1 files changed, 47 insertions, 0 deletions
diff --git a/app/src/main/java/se/leap/bitmaskclient/base/utils/TimezoneHelper.java b/app/src/main/java/se/leap/bitmaskclient/base/utils/TimezoneHelper.java
new file mode 100644
index 00000000..63b12fd3
--- /dev/null
+++ b/app/src/main/java/se/leap/bitmaskclient/base/utils/TimezoneHelper.java
@@ -0,0 +1,47 @@
+package se.leap.bitmaskclient.base.utils;
+
+import androidx.annotation.VisibleForTesting;
+
+import java.util.Calendar;
+
+import de.blinkt.openvpn.core.NativeUtils;
+
+public class TimezoneHelper {
+
+    public interface TimezoneInterface {
+        int getCurrentTimezone();
+    }
+
+    private static TimezoneInterface instance = new DefaultTimezoneHelper();
+
+    @VisibleForTesting
+    public TimezoneHelper(TimezoneInterface timezoneInterface) {
+        if (!NativeUtils.isUnitTest()) {
+            throw new IllegalStateException("TimezoneHelper injected with timezoneInterface outside of an unit test");
+        }
+        instance = timezoneInterface;
+    }
+
+    public static TimezoneInterface get() {
+        return instance;
+    }
+
+    public static int timezoneDistance(int localTimezone, int remoteTimezone) { // Distance along the numberline of Prime Meridian centric, assumes UTC-11 through UTC+12
+        int dist = Math.abs(localTimezone - remoteTimezone);
+        // 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;
+    }
+
+    public static int getCurrentTimezone() {
+        return get().getCurrentTimezone();
+    }
+
+    private static class DefaultTimezoneHelper implements TimezoneInterface {
+        @Override
+        public int getCurrentTimezone() {
+            return Calendar.getInstance().get(Calendar.ZONE_OFFSET) / 3600000;
+        }
+    }
+}