todolist-reducer.js

import { fromJS } from 'immutable';
import { TOGGLE_TASK_COMPLETION, ADD_TASK, DELETE_TASK } from './constants';

const initialState = fromJS([
  { text:'Buy milk', id: '1', isComplete: false },
  { text:'Drink milk', id: '2', isComplete: false  },
  { text:'Repeat', id:'3', isComplete: false  }
]);

function todos(state = initialState, action) {
  switch (action.type) {
    case TOGGLE_TASK_COMPLETION:
      const itemIndex = state.findIndex( i => i.get('id') === action.payload.id);
      if (itemIndex !== -1) {
        return state.update(itemIndex, (i) => i.updateIn(['isComplete'], ic => !ic));
      }
      return state;
    case ADD_TASK:
      return state.push(fromJS({
        text: action.payload.text,
        id: new Date().getTime().toString(),
        isComplete: false
      }));
    case DELETE_TASK:
      return state.filter(todo => todo.get('id') !== action.payload.id);
    default:
      return state;
  }
}

export default todos;

export function selectAllTodos(state) {
  return state.get('todos');
}

export function selectCompletedTodos(state) {
  return state.get('todos').filter(todo => todo.get('isComplete'));
}

export function selectActiveTodos(state) {
  return state.get('todos').filter(todo => !todo.get('isComplete'));
}