function cache(option) {
  option = option || {}
  this.data = {}
  this.size = 0
  this.maxSize = option.size || 100
  this.defaultTime = option.time || 0
  this.defaultTime *= 1000
}
cache.prototype.set = function (key, val, ttl) {
  if (this.size >= this.maxSize) {
    return false
  }
  this.data[key] = this._wrap(val, ttl)
  this.size++
  return true
}
cache.prototype.get = function (key) {
  if (!this.data[key]) {
    return false
  }
  const val = this._unwrap(this.data[key])
  if (val === false) {
    delete this.data[key]
    this.size--
  }
  return val
}
cache.prototype._wrap = function (val, ttl) {
  return {
    data: val,
    expires: ttl ? Date.now() + ttl * 1000 : this.defaultTime,
  }
}
cache.prototype._unwrap = function (data) {
  return data.expires === 0 || data.expires >= Date.now() ? data.data : false
}
module.exports = cache