我在这个练习中试图实现一个简单的游戏。我是Redux的新手，很难理解有效负载和状态是如何联系在一起的，在这个练习中卡住了。
我仍然不确定是应该更新访问payload属性的状态，还是必须在switch语句中直接返回它。
任何帮助都是非常感谢的。

const initialWagonState = {
  supplies: 100,
  distance: 0,
  days: 0
}

const gather = {
  type:'gather',
  payload: {
  }
}
const travel = {
  type:'travel',
  payload:{
  }
}

const tippedWagon = {
  type:'tippedWagon',
  payload:{
  }
}

const reducer = (state=initialWagonState,action=gather) => {
  switch (action.type) {
    case 'gather':{
      return {
      ...state,supplies:state.supplies + 15,
      ...state,distance: state.distance,
      ...state,days: state.days + 1
      }
    }
    case 'travel':{
      return {
    ...state,supplies: state.supplies - (20 * daysOfTravel),
      ...state,distance: state.distance + (10 * daysOfTravel),
      ...state,days: state.days + daysOfTravel
      }
    }
    case 'tippedWagon':{
      return {
      ...state,supplies:state.supplies - 30,
      ...state,distance:state.distance,
      ...state,days: state.days + 1
      }
    }
    default: {
      return state;
    }
  }
}

let wagon = reducer('travel');
console.log(wagon)