gistfile1.txt

require 'bundler/inline'

gemfile(true) do
  source "https://rubygems.org"

  gem 'rom'
  gem 'rom-sql'
  gem 'sequel'
  gem 'sqlite3'
end

config  = ROM::Configuration.new(:sql, "sqlite::memory")
gateway = config.gateways[:default]

migration = gateway.migration do
  change do
    create_table :products do
      primary_key :id
      column :name, String, null: false
    end

    create_table :attachments do
      primary_key :id
      column :document_id, Integer, null: false
      column :test_id,  Integer, null: false
    end

    create_table :documents do
      primary_key :id
      column :name, String, null: false
    end
  end
end

migration.apply gateway.connection, :up

class ProductsRelation < ROM::Relation[:sql]
  schema :products, infer: true do
    associations do
      has_many :attachments, foreign_key: :test_id
      has_many :documents, through: :attachments
    end
  end
end

class AttachmentsRelation < ROM::Relation[:sql]
  schema :attachments, infer: true do
    associations do
      belongs_to :document
      belongs_to :product, foreign_key: :test_id
    end
  end
end

class DocumentsRelation < ROM::Relation[:sql]
  schema :documents, infer: true
end

config.register_relation ProductsRelation
config.register_relation AttachmentsRelation
config.register_relation DocumentsRelation

rom = ROM.container(config)


rom.relations[:products].command(:create).call(name: "test 1", id: 1)
rom.relations[:documents].command(:create).call(name: 'test document', id: 100)
rom.relations[:attachments].command(:create).call(document_id: 100, test_id: 1)


puts rom.relations[:products].combine(:attachments).to_a
puts rom.relations[:attachments].combine(:documents).to_a
puts rom.relations[:products].combine(:documents).to_a