[proposal] Add class definition style

lib/verdict.rb

@@ -48,6 +48,7 @@ def initialize(handle)
 require "verdict/railtie" if defined?(Rails::Railtie)
 
 require "verdict/metadata"
+require "verdict/experiment_definition"
 require "verdict/experiment"
 require "verdict/group"
 require "verdict/assignment"

lib/verdict/experiment_definition.rb

@@ -0,0 +1,247 @@
+module Verdict
+  class ExperimentDefinition
+    extend Verdict::Metadata
+
+    class << self
+      attr_reader :handle
+
+      def inherited(subclass)
+        @handle = subclass.to_s.underscore.gsub('/', '_')
+      end
+
+      def event_logger
+        Verdict::EventLogger.new(Verdict.default_logger)
+      end
+
+      def subject_type
+        nil
+      end
+
+      def store_unqualified?
+        !!@store_unqualified
+      end
+
+      def manual_assignment_timestamps?
+        nil
+      end
+
+      def group(handle)
+        segmenter.groups[handle.to_s]
+      end
+
+      def groups(segmenter_class = Verdict::Segmenters::FixedPercentageSegmenter, &block)
+        return segmenter.groups unless block_given?
+        @segmenter ||= segmenter_class.new(self)
+        @segmenter.instance_eval(&block)
+        @segmenter.verify!
+        return self
+      end
+
+      def rollout_percentage(percentage, rollout_group_name = :enabled)
+        groups(Verdict::Segmenters::RolloutSegmenter) do
+          group(rollout_group_name, percentage)
+        end
+      end
+
+      def qualifiers
+        @qualifiers ||= []
+      end
+
+      def qualify(method_name = nil, &block)
+        if block_given?
+          qualifiers << block
+        elsif method_name.nil?
+          raise ArgumentError, "no method nor blocked passed!"
+        elsif respond_to?(method_name, true)
+          qualifiers << method(method_name).to_proc
+        else
+          raise ArgumentError, "No helper for #{method_name.inspect}"
+        end
+      end
+
+      def storage(storage = :memory, options = {})
+        @store_unqualified = options[:store_unqualified] if options.has_key?(:store_unqualified)
+        case storage
+        when :memory
+          Verdict::Storage::MemoryStorage.new
+        when :none
+          Verdict::Storage::MockStorage.new
+        when Class
+          storage.new
+        end
+      end
+
+      def segmenter
+        raise Verdict::Error, "No groups defined for experiment #{@handle.inspect}." if @segmenter.nil?
+        @segmenter
+      end
+
+      def started_at
+        @started_at ||= storage.retrieve_start_timestamp(self)
+      rescue Verdict::StorageError
+        nil
+      end
+
+      def started?
+        !@started_at.nil?
+      end
+
+      def group_handles
+        segmenter.groups.keys
+      end
+
+      def subject_assignment(subject, group, originally_created_at = nil, temporary = false)
+        Verdict::Assignment.new(self, subject, group, originally_created_at, temporary)
+      end
+
+      def subject_conversion(subject, goal, created_at = Time.now.utc)
+        Verdict::Conversion.new(self, subject, goal, created_at)
+      end
+
+      def convert(subject, goal)
+        identifier = retrieve_subject_identifier(subject)
+        conversion = subject_conversion(subject, goal)
+        event_logger.log_conversion(conversion)
+        segmenter.conversion_feedback(identifier, subject, conversion)
+        conversion
+      rescue Verdict::EmptySubjectIdentifier
+        raise unless disqualify_empty_identifier?
+      end
+
+      def assign(subject, context = nil)
+        previous_assignment = lookup(subject)
+
+        subject_identifier = retrieve_subject_identifier(subject)
+        assignment = if previous_assignment
+          previous_assignment
+        elsif subject_qualifies?(subject, context)
+          group = segmenter.assign(subject_identifier, subject, context)
+          subject_assignment(subject, group, nil, group.nil?)
+        else
+          nil_assignment(subject)
+        end
+
+        store_assignment(assignment)
+      rescue Verdict::StorageError
+        nil_assignment(subject)
+      rescue Verdict::EmptySubjectIdentifier
+        if disqualify_empty_identifier?
+          nil_assignment(subject)
+        else
+          raise
+        end
+      end
+
+      def assign_manually(subject, group)
+        assignment = subject_assignment(subject, group)
+        if !assignment.qualified? && !store_unqualified?
+          raise Verdict::Error, "Unqualified subject assignments are not stored for this experiment, so manual disqualification is impossible. Consider setting :store_unqualified to true for this experiment."
+        end
+
+        store_assignment(assignment)
+        assignment
+      end
+
+      def disqualify_manually(subject)
+        assign_manually(subject, nil)
+      end
+
+      def store_assignment(assignment)
+        storage.store_assignment(assignment) if should_store_assignment?(assignment)
+        event_logger.log_assignment(assignment)
+        assignment
+      end
+
+      def cleanup(options = {})
+        storage.cleanup(self, options)
+      end
+
+      def remove_subject_assignment(subject)
+        storage.remove_assignment(self, subject)
+      end
+
+      def switch(subject, context = nil)
+        assign(subject, context).to_sym
+      end
+
+      def lookup(subject)
+        storage.retrieve_assignment(self, subject)
+      end
+
+      def retrieve_subject_identifier(subject)
+        identifier = subject_identifier(subject).to_s
+        raise Verdict::EmptySubjectIdentifier, "Subject resolved to an empty identifier!" if identifier.empty?
+        identifier
+      end
+
+      def has_qualifier?
+        @qualifiers.any?
+      end
+
+      def everybody_qualifies?
+        !has_qualifier?
+      end
+
+      def as_json(options = {})
+        {
+          handle: handle,
+          has_qualifier: has_qualifier?,
+          groups: segmenter.groups.values.map { |group| group.as_json(options) },
+          metadata: metadata,
+          started_at: started_at.nil? ? nil : started_at.utc.strftime('%FT%TZ')
+        }.tap do |data|
+          data[:subject_type] = subject_type.to_s unless subject_type.nil?
+        end
+      end
+
+      def to_json(options = {})
+        as_json(options).to_json
+      end
+
+      def fetch_subject(subject_identifier)
+        raise NotImplementedError, "Fetching subjects based on identifier is not implemented for experiment #{handle.inspect}."
+      end
+
+      def disqualify_empty_identifier?
+        @disqualify_empty_identifier
+      end
+
+      def subject_qualifies?(subject, context = nil)
+        ensure_experiment_has_started
+        everybody_qualifies? || qualifiers.all? { |qualifier| qualifier.call(subject, context) }
+      end
+
+      protected
+
+      def default_options
+        {}
+      end
+
+      def should_store_assignment?(assignment)
+        assignment.permanent? && !assignment.returning? && (store_unqualified? || assignment.qualified?)
+      end
+
+      def subject_identifier(subject)
+        subject.respond_to?(:id) ? subject.id : subject.to_s
+      end
+
+      def set_start_timestamp
+        storage.store_start_timestamp(self, started_now = Time.now.utc)
+        started_now
+      rescue NotImplementedError
+        nil
+      end
+
+      def ensure_experiment_has_started
+        @started_at ||= started_at || set_start_timestamp
+      rescue Verdict::StorageError
+        @started_at ||= Time.now.utc
+      end
+
+      def nil_assignment(subject)
+        subject_assignment(subject, nil, nil)
+      end
+    end
+  end
+end
+

lib/verdict/railtie.rb

@@ -1,14 +1,7 @@
 class Verdict::Railtie < Rails::Railtie
   initializer "experiments.configure_rails_initialization" do |app|
-    app.config.eager_load_namespaces << Verdict
-
     Verdict.default_logger = Rails.logger
-
     Verdict.directory ||= Rails.root.join('app', 'experiments')
-    app.config.eager_load_paths -= Dir[Verdict.directory.to_s]
-
-    # Re-freeze eager load paths to ensure they blow up if modified at runtime, as Rails does
-    app.config.eager_load_paths.freeze
   end
 
   config.to_prepare do

lib/verdict/version.rb

@@ -1,3 +1,5 @@
 module Verdict
-  VERSION = "0.12.0"
+  class Version
+    VERSION = "0.13.0"
+  end
 end

verdict.gemspec

@@ -5,7 +5,7 @@ require 'verdict/version'
 
 Gem::Specification.new do |gem|
   gem.name          = "verdict"
-  gem.version       = Verdict::VERSION
+  gem.version       = Verdict::Version::VERSION
   gem.authors       = ["Shopify"]
   gem.email         = ["[email protected]", "[email protected]"]
   gem.description   = %q{Shopify Experiments classes}