'use strict'
const {RECEIVE_TODOS, RECEIVED_TODOS, ADD_TODO, ADDED_TODO} = require('./action_constants')
const INITIAL_STATE = {toBeAdded: [], items: [], size: 0, lastUpdated: null, fetching: false, error: null}

// create an array of todos that are still queued, but not yet added
const removeToBeAdded = (current, itemToBeRemoved) => {
  if (current.length === 1) return []
  return current.map(item => {
    if (item.text !== itemToBeRemoved.text) return item
  })
}

module.exports = (state = INITIAL_STATE, action) => {
  switch (action.type) {
    // received all todos
    case RECEIVED_TODOS:
      return Object.assign({}, state, {
        items: action.items,
        size: action.items.length,
        lastUpdated: Date.now(),
      })
    // trying to add a todo (request to amazon not yet made)
    case ADD_TODO:
      return Object.assign({}, state, {
        toBeAdded: state.toBeAdded.push(action.item),
        lastUpdated: Date.now(),
      })
    // todo has been added successfully 
    case ADDED_TODO:
      // remove the item from the toBeadded array
      const toBeAdded = removeToBeAdded(state.toBeAdded, action.item)
      state.items.push(action.item)
      return Object.assign({}, state, {
        items: state.items,
        size: state.size + 1,
        toBeAdded: toBeAdded,
        lastUpdated: Date.now(),
      })      
    default:
      return state
  }
}