from langchain_core.messages import HumanMessage, RemoveMessage



def build_instrument_context(ticker: str) -> str:
    """Describe the exact instrument so agents preserve exchange-qualified tickers."""
    return (
        f"The instrument to analyze is `{ticker}`. "
        "Use this exact ticker in every tool call, report, and recommendation, "
        "preserving any exchange suffix (e.g. `.TO`, `.L`, `.HK`, `.T`)."
    )

def create_msg_delete():
    def delete_messages(state):
        """Clear messages and add placeholder for Anthropic compatibility"""
        messages = state["messages"]

        # Remove all messages
        removal_operations = [RemoveMessage(id=m.id) for m in messages]

        # Add a minimal placeholder message
        placeholder = HumanMessage(content="Continue")

        return {"messages": removal_operations + [placeholder]}

    return delete_messages