handler: move mqttping into handler package; clean up main.go

internal/handler/mqttping.go

@@ -0,0 +1,24 @@
+package handler
+
+import (
+    "net/http"
+    "os"
+    "time"
+
+    "github.com/gin-gonic/gin"
+    "git.piskot.si/SeminarM2/lambdaiot-core/internal/mqtt"
+)
+
+// MQTTPing publishes the current timestamp to the configured MQTT topic
+func MQTTPing(c *gin.Context) {
+    ts := time.Now().Format(time.RFC3339)
+    topic := os.Getenv("MQTT_TOPIC")
+    if topic == "" {
+        topic = "lambdaiot"
+    }
+    if err := mqtt.PublishDefault(topic, []byte(ts)); err != nil {
+        c.JSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
+        return
+    }
+    c.JSON(http.StatusOK, gin.H{"timestamp": ts})
+}