module Slack::Web::Api::Mixins::Users

def users_id(options = {})
  name = options[:user]
  throw ArgumentError.new('Required arguments :user missing') if name.nil?
  return { 'ok' => true, 'user' => { 'id' => name } } unless name[0] == '@'
  users_list.tap do |list|
    list.members.each do |user|
      return Slack::Messages::Message.new('ok' => true, 'user' => { 'id' => user.id }) if user.name == name[1..-1]
    end
  end
  fail Slack::Web::Api::Error, 'user_not_found'
end