"""
Slide 58: Slide 31
Section 2: LangGraph 1.0
Source: slides/section2-langgraph/section2.pptx

Сгенерировано автоматически из slide-NN.js / sectionN.pptx.
Паттерн провайдера скопирован из
bro-js/agents/teacher/assistant/src/angry_teacher/llm.py.

Запуск:
  cd langchain-evolution-deck
  cp .env.example .env   # заполни OPENAI_API_KEY
  python examples/slide-058/script.py
"""
import os
from dotenv import load_dotenv
from langchain_openai import ChatOpenAI

load_dotenv()

llm = ChatOpenAI(
    # model="openrouter/free",
    # model="qwen/qwen3.5-35b-a3b",
    model="openai/gpt-oss-20b",
    # model="nvidia/nemotron-3-nano",
    # model="qwen/qwen3.5-9b",
    base_url="https://llm.brojs.ru/v1",
    # base_url="https://api.minimax.io/v1",
    # base_url="http://0.0.0.0:8090/v1",
    # base_url="https://openrouter.ai/api/v1",
    # api_key=os.getenv("MINIMAX_API_KEY"),
    api_key=(os.getenv("OPENAI_API_KEY") or "").strip() or None,
    temperature=0.7,
    stream_usage=True,
)


# === Code from slide 58 ===
> import { StateGraph, START, END, Annotation } from "@langchain/langgraph";
> import { MemorySaver }               from "@langchain/langgraph-checkpoint";

  const State = Annotation.Root({
    messages: Annotation({
      reducer: (a, b) => a.concat(b),
      default: () => [],
    }),
  });

  const g = new StateGraph(State)
    .addNode("echo", (s) => ({
      messages: [{ role: "assistant", content: "echo: " + s.messages.at(-1).content }],
    }))
    .addEdge(START, "echo")
    .addEdge("echo", END);

  const app = g.compile({ checkpointer: new MemorySaver() });
> const cfg = { configurable: { thread_id: "t1" } };
  const result = await app.invoke({ messages: [{ role: "user", content: "hi" }] }, cfg);

// note: snippet has 20 lines, card fits ~18