"""
Slide 52: Slide 25
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-052/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 52 ===
  from langgraph.graph import StateGraph, START, END
  from langgraph.config import get_stream_writer
  from typing_extensions import TypedDict

  class State(TypedDict):
      total: int

  def progress(state: State):
      writer = get_stream_writer()      # доступен только во время выполнения узла
>     for i in range(3):
>         writer({"progress": i, "phase": "thinking"})
>     return {"total": 3}

  g = StateGraph(State)
  g.add_node("progress", progress)
  g.add_edge(START, "progress")
  g.add_edge("progress", END)
  app = g.compile()
>  
> # в UI -- только custom-чанки, без промежуточного state
  for chunk in app.stream({"total": 0}, stream_mode="custom"):
      print(chunk)

// note: snippet has 22 lines, card fits ~18