nws: refactored the NWS source files to relocate normalization logic to internal/normalizers.

internal/normalizers/common/payload.go

@@ -0,0 +1,54 @@
+// FILE: ./internal/normalizers/common/payload.go
+package common
+
+import (
+	"encoding/json"
+	"fmt"
+
+	"gitea.maximumdirect.net/ejr/feedkit/event"
+)
+
+// PayloadBytes extracts a JSON-ish payload into bytes suitable for json.Unmarshal.
+//
+// Supported payload shapes (weatherfeeder convention):
+//   - json.RawMessage  (recommended for raw events)
+//   - []byte
+//   - string           (assumed to contain JSON)
+//   - map[string]any   (re-marshaled to JSON)
+//
+// If you add other raw representations later, extend this function.
+func PayloadBytes(e event.Event) ([]byte, error) {
+	if e.Payload == nil {
+		return nil, fmt.Errorf("payload is nil")
+	}
+
+	switch v := e.Payload.(type) {
+	case json.RawMessage:
+		if len(v) == 0 {
+			return nil, fmt.Errorf("payload is empty json.RawMessage")
+		}
+		return []byte(v), nil
+
+	case []byte:
+		if len(v) == 0 {
+			return nil, fmt.Errorf("payload is empty []byte")
+		}
+		return v, nil
+
+	case string:
+		if v == "" {
+			return nil, fmt.Errorf("payload is empty string")
+		}
+		return []byte(v), nil
+
+	case map[string]any:
+		b, err := json.Marshal(v)
+		if err != nil {
+			return nil, fmt.Errorf("marshal map payload: %w", err)
+		}
+		return b, nil
+
+	default:
+		return nil, fmt.Errorf("unsupported payload type %T", e.Payload)
+	}
+}