import requests

def retrieval_from_knowledge_base(
        query: str,
        topk: int
        ) -> str:
    """
    Retrieval for knowledge from the knowledge base based on the specified query and returns the topk results.
    
    Parameters:
    query (str): The query for knowledge retrieval.
    topk (int): The number of top results to return, default is 3.
    
    Returns:
    str: The result of the knowledge retrieval in JSON format.
    """
    url = 'http://127.0.0.1:7080/v1/chat-messages'
    headers = {
        'Authorization': f'Bearer app-uJgo3TQKcS1O9PMCDHko71Fp',
        'Content-Type': 'application/json'
    }
    data = {
        "inputs": {"topK": topk},
        "query": query,
        "response_mode": "blocking",
        "user": "tangger",
        "files": []
    }

    response = requests.post(url, headers=headers, json=data)

    if response.status_code == 524:
        print("Server is not responding. Please try again later. Maybe GPU was down in the container.")
        return None

    try:
        result = response.json()
    except ValueError:
        return [{"error": "Response is not in JSON format"}]

    useful_results = []
    try:
        answer = eval(result.get("answer", "[]"))
        for item in answer:
            metadata = item.get("metadata", {})
            useful_info = {
                "id": metadata.get("document_id"),
                "title": item.get("title"),
                "content": item.get("content"),
                "metadata": None,
                "embedding": None,
                "score": metadata.get("score")
            }
            useful_results.append(useful_info)
    except Exception as e:
        return [{"error": f"Error processing result: {e}", "status": "TERMINATE"}]
    if useful_results == []:
        useful_results = "NULL"
    return str(useful_results)