fix: robustify usage of maxspeed tag for ferry connections

Author: aoles

core/src/main/java/com/graphhopper/routing/util/FerrySpeedCalculator.java

@@ -74,9 +74,16 @@ public double getSpeed(ReaderWay way) {
             // OSM MOD start
             // Use maxspeed if available, see https://github.com/GIScience/openrouteservice/issues/620
             // Apply the same speed-reduction factor as in trip speed calculation above
-            double maxSpeed = com.graphhopper.routing.util.parsers.helpers.OSMValueExtractor.stringToKmh(way.getTag("maxspeed")) / 1.4;
-            if (maxSpeed > speedFactor / 2)
-                return maxSpeed;
+            if (way.hasTag("maxspeed")) {
+                String maxspeedTagValue = way.getTag("maxspeed");
+                double avarageSpeed = com.graphhopper.routing.util.parsers.helpers.OSMValueExtractor.stringToKmh(maxspeedTagValue) / 1.4;
+                if (avarageSpeed < speedFactor / 2)
+                    return speedFactor / 2;
+                if (avarageSpeed > maxSpeed)
+                    return maxSpeed;
+                if (Double.isFinite(avarageSpeed))
+                    return avarageSpeed;
+            }
             // OSM MOD end
             // unknown speed -> put penalty on ferry transport
             return unknownSpeed;

core/src/test/java/com/graphhopper/routing/util/FerrySpeedCalculatorTest.java

@@ -71,15 +71,26 @@ private void checkSpeed(FerrySpeedCalculator calc, String duration, Double dista
     @Test
     void testMaxSpeedTag() {
         double speedFactor = 2;
-        double maxSpeed = 55;
+        double maxSpeed = 30;
         double longSpeed = 30;
         double shortSpeed = 20;
         double unknownSpeed = 5;
         FerrySpeedCalculator c = new FerrySpeedCalculator(speedFactor, maxSpeed, longSpeed, shortSpeed, unknownSpeed);
 
+        // valid
+        checkMaxSpeed(c, "14", 10);
+        // above max (capped to max)
+        checkMaxSpeed(c, "45", maxSpeed);
+        // below smallest storable non-zero value
+        checkMaxSpeed(c, "1", speedFactor / 2);
+        // invalid value
+        checkMaxSpeed(c, "foo", unknownSpeed);
+    }
+
+    private void checkMaxSpeed(FerrySpeedCalculator calc, String maxspeed, double expected) {
         ReaderWay way = new ReaderWay(0L);
-        way.setTag("maxspeed", "14");
-        assertEquals(10, c.getSpeed(way));
+        way.setTag("maxspeed", maxspeed);
+        assertEquals(expected, calc.getSpeed(way));
     }
     // ORS-GH MOD END
 }