"""
Slide 41: Slide 14
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-041/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 41 ===
  from typing import Annotated
  from typing_extensions import TypedDict
  from langgraph.graph import StateGraph, START, END
  from langgraph.graph.message import add_messages
  from langgraph.checkpoint.memory import InMemorySaver

  class State(TypedDict):
      messages: Annotated[list, add_messages]

  def echo(state: State):
      last = state["messages"][-1]
      return {"messages": [{"role": "assistant", "content": f"echo: {last.content}"}]}

  g = StateGraph(State)
  g.add_node("echo", echo)
  g.add_edge(START, "echo")
  g.add_edge("echo", END)

  # checkpointer -- обязателен для thread persistence
  checkpointer = InMemorySaver()
  app = g.compile(checkpointer=checkpointer)
>  
> cfg = {"configurable": {"thread_id": "user-1"}}
  app.invoke({"messages": [{"role": "user", "content": "hi"}]},   cfg)
> app.invoke({"messages": [{"role": "user", "content": "again"}]}, cfg)
> # второй вызов видит все сообщения первого: thread persistence работает

// note: snippet has 26 lines, card fits ~18