"""LangGraph / LangChain adapter (scaffold).

Wrap `Pipeline.run` as a LangGraph node or a LangChain tool. Safe to import
even if LangGraph/LangChain aren't installed — the adapter is just a callable.
"""
from __future__ import annotations

from typing import Any, Dict

from ..core.config import Config
from ..core.types import Query
from ..pipeline import Pipeline


_pipeline: Pipeline = Pipeline.from_config(Config.default())


def set_pipeline(pipe: Pipeline) -> None:
    global _pipeline
    _pipeline = pipe


def tau_rag_node(state: Dict[str, Any]) -> Dict[str, Any]:
    """LangGraph node: reads `state['query']`, returns fields merged into state.

    Example:
        from langgraph.graph import StateGraph
        g = StateGraph(dict)
        g.add_node("rag", tau_rag_node)
        ...
    """
    q_text: str = state.get("query", "")
    resp = _pipeline.run(Query(text=q_text, lang=state.get("lang", "he")))
    return {
        **state,
        "answer": resp.answer,
        "sources": resp.sources,
        "omega": resp.signals.omega,
        "verification_passed": resp.verification.passed,
        "alerts": [a.__dict__ for a in resp.verification.alerts],
    }


# ----------------------------------------------------------------------- LangChain
def as_langchain_tool():
    """Return a LangChain Tool if langchain is installed, else a ValueError.

    Usage:
        from tau_rag.api.langgraph_node import as_langchain_tool
        tool = as_langchain_tool()
        agent_executor = initialize_agent([tool], llm)
    """
    try:
        from langchain.tools import Tool   # type: ignore
    except Exception as e:
        raise RuntimeError(
            "LangChain not installed. `pip install langchain`."
        ) from e

    def _call(q: str) -> str:
        r = _pipeline.run(Query(text=q))
        return r.answer

    return Tool(
        name="tau_rag",
        func=_call,
        description=(
            "Retrieval-augmented generation over the TAU-RAG knowledge base "
            "with structure-preservation guarantees."
        ),
    )