"""
Slide 38: Slide 11
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-038/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 38 ===
  from langgraph.graph import StateGraph, START, END
  from langgraph.types import Command
  from typing_extensions import TypedDict
  from typing import Literal
  class State(TypedDict):
      n: int
> def decide(state: State) -> Command[Literal["inc", "halt"]]:
>     # Command(update, goto) -- обновляет state и сам выбирает узел
      if state["n"] < 3:
>         return Command(update={"n": state["n"] + 1}, goto="inc")
      return Command(update={}, goto="halt")
  g = StateGraph(State)
  g.add_node("decide", decide)
  g.add_node("inc",    inc)
  g.add_node("halt",   lambda s: s)
  g.add_edge(START, "decide")
  g.add_edge("inc", "decide")
  g.add_edge("halt", END)
  app = g.compile()
  print(app.invoke({"n": 0}))

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