export type RUAState = Record<string, unknown> | unknown[];
export type StateKey = keyof RUAState;
export type RUAAction<P = unknown, T extends string = string> = {
  payload: P;
  type: T;
};
export type RUAReducer<S extends RUAState, A extends RUAAction> = (
  state: S,
  action: A
) => S;
export type RUADispatch<A extends RUAAction> = (action: A) => void;
export type GetSnapshot<S> = () => S;
export type Subscribe = (listener: () => void) => () => void;

export const createStore = <S extends RUAState, A extends RUAAction>(
  reducer: RUAReducer<S, A>,
  initialState: S
) => {
  let state = initialState;

  const listeners = new Set<() => void>();
  const getSnapshot = () => state;
  const dispatch: RUADispatch<A> = (action) => {
    state = reducer(state, action);
    listeners.forEach((listener) => listener());
  };
  const subscribe = (listener: () => void) => {
    listeners.add(listener);
    return () => {
      listeners.delete(listener);
    };
  };

  return {
    subscribe,
    getSnapshot,
    dispatch,
  };
};

import { useSyncExternalStore } from 'react';

export type Todo = {
  id: number;
  content: string;
}[];
const initialTodo: Todo = [
  { id: 0, content: 'React' },
  { id: 1, content: 'Vue' },
];
export type TodoAction = RUAAction<number | string, 'add' | 'delete'>;

const reducer: RUAReducer<Todo, TodoAction> = (state, action) => {
  switch (action.type) {
    case 'add': {
      if (action.payload == null) throw new Error('Add todo without payload!');
      return [
        ...state,
        {
          id: state[state.length - 1].id + 1,
          content: action.payload.toString(),
        },
      ];
    }
    case 'delete': {
      if (action.payload == null)
        throw new Error('Delete todo without payload!');
      return state.filter((todo) => todo.id !== action.payload);
    }
    default:
      throw new Error('Dispatch a reducer without action!');
  }
};

const todoStore = createStore(reducer, initialTodo);
export const useTodoStore = (): [Todo, RUADispatch<TodoAction>] => [
  useSyncExternalStore(todoStore.subscribe, todoStore.getSnapshot),
  todoStore.dispatch,
];