Storage

let storage = {}
let fs = require('fs')
const filePath = './storage.json'
let checkIfKeyString = (key) => {
  if (typeof key !== 'string') {
    throw new Error('key is not a string!')
  }
}

let checkIfKeyExist = (key, storage) => {
  if (storage.hasOwnProperty(key)) {
    throw new Error('Key already exist!')
  }
}

let checkIfKeyNotExist = (key, storage) => {
  if (!storage.hasOwnProperty(key)) {
    throw new Error('Key does not exist!')
  }
}

let put = (key, value) => {
  checkIfKeyString(key)
  checkIfKeyExist(key, storage)
  storage[key] = value
  return storage
}

let get = (key) => {
  checkIfKeyString(key)
  checkIfKeyNotExist(key, storage)
  return storage[key]
}

let update = (key, value) => {
  checkIfKeyString(key)
  checkIfKeyNotExist(key, storage)
  storage[key] = value
  return storage
}

let deleteItem = (key) => {
  checkIfKeyString(key)
  checkIfKeyNotExist(key, storage)
  delete storage[key]
  return storage
}

let clear = () => {
  storage = {}
  return storage
}

// This is with callback
// let save = (callback) => {
//   fs.writeFile(filePath, JSON.stringify(storage, null, 2), (err) => {
//     if (err) console.log(err)
//     callback()
//   })
// }

// let load = (callback) => { // приемаме callback като параметър на функцията и когато е изпълнен промиса викаме callback-a
//   fs.readFile(filePath, 'utf8', (err, data) => {
//     if (err) throw err
//     callback(data)
//   })
// }

// This is with Promises
let save = () => {
  return new Promise((resolve, reject) => {
    fs.writeFile(filePath, JSON.stringify(storage, null, 2), (err) => {
      if (err) {
        reject(err)
        return
      }
      resolve()
    })
  })
}

let load = () => {
  return new Promise((resolve, reject) => {
    fs.readFile(filePath, 'utf8', (err, data) => {
      if (err) {
        reject(err)
        return
      }
      resolve(data)
    })
  })
}

let getAll = () => {
  return storage
}

module.exports = {
  put,
  get,
  getAll,
  update,
  delete: deleteItem,
  clear,
  save,
  load
}