store.js

// global state of our app i.e. our global data state - store
//this is kind of where the business logic of our app is kept

function createStore(reducer) {
  let currentState = reducer(undefined, {});

  return {
    getState: () => currentState,
    dispatch: (action) => {
      currentState = reducer(currentState, action);
    },
  };
}

const initialState = {
  favourites: [],
};

//reducer is a pure function
function addFavouritesReducer(state = initialState, action) {
  switch (action.type) {
    case "ADD_FAVOURITE": {
      const addedFavourite = action.payload.favourite;
      const favourites = [...state.favourites, addedFavourite];
      return { favourites };
    }

    case "REMOVE_FAVOURITE": {
      const removedFavourite = action.payload.favourite;
      const favourites = state.favourites.filter(
        (favourite) => favourite.id !== removedFavourite.id
      );
      return { favourites };
    }

    default:
      return state;
  }
}

// const action = {
//   type: "ADD_FAVOURITE",
//   payload: { favourite: { title: "story1", id: 1 } },
// };

const store = createStore(addFavouritesReducer);

// store.dispatch(action);
// console.log(store.getState());

export default store;