isLineStrait.swift

    func isLineStrait(polyline: GMSPath) -> Bool {
        
        let pointFrom = CLLocationCoordinate2D(latitude: polyline.coordinate(at: 0).latitude, longitude: polyline.coordinate(at: 0).longitude)
        let pointTo = CLLocationCoordinate2D(latitude: polyline.coordinate(at: polyline.count() - 1).latitude, longitude: polyline.coordinate(at: polyline.count() - 1).longitude)
        var equation = (slope: 0.0, intercept: 0.0)
        equation = getLineEquation(locationFrom: pointFrom, locationTo: pointTo)
        var numberOfPointNotInThePath = 0
        
        for i in 0...(polyline.count() - 1) {
            let location = CLLocationCoordinate2D(latitude: polyline.coordinate(at: i).latitude, longitude: polyline.coordinate(at: i).longitude)
            var distance = ((equation.slope * location.latitude) - location.longitude + equation.intercept) / sqrt((pow(equation.slope, 2) + pow (-1, 2)))
            distance = distance * 100000
            //print("distance = \(distance)")
            if (distance < 0) {
                distance = distance * -1
            }
            if (distance >= 7) {
                numberOfPointNotInThePath += 1
            }
        }
        if Double(numberOfPointNotInThePath) > (Double(polyline.count()) - 2) / 2 {
            return false
        }
        return true
    }
    
    //line equation with 2 point
    func getLineEquation(locationFrom: CLLocationCoordinate2D, locationTo: CLLocationCoordinate2D) ->(slope: Double, intercept: Double) {
        
        let slope = (locationTo.longitude - locationFrom.longitude) / (locationTo.latitude - locationFrom.latitude)
        let intercept = locationFrom.longitude - (slope * locationFrom.latitude)
        return (slope, intercept)
    }