JSON-API mocking library/script - in Ruby

json_api_mocking.rb

# JSON-API mocking library - a very, very simple script to help mock JSON-API
# JSON. This is more designed to return scaffolding that can then be manually
# edited.  It supports only single resource objects, with included or linked
# children, but only one child per relationship. This might be useful for
# specing out what your API could look like for frontend and backend developers.

# Example usage is at the bottom. If I were to take this further, I'd make it
# more recursive.

class JsonApiMock
  BASE_URL = 'https://hostmaker.co/api/v1/'

  attr_accessor :output, :serializable_objects

  def initialize(*serializable_objects)
    self.serializable_objects = serializable_objects
    self.output = {}

    populate_object_data
    populate_included_relationship_data
  end

  def print_output
    puts JSON.pretty_generate(output)
  end

  private

  def single_resource?
    serializable_objects == 1
  end

  def populate_object_data
    object_data = serializable_objects.map(&:object_data)
    output[:data] = single_resource? ? object_data.first : object_data
  end

  def populate_included_relationship_data
    included_data = serializable_objects.map(&:included_relationship_data)
      .compact.flatten.sort_by{|o| o[:type]}
    if included_data.any?
      output[:included] = included_data
    end
  end

end

# Relationship represents the child relations of the root_object. Parameters:
# * included - boolean - specify if data in included in request - default: false
# * ar_object - ActiveRecord object - if child is AR object, pass in
# * type - relationship type - only required if ar_object is nil
# * relationship_name - name of relationship - defaults to type
# * attributes - the child objects attributes - defaults to null, pulls from
#    ar_object if present
# * related_objects - Any child related objects


class SerializeableObject
  include ActiveModel::Model #from Rails, just to be lazy about setting attrs
  attr_accessor :relationship_name, :ar_object, :included, :type, :attributes, :related_objects,
    :id, :base_object_data, :passed_attributes

  def initialize(*args)
    super(*args)
    if built_from_ar_object?
      self.attributes ||= {}
      self.id ||= rand_id
    else
      self.attributes ||= ar_object.try(:attributes) | {}
      self.type ||= ar_object.class.name.underscore.pluralize
      self.id ||= attributes.id
    end
    self.attributes = attributes.slice(*passed_attributes) if passed_attributes && passed_attributes.any?
    self.relationship_name ||= type
    self.related_objects = Array(related_objects)
  end

  def object_data
    @object_data ||= build_object_data
  end

  def included_relationship_data
    related_objects.select(&:included).map(&:object_data) + related_objects.map(&:included_relationship_data)
  end

  protected

  def add_relationship_data(output:{})
    if output[relationship_name]
      output[relationship_name][:links][:related] = self_collection_url
    else
      output[relationship_name] = {links: {related: self_single_url}}
    end

    if included
      output[relationship_name][:data] ||= []
      output[relationship_name][:data] << {type: type, id: id}
    end
  end

  private

  def build_object_data
    self.base_object_data = {
      type: type.to_s,
      id: id,
      attributes: attributes,
      links: {self: self_single_url}
    }

    collect_child_relationships
    base_object_data
  end

  def collect_child_relationships
    if related_objects && related_objects.any?
      base_object_data[:relationships] ||= {}
      related_objects.each do |rel|
        rel.add_relationship_data(output: base_object_data[:relationships])
      end
    end
  end

  def built_from_ar_object?
    @built_from_ar_object ||= ar_object.nil?
  end

  def rand_id
    @rand_id ||= Random.rand(9999)
  end

  def self_single_url
    @self_url ||=  self_collection_url + '/' + id.to_s
  end

  def self_collection_url
    JsonApiMock::BASE_URL + type.to_s
  end
end

# USAGE ##########

# below we load a user from our rails backend, but any
# object that responds to at least attributes and class is fine.

included_profile_photo = SerializeableObject.new(
  included: true,
  type: :profile_photos,
  relationship_name: :active_profile_photo,
  attributes: {
    "60x60": "/path/to/60x60/image.jpg",
    "120x120": "/path/to/120x120/image.jpg",
    "240x240": "/path/to/240x240/image.jpg"
  })
parent_object = SerializeableObject.new(ar_object: User.first, related_objects: [included_profile_photo])
JsonApiMock.new(parent_object).print_output

# After generating the above, then you can copy and paste to create has_many
# relations or  add/remove attributes for unimplemented objects.

# Here is another example with multiple objects
mock_objects = Article.last(10).map do |article|
  author = SerializeableObject.new(ar_object: article.author, included: true)
  SerializeableObject.new(ar_object: article, related_objects: author)
end
JsonApiMock.new(*mock_objects).print_output

json_response_example.json

{
  "data": {
    "type": "user",
    "id": 1,
    "attributes": {
      "email": "user@domain.com",
      "sign_in_count": 234,
      "current_sign_in_at": "2016-08-11 22:31:50 UTC",
      "last_sign_in_at": "2016-08-09 05:29:01 UTC",
      "current_sign_in_ip": "54.240.197.234",
      "last_sign_in_ip": "67.170.10.201",
      "name": "John Doe",
      "role": "supervisor",
      "phone_number": null,
      "created_at": "2015-10-11 01:00:16 UTC",
      "updated_at": "2016-08-11 22:31:50 UTC"
    },
    "links": {
      "self": "https://domain.com/api/v1/user/1"
    },
    "relationships": {
      "active_profile_photo": {
        "links": {
          "related": "https://domain.com/api/v1/profile_photos/1884"
        },
        "data": [
          {
            "type": "profile_photos",
            "id": 1884
          }
        ]
      }
    }
  },
  "included": [
    {
      "type": "profile_photos",
      "id": 1884,
      "attributes": {
        "60x60": "/path/to/60x60/image.jpg",
        "120x120": "/path/to/120x120/image.jpg",
        "240x240": "/path/to/240x240/image.jpg"
      },
      "links": {
        "self": "https://domain.com/api/v1/profile_photos/1884"
      }
    }
  ]
}