from typing import Dict, List, Optional

from models import Message


def validate_chat_request(
    messages: List[Message], req_id: str
) -> Dict[str, Optional[str]]:
    if not messages:
        raise ValueError(
            f"[{req_id}] Invalid request: 'messages' array is missing or empty."
        )

    if not any(msg.role != "system" for msg in messages):
        raise ValueError(
            f"[{req_id}] Invalid request: All messages are system messages. At least one user or assistant message is required."
        )

    return {"error": None, "warning": None}