MQTT gateway: add support for CO2 measurements

gateway/build.sh

@@ -0,0 +1,10 @@
+#!/usr/bin/bash
+
+set -euo pipefail
+
+cd "$(dirname "$0")"
+
+rm --force airmon
+
+podman run --rm -it -v .:/app golang:buster bash -c 'cd /app && go build .'
+

gateway/mon/co2.go

@@ -0,0 +1,37 @@
+package mon
+
+import (
+	"encoding/json"
+	influxdb2 "github.com/influxdata/influxdb-client-go/v2"
+	influxdb2Write "github.com/influxdata/influxdb-client-go/v2/api/write"
+	"log"
+	"time"
+)
+
+type co2 struct {
+	Device string `json:"dev"`
+	Time   int64  `json:"time"`
+	Sensor string `json:"sens"`
+	Co2    uint16 `json:"co2"`
+}
+
+func (t *co2) toPoint() *influxdb2Write.Point {
+	return influxdb2.NewPoint("co2",
+		map[string]string{
+			"device": t.Device,
+			"sensor": t.Sensor,
+		},
+		map[string]interface{}{
+			"co2": t.Co2,
+		},
+		time.Unix(t.Time, 0))
+}
+
+func ParseCarbonDioxide(data []byte) (*influxdb2Write.Point, error) {
+	var co2 co2
+	if err := json.Unmarshal(data, &co2); err != nil {
+		log.Print("could not parse co2 json: ", err)
+		return nil, err
+	}
+	return co2.toPoint(), nil
+}

gateway/mqtt/mqtt.go

@@ -54,30 +54,36 @@ type connHandler struct {
 	write chan<- *influxdb2Write.Point
 }
 
-func (h *connHandler) onConnect(client mqtt.Client) {
-	checkError := func(token mqtt.Token) {
-		if token.Wait() && token.Error() != nil {
-			log.Print(errors.Wrap(token.Error(), "could not subscribe to mqtt topic"))
-		}
-	}
+type topic struct {
+	topic  string
+	mapper func(data []byte) (*influxdb2Write.Point, error)
+}
 
-	token := client.Subscribe("meas/temp", 0, func(client mqtt.Client, msg mqtt.Message) {
-		if point, err := mon.ParseTemperature(msg.Payload()); err == nil {
-			h.write <- point
-		} else {
-			log.Print("could not parse temperature: ", err)
-		}
-	})
-	checkError(token)
+var topics = []*topic{
+	{"meas/part", mon.ParseParticulates},
+	{"meas/temp", mon.ParseTemperature},
+	{"meas/co2", mon.ParseCarbonDioxide},
+}
 
-	token = client.Subscribe("meas/part", 0, func(client mqtt.Client, msg mqtt.Message) {
-		if point, err := mon.ParseParticulates(msg.Payload()); err == nil {
-			h.write <- point
+func subscribe(t *topic, client mqtt.Client, writeCh chan<- *influxdb2Write.Point) {
+	token := client.Subscribe(t.topic, 0, func(client mqtt.Client, msg mqtt.Message) {
+		if point, err := t.mapper(msg.Payload()); err == nil {
+			writeCh <- point
 		} else {
-			log.Print("could not parse particulates: ", err)
+			log.Print("could not parse ", t.topic, " data: ", err)
 		}
 	})
-	checkError(token)
+
+	if token.Wait() && token.Error() != nil {
+		log.Print(errors.Wrap(token.Error(), "could not subscribe to mqtt topic "+t.topic))
+	}
+}
+
+func (h *connHandler) onConnect(client mqtt.Client) {
+	for _, t := range topics {
+		log.Print("subscribing to topic ", t.topic)
+		go subscribe(t, client, h.write)
+	}
 }
 
 func StartMqtt(settings *Settings, write chan<- *influxdb2Write.Point) error {