yey it work

todo.js

//xs.filter((el, i) => i != 0)*/
// {
//   todos: [
//     {
//       id: 1,
//       text: "first",
//       status: "active",
//     },
//     {
//       id: 2,
//       text: "second",
//       status: "done",
//     }
//   ],
//   filter: "all",
// }


// Action types

const ActionType = {
  setTodoText: Symbol(),
  toggleTodoStatus: Symbol(),
  addTodo: Symbol(),
  deleteTodo: Symbol(),
  setFilter: Symbol(),
}


// Actions

let nextID = 0
const addTodo = text =>
  ({ type: ActionType.addTodo, payload: { id: nextID++, text, status: "active" } })

const deleteTodo = id =>
  ({ type: ActionType.deleteTodo, payload: id })

const toggleTodoStatus = id =>
  ({ type: ActionType.toggleTodoStatus, payload: { id } })

const setTodoText = (text, id) =>
  ({ type: ActionType.setTodoText, payload: { text, id } })

const setFilter = filter =>
  ({ type: ActionType.setFilter, payload: filter })

const state = (state, action) => ({
  todos: todos(state.todos, action),
  filter: filter(state.filter, action),
})


const filter = (filter = "all", action) => {
  switch (action.type) {
    case ActionType.setFilter:
      return action.payload

    default:
      return filter
  }
}


const todos = (todos = [], action) => {
  switch (action.type) {
    case ActionType.addTodo:
      return [ ...todos, action.payload ]

    case ActionType.deleteTodo:
      return todos.filter(todo => todo.id !== action.payload)

    default:
      return todos.map(_todo => todo(_todo, action))
  }
}


const todo = (todo = {
  id: null,
  text: "",
  status: "active",
}, action) => {
  if (action.payload.id !== todo.id) {
    return todo
  }

  switch (action.type) {
    case ActionType.toggleTodoStatus:
      return {
        ...todo,
        status: toggleStatus(todo.status),
      }

    case ActionType.setTodoText:
      return { ...todo, text: action.payload.text }

    default:
      return todo
  }
}


const toggleStatus = status => {
  switch (status) {
    case "done":
      return "active"

    case "active":
      return "done"
  }
}

console.log(
  [
    addTodo("hello"),
    addTodo("world"),
    setFilter("active"),
    toggleTodoStatus(0),
    setTodoText("---", 0)
  ].reduce(state, {})
)