discourse/app/services/user_blocker.rb

class UserBlocker

  def initialize(user, by_user=nil, opts={})
    @user, @by_user, @opts = user, by_user, opts
  end

  def self.block(user, by_user=nil, opts={})
    UserBlocker.new(user, by_user, opts).block
  end

  def self.unblock(user, by_user=nil, opts={})
    UserBlocker.new(user, by_user, opts).unblock
  end

  def block
    hide_posts
    @user.blocked = true
    if @user.save
      SystemMessage.create(@user, @opts[:message] || :blocked_by_staff)
    end
  end

  def hide_posts
    Post.where(user_id: @user.id).update_all(["hidden = true, hidden_reason_id = COALESCE(hidden_reason_id, ?)", Post.hidden_reasons[:new_user_spam_threshold_reached]])
    topic_ids = Post.where('user_id = ? and post_number = ?', @user.id, 1).pluck(:topic_id)
    Topic.update_all({ visible: false }, id: topic_ids) unless topic_ids.empty?
  end

  def unblock
    @user.blocked = false
    if @user.save
      SystemMessage.create(@user, :unblocked)
    end
  end

end