Add Noten parsing and rework some existing code

cmd/lsf/main.go

@@ -19,6 +19,7 @@ import (
 var (
 	sessionCache string
 	username     string
+	showGrades   bool
 )
 
 func init() {
@@ -29,6 +30,7 @@ func init() {
 	defaultCacheDir := path.Join(homeDir, ".cache/go-lsf/sessions")
 	flag.StringVar(&sessionCache, "session-cache", defaultCacheDir, "path where the session tokens are located")
 	flag.StringVar(&username, "username", "", "username to login with in lsf")
+	flag.BoolVar(&showGrades, "noten", false, "list grades")
 	flag.Parse()
 
 	err = os.MkdirAll(sessionCache, os.ModePerm)
@@ -51,7 +53,16 @@ func main() {
 		log.Fatal(err)
 	}
 
-	fmt.Printf("s: %+v\n", s)
+	if showGrades {
+		noten, err := s.Noten()
+		if err != nil {
+			log.Fatal(err)
+		}
+		fmt.Println("Noten:")
+		for _, note := range noten {
+			fmt.Println(note)
+		}
+	}
 }
 
 func readUsername() (string, error) {
@@ -69,7 +80,7 @@ func readPassword() (string, error) {
 	fmt.Print("Password: ")
 	b, err := terminal.ReadPassword(int(syscall.Stdin))
 	if err != nil {
-		return "", errors.Wrap(err, "could not read password")
+		return "", err
 	}
 	fmt.Print("\n")
 	password = string(b)
@@ -101,20 +112,16 @@ func session(username string) (*lsf.Session, error) {
 		return nil, errors.Wrapf(err, "could not read session file %s", sessionPath)
 	}
 	sid := strings.TrimSuffix(string(b), "\n")
-	s := &lsf.Session{
-		SID: sid,
-	}
-	valid, err := s.Valid()
-	if err != nil {
-		return nil, errors.Wrap(err, "could not check session")
-	}
-	if !valid {
-		fmt.Println("session is not valid")
+	s, err := lsf.NewSessionBySID(sid)
+	if err == lsf.ErrInvalSID {
+		log.Println("session is not valid")
 		err := os.Remove(sessionPath)
 		if err != nil {
 			log.Println(errors.Wrap(err, "could not remove invalid session file"))
 		}
 		return login(username)
+	} else if err != nil {
+		return nil, errors.Wrap(err, "could not get session by existing sid")
 	}
 	return s, nil
 }
@@ -122,7 +129,7 @@ func session(username string) (*lsf.Session, error) {
 func login(username string) (*lsf.Session, error) {
 	password, err := readPassword()
 	if err != nil {
-		return nil, errors.Wrap(err, "could not login")
+		return nil, errors.Wrap(err, "could not read password")
 	}
 	s, err := lsf.Login(username, password)
 	if err != nil {