Extract methods in tag cloud

This gets rid of the compute method, and makes each value that got set
in it its own little method.

app/controllers/stats_controller.rb

@@ -553,14 +553,12 @@ class StatsController < ApplicationController
 
   def get_stats_tags
     cloud = Stats::TagCloud.new(current_user)
-    cloud.compute
 
     @tags_for_cloud = cloud.tags
     @tags_min = cloud.min
     @tags_divisor = cloud.divisor
 
     cloud = Stats::TagCloud.new(current_user, @cut_off_3months)
-    cloud.compute
     @tags_for_cloud_90days = cloud.tags
     @tags_min_90days = cloud.min
     @tags_divisor_90days = cloud.divisor

app/models/stats/tag_cloud.rb

@@ -3,30 +3,47 @@
 module Stats
   class TagCloud
 
-    attr_reader :user, :cutoff, :levels,
-      :tags, :min, :divisor
+    attr_reader :user, :cutoff, :levels
     def initialize(user, cutoff = nil)
       @user = user
       @cutoff = cutoff
       @levels = 10
     end
 
-    def compute
-      @tags = top_tags
-      max, @min = 0, 0
-      @tags.each { |t|
-        max = [t.count.to_i, max].max
-        @min = [t.count.to_i, @min].min
-      }
-      @divisor = ((max - @min) / levels) + 1
+    def tags
+      @tags ||= top_tags
+    end
+
+    def max
+      @max ||= tag_counts.max
+    end
+
+    # 2013-02-28: Possible bug.
+    # The original code always set the minimum to zero.
+    # This might need to use tag_counts.min
+    # https://github.com/TracksApp/tracks/commit/8c26ea7cb596c97e37213c0cc994e66ee5fd27b0#commitcomment-2719199
+    def min
+      0
+    end
+
+    def divisor
+      @divisor ||= ((max - min) / levels) + 1
     end
 
     private
 
+    def tag_counts
+      @tag_counts ||= tags.map {|t| t.count.to_i}
+    end
+
     def top_tags
-      params = [sql, user.id]
-      params += [cutoff, cutoff] if cutoff
-      Tag.find_by_sql(params).sort_by { |tag| tag.name.downcase }
+      Tag.find_by_sql(query_options).sort_by { |tag| tag.name.downcase }
+    end
+
+    def query_options
+      options = [sql, user.id]
+      options += [cutoff, cutoff] if cutoff
+      options
     end
 
     def sql