class CourseGroup < ActiveRecord::Base
  # attr_accessible :title, :body
  belongs_to :course
  has_many :members
  has_many :memberships, :class_name => 'Member'
  has_many :member_principals, :class_name => 'Member',
           :include => :principal,
           :conditions => "#{Principal.table_name}.type='Group' OR (#{Principal.table_name}.type='User' AND #{Principal.table_name}.status=#{Principal::STATUS_ACTIVE})"
  has_many :principals, :through => :member_principals, :source => :principal
  has_many :users, :through => :members
  has_many :homework_group_settings, :dependent => :destroy
  has_many :exercise_group_settings, :dependent => :destroy
  has_many :homework_group_reviews, :dependent => :destroy
  has_many :poll_group_settings, :dependent => :destroy
  has_many :attachment_group_settings, :dependent => :destroy
  has_many :teacher_course_groups, :dependent => :destroy


  before_destroy :set_member_nil

  # attr_accessible :name
  validates :name, :presence => true, :length => {:maximum => 20}, :uniqueness => { :scope => :course_id}

  # 延迟生成邀请码
  def invite_code
    return generate_invite_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_invite_code
    code = read_attribute(:invite_code)
    if !code || code.size < 6
      code = CODES.sample(6).join
      return generate_invite_code if CourseGroup.where(invite_code: code).present?
      update_attribute(:invite_code, code)
    end
    code
  end

  def set_member_nil
    if self.members && self.members.count > 0
       self.members.update_all("course_group_id = 0")
    end
  end

end