modularize code, add dummy version of roverd

pi/roverd/sensor_stream_dummy.go

@@ -0,0 +1,73 @@
+//go:build dummy
+
+package roverd
+
+import (
+	"context"
+	"log"
+	"math/rand"
+	"time"
+)
+
+const sensorHeader = 19
+
+type SensorStreamer struct {
+	rawOut chan<- []byte
+	parsed chan<- SensorSample
+	logger *log.Logger
+}
+
+func NewSensorStreamer(_ interface{}, rawOut chan<- []byte, parsed chan<- SensorSample, logger *log.Logger) *SensorStreamer {
+	return &SensorStreamer{rawOut: rawOut, parsed: parsed, logger: logger}
+}
+
+func (s *SensorStreamer) Run(ctx context.Context) {
+	ticker := time.NewTicker(200 * time.Millisecond)
+	defer ticker.Stop()
+	for {
+		select {
+		case <-ctx.Done():
+			return
+		case <-ticker.C:
+			frame := buildDummyFrame()
+			select {
+			case s.rawOut <- frame:
+			default:
+			}
+			sample := SensorSample{
+				Timestamp:     time.Now().UnixMilli(),
+				ChargingState: 3,    // trickle charging
+				ChargeSources: 0b10, // home base present
+			}
+			select {
+			case s.parsed <- sample:
+			default:
+			}
+		}
+	}
+}
+
+func buildDummyFrame() []byte {
+	payload := make([]byte, 0, expectedPayloadLength)
+	payload = append(payload, 100)
+	group := make([]byte, packetSizes[100])
+	group[0] = byte(rand.Intn(16)) // bumps
+	payload = append(payload, group...)
+	payload = append(payload, 21, 3)
+	payload = append(payload, 34, 0b10)
+
+	buf := make([]byte, 0, len(payload)+3)
+	buf = append(buf, sensorHeader, byte(len(payload)))
+	buf = append(buf, payload...)
+	checksum := calcChecksum(buf)
+	buf = append(buf, checksum)
+	return buf
+}
+
+func calcChecksum(buf []byte) byte {
+	sum := 0
+	for _, b := range buf {
+		sum += int(b)
+	}
+	return byte((-sum) & 0xFF)
+}