fix: refine OC API parameters and handle 500 errors gracefully

backend/app/services/mercado_publico_oc.py

@@ -80,9 +80,18 @@ async def _fetch_oc(params: Dict[str, str]) -> List[PurchaseOrder]:
     
     params["ticket"] = settings.mercado_publico_ticket
     
+    # Cleaning params: if status is "todos", it's better to omit it when fecha is present
+    if params.get("estado") == "todos":
+        del params["estado"]
+
     try:
         async with httpx.AsyncClient(timeout=45.0) as client:
             response = await client.get(API_BASE_OC, params=params)
+            # Handle MP API quirks: sometimes it returns 500 when no data is found for a date
+            if response.status_code == 500:
+                print(f"⚠️ API returned 500 for {response.url} - Likely no data for this query.")
+                return []
+                
             response.raise_for_status()
             data = response.json()
             
@@ -100,7 +109,17 @@ async def get_oc_by_code(code: str) -> Optional[PurchaseOrder]:
     return results[0] if results else None
 
 async def get_ocs_by_date(date: str, status: str = "todos") -> List[PurchaseOrder]:
-    return await _fetch_oc({"fecha": date, "estado": status})
+    params = {"estado": status}
+    
+    # Logic based on documentation examples:
+    # If it's today, the doc suggests using estado=todos without fecha
+    today_str = datetime.now().strftime("%d%m%Y")
+    if date == today_str and status == "todos":
+        return await _fetch_oc({"estado": "todos"})
+    
+    # Otherwise, use the date
+    params["fecha"] = date
+    return await _fetch_oc(params)
 
 async def get_ocs_by_provider(provider_code: str, date: str) -> List[PurchaseOrder]:
     return await _fetch_oc({"CodigoProveedor": provider_code, "fecha": date})