Add MQTT client wrapper; wire startup publish; support env-config

internal/config/config.go

@@ -0,0 +1,94 @@
+package config
+
+import (
+	"os"
+	"strconv"
+
+	"github.com/joho/godotenv"
+	"github.com/pelletier/go-toml/v2"
+)
+
+// Config holds application configuration loaded from TOML
+type Config struct {
+	Server ServerConfig `toml:"server"`
+	MQTT   MQTTConfig   `toml:"mqtt"`
+}
+
+type ServerConfig struct {
+	Address   string `toml:"address"`
+	Port      int    `toml:"port"`
+	JWTSecret string `toml:"jwt_secret"`
+}
+
+type MQTTConfig struct {
+	Broker   string `toml:"broker"`
+	ClientID string `toml:"client_id"`
+	Username string `toml:"username"`
+	Password string `toml:"password"`
+	Topic    string `toml:"topic"`
+}
+
+// Load loads configuration from the given path. If path is empty, it tries
+// to load ./config.toml or falls back to environment defaults.
+func Load(path string) (*Config, error) {
+	cfg := &Config{
+		Server: ServerConfig{
+			Address:   "0.0.0.0",
+			Port:      8080,
+			JWTSecret: "secret",
+		},
+		MQTT: MQTTConfig{
+			Broker:   "tcp://localhost:1883",
+			ClientID: "lambda-iot-core",
+			Topic:    "lambda/iot",
+		},
+	}
+
+	// try to load TOML if provided or present
+	if path == "" {
+		path = "config.toml"
+	}
+	if _, err := os.Stat(path); err == nil {
+		f, err := os.ReadFile(path)
+		if err != nil {
+			return nil, err
+		}
+		if err := toml.Unmarshal(f, cfg); err != nil {
+			return nil, err
+		}
+	}
+
+	// load .env (if present) so env vars are populated for overrides
+	_ = godotenv.Load()
+
+	// environment overrides (common for Docker/.env)
+	if v := os.Getenv("SERVER_ADDRESS"); v != "" {
+		cfg.Server.Address = v
+	}
+	if v := os.Getenv("SERVER_PORT"); v != "" {
+		if p, err := strconv.Atoi(v); err == nil {
+			cfg.Server.Port = p
+		}
+	}
+	if v := os.Getenv("JWT_SECRET"); v != "" {
+		cfg.Server.JWTSecret = v
+	}
+
+	if v := os.Getenv("MQTT_BROKER"); v != "" {
+		cfg.MQTT.Broker = v
+	}
+	if v := os.Getenv("MQTT_CLIENT_ID"); v != "" {
+		cfg.MQTT.ClientID = v
+	}
+	if v := os.Getenv("MQTT_USERNAME"); v != "" {
+		cfg.MQTT.Username = v
+	}
+	if v := os.Getenv("MQTT_PASSWORD"); v != "" {
+		cfg.MQTT.Password = v
+	}
+	if v := os.Getenv("MQTT_TOPIC"); v != "" {
+		cfg.MQTT.Topic = v
+	}
+
+	return cfg, nil
+}

internal/mqtt/mqtt.go

@@ -0,0 +1,56 @@
+package mqtt
+
+import (
+    "fmt"
+    "time"
+
+    paho "github.com/eclipse/paho.mqtt.golang"
+    "git.piskot.si/SeminarM2/lambdaiot-core/internal/config"
+)
+
+type Client struct {
+    client paho.Client
+}
+
+func Connect(cfg config.MQTTConfig) (*Client, error) {
+    opts := paho.NewClientOptions()
+    opts.AddBroker(cfg.Broker)
+    if cfg.ClientID != "" {
+        opts.SetClientID(cfg.ClientID)
+    }
+    if cfg.Username != "" {
+        opts.SetUsername(cfg.Username)
+        opts.SetPassword(cfg.Password)
+    }
+    opts.SetAutoReconnect(true)
+    opts.SetConnectRetry(true)
+    opts.SetConnectTimeout(5 * time.Second)
+
+    c := paho.NewClient(opts)
+    token := c.Connect()
+    if ok := token.WaitTimeout(10 * time.Second); !ok {
+        return nil, fmt.Errorf("mqtt connect timeout")
+    }
+    if err := token.Error(); err != nil {
+        return nil, err
+    }
+    return &Client{client: c}, nil
+}
+
+func (c *Client) Publish(topic string, payload []byte) error {
+    if c == nil || c.client == nil {
+        return fmt.Errorf("mqtt client not connected")
+    }
+    token := c.client.Publish(topic, 0, false, payload)
+    if ok := token.WaitTimeout(5 * time.Second); !ok {
+        return fmt.Errorf("publish timeout")
+    }
+    return token.Error()
+}
+
+func (c *Client) Close() {
+    if c == nil || c.client == nil {
+        return
+    }
+    c.client.Disconnect(250)
+}