discourse/app/models/user.rb

require_dependency 'email'
require_dependency 'email_token'
require_dependency 'trust_level'
require_dependency 'pbkdf2'
require_dependency 'discourse'
require_dependency 'post_destroyer'
require_dependency 'user_name_suggester'
require_dependency 'pretty_text'
require_dependency 'url_helper'
require_dependency 'letter_avatar'
require_dependency 'promotion'

class User < ActiveRecord::Base
  include Roleable
  include UrlHelper
  include HasCustomFields

  has_many :posts
  has_many :notifications, dependent: :destroy
  has_many :topic_users, dependent: :destroy
  has_many :topics
  has_many :user_open_ids, dependent: :destroy
  has_many :user_actions, dependent: :destroy
  has_many :post_actions, dependent: :destroy
  has_many :user_badges, -> {where('user_badges.badge_id IN (SELECT id FROM badges where enabled)')}, dependent: :destroy
  has_many :badges, through: :user_badges
  has_many :email_logs, dependent: :delete_all
  has_many :post_timings
  has_many :topic_allowed_users, dependent: :destroy
  has_many :topics_allowed, through: :topic_allowed_users, source: :topic
  has_many :email_tokens, dependent: :destroy
  has_many :views
  has_many :user_visits, dependent: :destroy
  has_many :invites, dependent: :destroy
  has_many :topic_links, dependent: :destroy
  has_many :uploads
  has_many :warnings

  has_one :user_avatar, dependent: :destroy
  has_one :facebook_user_info, dependent: :destroy
  has_one :twitter_user_info, dependent: :destroy
  has_one :github_user_info, dependent: :destroy
  has_one :google_user_info, dependent: :destroy
  has_one :oauth2_user_info, dependent: :destroy
  has_one :user_stat, dependent: :destroy
  has_one :user_profile, dependent: :destroy, inverse_of: :user
  has_one :single_sign_on_record, dependent: :destroy
  belongs_to :approved_by, class_name: 'User'
  belongs_to :primary_group, class_name: 'Group'

  has_many :group_users, dependent: :destroy
  has_many :groups, through: :group_users
  has_many :secure_categories, through: :groups, source: :categories

  has_many :group_managers, dependent: :destroy
  has_many :managed_groups, through: :group_managers, source: :group

  has_many :muted_user_records, class_name: 'MutedUser'
  has_many :muted_users, through: :muted_user_records

  has_one :user_search_data, dependent: :destroy
  has_one :api_key, dependent: :destroy

  belongs_to :uploaded_avatar, class_name: 'Upload'

  delegate :last_sent_email_address, :to => :email_logs

  before_validation :strip_downcase_email

  validates_presence_of :username
  validate :username_validator
  validates :email, presence: true, uniqueness: true
  validates :email, email: true, if: :email_changed?
  validate :password_validator
  validates :name, user_full_name: true, if: :name_changed?
  validates :ip_address, allowed_ip_address: {on: :create, message: :signup_not_allowed}

  after_initialize :add_trust_level
  after_initialize :set_default_email_digest
  after_initialize :set_default_external_links_in_new_tab

  after_create :create_email_token
  after_create :create_user_stat
  after_create :create_user_profile
  after_create :ensure_in_trust_level_group
  after_create :automatic_group_membership

  before_save :update_username_lower
  before_save :ensure_password_is_hashed

  after_save :update_tracked_topics
  after_save :clear_global_notice_if_needed
  after_save :refresh_avatar
  after_save :badge_grant

  before_destroy do
    # These tables don't have primary keys, so destroying them with activerecord is tricky:
    PostTiming.delete_all(user_id: self.id)
    TopicViewItem.delete_all(user_id: self.id)
  end

  # Whether we need to be sending a system message after creation
  attr_accessor :send_welcome_message

  # This is just used to pass some information into the serializer
  attr_accessor :notification_channel_position

  # set to true to optimize creation and save for imports
  attr_accessor :import_mode

  # excluding fake users like the system user
  scope :real, -> { where('id > 0') }

  scope :staff, -> { where("admin OR moderator") }

  # TODO-PERF: There is no indexes on any of these
  # and NotifyMailingListSubscribers does a select-all-and-loop
  # may want to create an index on (active, blocked, suspended_till, mailing_list_mode)?
  scope :blocked, -> { where(blocked: true) }
  scope :not_blocked, -> { where(blocked: false) }
  scope :suspended, -> { where('suspended_till IS NOT NULL AND suspended_till > ?', Time.zone.now) }
  scope :not_suspended, -> { where('suspended_till IS NULL OR suspended_till <= ?', Time.zone.now) }
  scope :activated, -> { where(active: true) }

  module NewTopicDuration
    ALWAYS = -1
    LAST_VISIT = -2
  end

  def self.max_password_length
    200
  end

  def self.username_length
    SiteSetting.min_username_length.to_i..SiteSetting.max_username_length.to_i
  end

  def custom_groups
    groups.where(automatic: false, visible: true)
  end

  def self.username_available?(username)
    lower = username.downcase
    User.where(username_lower: lower).blank?
  end

  def effective_locale
    if SiteSetting.allow_user_locale && self.locale.present?
      self.locale
    else
      SiteSetting.default_locale
    end
  end

  EMAIL = %r{([^@]+)@([^\.]+)}

  def self.new_from_params(params)
    user = User.new
    user.name = params[:name]
    user.email = params[:email]
    user.password = params[:password]
    user.username = params[:username]
    user
  end

  def self.suggest_name(email)
    return "" unless email
    name = email.split(/[@\+]/)[0]
    name = name.gsub(".", " ")
    name.titleize
  end

  def self.find_by_username_or_email(username_or_email)
    if username_or_email.include?('@')
      find_by_email(username_or_email)
    else
      find_by_username(username_or_email)
    end
  end

  def self.find_by_email(email)
    find_by(email: Email.downcase(email))
  end

  def self.find_by_username(username)
    find_by(username_lower: username.downcase)
  end


  def enqueue_welcome_message(message_type)
    return unless SiteSetting.send_welcome_message?
    Jobs.enqueue(:send_system_message, user_id: id, message_type: message_type)
  end

  def change_username(new_username, actor=nil)
    UsernameChanger.change(self, new_username, actor)
  end

  def created_topic_count
    stat = user_stat || create_user_stat
    stat.topic_count
  end

  alias_method :topic_count, :created_topic_count

  # tricky, we need our bus to be subscribed from the right spot
  def sync_notification_channel_position
    @unread_notifications_by_type = nil
    self.notification_channel_position = DiscourseBus.last_id("/notification/#{id}")
  end

  def invited_by
    used_invite = invites.where("redeemed_at is not null").includes(:invited_by).first
    used_invite.try(:invited_by)
  end

  # Approve this user
  def approve(approved_by, send_mail=true)
    self.approved = true

    if approved_by.is_a?(Fixnum)
      self.approved_by_id = approved_by
    else
      self.approved_by = approved_by
    end

    self.approved_at = Time.now

    send_approval_email if save and send_mail
  end

  def self.email_hash(email)
    Digest::MD5.hexdigest(email.strip.downcase)
  end

  def email_hash
    User.email_hash(email)
  end

  def reload
    @unread_notifications = nil
    @unread_total_notifications = nil
    @unread_pms = nil
    super
  end

  def unread_private_messages
    @unread_pms ||=
      begin
        # perf critical, much more efficient than AR
        sql = "
           SELECT COUNT(*) FROM notifications n
           LEFT JOIN topics t ON n.topic_id = t.id
           WHERE
            t.deleted_at IS NULL AND
            n.notification_type = :type AND
            n.user_id = :user_id AND
            NOT read"

        User.exec_sql(sql, user_id: id,
                           type:  Notification.types[:private_message])
            .getvalue(0,0).to_i
      end
  end

  def unread_notifications
    @unread_notifications ||=
      begin
        # perf critical, much more efficient than AR
        sql = "
           SELECT COUNT(*) FROM notifications n
           LEFT JOIN topics t ON n.topic_id = t.id
           WHERE
            t.deleted_at IS NULL AND
            n.notification_type <> :pm AND
            n.user_id = :user_id AND
            NOT read AND
            n.id > :seen_notification_id"

        User.exec_sql(sql, user_id: id,
                           seen_notification_id: seen_notification_id,
                           pm:  Notification.types[:private_message])
            .getvalue(0,0).to_i
      end
  end

  def total_unread_notifications
    @unread_total_notifications ||= notifications.where("read = false").count
  end

  def saw_notification_id(notification_id)
    User.where("id = ? and seen_notification_id < ?", id, notification_id)
        .update_all ["seen_notification_id = ?", notification_id]

    # mark all badge notifications read
    Notification.where('user_id = ? AND NOT read AND notification_type = ?', id, Notification.types[:granted_badge])
        .update_all ["read = ?", true]
  end

  def publish_notifications_state
    DiscourseBus.publish("/notification/#{id}",
                       {unread_notifications: unread_notifications,
                        unread_private_messages: unread_private_messages,
                        total_unread_notifications: total_unread_notifications},
                       user_ids: [id] # only publish the notification to this user
    )
  end

  # A selection of people to autocomplete on @mention
  def self.mentionable_usernames
    User.select(:username).order('last_posted_at desc').limit(20)
  end

  def password=(password)
    # special case for passwordless accounts
    @raw_password = password unless password.blank?
  end

  def password
    '' # so that validator doesn't complain that a password attribute doesn't exist
  end

  # Indicate that this is NOT a passwordless account for the purposes of validation
  def password_required!
    @password_required = true
  end

  def password_required?
    !!@password_required
  end

  def has_password?
    password_hash.present?
  end

  def password_validator
    PasswordValidator.new(attributes: :password).validate_each(self, :password, @raw_password)
  end

  def confirm_password?(password)
    return false unless password_hash && salt
    self.password_hash == hash_password(password, salt)
  end

  def first_day_user?
    !staff? &&
    trust_level < TrustLevel[2] &&
    created_at >= 24.hours.ago
  end

  def new_user?
    (created_at >= 24.hours.ago || trust_level == TrustLevel[0]) &&
      trust_level < TrustLevel[2] &&
      !staff?
  end

  def seen_before?
    last_seen_at.present?
  end

  def visit_record_for(date)
    user_visits.find_by(visited_at: date)
  end

  def update_visit_record!(date)
    create_visit_record!(date) unless visit_record_for(date)
  end

  def update_posts_read!(num_posts, now=Time.zone.now)
    if user_visit = visit_record_for(now.to_date)
      user_visit.posts_read += num_posts
      user_visit.save
      user_visit
    else
      create_visit_record!(now.to_date, num_posts)
    end
  end

  def update_ip_address!(new_ip_address)
    unless ip_address == new_ip_address || new_ip_address.blank?
      update_column(:ip_address, new_ip_address)
    end
  end

  def update_last_seen!(now=Time.zone.now)
    now_date = now.to_date
    # Only update last seen once every minute
    redis_key = "user:#{id}:#{now_date}"
    return unless $redis.setnx(redis_key, "1")

    $redis.expire(redis_key, SiteSetting.active_user_rate_limit_secs)
    update_previous_visit(now)
    # using update_column to avoid the AR transaction
    update_column(:last_seen_at, now)
  end

  def self.gravatar_template(email)
    email_hash = self.email_hash(email)
    "//www.gravatar.com/avatar/#{email_hash}.png?s={size}&r=pg&d=identicon"
  end

  # Don't pass this up to the client - it's meant for server side use
  # This is used in
  #   - self oneboxes in open graph data
  #   - emails
  def small_avatar_url
    avatar_template_url.gsub("{size}", "45")
  end

  def avatar_template_url
    schemaless absolute avatar_template
  end

  def self.avatar_template(username,uploaded_avatar_id)
    return letter_avatar_template(username) if !uploaded_avatar_id
    id = uploaded_avatar_id
    username ||= ""
    "#{Discourse.base_uri}/user_avatar/#{RailsMultisite::ConnectionManagement.current_hostname}/#{username.downcase}/{size}/#{id}.png"
  end

  def self.letter_avatar_template(username)
    "#{Discourse.base_uri}/letter_avatar/#{username.downcase}/{size}/#{LetterAvatar.version}.png"
  end

  def avatar_template
    self.class.avatar_template(username,uploaded_avatar_id)
  end

  # The following count methods are somewhat slow - definitely don't use them in a loop.
  # They might need to be denormalized
  def like_count
    UserAction.where(user_id: id, action_type: UserAction::WAS_LIKED).count
  end

  def like_given_count
    UserAction.where(user_id: id, action_type: UserAction::LIKE).count
  end

  def post_count
    stat = user_stat || create_user_stat
    stat.post_count
  end

  def flags_given_count
    PostAction.where(user_id: id, post_action_type_id: PostActionType.flag_types.values).count
  end

  def warnings_received_count
    warnings.count
  end

  def flags_received_count
    posts.includes(:post_actions).where('post_actions.post_action_type_id' => PostActionType.flag_types.values).count
  end

  def private_topics_count
    topics_allowed.where(archetype: Archetype.private_message).count
  end

  def posted_too_much_in_topic?(topic_id)

    # Does not apply to staff, non-new members or your own topics
    return false if staff? ||
                    (trust_level != TrustLevel[0]) ||
                    Topic.where(id: topic_id, user_id: id).exists?

    last_action_in_topic = UserAction.last_action_in_topic(id, topic_id)
    since_reply = Post.where(user_id: id, topic_id: topic_id)
    since_reply = since_reply.where('id > ?', last_action_in_topic) if last_action_in_topic

    (since_reply.count >= SiteSetting.newuser_max_replies_per_topic)
  end

  def delete_all_posts!(guardian)
    raise Discourse::InvalidAccess unless guardian.can_delete_all_posts? self

    QueuedPost.where(user_id: id).delete_all

    posts.order("post_number desc").each do |p|
      PostDestroyer.new(guardian.user, p).destroy
    end
  end

  def suspended?
    suspended_till && suspended_till > DateTime.now
  end

  def suspend_record
    UserHistory.for(self, :suspend_user).order('id DESC').first
  end

  def suspend_reason
    suspend_record.try(:details) if suspended?
  end

  # Use this helper to determine if the user has a particular trust level.
  # Takes into account admin, etc.
  def has_trust_level?(level)
    raise "Invalid trust level #{level}" unless TrustLevel.valid?(level)
    admin? || moderator? || TrustLevel.compare(trust_level, level)
  end

  # a touch faster than automatic
  def admin?
    admin
  end

  def guardian
    Guardian.new(self)
  end

  def username_format_validator
    UsernameValidator.perform_validation(self, 'username')
  end

  def email_confirmed?
    email_tokens.where(email: email, confirmed: true).present? || email_tokens.empty?
  end

  def activate
    email_token = self.email_tokens.active.first
    if email_token
      EmailToken.confirm(email_token.token)
    else
      self.active = true
      save
    end
  end

  def deactivate
    self.active = false
    save
  end

  def change_trust_level!(level, opts=nil)
    Promotion.new(self).change_trust_level!(level, opts)
  end

  def treat_as_new_topic_start_date
    duration = new_topic_duration_minutes || SiteSetting.new_topic_duration_minutes
    [case duration
      when User::NewTopicDuration::ALWAYS
        created_at
      when User::NewTopicDuration::LAST_VISIT
        previous_visit_at || user_stat.new_since
      else
        duration.minutes.ago
    end, user_stat.new_since].max
  end

  def readable_name
    return "#{name} (#{username})" if name.present? && name != username
    username
  end

  def badge_count
    user_badges.select('distinct badge_id').count
  end

  def featured_user_badges
    user_badges
        .joins(:badge)
        .order("CASE WHEN badges.id = (SELECT MAX(ub2.badge_id) FROM user_badges ub2
                              WHERE ub2.badge_id IN (#{Badge.trust_level_badge_ids.join(",")}) AND
                                    ub2.user_id = #{self.id}) THEN 1 ELSE 0 END DESC")
        .order('badges.badge_type_id ASC, badges.grant_count ASC')
        .includes(:user, :granted_by, badge: :badge_type)
        .where("user_badges.id in (select min(u2.id)
                  from user_badges u2 where u2.user_id = ? group by u2.badge_id)", id)
        .limit(3)
  end

  def self.count_by_signup_date(start_date, end_date)
    where('created_at >= ? and created_at <= ?', start_date, end_date).group('date(created_at)').order('date(created_at)').count
  end


  def secure_category_ids
    cats = self.admin? ? Category.where(read_restricted: true) : secure_categories.references(:categories)
    cats.pluck('categories.id').sort
  end

  def topic_create_allowed_category_ids
    Category.topic_create_allowed(self.id).select(:id)
  end


  # Flag all posts from a user as spam
  def flag_linked_posts_as_spam
    admin = Discourse.system_user
    topic_links.includes(:post).each do |tl|
      begin
        PostAction.act(admin, tl.post, PostActionType.types[:spam], message: I18n.t('flag_reason.spam_hosts'))
      rescue PostAction::AlreadyActed
        # If the user has already acted, just ignore it
      end
    end
  end

  def has_uploaded_avatar
    uploaded_avatar.present?
  end

  def generate_api_key(created_by)
    if api_key.present?
      api_key.regenerate!(created_by)
      api_key
    else
      ApiKey.create(user: self, key: SecureRandom.hex(32), created_by: created_by)
    end
  end

  def revoke_api_key
    ApiKey.where(user_id: self.id).delete_all
  end

  def find_email
    last_sent_email_address || email
  end

  def tl3_requirements
    @lq ||= TrustLevel3Requirements.new(self)
  end

  def on_tl3_grace_period?
    UserHistory.for(self, :auto_trust_level_change)
      .where('created_at >= ?', SiteSetting.tl3_promotion_min_duration.to_i.days.ago)
      .where(previous_value: TrustLevel[2].to_s)
      .where(new_value: TrustLevel[3].to_s)
      .exists?
  end

  def should_be_redirected_to_top
    redirected_to_top_reason.present?
  end

  def redirected_to_top_reason
    # redirect is enabled
    return unless SiteSetting.redirect_users_to_top_page
    # top must be in the top_menu
    return unless SiteSetting.top_menu =~ /top/i
    # there should be enough topics
    return unless SiteSetting.has_enough_topics_to_redirect_to_top

    if !seen_before? || (trust_level == 0 && !redirected_to_top_yet?)
      update_last_redirected_to_top!
      return I18n.t('redirected_to_top_reasons.new_user')
    elsif last_seen_at < 1.month.ago
      update_last_redirected_to_top!
      return I18n.t('redirected_to_top_reasons.not_seen_in_a_month')
    end

    # no reason
    nil
  end

  def redirected_to_top_yet?
    last_redirected_to_top_at.present?
  end

  def update_last_redirected_to_top!
    key = "user:#{id}:update_last_redirected_to_top"
    delay = SiteSetting.active_user_rate_limit_secs

    # only update last_redirected_to_top_at once every minute
    return unless $redis.setnx(key, "1")
    $redis.expire(key, delay)

    # delay the update
    Jobs.enqueue_in(delay / 2, :update_top_redirection, user_id: self.id, redirected_at: Time.zone.now)
  end

  def refresh_avatar
    return if @import_mode

    avatar = user_avatar || create_user_avatar

    if SiteSetting.automatically_download_gravatars? && !avatar.last_gravatar_download_attempt
      Jobs.enqueue(:update_gravatar, user_id: self.id, avatar_id: avatar.id)
    end

    # mark all the user's quoted posts as "needing a rebake"
    Post.rebake_all_quoted_posts(self.id) if self.uploaded_avatar_id_changed?
  end

  def first_post_created_at
    user_stat.try(:first_post_created_at)
  end

  def associated_accounts
    result = []

    result << "Twitter(#{twitter_user_info.screen_name})" if twitter_user_info
    result << "Facebook(#{facebook_user_info.username})"  if facebook_user_info
    result << "Google(#{google_user_info.email})"         if google_user_info
    result << "Github(#{github_user_info.screen_name})"   if github_user_info

    user_open_ids.each do |oid|
      result << "OpenID #{oid.url[0..20]}...(#{oid.email})"
    end

    result.empty? ? I18n.t("user.no_accounts_associated") : result.join(", ")
  end

  def user_fields
    return @user_fields if @user_fields
    user_field_ids = UserField.pluck(:id)
    if user_field_ids.present?
      @user_fields = {}
      user_field_ids.each do |fid|
        @user_fields[fid.to_s] = custom_fields["user_field_#{fid}"]
      end
    end
    @user_fields
  end

  def title=(val)
    write_attribute(:title, val)
    if !new_record? && user_profile
      user_profile.update_column(:badge_granted_title, false)
    end
  end

  def number_of_deleted_posts
    Post.with_deleted
        .where(user_id: self.id)
        .where.not(deleted_at: nil)
        .count
  end

  def number_of_flagged_posts
    Post.with_deleted
        .where(user_id: self.id)
        .where(id: PostAction.where(post_action_type_id: PostActionType.notify_flag_type_ids)
                             .where(disagreed_at: nil)
                             .select(:post_id))
        .count
  end

  def number_of_flags_given
    PostAction.where(user_id: self.id)
              .where(disagreed_at: nil)
              .where(post_action_type_id: PostActionType.notify_flag_type_ids)
              .count
  end

  def number_of_warnings
    self.warnings.count
  end

  def number_of_suspensions
    UserHistory.for(self, :suspend_user).count
  end

  def create_user_profile
    UserProfile.create(user_id: id)
  end

  def anonymous?
    SiteSetting.allow_anonymous_posting &&
      trust_level >= 1 &&
      custom_fields["master_id"].to_i > 0
  end

  protected

  def badge_grant
    BadgeGranter.queue_badge_grant(Badge::Trigger::UserChange, user: self)
  end

  def update_tracked_topics
    return unless auto_track_topics_after_msecs_changed?
    TrackedTopicsUpdater.new(id, auto_track_topics_after_msecs).call
  end

  def clear_global_notice_if_needed
    if admin && SiteSetting.has_login_hint
      SiteSetting.has_login_hint = false
      SiteSetting.global_notice = ""
    end
  end

  def ensure_in_trust_level_group
    Group.user_trust_level_change!(id, trust_level)
  end

  def automatic_group_membership
    Group.where(automatic: false)
         .where("LENGTH(COALESCE(automatic_membership_email_domains, '')) > 0")
         .each do |group|
      domains = group.automatic_membership_email_domains.gsub('.', '\.')
      if self.email =~ Regexp.new("@(#{domains})$", true)
        group.add(self) rescue ActiveRecord::RecordNotUnique
      end
    end
  end

  def create_user_stat
    stat = UserStat.new(new_since: Time.now)
    stat.user_id = id
    stat.save!
  end

  def create_email_token
    email_tokens.create(email: email)
  end

  def create_visit_record!(date, posts_read=0)
    user_stat.update_column(:days_visited, user_stat.days_visited + 1)
    user_visits.create!(visited_at: date, posts_read: posts_read)
  end

  def ensure_password_is_hashed
    if @raw_password
      self.salt = SecureRandom.hex(16)
      self.password_hash = hash_password(@raw_password, salt)
    end
  end

  def hash_password(password, salt)
    raise "password is too long" if password.size > User.max_password_length
    Pbkdf2.hash_password(password, salt, Rails.configuration.pbkdf2_iterations, Rails.configuration.pbkdf2_algorithm)
  end

  def add_trust_level
    # there is a possibility we did not load trust level column, skip it
    return unless has_attribute? :trust_level
    self.trust_level ||= SiteSetting.default_trust_level
  end

  def update_username_lower
    self.username_lower = username.downcase
  end

  def strip_downcase_email
    if self.email
      self.email = self.email.strip
      self.email = self.email.downcase
    end
  end

  def username_validator
    username_format_validator || begin
      lower = username.downcase
      existing = User.find_by(username_lower: lower)
      if username_changed? && existing && existing.id != self.id
        errors.add(:username, I18n.t(:'user.username.unique'))
      end
    end
  end

  def send_approval_email
    Jobs.enqueue(:user_email,
      type: :signup_after_approval,
      user_id: id,
      email_token: email_tokens.first.token
    )
  end

  def set_default_email_digest
    if has_attribute?(:email_digests) && self.email_digests.nil?
      if SiteSetting.default_digest_email_frequency.blank?
        self.email_digests = false
      else
        self.email_digests = true
        self.digest_after_days ||= SiteSetting.default_digest_email_frequency.to_i if has_attribute?(:digest_after_days)
      end
    end
  end

  def set_default_external_links_in_new_tab
    if has_attribute?(:external_links_in_new_tab) && self.external_links_in_new_tab.nil?
      self.external_links_in_new_tab = !SiteSetting.default_external_links_in_new_tab.blank?
    end
  end

  # Delete unactivated accounts (without verified email) that are over a week old
  def self.purge_unactivated

    to_destroy = User.where(active: false)
                     .joins('INNER JOIN user_stats AS us ON us.user_id = users.id')
                     .where("created_at < ?", SiteSetting.purge_unactivated_users_grace_period_days.days.ago)
                     .where('NOT admin AND NOT moderator')
                     .limit(100)

    destroyer = UserDestroyer.new(Discourse.system_user)
    to_destroy.each do |u|
      begin
        destroyer.destroy(u, context: I18n.t(:purge_reason))
      rescue Discourse::InvalidAccess
        # if for some reason the user can't be deleted, continue on to the next one
      end
    end
  end

  private

  def previous_visit_at_update_required?(timestamp)
    seen_before? && (last_seen_at < (timestamp - SiteSetting.previous_visit_timeout_hours.hours))
  end

  def update_previous_visit(timestamp)
    update_visit_record!(timestamp.to_date)
    if previous_visit_at_update_required?(timestamp)
      update_column(:previous_visit_at, last_seen_at)
    end
  end

end

# == Schema Information
#
# Table name: users
#
#  id                            :integer          not null, primary key
#  username                      :string(60)       not null
#  created_at                    :datetime         not null
#  updated_at                    :datetime         not null
#  name                          :string(255)
#  seen_notification_id          :integer          default(0), not null
#  last_posted_at                :datetime
#  email                         :string(256)      not null
#  password_hash                 :string(64)
#  salt                          :string(32)
#  active                        :boolean          default(FALSE), not null
#  username_lower                :string(60)       not null
#  auth_token                    :string(32)
#  last_seen_at                  :datetime
#  admin                         :boolean          default(FALSE), not null
#  last_emailed_at               :datetime
#  email_digests                 :boolean          not null
#  trust_level                   :integer          not null
#  email_private_messages        :boolean          default(TRUE)
#  email_direct                  :boolean          default(TRUE), not null
#  approved                      :boolean          default(FALSE), not null
#  approved_by_id                :integer
#  approved_at                   :datetime
#  digest_after_days             :integer
#  previous_visit_at             :datetime
#  suspended_at                  :datetime
#  suspended_till                :datetime
#  date_of_birth                 :date
#  auto_track_topics_after_msecs :integer
#  views                         :integer          default(0), not null
#  flag_level                    :integer          default(0), not null
#  ip_address                    :inet
#  new_topic_duration_minutes    :integer
#  external_links_in_new_tab     :boolean          not null
#  enable_quoting                :boolean          default(TRUE), not null
#  moderator                     :boolean          default(FALSE)
#  blocked                       :boolean          default(FALSE)
#  dynamic_favicon               :boolean          default(FALSE), not null
#  title                         :string(255)
#  uploaded_avatar_id            :integer
#  email_always                  :boolean          default(FALSE), not null
#  mailing_list_mode             :boolean          default(FALSE), not null
#  locale                        :string(10)
#  primary_group_id              :integer
#  registration_ip_address       :inet
#  last_redirected_to_top_at     :datetime
#  disable_jump_reply            :boolean          default(FALSE), not null
#  edit_history_public           :boolean          default(FALSE), not null
#  trust_level_locked            :boolean          default(FALSE), not null
#
# Indexes
#
#  index_users_on_auth_token      (auth_token)
#  index_users_on_last_posted_at  (last_posted_at)
#  index_users_on_last_seen_at    (last_seen_at)
#  index_users_on_username        (username) UNIQUE
#  index_users_on_username_lower  (username_lower) UNIQUE
#