from __future__ import annotations

from typing import Any

from src.config import LANGFUSE_ENABLED


def langfuse_config(user_id: str, session_id: str | None = None) -> dict[str, Any]:
    """Build LangChain/LangGraph runtime config with Langfuse tracing."""
    if not LANGFUSE_ENABLED:
        return {}

    from langfuse.langchain import CallbackHandler

    return {
        "callbacks": [CallbackHandler()],
        "metadata": {
            "langfuse_user_id": user_id,
            "langfuse_session_id": session_id or user_id,
            "langfuse_tags": ["agentic-rag", "langgraph", "gemini"],
        },
        "run_name": "agentic-rag-chat",
    }


def flush_langfuse() -> None:
    """Force pending Langfuse spans to be exported after a request."""
    if not LANGFUSE_ENABLED:
        return

    try:
        from langfuse import get_client

        get_client().flush()
    except Exception as exc:
        print(f"[LANGFUSE] Failed to flush traces: {exc}")