class CourseAttendance < ApplicationRecord
  # mode: 0 两种签到，1 二维码签到，2 数字签到
  belongs_to :course
  belongs_to :user

  has_many :course_attendance_groups, dependent: :destroy
  has_many :course_member_attendances, dependent: :destroy

  validates :name, presence: true
  validates :mode, presence: true
  validates :attendance_date, presence: true
  validates :start_time, presence: true
  validates :end_time, presence: true

  after_create :generate_attendance_code

  # 延迟生成邀请码
  def attendance_code
    return generate_attendance_code
  end

  # 生成邀请码
  CODES = %W(2 3 4 5 6 7 8 9 A B C D E F G H J K L N M O P Q R S T U V W X Y Z)
  def generate_attendance_code
    code = read_attribute(:attendance_code)
    if !code || code.size < 4
      code = CODES.sample(4).join
      return generate_attendance_code if CourseAttendance.where(attendance_code: code).present?
      update_attribute(:attendance_code, code)
    end
    code
  end
end