Event helper

@interface HCEventHelper()<EKEventEditViewDelegate>

@property (strong, nonatomic) EKEventStore *eventStore;
@property (weak, nonatomic) UIViewController *presentingViewController;
@property (weak, nonatomic) Session *session;

@end

@implementation HCEventHelper


#pragma mark - Interface

+(HCEventHelper *)sharedInstance
{
    static HCEventHelper *sharedInstance = nil;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        sharedInstance = [[HCEventHelper alloc] init];
    });
    return sharedInstance;
}


- (void)presentInViewController:(UIViewController *)viewController withSession:(Session *)session
{
    self.presentingViewController = viewController;
    self.session = session;
    [self checkEventStoreAccessForCalendar];
}


#pragma mark - Private


-(void)checkEventStoreAccessForCalendar
{
    EKAuthorizationStatus status = [EKEventStore authorizationStatusForEntityType:EKEntityTypeEvent];
    
    switch (status)
    {
        case EKAuthorizationStatusAuthorized:
            [self provideCalendarAccess];
            break;
        case EKAuthorizationStatusNotDetermined:
            [self requestCalendarAccess];
            break;
        case EKAuthorizationStatusDenied:
        case EKAuthorizationStatusRestricted:
            [self showMessage:@"Permission was not granted for Calendar" withTitle:@"Privacy Warning"];
            break;
        default:
            break;
    }
}

- (void) requestCalendarAccess
{
    __weak typeof (self) weakSelf = self;
    [self.eventStore requestAccessToEntityType:EKEntityTypeEvent completion:^(BOOL granted, NSError *error) {
        if (granted) {
            dispatch_async(dispatch_get_main_queue(), ^{
                [weakSelf provideCalendarAccess];
            });
        } else {
            dispatch_async(dispatch_get_main_queue(), ^{
                [weakSelf showMessage:@"Something went wrong. Try again." withTitle:@"Calendar Error"];
                NSLog(@"calendar error : %@", error);
            });
        }
    }];
}

- (void) provideCalendarAccess
{
    EKEventEditViewController *addController = [[EKEventEditViewController alloc] init];
	
    EKEvent *event = [EKEvent eventWithEventStore:self.eventStore];
    event.title = self.session.name;
    event.location = self.session.location.name;
    event.startDate = self.session.startDate;
    event.endDate = self.session.endDate;
    
    addController.event = event;
	addController.eventStore = self.eventStore;
    addController.editViewDelegate = self;
    [self.presentingViewController presentViewController:addController animated:YES completion:nil];
}

- (void) showMessage: (NSString *) message withTitle: (NSString *) title
{
    UIAlertView *alert = [[UIAlertView alloc] initWithTitle:title message: message
                                                   delegate:nil
                                          cancelButtonTitle:@"OK"
                                          otherButtonTitles:nil];
    [alert show];
}


-(instancetype)init
{
    if (!(self = [super init])) {
        return nil;
    }
    [self setup];
    return self;
}

-(void) setup
{
    self.eventStore = [[EKEventStore alloc] init];
}


#pragma mark - EKEventEditViewDelegate

- (void)eventEditViewController:(EKEventEditViewController *)controller didCompleteWithAction:(EKEventEditViewAction)action
{
    __weak typeof (self) weakSelf = self;
    [self.presentingViewController dismissViewControllerAnimated:YES completion:^{
        if (action != EKEventEditViewActionCanceled) {
            [weakSelf showMessage:@"Event saved to calendar!" withTitle:@"Saved"];
        }
    }];
}

@end