MBXViewController.mm

#import "MBXViewController.h"
#import "MBXCustomCalloutView.h"
#import "MBXOfflinePacksTableViewController.h"

#import <Mapbox/Mapbox.h>
#import "../../../include/mbgl/util/default_styles.hpp"

#import <CoreLocation/CoreLocation.h>
#import <OpenGLES/ES2/gl.h>

static UIColor *const kTintColor = [UIColor colorWithRed:0.120 green:0.550 blue:0.670 alpha:1.000];
static NSString * const kCustomCalloutTitle = @"Custom Callout";

static const CLLocationCoordinate2D WorldTourDestinations[] = {
    { 38.9131982, -77.0325453144239 },
    { 37.7757368, -122.4135302 },
    { 12.9810816, 77.6368034 },
    { -13.15589555, -74.2178961777998 },
};

@interface MBXViewController () <UIActionSheetDelegate, MGLMapViewDelegate>

@property (nonatomic) IBOutlet MGLMapView *mapView;
@property (nonatomic) NSUInteger styleIndex;

@end

@implementation MBXViewController
{
    BOOL _isTouringWorld;
    BOOL _isShowingCustomStyleLayer;
}

#pragma mark - Setup

+ (void)initialize
{
    if (self == [MBXViewController class])
    {
        [[NSUserDefaults standardUserDefaults] registerDefaults:@{
            @"MBXUserTrackingMode": @(MGLUserTrackingModeNone),
            @"MBXShowsUserLocation": @NO,
            @"MBXDebug": @NO,
        }];
    }
}

- (void)viewDidLoad
{
    [super viewDidLoad];
    
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(saveState:) name:UIApplicationDidEnterBackgroundNotification object:nil];
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(restoreState:) name:UIApplicationWillEnterForegroundNotification object:nil];
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(saveState:) name:UIApplicationWillTerminateNotification object:nil];

    self.styleIndex = 0;

    UIButton *titleButton = (UIButton *)self.navigationItem.titleView;
    [titleButton setTitle:@(mbgl::util::default_styles::orderedStyles[self.styleIndex].name) forState:UIControlStateNormal];

    [self restoreState:nil];
}

- (void)saveState:(__unused NSNotification *)notification
{
    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
    NSData *archivedCamera = [NSKeyedArchiver archivedDataWithRootObject:self.mapView.camera];
    [defaults setObject:archivedCamera forKey:@"MBXCamera"];
    [defaults setInteger:self.mapView.userTrackingMode forKey:@"MBXUserTrackingMode"];
    [defaults setBool:self.mapView.showsUserLocation forKey:@"MBXShowsUserLocation"];
    [defaults setInteger:self.mapView.debugMask forKey:@"MBXDebugMask"];
    [defaults synchronize];
}

- (void)restoreState:(__unused NSNotification *)notification
{
    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
    NSData *archivedCamera = [defaults objectForKey:@"MBXCamera"];
    MGLMapCamera *camera = archivedCamera ? [NSKeyedUnarchiver unarchiveObjectWithData:archivedCamera] : nil;
    if (camera)
    {
        self.mapView.camera = camera;
    }
    NSInteger uncheckedTrackingMode = [defaults integerForKey:@"MBXUserTrackingMode"];
    if (uncheckedTrackingMode >= 0 &&
        (NSUInteger)uncheckedTrackingMode >= MGLUserTrackingModeNone &&
        (NSUInteger)uncheckedTrackingMode <= MGLUserTrackingModeFollowWithCourse)
    {
        self.mapView.userTrackingMode = (MGLUserTrackingMode)uncheckedTrackingMode;
    }
    self.mapView.showsUserLocation = [defaults boolForKey:@"MBXShowsUserLocation"];
    NSInteger uncheckedDebugMask = [defaults integerForKey:@"MBXDebugMask"];
    if (uncheckedDebugMask >= 0)
    {
        self.mapView.debugMask = (MGLMapDebugMaskOptions)uncheckedDebugMask;
    }
}

- (NSUInteger)supportedInterfaceOrientations
{
    return UIInterfaceOrientationMaskAll;
}

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(__unused id)sender {
    if ([segue.identifier isEqualToString:@"ShowOfflinePacks"]) {
        MBXOfflinePacksTableViewController *controller = [segue destinationViewController];
        controller.mapView = self.mapView;
    }
}

#pragma mark - Actions

- (IBAction)showSettings:(__unused id)sender
{
    MGLMapDebugMaskOptions debugMask = self.mapView.debugMask;
    UIActionSheet *sheet = [[UIActionSheet alloc] initWithTitle:@"Map Settings"
                                                       delegate:self
                                              cancelButtonTitle:@"Cancel"
                                         destructiveButtonTitle:nil
                                              otherButtonTitles:
                            @"Reset Position",
                            ((debugMask & MGLMapDebugTileBoundariesMask)
                             ? @"Hide Tile Boundaries"
                             : @"Show Tile Boundaries"),
                            ((debugMask & MGLMapDebugTileInfoMask)
                             ? @"Hide Tile Info"
                             : @"Show Tile Info"),
                            ((debugMask & MGLMapDebugTimestampsMask)
                             ? @"Hide Tile Timestamps"
                             : @"Show Tile Timestamps"),
                            ((debugMask & MGLMapDebugCollisionBoxesMask)
                             ? @"Hide Collision Boxes"
                             : @"Show Collision Boxes"),
                            @"Empty Memory",
                            @"Add 100 Points",
                            @"Add 1,000 Points",
                            @"Add 10,000 Points",
                            @"Add Test Shapes",
                            @"Start World Tour",
                            @"Add Custom Callout Point",
                            @"Remove Annotations",
                            (_isShowingCustomStyleLayer
                             ? @"Hide Custom Style Layer"
                             : @"Show Custom Style Layer"),
                            @"Print Telemetry Logfile",
                            @"Delete Telemetry Logfile",
                            nil];

    [sheet showFromBarButtonItem:self.navigationItem.leftBarButtonItem animated:YES];
}

- (void)actionSheet:(UIActionSheet *)actionSheet didDismissWithButtonIndex:(NSInteger)buttonIndex
{
    if (buttonIndex == actionSheet.firstOtherButtonIndex)
    {
        [self.mapView resetPosition];
    }
    else if (buttonIndex == actionSheet.firstOtherButtonIndex + 1)
    {
        self.mapView.debugMask ^= MGLMapDebugTileBoundariesMask;
    }
    else if (buttonIndex == actionSheet.firstOtherButtonIndex + 2)
    {
        self.mapView.debugMask ^= MGLMapDebugTileInfoMask;
    }
    else if (buttonIndex == actionSheet.firstOtherButtonIndex + 3)
    {
        self.mapView.debugMask ^= MGLMapDebugTimestampsMask;
    }
    else if (buttonIndex == actionSheet.firstOtherButtonIndex + 4)
    {
        self.mapView.debugMask ^= MGLMapDebugCollisionBoxesMask;
    }
    else if (buttonIndex == actionSheet.firstOtherButtonIndex + 5)
    {
        [self.mapView emptyMemoryCache];
    }
    else if (buttonIndex == actionSheet.firstOtherButtonIndex + 6)
    {
        [self parseFeaturesAddingCount:100];
    }
    else if (buttonIndex == actionSheet.firstOtherButtonIndex + 7)
    {
        [self parseFeaturesAddingCount:1000];
    }
    else if (buttonIndex == actionSheet.firstOtherButtonIndex + 8)
    {
        [self parseFeaturesAddingCount:10000];
    }
    else if (buttonIndex == actionSheet.firstOtherButtonIndex + 9)
    {
        // PNW triangle
        //
        CLLocationCoordinate2D triangleCoordinates[3] =
        {
            CLLocationCoordinate2DMake(44, -122),
            CLLocationCoordinate2DMake(46, -122),
            CLLocationCoordinate2DMake(46, -121)
        };

        MGLPolygon *triangle = [MGLPolygon polygonWithCoordinates:triangleCoordinates count:3];

        [self.mapView addAnnotation:triangle];

        // Orcas Island hike
        //
        NSDictionary *hike = [NSJSONSerialization JSONObjectWithData:
                                 [NSData dataWithContentsOfFile:
                                     [[NSBundle mainBundle] pathForResource:@"polyline" ofType:@"geojson"]]
                                                             options:0
                                                               error:nil];

        NSArray *hikeCoordinatePairs = hike[@"features"][0][@"geometry"][@"coordinates"];

        CLLocationCoordinate2D *polylineCoordinates = (CLLocationCoordinate2D *)malloc([hikeCoordinatePairs count] * sizeof(CLLocationCoordinate2D));

        for (NSUInteger i = 0; i < [hikeCoordinatePairs count]; i++)
        {
            polylineCoordinates[i] = CLLocationCoordinate2DMake([hikeCoordinatePairs[i][1] doubleValue], [hikeCoordinatePairs[i][0] doubleValue]);
        }

        MGLPolyline *polyline = [MGLPolyline polylineWithCoordinates:polylineCoordinates
                                                               count:[hikeCoordinatePairs count]];

        [self.mapView addAnnotation:polyline];

        free(polylineCoordinates);

        // PA/NJ/DE polys
        //
        NSDictionary *threestates = [NSJSONSerialization JSONObjectWithData:
                              [NSData dataWithContentsOfFile:
                               [[NSBundle mainBundle] pathForResource:@"threestates" ofType:@"geojson"]]
                                                             options:0
                                                               error:nil];

        for (NSDictionary *feature in threestates[@"features"])
        {
            NSArray *stateCoordinatePairs = feature[@"geometry"][@"coordinates"];

            while ([stateCoordinatePairs count] == 1) stateCoordinatePairs = stateCoordinatePairs[0];

            CLLocationCoordinate2D *polygonCoordinates = (CLLocationCoordinate2D *)malloc([stateCoordinatePairs count] * sizeof(CLLocationCoordinate2D));

            for (NSUInteger i = 0; i < [stateCoordinatePairs count]; i++)
            {
                polygonCoordinates[i] = CLLocationCoordinate2DMake([stateCoordinatePairs[i][1] doubleValue], [stateCoordinatePairs[i][0] doubleValue]);
            }

            MGLPolygon *polygon = [MGLPolygon polygonWithCoordinates:polygonCoordinates count:[stateCoordinatePairs count]];

            [self.mapView addAnnotation:polygon];

            free(polygonCoordinates);
        }
    }
    else if (buttonIndex == actionSheet.firstOtherButtonIndex + 10)
    {
        [self startWorldTour:actionSheet];
    }
    else if (buttonIndex == actionSheet.firstOtherButtonIndex + 11)
    {
        [self presentAnnotationWithCustomCallout];
    }
    else if (buttonIndex == actionSheet.firstOtherButtonIndex + 12)
    {
        [self.mapView removeAnnotations:self.mapView.annotations];
    }
    else if (buttonIndex == actionSheet.firstOtherButtonIndex + 13)
    {
        if (_isShowingCustomStyleLayer)
        {
            [self removeCustomStyleLayer];
        }
        else
        {
            [self insertCustomStyleLayer];
        }
    }
    else if (buttonIndex == actionSheet.firstOtherButtonIndex + 14)
    {
        NSString *fileContents = [NSString stringWithContentsOfFile:[self telemetryDebugLogfilePath] encoding:NSUTF8StringEncoding error:nil];
        NSLog(@"%@", fileContents);
    }
    else if (buttonIndex == actionSheet.firstOtherButtonIndex + 15)
    {
        NSString *filePath = [self telemetryDebugLogfilePath];
        if ([[NSFileManager defaultManager] isDeletableFileAtPath:filePath]) {
            NSError *error;
            BOOL success = [[NSFileManager defaultManager] removeItemAtPath:filePath error:&error];
            if (success) {
                NSLog(@"Deleted telemetry log.");
            } else {
                NSLog(@"Error deleting telemetry log: %@", error.localizedDescription);
            }
        }
    }
}

- (void)parseFeaturesAddingCount:(NSUInteger)featuresCount
{
    [self.mapView removeAnnotations:self.mapView.annotations];

    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^
    {
        NSData *featuresData = [NSData dataWithContentsOfFile:[[NSBundle mainBundle] pathForResource:@"points" ofType:@"geojson"]];

        id features = [NSJSONSerialization JSONObjectWithData:featuresData
                                                      options:0
                                                        error:nil];

        if ([features isKindOfClass:[NSDictionary class]])
        {
            NSMutableArray *annotations = [NSMutableArray array];

            for (NSDictionary *feature in features[@"features"])
            {
                CLLocationCoordinate2D coordinate = CLLocationCoordinate2DMake([feature[@"geometry"][@"coordinates"][1] doubleValue],
                                                                               [feature[@"geometry"][@"coordinates"][0] doubleValue]);
                NSString *title = feature[@"properties"][@"NAME"];

                MGLPointAnnotation *annotation = [MGLPointAnnotation new];
                annotation.coordinate = coordinate;
                annotation.title = title;

                [annotations addObject:annotation];

                if (annotations.count == featuresCount) break;
            }

            dispatch_async(dispatch_get_main_queue(), ^
            {
                [self.mapView addAnnotations:annotations];
                [self.mapView showAnnotations:annotations animated:YES];
            });
        }
    });
}

- (void)insertCustomStyleLayer
{
    _isShowingCustomStyleLayer = YES;

    static const GLchar *vertexShaderSource = "attribute vec2 a_pos; void main() { gl_Position = vec4(a_pos, 0, 1); }";
    static const GLchar *fragmentShaderSource = "void main() { gl_FragColor = vec4(0, 1, 0, 1); }";
    
    __block GLuint program = 0;
    __block GLuint vertexShader = 0;
    __block GLuint fragmentShader = 0;
    __block GLuint buffer = 0;
    __block GLuint a_pos = 0;
    [self.mapView insertCustomStyleLayerWithIdentifier:@"mbx-custom" preparationHandler:^{
        program = glCreateProgram();
        vertexShader = glCreateShader(GL_VERTEX_SHADER);
        fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
        
        glShaderSource(vertexShader, 1, &vertexShaderSource, nullptr);
        glCompileShader(vertexShader);
        glAttachShader(program, vertexShader);
        glShaderSource(fragmentShader, 1, &fragmentShaderSource, nullptr);
        glCompileShader(fragmentShader);
        glAttachShader(program, fragmentShader);
        glLinkProgram(program);
        a_pos = glGetAttribLocation(program, "a_pos");
        
        GLfloat background[] = { -1,-1, 1,-1, -1,1, 1,1 };
        glGenBuffers(1, &buffer);
        glBindBuffer(GL_ARRAY_BUFFER, buffer);
        glBufferData(GL_ARRAY_BUFFER, 8 * sizeof(GLfloat), background, GL_STATIC_DRAW);
    } drawingHandler:^(__unused CGSize size,
                       __unused CLLocationCoordinate2D centerCoordinate,
                       __unused double zoomLevel,
                       __unused CLLocationDirection direction,
                       __unused CGFloat pitch,
                       __unused CGFloat perspectiveSkew) {
        glUseProgram(program);
        glBindBuffer(GL_ARRAY_BUFFER, buffer);
        glEnableVertexAttribArray(a_pos);
        glVertexAttribPointer(a_pos, 2, GL_FLOAT, GL_FALSE, 0, NULL);
        glDisable(GL_STENCIL_TEST);
        glDisable(GL_DEPTH_TEST);
        glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
    } completionHandler:^{
        if (program) {
            glDeleteBuffers(1, &buffer);
            glDetachShader(program, vertexShader);
            glDetachShader(program, fragmentShader);
            glDeleteShader(vertexShader);
            glDeleteShader(fragmentShader);
            glDeleteProgram(program);
        }
    } belowStyleLayerWithIdentifier:@"housenum-label"];
}

- (void)removeCustomStyleLayer
{
    _isShowingCustomStyleLayer = NO;
    [self.mapView removeCustomStyleLayerWithIdentifier:@"mbx-custom"];
}

- (void)presentAnnotationWithCustomCallout
{
    [self.mapView removeAnnotations:self.mapView.annotations];
    
    MGLPointAnnotation *annotation = [MGLPointAnnotation new];
    annotation.coordinate = CLLocationCoordinate2DMake(48.8533940, 2.3775439);
    annotation.title = kCustomCalloutTitle;
    
    [self.mapView addAnnotation:annotation];
    [self.mapView showAnnotations:@[annotation] animated:YES];
}

- (IBAction)handleLongPress:(UILongPressGestureRecognizer *)longPress
{
    if (longPress.state == UIGestureRecognizerStateBegan)
    {
        MGLPointAnnotation *point = [MGLPointAnnotation new];
        point.coordinate = [self.mapView convertPoint:[longPress locationInView:longPress.view]
                                 toCoordinateFromView:self.mapView];
        point.title = @"Dropped Marker";
        point.subtitle = [NSString stringWithFormat:@"lat: %.3f, lon: %.3f", point.coordinate.latitude, point.coordinate.longitude];
        [self.mapView addAnnotation:point];
        [self.mapView selectAnnotation:point animated:YES];
    }
}

- (IBAction)cycleStyles:(__unused id)sender
{
    UIButton *titleButton = (UIButton *)self.navigationItem.titleView;

    self.styleIndex = (self.styleIndex + 1) % mbgl::util::default_styles::numOrderedStyles;

    self.mapView.styleURL = [NSURL URLWithString:@(mbgl::util::default_styles::orderedStyles[self.styleIndex].url)];

    [titleButton setTitle:@(mbgl::util::default_styles::orderedStyles[self.styleIndex].name) forState:UIControlStateNormal];
}

- (IBAction)locateUser:(__unused id)sender
{
    MGLUserTrackingMode nextMode;
    switch (self.mapView.userTrackingMode) {
        case MGLUserTrackingModeNone:
            nextMode = MGLUserTrackingModeFollow;
            break;
        case MGLUserTrackingModeFollow:
            nextMode = MGLUserTrackingModeFollowWithHeading;
            break;
        case MGLUserTrackingModeFollowWithHeading:
            nextMode = MGLUserTrackingModeFollowWithCourse;
            break;
        case MGLUserTrackingModeFollowWithCourse:
            nextMode = MGLUserTrackingModeNone;
            break;
    }
    self.mapView.userTrackingMode = nextMode;
}

- (IBAction)startWorldTour:(__unused id)sender
{
    _isTouringWorld = YES;
    
    [self.mapView removeAnnotations:self.mapView.annotations];
    NSUInteger numberOfAnnotations = sizeof(WorldTourDestinations) / sizeof(WorldTourDestinations[0]);
    NSMutableArray *annotations = [NSMutableArray arrayWithCapacity:numberOfAnnotations];
    for (NSUInteger i = 0; i < numberOfAnnotations; i++)
    {
        MGLPointAnnotation *annotation = [[MGLPointAnnotation alloc] init];
        annotation.coordinate = WorldTourDestinations[i];
        [annotations addObject:annotation];
    }
    [self.mapView addAnnotations:annotations];
    [self continueWorldTourWithRemainingAnnotations:annotations];
}

- (void)continueWorldTourWithRemainingAnnotations:(NS_MUTABLE_ARRAY_OF(MGLPointAnnotation *) *)annotations
{
    MGLPointAnnotation *nextAnnotation = annotations.firstObject;
    if (!nextAnnotation || !_isTouringWorld)
    {
        _isTouringWorld = NO;
        return;
    }
    
    [annotations removeObjectAtIndex:0];
    MGLMapCamera *camera = [MGLMapCamera cameraLookingAtCenterCoordinate:nextAnnotation.coordinate
                                                            fromDistance:10
                                                                   pitch:arc4random_uniform(60)
                                                                 heading:arc4random_uniform(360)];
    __weak MBXViewController *weakSelf = self;
    [self.mapView flyToCamera:camera completionHandler:^{
        MBXViewController *strongSelf = weakSelf;
        [strongSelf performSelector:@selector(continueWorldTourWithRemainingAnnotations:)
                         withObject:annotations
                         afterDelay:2];
    }];
}

- (NSString *)telemetryDebugLogfilePath
{
    NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
    [dateFormatter setDateFormat:@"yyyy'-'MM'-'dd"];
    [dateFormatter setTimeZone:[NSTimeZone systemTimeZone]];
    NSString *filePath = [[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) firstObject] stringByAppendingPathComponent:[NSString stringWithFormat:@"telemetry_log-%@.json", [dateFormatter stringFromDate:[NSDate date]]]];

    return filePath;
}

- (IBAction)unwindToMapViewController:(__unused UIStoryboardSegue *)sender {
}

#pragma mark - Destruction

- (void)dealloc
{
    [[NSNotificationCenter defaultCenter] removeObserver:self];

    [self saveState:nil];
}

#pragma mark - MGLMapViewDelegate

- (MGLAnnotationImage *)mapView:(MGLMapView * __nonnull)mapView imageForAnnotation:(id <MGLAnnotation> __nonnull)annotation
{
    if ([annotation.title isEqualToString:@"Dropped Marker"]
        || [annotation.title isEqualToString:kCustomCalloutTitle])
    {
        return nil; // use default marker
    }

    NSString *title = [(MGLPointAnnotation *)annotation title];
    if (!title.length) return nil;
    NSString *lastTwoCharacters = [title substringFromIndex:title.length - 2];

    UIColor *color;

    // make every tenth annotation blue
    if ([lastTwoCharacters hasSuffix:@"0"]) {
        color = [UIColor blueColor];
    } else {
        color = [UIColor redColor];
    }

    MGLAnnotationImage *image = [mapView dequeueReusableAnnotationImageWithIdentifier:lastTwoCharacters];

    if ( ! image)
    {
        CGRect rect = CGRectMake(0, 0, 20, 15);

        UIGraphicsBeginImageContextWithOptions(rect.size, NO, [[UIScreen mainScreen] scale]);

        CGContextRef ctx = UIGraphicsGetCurrentContext();

        CGContextSetFillColorWithColor(ctx, [[color colorWithAlphaComponent:0.75] CGColor]);
        CGContextFillRect(ctx, rect);

        CGContextSetStrokeColorWithColor(ctx, [[UIColor blackColor] CGColor]);
        CGContextStrokeRectWithWidth(ctx, rect, 2);

        NSAttributedString *drawString = [[NSAttributedString alloc] initWithString:lastTwoCharacters attributes:@{
            NSFontAttributeName: [UIFont fontWithName:@"Arial-BoldMT" size:12],
            NSForegroundColorAttributeName: [UIColor whiteColor] }];
        CGSize stringSize = drawString.size;
        CGRect stringRect = CGRectMake((rect.size.width - stringSize.width) / 2,
                                       (rect.size.height - stringSize.height) / 2,
                                       stringSize.width,
                                       stringSize.height);
        [drawString drawInRect:stringRect];

        image = [MGLAnnotationImage annotationImageWithImage:UIGraphicsGetImageFromCurrentImageContext() reuseIdentifier:lastTwoCharacters];

        // don't allow touches on blue annotations
        if ([color isEqual:[UIColor blueColor]]) image.enabled = NO;

        UIGraphicsEndImageContext();
    }

    return image;
}

- (BOOL)mapView:(__unused MGLMapView *)mapView annotationCanShowCallout:(__unused id <MGLAnnotation>)annotation
{
    return YES;
}

- (CGFloat)mapView:(__unused MGLMapView *)mapView alphaForShapeAnnotation:(MGLShape *)annotation
{
    return ([annotation isKindOfClass:[MGLPolygon class]] ? 0.5 : 1.0);
}

- (UIColor *)mapView:(__unused MGLMapView *)mapView strokeColorForShapeAnnotation:(MGLShape *)annotation
{
    return ([annotation isKindOfClass:[MGLPolyline class]] ? [UIColor purpleColor] : [UIColor blackColor]);
}

- (UIColor *)mapView:(__unused MGLMapView *)mapView fillColorForPolygonAnnotation:(__unused MGLPolygon *)annotation
{
    return (annotation.pointCount > 3 ? [UIColor greenColor] : [UIColor redColor]);
}

- (void)mapView:(__unused MGLMapView *)mapView didChangeUserTrackingMode:(MGLUserTrackingMode)mode animated:(__unused BOOL)animated
{
    UIImage *newButtonImage;
    NSString *newButtonTitle;

    switch (mode) {
        case MGLUserTrackingModeNone:
            newButtonImage = [UIImage imageNamed:@"TrackingLocationOffMask.png"];
            break;

        case MGLUserTrackingModeFollow:
            newButtonImage = [UIImage imageNamed:@"TrackingLocationMask.png"];
            break;

        case MGLUserTrackingModeFollowWithHeading:
            newButtonImage = [UIImage imageNamed:@"TrackingHeadingMask.png"];
            break;
        case MGLUserTrackingModeFollowWithCourse:
            newButtonImage = nil;
            newButtonTitle = @"Course";
            break;
    }

    self.navigationItem.rightBarButtonItem.title = newButtonTitle;
    [UIView animateWithDuration:0.25 animations:^{
        self.navigationItem.rightBarButtonItem.image = newButtonImage;
    }];
}

- (UIView<MGLCalloutView> *)mapView:(__unused MGLMapView *)mapView calloutViewForAnnotation:(id<MGLAnnotation>)annotation
{
    if ([annotation respondsToSelector:@selector(title)]
        && [annotation.title isEqualToString:kCustomCalloutTitle])
    {
        MBXCustomCalloutView *calloutView = [[MBXCustomCalloutView alloc] init];
        calloutView.representedObject = annotation;
        return calloutView;
    }
    return nil;
}

@end