mapbox · zugaldia · May 13, 2016
diff --git a/libjava/lib/src/main/java/com/mapbox/services/commons/turf/TurfMisc.java b/libjava/lib/src/main/java/com/mapbox/services/commons/turf/TurfMisc.java
@@ -55,7 +55,7 @@ public static LineString lineSlice(Point startPt, Point stopPt, LineString line)
         return clipLine;
     }
 
-    private static Feature pointOnLine(Point pt, List<Position> coords) throws TurfException {
+    public static Feature pointOnLine(Point pt, List<Position> coords) throws TurfException {
         String units = TurfConstants.UNIT_MILES;
 
         Feature closestPt = Feature.fromGeometry(

diff --git a/libjava/lib/src/main/java/com/mapbox/services/navigation/CurrentStepModel.java b/libjava/lib/src/main/java/com/mapbox/services/navigation/CurrentStepModel.java
@@ -0,0 +1,22 @@
+package com.mapbox.services.navigation;
+
+import com.mapbox.services.commons.geojson.Point;
+import com.mapbox.services.commons.turf.TurfMeasurement;
+
+/**
+ * Created by antonio on 5/13/16.
+ */
+public class CurrentStepModel {
+
+    public double step;
+    public double distance;
+    public Point snapToLocation;
+
+    public double stepDistance;
+    public boolean shouldReRoute;
+    public double absoluteDistance;
+
+    public boolean alertUserLevelLow;
+    public boolean alertUserLevelHigh;
+
+}
diff --git a/libjava/lib/src/main/java/com/mapbox/services/navigation/NavigationUtils.java b/libjava/lib/src/main/java/com/mapbox/services/navigation/NavigationUtils.java
@@ -0,0 +1,109 @@
+package com.mapbox.services.navigation;
+
+import com.mapbox.services.Constants;
+import com.mapbox.services.commons.geojson.Feature;
+import com.mapbox.services.commons.geojson.LineString;
+import com.mapbox.services.commons.geojson.Point;
+import com.mapbox.services.commons.models.Position;
+import com.mapbox.services.commons.turf.TurfConstants;
+import com.mapbox.services.commons.turf.TurfException;
+import com.mapbox.services.commons.turf.TurfMeasurement;
+import com.mapbox.services.commons.turf.TurfMisc;
+import com.mapbox.services.directions.v5.models.RouteLeg;
+
+import java.util.List;
+
+/**
+ * This is a port of https://github.com/mapbox/navigation.js to Java, an utility for monitoring
+ * a user location in relation to a route.
+ */
+public class NavigationUtils {
+
+    // Constants
+    private final static double feetToMiles = 0.000189394;
+    private final static double metersToMiles = 0.000621371;
+    private final static double feetToKilometers = 0.0003048;
+    private final static double metersToKilometers = 1000;
+    private final static double metersToFeet = 3.28084;
+
+    // Either `miles` or `km`
+    private final String units = TurfConstants.UNIT_MILES;
+
+    // Number of seconds ahead of maneuver to warn user about maneuver.
+    private final double warnUserTime = 30;
+
+    // Bearing threshold for the user to complete a step.
+    private final double userBearingCompleteThreshold = 30;
+
+    // Max distance the user can be from the route.
+    private final double maxReRouteDistance = 150 * feetToMiles;
+
+    // Max distance to snap user to route.
+    private final double maxSnapToLocation = 50 * feetToMiles;
+
+    // Distance away from end of step that is considered a completion. If this distance is
+    // shorter than the step distance, it will be changed to 10ft.
+    private final double completionDistance = 50 * feetToMiles;
+
+    // If the step is shorter than the `completionDistance`, this distance will be used to
+    // calculate if the step has been completed.
+    private final double shortCompletionDistance = 10 * feetToMiles;
+
+    /**
+     * Given a user location and route, calculates closest step to user.
+     */
+    public CurrentStepModel getCurrentStep(Point user, RouteLeg route, int userCurrentStep, Double userBearing) throws TurfException {
+        CurrentStepModel currentStep = new CurrentStepModel();
+
+        LineString lineString = LineString.fromPolyline(route.getSteps().get(userCurrentStep).getGeometry(), Constants.OSRM_PRECISION_V5);
+        List<Position> stepCoordinates = lineString.getCoordinates();
+
+        Feature segmentRoute = Feature.fromGeometry(LineString.fromCoordinates(stepCoordinates));
+
+        Feature closestPoint = TurfMisc.pointOnLine(user, stepCoordinates);
+        double distance = TurfMeasurement.distance(user, (Point)closestPoint.getGeometry(), this.units);
+
+        Feature segmentEndPoint = Feature.fromGeometry(Point.fromCoordinates(stepCoordinates.get(stepCoordinates.size() - 1)));
+        LineString segmentSlicedToUser = TurfMisc.lineSlice(user, (Point) segmentEndPoint.getGeometry(), segmentRoute);
+        double userDistanceToEndStep = TurfMeasurement.lineDistance(segmentSlicedToUser, this.units);
+
+        //
+        // Check if user has completed step. Two factors:
+        //   1. Are they within a certain threshold of the end of the step?
+        //   2. If a bearing is provided, is their bearing within a current threshold of the exit bearing for the step
+        //
+        double stepDistance = (this.units == "miles")
+                ? route.getSteps().get(userCurrentStep).getDistance() * metersToMiles
+                : route.getSteps().get(userCurrentStep).getDistance() * metersToKilometers;
+
+        // If the step distance is less than this.completionDistance, modify it and make it 10 ft
+        double modifiedCompletionDistance = stepDistance < this.completionDistance
+                ? this.shortCompletionDistance : this.completionDistance;
+
+        // Check if users bearing is within threshold of the steps exit bearing
+        boolean withinBearingThreshold = userBearing != null
+                ? Math.abs(userBearing - route.getSteps().get(userCurrentStep).getManeuver().getBearingAfter()) <= this.userBearingCompleteThreshold ? true : false
+                : true;
+
+        // Do not increment userCurrentStep if the user is approaching the final step
+        if (userCurrentStep < route.getSteps().size()- 2) {
+            currentStep.step = withinBearingThreshold && (userDistanceToEndStep < modifiedCompletionDistance)
+                    ? userCurrentStep + 1 : userCurrentStep; // Don't set next step + 1 if at the end of the route
+        } else {
+            currentStep.step = userCurrentStep;
+        }
+
+        currentStep.distance = userDistanceToEndStep;
+        currentStep.stepDistance = stepDistance;
+        currentStep.shouldReRoute = TurfMeasurement.distance(user, (Point)closestPoint.getGeometry(), this.units) > this.maxReRouteDistance ? true : false;
+        currentStep.absoluteDistance = TurfMeasurement.distance(user, (Point)segmentEndPoint.getGeometry(), this.units);
+        currentStep.snapToLocation = distance < this.maxSnapToLocation ? (Point)closestPoint.getGeometry() : user;
+
+        // Alert levels
+        currentStep.alertUserLevelLow = userDistanceToEndStep < 1 && route.getSteps().get(userCurrentStep).getDistance() * metersToMiles > 1; // Step must be longer than 1 miles
+        currentStep.alertUserLevelHigh = (userDistanceToEndStep < 150 * feetToMiles) && route.getSteps().get(userCurrentStep).getDistance() * metersToFeet > 150; // Step must be longer than 150 ft
+
+        return currentStep;
+    }
+
+}