Switch route on tap like Google Maps

SwitchRoutes.swift

class RoutesViewController {
    
    /// ...
    
    func mapView(_ mapView: GMSMapView, didTapAt coordinate: CLLocationCoordinate2D) {
        if let index = self.shouldSelectPath(mapView, coordinate: coordinate, routes: results, currentRouteIndex: routeIndex) {
            routeIndex = index
            updateRoute()
        }
    }

    private func shouldSelectPath(_ mapView: GMSMapView, coordinate: CLLocationCoordinate2D, routes: [PXGoogleDirectionsRoute], currentRouteIndex: Int) -> Int? {
        for (index, route) in routes.enumerated() where index != currentRouteIndex  {
            if self.getMinDistance(mapView, path: route.path!, coordinate: coordinate) < 20 {
                return index
            }
        }
        return nil
    }

    private func getMinDistance(_ mapView: GMSMapView, path: GMSPath, coordinate: CLLocationCoordinate2D) -> Double {
        var minDistance: Double = Double.infinity
        for pathPointIndex in 0..<path.count() {
            let pathCoordinate = path.coordinate(at: pathPointIndex)
            let distance = mapView.distanceInPoints(coordinate1: coordinate, coordinate2: pathCoordinate)
            if distance < minDistance {
                minDistance = distance
            }
        }
        return minDistance
    }
}

// MARK: GMSMapView
extension GMSMapView {

    /// Returns the distance in point between CLLocationCoordinate2D
    ///
    /// - Parameters:
    ///   - coordinate1: The first coordinate
    ///   - coordinate2: The second coordinate
    /// - Returns: The distance
    func distanceInPoints(coordinate1: CLLocationCoordinate2D, coordinate2: CLLocationCoordinate2D) -> Double {
        let selectedPoint = self.projection.point(for: coordinate1)
        let pathPoint = self.projection.point(for: coordinate2)
        return Double(selectedPoint.distance(toPoint: pathPoint))
    }
}

// MARK: CGPoint
extension CGPoint {

    /// Get the distance from a point
    ///
    /// - Parameter p: The point
    /// - Returns: The distance
    func distance(toPoint p:CGPoint) -> CGFloat {
        return sqrt(pow(x - p.x, 2) + pow(y - p.y, 2))
    }
}