"""Small LangChain agent used by the stream-mode console demo."""

from __future__ import annotations

import os

from langchain.agents import create_agent
from langchain_core.tools import tool
from langchain_openai import ChatOpenAI


@tool
def shopping_list(query: str) -> str:
    """Return a compact shopping list for a grocery-related request."""

    normalized = query.lower()
    if "молоко" in normalized or "хлеб" in normalized or "яблок" in normalized:
        return "молоко, хлеб, яблоки"
    return "молоко, хлеб, яблоки, чай"


def build_model() -> ChatOpenAI:
    """Create an OpenAI-compatible chat model from environment variables."""

    return ChatOpenAI(
        model=os.getenv("OPENAI_MODEL", "gpt-4o-mini"),
        base_url=os.getenv("OPENAI_BASE_URL") or None,
        api_key=os.getenv("OPENAI_API_KEY", "not-needed"),
        temperature=0,
        streaming=True,
    )


agent = create_agent(
    model=build_model(),
    tools=[shopping_list],
    system_prompt=(
        "Ты полезный консольный AI-агент. Отвечай кратко. "
        "Если пользователь просит список покупок, используй shopping_list."
    ),
)