"""
Slide 33: Slide 6
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-033/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 33 ===
  import operator
  from typing import Annotated
  from typing_extensions import TypedDict
  from langgraph.graph import StateGraph, START, END

  class State(TypedDict):
      # каждый узел возвращает кусок списка, operator.add склеивает
      log:    Annotated[list[str], operator.add]
>     tokens: Annotated[int,   operator.add]
>  
  def step(state: State):
      return {"log": ["step-1"], "tokens": 12}

  def another(state: State):
      return {"log": ["step-2"], "tokens": 7}

  g = StateGraph(State)
  g.add_node("a", step)
  g.add_node("b", another)
  g.add_edge(START, "a")
  g.add_edge("a", "b")
  g.add_edge("b", END)
  app = g.compile()
  print(app.invoke({"log": [], "tokens": 0}))
  # -> {'log': ['step-1', 'step-2'], 'tokens': 19}

// note: snippet has 25 lines, card fits ~18