Extract score calculation to a module

app/models/debate.rb

@@ -102,24 +102,15 @@ class Debate < ActiveRecord::Base
   end
 
   def calculate_hot_score
-    start           = Time.new(2015, 6, 15)
-    comments_weight = 1.0/20 # 1 positive vote / x comments
-    time_unit       = 12.hours.to_f
-
-    total   = cached_votes_total + comments_weight * comments_count
-    ups     = cached_votes_up    + comments_weight * comments_count
-    downs   = total - ups
-    score   = ups - downs
-    order   = Math.log([score.abs, 1].max, 10)
-    sign    = (score <=> 0).to_f
-    seconds = ((created_at || Time.now) - start).to_f
-
-    self.hot_score = (((order * sign) + (seconds/time_unit)) * 1000000).round
+    self.hot_score = ScoreCalculator.hot_score(created_at,
+                                               cached_votes_total,
+                                               cached_votes_up,
+                                               comments_count)
   end
 
   def calculate_confidence_score
-    return unless cached_votes_total > 0
-    self.confidence_score = cached_votes_score * (cached_votes_up / cached_votes_total.to_f) * 100
+    self.confidence_score = ScoreCalculator.confidence_score(cached_votes_total,
+                                                             cached_votes_up)
   end
 
   def self.search(terms)

lib/score_calculator.rb

@@ -0,0 +1,30 @@
+module ScoreCalculator
+
+  EPOC           = Time.new(2015, 6, 15)
+  COMMENT_WEIGHT = 1.0/20 # 1 positive vote / x comments
+  TIME_UNIT      = 12.hours.to_f
+
+  def self.hot_score(date, votes_total, votes_up,  comments_count)
+    total   = votes_total + COMMENT_WEIGHT * comments_count
+    ups     = votes_up    + COMMENT_WEIGHT * comments_count
+    downs   = total - ups
+    score   = ups - downs
+    order   = Math.log([score.abs, 1].max, 10)
+    sign    = (score <=> 0).to_f
+    seconds = ((date || Time.now) - EPOC).to_f
+
+    (((order * sign) + (seconds/TIME_UNIT)) * 10000000).round
+  end
+
+  def self.confidence_score(votes_total, votes_up)
+    return 0 unless votes_total > 0
+
+    votes_total = votes_total.to_f
+    votes_up    = votes_up.to_f
+    votes_down  = votes_total - votes_up
+    score       = votes_up - votes_down
+
+    score * (votes_up / votes_total) * 100
+  end
+
+end

spec/models/debate_spec.rb

@@ -244,16 +244,16 @@ describe Debate do
       debate = create(:debate, :with_confidence_score, cached_votes_up: 100, cached_votes_score: 100, cached_votes_total: 100)
       expect(debate.confidence_score).to eq(10000)
 
-      debate = create(:debate, :with_confidence_score, cached_votes_up: 0, cached_votes_score: -100, cached_votes_total: 100)
+      debate = create(:debate, :with_confidence_score, cached_votes_up: 0, cached_votes_total: 100)
       expect(debate.confidence_score).to eq(0)
 
-      debate = create(:debate, :with_confidence_score, cached_votes_up: 50, cached_votes_score: 50, cached_votes_total: 100)
-      expect(debate.confidence_score).to eq(2500)
+      debate = create(:debate, :with_confidence_score, cached_votes_up: 75, cached_votes_total: 100)
+      expect(debate.confidence_score).to eq(3750)
 
-      debate = create(:debate, :with_confidence_score, cached_votes_up: 500, cached_votes_score: 500, cached_votes_total: 1000)
-      expect(debate.confidence_score).to eq(25000)
+      debate = create(:debate, :with_confidence_score, cached_votes_up: 750, cached_votes_total: 1000)
+      expect(debate.confidence_score).to eq(37500)
 
-      debate = create(:debate, :with_confidence_score, cached_votes_up: 10, cached_votes_score: -80, cached_votes_total: 100)
+      debate = create(:debate, :with_confidence_score, cached_votes_up: 10, cached_votes_total: 100)
       expect(debate.confidence_score).to eq(-800)
     end