discourse/app/models/group.rb

class Group < ActiveRecord::Base
  has_many :category_groups
  has_many :group_users

  has_many :categories, through: :category_groups
  has_many :users, through: :group_users

  AUTO_GROUPS = {
    :admins => 1,
    :moderators => 2,
    :staff => 3,
    :trust_level_1 => 11,
    :trust_level_2 => 12,
    :trust_level_3 => 13,
    :trust_level_4 => 14,
    :trust_level_5 => 15
  }

  def self.trust_group_ids
    (10..19).to_a
  end

  def self.refresh_automatic_group!(name)

    id = AUTO_GROUPS[name]

    unless group = self[name]
      group = Group.new(name: name.to_s, automatic: true)
      group.id = id
      group.save!
    end


    real_ids = case name
               when :admins
                 "SELECT u.id FROM users u WHERE u.admin = 't'"
               when :moderators
                 "SELECT u.id FROM users u WHERE u.moderator = 't'"
               when :staff
                 "SELECT u.id FROM users u WHERE u.moderator = 't' OR u.admin = 't'"
               when :trust_level_1, :trust_level_2, :trust_level_3, :trust_level_4, :trust_level_5
                 "SELECT u.id FROM users u WHERE u.trust_level = #{id-10}"
               end


    extra_users = group.users.where("users.id NOT IN (#{real_ids})").select('users.id')
    missing_users = GroupUser.joins("RIGHT JOIN (#{real_ids}) X ON X.id = user_id AND group_id = #{group.id}")
      .where("user_id IS NULL")
      .select("X.id")

    group.group_users.where("user_id IN (#{extra_users.to_sql})").delete_all

    missing_users.each do |u|
      group.group_users.build(user_id: u.id)
    end

    group.save!
  end

  def self.refresh_automatic_groups!(*args)
    args.each do |group|
      refresh_automatic_group!(group)
    end
  end

  def self.[](name)
    raise ArgumentError, "unknown group" unless id = AUTO_GROUPS[name]

    Group.where(id: id).first
  end


  def self.user_trust_level_change!(user_id, trust_level)
    name = "trust_level_#{trust_level}".to_sym

    GroupUser.where(group_id: trust_group_ids, user_id: user_id).delete_all

    if group = Group[name]
      group_users.build(user_id: user_id)
      group_users.save!
    else
      refresh_automatic_group!(name)
    end
  end

  def user_ids
    users.select('users.id').map(&:id)
  end

  def self.builtin
    Enum.new(:moderators, :admins, :trust_level_1, :trust_level_2)
  end

  def add(user)
    self.users.push(user)
  end
end