feat: normalize RDS PS and radiotext fields

internal/rds/encoder.go

@@ -1,7 +1,7 @@
 package rds
 
 import (
-	"math"
+    "math"
 )
 
 const (
@@ -29,6 +29,8 @@ func NewEncoder(cfg RDSConfig) (*Encoder, error) {
 	if cfg.SampleRate <= 0 {
 		cfg.SampleRate = 48000
 	}
+    cfg.PS = normalizePS(cfg.PS)
+    cfg.RT = normalizeRT(cfg.RT)
 
 	bits := buildBits(cfg)
 	if len(bits) == 0 {

internal/rds/encoder_test.go

@@ -2,6 +2,7 @@ package rds
 
 import (
 	"math"
+	"strings"
 	"testing"
 )
 
@@ -49,3 +50,18 @@ func TestEncoderReset(t *testing.T) {
 		t.Fatalf("expected reset to replay initial sample: %v vs %v", sampleA, sampleB)
 	}
 }
+
+func TestNormalizePS(t *testing.T) {
+    got := normalizePS("radiox")
+    if got != "RADIOX  " {
+        t.Fatalf("unexpected PS: %q", got)
+    }
+}
+
+func TestNormalizeRT(t *testing.T) {
+    long := strings.Repeat("a", 80)
+    got := normalizeRT(long)
+    if len(got) != 64 {
+        t.Fatalf("unexpected RT length: %d", len(got))
+    }
+}

internal/rds/normalize.go

@@ -0,0 +1,21 @@
+package rds
+
+import "strings"
+
+func normalizePS(ps string) string {
+    ps = strings.ToUpper(ps)
+    if len(ps) > 8 {
+        ps = ps[:8]
+    }
+    if len(ps) < 8 {
+        ps = ps + strings.Repeat(" ", 8-len(ps))
+    }
+    return ps
+}
+
+func normalizeRT(rt string) string {
+    if len(rt) > 64 {
+        rt = rt[:64]
+    }
+    return rt
+}