add WebSocket support for real-time delivery updates with JWT authentication and automatic reconnection

backend/internal/ws/event.go

@@ -0,0 +1,40 @@
+package ws
+
+import (
+	"encoding/json"
+	"log"
+)
+
+type EventType string
+
+const (
+	DeliveryCreated       EventType = "delivery.created"
+	DeliveryUpdated       EventType = "delivery.updated"
+	DeliveryStatusChanged EventType = "delivery.status_changed"
+	DeliveryDeleted       EventType = "delivery.deleted"
+)
+
+type Event struct {
+	Type    EventType `json:"type"`
+	Payload any       `json:"payload"`
+}
+
+type StatusPayload struct {
+	ID     string `json:"id"`
+	Status string `json:"status"`
+}
+
+type DeletePayload struct {
+	ID string `json:"id"`
+}
+
+// NewEvent serializes an event to JSON. Returns nil on marshal failure;
+// callers should treat nil as "skip broadcast".
+func NewEvent(eventType EventType, payload any) []byte {
+	data, err := json.Marshal(Event{Type: eventType, Payload: payload})
+	if err != nil {
+		log.Printf("ws: failed to marshal event %s: %v", eventType, err)
+		return nil
+	}
+	return data
+}