1 files changed, 44 insertions, 0 deletions
diff --git a/app/src/main/java/se/leap/bitmaskclient/eip/GatewaySelector.java b/app/src/main/java/se/leap/bitmaskclient/eip/GatewaySelector.java
new file mode 100644
index 00000000..36b5fb41
--- /dev/null
+++ b/app/src/main/java/se/leap/bitmaskclient/eip/GatewaySelector.java
@@ -0,0 +1,44 @@
+package se.leap.bitmaskclient.eip;
+
+import java.security.cert.*;
+import java.util.*;
+import org.json.*;
+
+public class GatewaySelector {
+    List<Gateway> gateways;
+
+    public GatewaySelector(List<Gateway> gateways) {
+	this.gateways = gateways;
+    }
+
+    public Gateway select() {
+	return closestGateway();
+    }
+    
+    private Gateway closestGateway() {
+	TreeMap<Integer, Set<Gateway>> offsets = calculateOffsets();
+	return offsets.isEmpty() ? null : offsets.firstEntry().getValue().iterator().next();
+    }
+    
+    private TreeMap<Integer, Set<Gateway>> calculateOffsets() {
+	TreeMap<Integer, Set<Gateway>> offsets = new TreeMap<Integer, Set<Gateway>>();
+	int localOffset = Calendar.getInstance().get(Calendar.ZONE_OFFSET) / 3600000;
+	for(Gateway gateway : gateways) {
+	    int dist = timezoneDistance(localOffset, gateway.getTimezone());
+	    Set<Gateway> set = (offsets.get(dist) != null) ?
+		offsets.get(dist) : new HashSet<Gateway>();
+	    set.add(gateway);
+	    offsets.put(dist, set);
+	}
+	return offsets;
+    }
+    
+    private int timezoneDistance(int local_timezone, int remote_timezone) {
+	// Distance along the numberline of Prime Meridian centric, assumes UTC-11 through UTC+12
+	int dist = Math.abs(local_timezone - remote_timezone);
+	// Farther than 12 timezones and it's shorter around the "back"
+	if (dist > 12)
+	    dist = 12 - (dist -12); // Well i'll be. Absolute values make equations do funny things.
+	return dist;
+    }
+}