feat(db): get mapping dynamically from file

Assisted-by: Junie:claude-sonnet-4.6
Signed-off-by: Klagarge <remi@heredero.ch>

db/src/main.go

@@ -92,13 +92,9 @@ func influxConnection() *influx.InfluxGateway {
 // @BasePath /api/v1
 // @securityDefinitions.basic BasicAuth
 func main() {
-	// Load mapping configuration
+	// Load mapping configuration (reloaded dynamically on each access)
 	mappingPath := getEnv("MAPPING_CONFIG_PATH", "mapping.json")
-	mapping, err := LoadMapping(mappingPath)
-	if err != nil {
-		log.Printf("[Main] Warning: could not load mapping file: %v. Using defaults.", err)
-		mapping = EmptyMapping()
-	}
+	mapping := NewDynamicMapping(mappingPath)
 
 	mqttGateway := mqttConnection()
 	defer mqttGateway.Disconnect()
@@ -112,7 +108,7 @@ func main() {
 	provenceMeasurement := point.CreateMeasurement[ProvenceData](measurementName)
 	// The incoming MQTT topic structure is: <gateway_id>/<node_id>/update
 	topicStructur := []string{"gateway", "node"}
-	err = mqtt.SubscribeTyped(mqttGateway, "+/+/update", provenceMeasurement, topicStructur, func(dp point.DataPoint[ProvenceData]) {
+	err := mqtt.SubscribeTyped(mqttGateway, "+/+/update", provenceMeasurement, topicStructur, func(dp point.DataPoint[ProvenceData]) {
 		var gatewayID, nodeID string
 		for _, tag := range dp.Tags() {
 			switch tag.Subject {

db/src/mapping.go

@@ -23,6 +23,45 @@ type MappingConfig struct {
 	nodeToRoom      map[string]string
 }
 
+// DynamicMapping reloads the mapping file on every access so that changes
+// to the JSON file take effect without restarting the programme.
+type DynamicMapping struct {
+	path string
+}
+
+// NewDynamicMapping creates a DynamicMapping that reads from the given path.
+func NewDynamicMapping(path string) *DynamicMapping {
+	return &DynamicMapping{path: path}
+}
+
+func (d *DynamicMapping) load() *MappingConfig {
+	cfg, err := LoadMapping(d.path)
+	if err != nil {
+		return EmptyMapping()
+	}
+	return cfg
+}
+
+func (d *DynamicMapping) GetCampus(gatewayID string) (string, bool) {
+	return d.load().GetCampus(gatewayID)
+}
+
+func (d *DynamicMapping) GetRoom(nodeID string) (string, bool) {
+	return d.load().GetRoom(nodeID)
+}
+
+func (d *DynamicMapping) NodesForRoom(room string) []string {
+	return d.load().NodesForRoom(room)
+}
+
+func (d *DynamicMapping) AllNodes() []string {
+	return d.load().AllNodes()
+}
+
+func (d *DynamicMapping) Rooms() []string {
+	return d.load().Rooms()
+}
+
 // EmptyMapping returns a MappingConfig with no entries.
 // GetCampus and GetRoom will return their "unknown_*" fallback values.
 func EmptyMapping() *MappingConfig {