last_ele;
				}
				$point->{'ele'} = $ele;
				$last_ele = $ele;
			}
			print STDERR $point->{'lat'}.', '.$point->{'lon'}.', >'.$point->{'ele'}."<\n";
		}
	}
}

print $gpx->xml();

sub get_ele {
	my $point = shift();
	my $ele;
	my $response = $ua->get('http://ws.geonames.org/srtm3?lat='.$point->{'lat'}.'&lng='.$point->{'lon'});

	if(!$response->is_success) {
		warn($response->status_line);
		return();
	}

	$ele = $response->content;
	$ele =~ s/[\r\n]+$//;
	return($ele);
}