# this is a tricky method used to pull a report to review out of the pool of
  # possible reports, it can return nothing when there are no reports or when
  # there are simply no qualifying reports for the student to review.  read
  # *carefully* if you plan on modifying it
  #
    def find_lettuce_report_to_review options = {}
      options.to_options!
      student = options.delete(:student) or raise 'no student'

      transaction do
        pool = pool_for(student)
        unit = self

        report_table = Report.table_name
        report_review_table = ReportReview.table_name

      # find the list of any report the student has already reviewed - we'll
      # use this to prevent a double review of any report
      #
        select = [:id, :report_id].join(', ')
        conditions = { :user_id => student.id, :pool_id => pool.id }
        reviews = ReportReview.find(:all, :select => select, :conditions => conditions, :include => :report)

      # setup a list of previously reviewed report ids - we don't want to do
      # these again....
      #
        report_ids = reviews.map{|review| review.report.id}.compact

      # now look for a report to review, we want one that is published, in the
      # correct unit, in the correct pool, that is not written by the student
      # and which has not already been review by the student.  furthermore, we
      # want to select one which is most likely to be needing a review, we do
      # this be selecting the ones with the lowest review count and the from
      # those selecting the ones which haven't had a reviewer look at them in
      # a while (reviewed_at).
      #
        conditions = [
          "
            #{ report_table }.is_published=? AND
            #{ report_table }.unit_id=? AND
            #{ report_table }.user_id!=? AND
            #{ report_table }.pool_id=?
          ",
          true, unit.id, student.id, pool.id
        ]

        unless report_ids.empty?
          condition_clause = conditions.first
          list = report_ids.join(', ')
          condition_clause << " AND #{ report_table }.id NOT IN(#{ list }) "
        end

        order = "
          #{ report_table }.reviews_count, #{ report_table }.reviewed_at
        "

        Report.find(:first,
          options.reverse_merge(:conditions => conditions, :order => order, :include => :questionnaire)
        )
      end
    end