package rwgps import ( "bytes" "fmt" "io/ioutil" "net/http" ) type ErrNotFound struct { RouteId int } func (e *ErrNotFound) Error() string { return fmt.Sprintf("RideWithGPS track %d not found", e.RouteId) } func FetchTrack(routeId int) ([]byte, error) { url := fmt.Sprintf("https://ridewithgps.com/routes/%d.gpx?sub_format=track", routeId) resp, err := http.Get(url) if err != nil { return nil, fmt.Errorf("error getting %s: %v", url, err) } defer resp.Body.Close() data, err := ioutil.ReadAll(resp.Body) if err != nil { return nil, fmt.Errorf("error reading response from %s: %v", url, err) } if IsNotFound(data) { return nil, &ErrNotFound{routeId} } return data, nil } func IsNotFound(data []byte) bool { return bytes.HasPrefix(data, []byte("")) && bytes.Contains(data, []byte("Error (404 not found)")) }