from fastapi import Request
from openai import OpenAI

from core.graph import create_agent_graph


def get_llm_client(request: Request) -> OpenAI:
    """FastAPI dependency — returns the singleton OpenAI client from app.state."""
    return request.app.state.llm_client


def get_agent_graph(agent_id: str, request: Request):
    """
    FastAPI dependency — returns the compiled LangGraph graph for *agent_id*.

    Graphs are lazily compiled on first use and cached on app.state so each
    agent's graph is only built once per process lifetime.
    """
    cache: dict = request.app.state.agent_graphs

    if agent_id not in cache:
        from agents import get as get_agent

        agent = get_agent(agent_id)
        if agent is None:
            # Fall back to the naked agent if the requested one doesn't exist
            agent_id = "naked"
            agent = get_agent(agent_id)

        cache[agent_id] = create_agent_graph(
            client=request.app.state.llm_client,
            agent_skills=agent.skills,
            system_prompt=agent.build_system_prompt(),
        )

    return cache[agent_id]