refactor flag set methods

cmd/common.go

@@ -33,8 +33,14 @@ func keys[V any](m map[string]V) []string {
 	return keys
 }
 
-func flagValueError(allowed []string) error {
+func validateFlag[V any](v string, m map[string]V) error {
+	var err error
+	_, ok := m[v]
+	if !ok {
+		allowed := keys(m)
 		sort.Strings(allowed)
 		allowedList := strings.Join(allowed, ", ")
-	return errors.New("must be one of " + allowedList)
+		err = errors.New("must be one of " + allowedList)
+	}
+	return err
 }

cmd/leagueflag.go

@@ -44,17 +44,15 @@ func (t *leagueFlag) String() string {
 }
 
 func (t *leagueFlag) Set(v string) error {
-	var err error
 	v = strings.ToLower(v)
 
-	_, ok := leagueIDs[v]
+	err := validateFlag(v, leagueIDs)
-	if !ok {
+	if err != nil {
-		allowed := keys(leagueIDs)
-		err = flagValueError(allowed)
-	} else {
-		*t = leagueFlag(v)
-	}
 		return err
+	}
+
+	*t = leagueFlag(v)
+	return nil
 }
 
 func (t *leagueFlag) Type() string {

cmd/sportflag.go

@@ -49,17 +49,15 @@ func (t *sportFlag) String() string {
 }
 
 func (t *sportFlag) Set(v string) error {
-	var err error
 	v = strings.ToLower(v)
 
-	_, ok := sportIDs[v]
+	err := validateFlag(v, sportIDs)
-	if !ok {
+	if err != nil {
-		allowed := keys(sportIDs)
-		err = flagValueError(allowed)
-	} else {
-		*t = sportFlag(v)
-	}
 		return err
+	}
+
+	*t = sportFlag(v)
+	return nil
 }
 
 func (t *sportFlag) Type() string {

cmd/teamflag.go

@@ -61,17 +61,15 @@ func (t *teamFlag) String() string {
 }
 
 func (t *teamFlag) Set(v string) error {
-	var err error
 	v = strings.ToLower(v)
 
-	_, ok := teamIDs[v]
+	err := validateFlag(v, teamIDs)
-	if !ok {
+	if err != nil {
-		allowed := keys(teamIDs)
-		err = flagValueError(allowed)
-	} else {
-		*t = teamFlag(v)
-	}
 		return err
+	}
+
+	*t = teamFlag(v)
+	return nil
 }
 
 func (t *teamFlag) Type() string {