Initial pass at active record adapter

Gemfile

@@ -13,6 +13,7 @@ gem 'statsd-ruby', '~> 1.2.1'
 gem 'rspec', '~> 3.0'
 gem 'rack-test', '~> 0.6.3'
 gem 'activesupport', '~> 4.2.0'
+gem 'sqlite3', '~> 1.3.11'
 
 group(:guard) do
   gem 'guard', '~> 2.12.5'

flipper-active_record.gemspec

@@ -0,0 +1,24 @@
+# -*- encoding: utf-8 -*-
+require File.expand_path('../lib/flipper/version', __FILE__)
+
+flipper_mongo_files = lambda { |file|
+  file =~ /active_record/
+}
+
+Gem::Specification.new do |gem|
+  gem.authors       = ["John Nunemaker"]
+  gem.email         = ["[email protected]"]
+  gem.summary       = "ActiveRecord adapter for Flipper"
+  gem.description   = "ActiveRecord adapter for Flipper"
+  gem.license       = "MIT"
+  gem.homepage      = "https://github.com/jnunemaker/flipper"
+
+  gem.files         = `git ls-files`.split("\n").select(&flipper_mongo_files) + ["lib/flipper/version.rb"]
+  gem.test_files    = `git ls-files -- {test,spec,features}/*`.split("\n").select(&flipper_mongo_files)
+  gem.name          = "flipper-active_record"
+  gem.require_paths = ["lib"]
+  gem.version       = Flipper::VERSION
+
+  gem.add_dependency 'flipper', "~> #{Flipper::VERSION}"
+  gem.add_dependency 'activerecord', '~> 4.2.0'
+end

lib/flipper-active_record.rb

@@ -0,0 +1 @@
+require 'flipper/adapters/active_record'

lib/flipper/adapters/active_record.rb

@@ -0,0 +1,142 @@
+require 'set'
+require 'flipper'
+require 'active_record'
+
+module Flipper
+  module Adapters
+    class ActiveRecord
+      include Flipper::Adapter
+
+      class Feature < ::ActiveRecord::Base
+        self.table_name = "flipper_features"
+      end
+
+      class Gate < ::ActiveRecord::Base
+        self.table_name = "flipper_gates"
+      end
+
+      # Public: The name of the adapter.
+      attr_reader :name
+
+      def initialize
+        @name = :active_record
+      end
+
+      # Public: The set of known features.
+      def features
+        Feature.select(:key).map(&:key).to_set
+      end
+
+      # Public: Adds a feature to the set of known features.
+      def add(feature)
+        attributes = {key: feature.key}
+        # race condition, but add is only used by enable/disable which happen
+        # super rarely, so it shouldn't matter in practice
+        Feature.where(attributes).first || Feature.create!(attributes)
+        true
+      end
+
+      # Public: Removes a feature from the set of known features.
+      def remove(feature)
+        Feature.transaction do
+          Feature.delete_all(key: feature.key)
+          clear(feature)
+        end
+        true
+      end
+
+      # Public: Clears the gate values for a feature.
+      def clear(feature)
+        Gate.delete_all(feature_key: feature.key)
+        true
+      end
+
+      # Public: Gets the values for all gates for a given feature.
+      #
+      # Returns a Hash of Flipper::Gate#key => value.
+      def get(feature)
+        result = {}
+
+        db_gates = Gate.where(feature_key: feature.key)
+
+        feature.gates.each do |gate|
+          result[gate.key] = case gate.data_type
+          when :boolean
+            if db_gate = db_gates.detect { |db_gate| db_gate.key == gate.key.to_s }
+              db_gate.value
+            end
+          when :integer
+            if db_gate = db_gates.detect { |db_gate| db_gate.key == gate.key.to_s }
+              db_gate.value
+            end
+          when :set
+            db_gates.select { |db_gate| db_gate.key == gate.key.to_s }.map(&:value).to_set
+          else
+            unsupported_data_type gate.data_type
+          end
+        end
+
+        result
+      end
+
+      # Public: Enables a gate for a given thing.
+      #
+      # feature - The Flipper::Feature for the gate.
+      # gate - The Flipper::Gate to disable.
+      # thing - The Flipper::Type being disabled for the gate.
+      #
+      # Returns true.
+      def enable(feature, gate, thing)
+        case gate.data_type
+        when :boolean, :integer
+          Gate.create!({
+            feature_key: feature.key,
+            key: gate.key,
+            value: thing.value.to_s,
+          })
+        when :set
+          Gate.create!({
+            feature_key: feature.key,
+            key: gate.key,
+            value: thing.value.to_s,
+          })
+        else
+          unsupported_data_type gate.data_type
+        end
+
+        true
+      end
+
+      # Public: Disables a gate for a given thing.
+      #
+      # feature - The Flipper::Feature for the gate.
+      # gate - The Flipper::Gate to disable.
+      # thing - The Flipper::Type being disabled for the gate.
+      #
+      # Returns true.
+      def disable(feature, gate, thing)
+        case gate.data_type
+        when :boolean
+          clear(feature)
+        when :integer
+          Gate.create!({
+            feature_key: feature.key,
+            key: gate.key,
+            value: thing.value.to_s,
+          })
+        when :set
+          Gate.delete_all(feature_key: feature.key, key: gate.key, value: thing.value)
+        else
+          unsupported_data_type gate.data_type
+        end
+
+        true
+      end
+
+      # Private
+      def unsupported_data_type(data_type)
+        raise "#{data_type} is not supported by this adapter"
+      end
+    end
+  end
+end

spec/flipper/adapters/active_record_spec.rb

@@ -0,0 +1,50 @@
+require 'helper'
+require 'flipper/adapters/active_record'
+require 'flipper/spec/shared_adapter_specs'
+
+# Turn off migration logging for specs
+ActiveRecord::Migration.verbose = false
+
+class CreateFlipperTables < ActiveRecord::Migration
+  def self.up
+    create_table :flipper_features do |t|
+      t.string :key, null: false
+      t.timestamps null: false
+    end
+    add_index :flipper_features, :key, unique: true
+
+    create_table :flipper_gates do |t|
+      t.string :feature_key, null: false
+      t.string :key, null: false
+      t.string :value
+      t.timestamps null: false
+    end
+    add_index :flipper_gates, [:feature_key, :key, :value], unique: true
+  end
+
+  def self.down
+    drop_table :flipper_gates
+    drop_table :flipper_features
+  end
+end
+
+RSpec.describe Flipper::Adapters::ActiveRecord do
+  subject { described_class.new }
+
+  before(:all) do
+    ActiveRecord::Base.establish_connection({
+      adapter: "sqlite3",
+      database: ":memory:",
+    })
+  end
+
+  before(:each) do
+    CreateFlipperTables.up
+  end
+
+  after(:each) do
+    CreateFlipperTables.down
+  end
+
+  it_should_behave_like 'a flipper adapter'
+end