add get_stations_by_location method

3 files changed, 27 insertions, 0 deletions

diff --git a/Build.PL b/Build.PL
index 2c9237e..b0bcaa7 100644
--- a/Build.PL
+++ b/Build.PL
@@ -25,6 +25,7 @@ Module::Build->new(
 		'DateTime' => 0,
 		'DateTime::Format::Strptime' => 0,
 		'Encode' => 0,
+		'Geo::Distance' => 0,
 		'Getopt::Long' => 0,
 		'List::Compare' => '0.29',
 		'List::MoreUtils' => 0,
diff --git a/README b/README
index a2e7ec8..a5e842a 100644
--- a/README
+++ b/README
@@ -11,6 +11,7 @@ Dependencies
 * Class::Accessor
 * DateTime
 * DateTime::Format::Strptime
+* Geo::Distance
 * List::Compare
 * List::MoreUtils
 * List::UtilsBy
diff --git a/lib/Travel/Status/DE/IRIS/Stations.pm b/lib/Travel/Status/DE/IRIS/Stations.pm
index c9863ac..54245ca 100644
--- a/lib/Travel/Status/DE/IRIS/Stations.pm
+++ b/lib/Travel/Status/DE/IRIS/Stations.pm
@@ -5,11 +5,16 @@ use warnings;
 use 5.014;
 use utf8;
 
+use Geo::Distance;
 use List::Util qw(min);
 use List::UtilsBy qw(uniq_by);
 use List::MoreUtils qw(firstval pairwise);
 use Text::LevenshteinXS qw(distance);
 
+# TODO Geo::Distance is kinda deprecated, it is recommended to use GIS::Distance
+# instead. However, since GIS::Distance is not packaged for Debian, I'll stick
+# with Geo::Distance for now (which works fine enough here)
+
 # TODO switch to Text::Levenshtein::XS once AUR/Debian packages become available
 
 our $VERSION = '1.05';
@@ -8487,6 +8492,26 @@ sub get_station {
 	return get_station_by_name($name);
 }
 
+sub get_stations_by_location {
+	my ($lon, $lat, $num_matches) = @_;
+
+	$num_matches //= 10;
+
+	my $geo = Geo::Distance->new();
+
+	# we only use geolocations inside germany.
+	# For these, this fast preprocessing step will let through all
+	# coordinates inside a 60km radius (and a bunch which are farther out)
+	my @candidates = grep { $#{$_} >= 4 and abs($_->[3] - $lon) < 1 and abs($_->[4] - $lat) < 1 } @stations;
+	my @distances = map { $geo->distance('kilometer', $lon, $lat, $_->[3], $_->[4]) } @candidates;
+	my @station_map = pairwise { [ $a, $b ] } @candidates, @distances;
+
+	@station_map = sort { $a->[1] <=> $b->[1] } @station_map;
+	splice(@station_map, 10);
+
+	return @station_map;
+}
+
 sub get_station_by_name {
 	my ($name) = @_;