from operator import add
from typing import Annotated

from langgraph.checkpoint.memory import InMemorySaver
from langgraph.graph import START, StateGraph
from typing_extensions import NotRequired, TypedDict


class ThreadState(TypedDict):
    events: Annotated[list[str], add]
    event_count: NotRequired[int]


def count_events(state: ThreadState) -> dict[str, int]:
    return {"event_count": len(state["events"])}