check if the URL or dataset name already exists to avoid duplication

app.py

@@ -98,6 +98,14 @@ def submit_entry(
         errors.append("Approximate size must be a non-negative number.")
     if not field.strip():
         errors.append("Please provide a field.")
+    
+    # Check for existing dataset URL and name
+    existing_records = read_all_records()
+    for record in existing_records:
+        if record.get("dataset_url", "").strip().lower() == dataset_url.strip().lower():
+            errors.append(f"Dataset URL already exists: {record.get('dataset_url')}")
+        if record.get("dataset_name", "").strip().lower() == dataset_name.strip().lower():
+            errors.append(f"Dataset name already exists: {record.get('dataset_name')}")
 
     if errors:
         return gr.update(value=f"Submission failed:\n- " + "\n- ".join(errors), visible=True), gr.update(visible=False)