reorganise some of the internals of the package.

functional options added.

option.go

@@ -0,0 +1,35 @@
+package vbantxt
+
+import (
+	"time"
+
+	log "github.com/sirupsen/logrus"
+)
+
+// Option is a functional option type that allows us to configure the VbanTxt.
+type Option func(*VbanTxt)
+
+// WithRateLimit is a functional option to set the ratelimit for requests
+func WithRateLimit(ratelimit time.Duration) Option {
+	return func(vt *VbanTxt) {
+		vt.ratelimit = ratelimit
+	}
+}
+
+// WithBPSOpt is a functional option to set the bps index for {VbanTx}.{Packet}.bpsIndex
+func WithBPSOpt(bpsIndex int) Option {
+	return func(vt *VbanTxt) {
+		if bpsIndex < 0 || bpsIndex >= len(BpsOpts) {
+			log.Warnf("invalid bpsIndex %d, defaulting to 0", bpsIndex)
+			return
+		}
+		vt.packet.bpsIndex = bpsIndex
+	}
+}
+
+// WithChannel is a functional option to set the bps index for {VbanTx}.{Packet}.channel
+func WithChannel(channel int) Option {
+	return func(vt *VbanTxt) {
+		vt.packet.channel = channel
+	}
+}