http_repo_model_mapping.rb

# gem install anima rom rom-http rom-repository inflecto
require 'anima'
require 'rom'
require 'rom/memory'
require 'rom-http'
require 'rom-repository'
require 'json'
require 'uri'
require 'inflecto'
require 'net/http'

module Transformer
  extend Transproc::Registry

  import :map_array, from: Transproc::ArrayTransformations
  import :hash_recursion, from: Transproc::Recursion
  import :map_keys, from: Transproc::HashTransformations
  import :underscore, from: Inflecto
  import :to_symbol, from: Transproc::Coercions

  module_function

  def transform_tuples(tuples)
    t(:map_array, t(:hash_recursion, t(:map_keys, t(:underscore) >> t(:to_symbol))))[tuples]
  end
end

class RequestHandler
  def call(dataset)
    uri = URI(dataset.uri)
    uri.path = "/#{dataset.name}/#{dataset.path}"
    uri.query = URI.encode_www_form(dataset.params)

    http = Net::HTTP.new(uri.host, uri.port)
    request_klass = Net::HTTP.const_get(ROM::Inflector.classify(dataset.request_method))

    request = request_klass.new(uri.request_uri)
    dataset.headers.each_with_object(request) do |(header, value), req|
      req[header.to_s] = value
    end

    http.request(request)
  end
end

class ResponseHandler
  def call(response, dataset)
    Transformer[:transform_tuples][Array([JSON.parse(response.body)]).flatten]
  end
end

rom = ROM::Environment.new
rom.setup(:http, {
  uri: 'http://jsonplaceholder.typicode.com',
  headers: {
    Accept: 'application/json'
  },
  request_handler: RequestHandler.new,
  response_handler: ResponseHandler.new
})

class Users < ROM::Relation[:http]
  dataset :users

  use :view
  use :key_inference

  def primary_key
    :id
  end

  view(:base, [:id, :name, :username, :email, :address, :phone, :website, :company]) do
    self
  end

  def by_id(id)
    with_path(id.to_s)
  end
end

class User
  include Anima.new(:id, :name, :username, :email, :address, :phone, :website, :company)

  def initialize(attributes = {})
    super(attributes.to_hash)
  end
end

class UserMapper < ROM::Mapper
  relation :users
  register_as :entity

  model User
end

rom.register_relation(Users)
rom.register_mapper(UserMapper)

container = rom.finalize.env

class UserRepository < ROM::Repository::Base
  relations :users

  def by_id(id)
    users.by_id(id)
  end
end

user_repo = UserRepository.new(container)

user_repo.by_id(1).as(:entity).first
# => #<User id=1 name="Leanne Graham" username="Bret" email="Sincere@april.biz" address={:street=>"Kulas Light", :suite=>"Apt. 556", :city=>"Gwenborough", :zipcode=>"92998-3874", :geo=>{:lat=>"-37.3159", :lng=>"81.1496"}} phone="1-770-736-8031 x56442" website="hildegard.org" company={:name=>"Romaguera-Crona", :catch_phrase=>"Multi-layered client-server neural-net", :bs=>"harness real-time e-markets"}>