Revert "rm experiment data methods for stability"

This reverts commit 211731b.

lib/modesty/datastore/redis.rb

@@ -127,6 +127,54 @@ def track!(count, with_args)
           end
         end
       end
+
+    end
+
+    class ExperimentData < Datastore::ExperimentData
+      def data
+        Modesty.data
+      end
+
+      def key(*args)
+        RedisData.keyify(:experiments, @experiment.slug, *args)
+      end
+
+      def register!(alt, identity)
+        old_alt = self.get_cached_alternative(identity)
+        if old_alt
+          data.srem(self.key(old_alt), identity)
+        end
+        data.sadd(self.key(alt), identity)
+        return alt
+      end
+
+      def get_cached_alternative(identity)
+        @experiment.alternatives.each do |alt|
+          if data.sismember(self.key(alt), identity)
+            return alt
+          end
+        end
+        return nil
+      end
+
+      def users(alt=nil)
+        if alt.nil? #return the union
+          data.sunion(*@experiment.alternatives.map {|a| self.key(a) })
+        else
+          data.smembers(self.key(alt))
+        end.map(&:to_i)
+      end
+
+      def num_users(alt=nil)
+        if alt.nil?
+          @experiment.alternatives.map do |alt|
+            data.scard(self.key(alt)).to_i
+          end.sum
+        else
+          data.scard(self.key(alt)).to_i
+        end
+      end
+
     end
   end
 end

lib/modesty/experiment/data.rb

@@ -1,15 +1,75 @@
 module Modesty
   class Experiment
+    def data
+      @data ||= (Modesty.data.class)::ExperimentData.new(self)
+    end
+
+    def chooses(alt, options={})
+      raise Experiment::Error, <<-msg.squish unless self.alternatives.include? alt
+        Unknown alternative #{alt.inspect}
+      msg
+
+      id = options.include?(:for) ? options[:for] : Modesty.identity
+
+      raise IdentityError, <<-msg.squish unless id
+        Experiment#chooses doesn't work for guests.
+        Either identify globally or pass in :for => id
+      msg
+
+      self.data.register!(alt, id)
+    rescue Datastore::ConnectionError => e
+      Modesty.handle_error(e)
+      alt
+    end
+
     def group(id=Modesty.identity)
       return :control unless id
-      self.alternatives[
-        "#{@slug}#{id}".hash % self.alternatives.count
-      ]
+      fetch_or_generate_group(id)
     end
 
     # usage: `e.group?(:experiment)`
     def group?(alt)
       self.group == alt
     end
+
+    def num_users(alt=nil)
+      if self.data.respond_to? :num_users
+        self.data.num_users(alt)
+      else
+        self.users(alt).count
+      end
+    end
+
+    def users(alt=nil)
+      self.data.users(alt)
+    end
+
+  private
+    # used to fetch the cached alternative from redis
+    def fetch_group(identity)
+      self.data.get_cached_alternative(identity)
+    rescue Datastore::ConnectionError => e
+      Modesty.handle_error(e)
+      nil
+    end
+
+    # this is the method with the fallbacks - fetch it from redis or create it.
+    def fetch_or_generate_group(id=Modesty.identity)
+      alt = begin
+        fetch_group(id)
+      rescue Datastore::ConnectionError
+        nil
+      end || generate_group(id)
+    end
+
+    # generates an alternative and stores it in redis
+    def generate_group(identity)
+      alternative = self.alternatives[
+        "#{@slug}#{identity}".hash % self.alternatives.count
+      ]
+      self.chooses(alternative, :for => identity)
+      return alternative
+    end
+
   end
 end