first commit

internal/mqttingest/mqtt.go

@@ -0,0 +1,53 @@
+package mqttingest
+
+import (
+	"context"
+	"fmt"
+	"time"
+
+	mqtt "github.com/eclipse/paho.mqtt.golang"
+)
+
+type MQTTConfig struct {
+	Broker   string
+	ClientID string
+	Username string
+	Password string
+	Topic    string
+	QoS      byte
+}
+
+type Handler func(ctx context.Context, topic string, payload []byte) error
+
+func RunSubscriber(ctx context.Context, cfg MQTTConfig, h Handler) error {
+	opts := mqtt.NewClientOptions().
+		AddBroker(cfg.Broker).
+		SetClientID(cfg.ClientID).
+		SetAutoReconnect(true).
+		SetConnectRetry(true).
+		SetConnectRetryInterval(5 * time.Second)
+
+	if cfg.Username != "" {
+		opts.SetUsername(cfg.Username)
+		opts.SetPassword(cfg.Password)
+	}
+
+	client := mqtt.NewClient(opts)
+	if tok := client.Connect(); tok.Wait() && tok.Error() != nil {
+		return fmt.Errorf("mqtt connect: %w", tok.Error())
+	}
+
+	// Subscribe
+	if tok := client.Subscribe(cfg.Topic, cfg.QoS, func(_ mqtt.Client, msg mqtt.Message) {
+		// Keep callback short; do work with context
+		_ = h(ctx, msg.Topic(), msg.Payload())
+	}); tok.Wait() && tok.Error() != nil {
+		client.Disconnect(250)
+		return fmt.Errorf("mqtt subscribe: %w", tok.Error())
+	}
+
+	// Block until ctx cancelled
+	<-ctx.Done()
+	client.Disconnect(250)
+	return nil
+}