Refactoring Reducer

reducer.v3.js

import schema from './schema';
import { ACTIONS } from './action';

const fetching = substate => (state, action) => {
  return {
    ...state,
    [substate]: {
      ...state[substate],
      ...action.value,
      fetching: true
    }
  };
};

const fetchComplete = substate => (state, action) => {
  return {
    ...state,
    [substate]: {
      ...state[substate],
      value: action.value,
      fetching: false
    }
  };
};

const unselectItem = (state) => {
  return {
    ...state,
    selected: {
      fetching: false,
      value: {}
    }
  };
}

const posting = (state) => {
  return {
    ...state,
    selected: {
      posting: true
    }
  };
}

const postComplete = (state) => {
  return {
    ...state,
    selected: {
      posting: false
    }
  };
}

const error = (state, action) => {
  return {
    ...state,
    isError: true,
    errorMessage: action.errorMessage
  };
}

const commands = {
  [ACTIONS.FETCHING_LIST]: fetching('list'),
  [ACTIONS.FETCHING_HEADER]: fetching('header'),
  [ACTIONS.FETCHING_ITEM]: fetching('selected'),

  [ACTIONS.FETCH_LIST_COMPLETE]: fetchComplete('list'),
  [ACTIONS.FETCH_HEADER_COMPLETE]: fetchComplete('header'),
  [ACTIONS.FETCH_ITEM_COMPLETE]: fetchComplete('selected'),

  [ACTIONS.UNSELECT_ITEM]: unselectItem,
  [ACTIONS.POSTING]: posting,
  [ACTIONS.ERROR]: error,

  [ACTIONS.CREATED]: postComplete,
  [ACTIONS.UPDATED]: postComplete
};

export default (state = schema, action) => {
  const command = commands[action.type];

  if (!command) return state;

  return command(state, action);
};