"""
Slide 35: Slide 8
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-035/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 35 ===
  from typing_extensions import TypedDict
  from langgraph.graph import StateGraph, START, END

  class State(TypedDict):
      n: int

  def inc(state: State):
      return {"n": state["n"] + 1}

  builder = StateGraph(State)
  builder.add_node("inc", inc)        # регистрируем узел
> builder.add_edge(START, "inc")      # поток входа
> builder.add_edge("inc", END)        # поток выхода
>  
  graph = builder.compile()           # компиляция -- граф готов к invoke

> print(graph.invoke({"n": 0}))       # -> {'n': 1}