# File lib/algorithms/prompt/popular.rb, line 16
16:     def prompts(question_id, voter_id, count)
17:       result = ActiveRecord::Base.connection.execute(
18:         "SELECT id,score FROM stats WHERE question_id=#{question_id} ORDER BY score;"
19:       )
20:       # TODO: choose min value with more justification
21:       return nil unless result.num_rows > 2
22:       # make all stats positive by adding |min(stats)| + 1 to all stats
23:       prompt_item_ids = {}
24:       norm = cur = 0
25:       stats = []
26:       stat = result.fetch_hash
27:       min = stat['score'].to_f.abs + 1
28:       while !stat.nil?
29:         norm += (adj = stat['score'].to_f + min)
30:         stats << [stat['id'].to_i, [cur, cur += adj]]
31:         stat = result.fetch_hash
32:       end
33:       result.free
34:       Prompt.transaction do
35:         count.times do |i|
36:           prompt = prompt_for_request(question_id, voter_id, ID)
37:           # choose the stat [0] <= r < [1]
38:           r = rand(norm)
39:           # detect treats hash as [key, value] array
40:           stat_id = stats.detect { |stat| stat[1][0] <= r && r < stat[1][1] }[0]
41:           item_ids = Stat.find(stat_id).item_ids
42:           prompt.item_ids = item_ids
43:           redo if bad_prompt?(prompt)
44:           prompt_item_ids[prompt.id] = item_ids
45:         end
46:       end
47:       prompt_item_ids
48:     end