ActiveRecord Playground in a Single File

inventory.rb

unless File.exist?('Gemfile')
  File.write('Gemfile', <<-GEMFILE)
    source 'https://rubygems.org'
    gem 'rails'
    gem 'sqlite3'
  GEMFILE
 
  system 'bundle'
end
 
require 'bundler'
Bundler.setup(:default)
 
require 'active_record'
require 'minitest/autorun'
require 'logger'
 
# This connection will do for database-independent bug reports.
ActiveRecord::Base.establish_connection(:adapter => 'sqlite3', :database => ':memory:')
ActiveRecord::Base.logger = Logger.new(STDOUT)
 
# Define a DB schema for the test we would run
ActiveRecord::Schema.define do
  create_table :quotas do |t|
    t.string :organization
    t.integer :instances
  end

  create_table :usages do |t|
    t.string :organization
    t.integer :bucket_id
    t.integer :instances
    t.string :type
  end

  create_table :buckets do |t|
    t.integer :quota_id
    t.string :organization
    t.string :project
    t.integer :instances, default: 0
  end
end
 
class Quota < ActiveRecord::Base
  self.table_name = "quotas"
end

class Usage < Quota
  def self.recalculate_organization(id)
    buckets   = Bucket.where(organization: id).all
    usage     = OrganizationUsage.find_or_create_by(organization: id)
    instances = buckets.map(&:usage).map(&:instances).compact.inject(&:+) 

    usage.update(instances: instances)
  end

  def self.recalculate_bucket(id)
    bucket = Bucket.find(id)
    usage  = BucketUsage.find_or_create_by(bucket: id)
    
    usage.update(instances: bucket.instances)
  end
end

class OrganizationUsage < Usage 
end

class BucketUsage < Usage
  belongs_to :bucket
end

class Bucket < ActiveRecord::Base
  has_one :usage, class_name: "BucketUsage", dependent: :destroy

  after_save :update_usages

  def update_usages
    Usage.recalculate_bucket(self)
    Usage.recalculate_organization(organization)
  end
end

describe 'The tests' do
  before do
    @bucket0 = Bucket.create(organization: "a", project: "a")
    @bucket1 = Bucket.create(organization: "a", project: "b")
  end
 
  after do
    Bucket.destroy_all
    Quota.destroy_all
    BucketUsage.destroy_all
    OrganizationUsage.destroy_all
  end

  it "updates bucket usages" do
    @bucket0.update(instances: 5)
    @bucket0.usage.instances.must_equal 5
  end

  it "updates organization usage" do
    @bucket0.update(instances: 3)
    @bucket1.update(instances: 4)

    OrganizationUsage.find_by_organization("a").instances.must_equal 7
  end
end