Redux Mutation Experiment 2

redux-mutations2.js

import _ from 'lodash';


export function setProperty(key) {
  return (state, action) => ({ [key]: action[key] })
}

export function increment(key) {
  return state => ({ [key]: state[key] + 1 });
}

export function decrement(key) {
  return state => ({ [key]: state[key] - 1 });
}

export function updateLoading() {
  return state => ({ loading: state.requestCount > 0 });
}

/**
 * Mutation  to set a boolean value
 *
 * e.g
 *
 * {
 *   "SET_FLAG": setBoolean('flag').to(false),
 *   "SET_LOADING_STATUS": setBoolean('isLoading')
 *      .eval('numberOfRequests')
 *      .gt(0)
 * }
 *
 * @export
 * @param {*} key
 * @returns
 */
export function setBoolValue(key) {
  return {
    to(val) {
      return (state) => ({ [key]: val })
    },
    eval(otherKey = key) {
      return {
        eq: (val) => (state) => ({ [key]: state[otherKey] === val }),
        gt: (val) => (state) => ({ [key]: state[otherKey] > val }),
        gte: (val) => (state) => ({ [key]: state[otherKey] >= val }),
        lt: (val) => (state) => ({ [key]: state[otherKey] < val }),
        lte: (val) => (state) => ({ [key]: state[otherKey] <= val })
      };
    }
  }
};

/**
 * Wraps multiple mutations as one
 *
 * @export
 * @param {*} muts
 * @returns
 */
export function combineMutations(...muts) {
  return function (state, action) {
    return _.reduce(muts, (changes, fn) => {
      return {
        ...changes,
        ...fn({ ...state, ...changes }, action)
      };
    }, {});
  };
}

// ---- Store State

const initialState = {
  users:        [],
  requestCount: 0,
	loading:      false
};


// ---- State Mutations

export const START_REQUEST  = 'START_REQUEST';
export const END_REQUEST    = 'END_REQUEST';
export const SET_USERS      = 'SET_USERS';

const mutations = {
  [SET_USERS]: setProperty('users'),

  [START_REQUEST]: combineMutations(
    increment('requestCount'),
    setBoolValue('loading').eval('requestCount').gt(0)
  ),

  [END_REQUEST]: combineMutations(
    decrement('requestCount'),
    setBoolValue('loading').eval('requestCount').gt(0)
  )
};

const reducer = function(state = initialState, action) {
  const mut = mutations[action.type];
  if (!mut) {
    return state;
  }
  return { ...state, ...mut(state, action) };
}

// ---- Initialize

let store = createStore(
  reducer,
  applyMiddleware(thunk)
);

export default store;