log at warn level invalid bps, channel values. inform user of default value.

option.go

@@ -19,18 +19,37 @@ func WithRateLimit(ratelimit time.Duration) Option {
 // WithBPSOpt is a functional option to set the bps index for {VbanTxt}.packet.
 func WithBPSOpt(bps int) Option {
 	return func(vt *VbanTxt) {
+		defaultBps := BpsOpts[vt.packet.bpsIndex]
+
 		bpsIndex := indexOf(BpsOpts, bps)
 		if bpsIndex == -1 {
-			log.Warnf("invalid bps value %d, expected one of %v, defaulting to 0", bps, BpsOpts)
+			log.Warnf(
+				"invalid bps value %d, expected one of %v, defaulting to %d",
+				bps,
+				BpsOpts,
+				defaultBps,
+			)
 			return
 		}
-		vt.packet.bpsIndex = bpsIndex
+		if bpsIndex > 255 {
+			log.Warnf("bps index %d too large for uint8, defaulting to %d", bpsIndex, defaultBps)
+			return
+		}
+		vt.packet.bpsIndex = uint8(bpsIndex)
 	}
 }
 
 // WithChannel is a functional option to set the channel for {VbanTxt}.packet.
 func WithChannel(channel int) Option {
 	return func(vt *VbanTxt) {
-		vt.packet.channel = channel
+		if channel < 0 || channel > 255 {
+			log.Warnf(
+				"channel value %d out of range [0,255], defaulting to %d",
+				channel,
+				vt.packet.channel,
+			)
+			return
+		}
+		vt.packet.channel = uint8(channel)
 	}
 }