arreglados varios temas además del DL (redsys, etc)

src/main/java/com/imprimelibros/erp/redsys/RedsysController.java

@@ -189,9 +189,9 @@ public class RedsysController {
         try {
             String idem = "refund-" + paymentId + "-" + amountCents + "-" + UUID.randomUUID();
             paymentService.refundViaRedsys(paymentId, amountCents, idem);
-            return ResponseEntity.ok("{success:true}");
+            return ResponseEntity.ok("{\"success\":true}");
         } catch (Exception e) {
-            return ResponseEntity.badRequest().body("{success:false, error: '" + e.getMessage() + "'}");
+            return ResponseEntity.badRequest().body("{\"success\":false, \"error\": \"" + e.getMessage() + "\"}");
         }
     }
 }

src/main/java/com/imprimelibros/erp/redsys/RedsysService.java

@@ -321,11 +321,33 @@ public class RedsysService {
         Map<String, Object> decoded = decodeMerchantParametersToMap(dsMerchantParametersResp);
 
         String dsResponse = String.valueOf(decoded.get("Ds_Response"));
-        if (!"0900".equals(dsResponse)) {
+        if (dsResponse == null) {
+            throw new IllegalStateException("Respuesta Redsys refund sin Ds_Response");
+        }
+
+        int code;
+        try {
+            code = Integer.parseInt(dsResponse);
+        } catch (NumberFormatException e) {
+            throw new IllegalStateException("Código Ds_Response no numérico en refund: " + dsResponse, e);
+        }
+
+        // ✅ Consideramos OK: 0–99 (éxito típico) o 900 (0900)
+        boolean ok = (code >= 0 && code <= 99) || code == 900;
+        if (!ok) {
             throw new IllegalStateException("Devolución rechazada, Ds_Response=" + dsResponse);
         }
 
-        return String.valueOf(decoded.getOrDefault("Ds_AuthorisationCode", order));
+        // Devolvemos algún identificador razonable para la transacción de refund
+        Object authCodeObj = decoded.get("Ds_AuthorisationCode");
+        String authCode = authCodeObj != null ? String.valueOf(authCodeObj).trim() : null;
+
+        if (authCode == null || authCode.isEmpty()) {
+            // Fallback: usa el Ds_Order original como ID de refund
+            return order;
+        }
+
+        return authCode;
     }
 
 }