fix(radio): use sentinel errors for Radio Browser query validation - #5239

Export ErrQueryTooShort and ErrQueryTooLong; native API uses errors.Is
instead of matching error strings.

Signed-off-by: elpatron <m.busche@gmail.com>

server/nativeapi/radios.go

@@ -87,7 +87,7 @@ func (api *Router) searchRadioBrowser() http.HandlerFunc {
 		}
 		stations, err := radiobrowser.Search(r.Context(), q, limit)
 		if err != nil {
-			if strings.Contains(err.Error(), "too short") || strings.Contains(err.Error(), "too long") {
+			if errors.Is(err, radiobrowser.ErrQueryTooShort) || errors.Is(err, radiobrowser.ErrQueryTooLong) {
 				http.Error(w, err.Error(), http.StatusBadRequest)
 				return
 			}

server/radiobrowser/radiobrowser.go

@@ -4,6 +4,7 @@ package radiobrowser
 import (
 	"context"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"io"
 	"math/rand"
@@ -39,6 +40,12 @@ type apiStation struct {
 	StationUUID string `json:"stationuuid"`
 }
 
+// Sentinel errors for query validation. Use errors.Is to detect them.
+var (
+	ErrQueryTooShort = errors.New("query too short")
+	ErrQueryTooLong  = errors.New("query too long")
+)
+
 var fallbackAPIHosts = []string{
 	"de1.api.radio-browser.info",
 	"nl1.api.radio-browser.info",
@@ -87,10 +94,10 @@ func shuffleHosts(hosts []string) []string {
 func Search(ctx context.Context, rawQuery string, limit int) ([]Station, error) {
 	q := strings.TrimSpace(rawQuery)
 	if len(q) < minQueryLen {
-		return nil, fmt.Errorf("query too short (min %d characters)", minQueryLen)
+		return nil, fmt.Errorf("query too short (min %d characters): %w", minQueryLen, ErrQueryTooShort)
 	}
 	if len(q) > maxQueryLen {
-		return nil, fmt.Errorf("query too long (max %d characters)", maxQueryLen)
+		return nil, fmt.Errorf("query too long (max %d characters): %w", maxQueryLen, ErrQueryTooLong)
 	}
 	if limit <= 0 {
 		limit = defaultLimit

server/radiobrowser/radiobrowser_test.go

@@ -1,6 +1,11 @@
 package radiobrowser
 
-import "testing"
+import (
+	"context"
+	"errors"
+	"strings"
+	"testing"
+)
 
 func TestNormalizeStations(t *testing.T) {
 	raw := []apiStation{
@@ -19,3 +24,16 @@ func TestNormalizeStations(t *testing.T) {
 		t.Fatalf("second stream: %q", got[1].StreamURL)
 	}
 }
+
+func TestSearchSentinelErrors(t *testing.T) {
+	ctx := context.Background()
+	_, err := Search(ctx, "x", 10)
+	if !errors.Is(err, ErrQueryTooShort) {
+		t.Fatalf("short query: want ErrQueryTooShort, got %v", err)
+	}
+	long := strings.Repeat("a", maxQueryLen+1)
+	_, err = Search(ctx, long, 10)
+	if !errors.Is(err, ErrQueryTooLong) {
+		t.Fatalf("long query: want ErrQueryTooLong, got %v", err)
+	}
+}