Nested attribute normalizer

son_api_spec_param_normalizer.rb

# Converts
# This
# {
#   attributes: {
#     name: 'jude',
#     address.street: 'main street',
#     address.city: 'cebu'
#   },
#   relationships: { checkout: { data: { id: 2, type: 'checkouts' } } }
# }
#
#
# To  this
# {:name=>"jude", :address_attributes=>{:street=>"main street", :city=>"cebu"}, :checkout_id=>2}
module JsonApiSpecParamNormalizer
  class << self
    def normalize(resource_permitted_params)
      hash = {}
      hash.merge!(direct_attributes(resource_permitted_params))
      hash.merge!(nested_attributes(resource_permitted_params))
      hash.merge!(foreign_key_attributes(resource_permitted_params))

      hash.to_h.deep_symbolize_keys
    end

    def direct_attributes(params)
      params.dig(:attributes).select{ |key, _val| !key.to_s.include?('.') } || {}
    end

    def nested_attributes(params)
      params.dig(:attributes).select{ |key, _val| key.to_s.include?('.') }.keys.each_with_object({}) do |key, hash|
        relation, attribute = key.to_s.split('.')

        hash["#{relation}_attributes"] ||= {}
        hash["#{relation}_attributes"][attribute] = params.dig(:attributes, key)
      end
    end

    def foreign_key_attributes(params)
      (params.dig(:relationships) || {}).keys.each_with_object({}) do |relation, hash|
        relation_data = params.dig(:relationships, relation)

        if !relation_data.is_a?(Array)
          hash["#{relation}_id".to_sym] = params.dig(:relationships, relation, :data, :id)
        end
      end
    end
  end
end

# Usage
params = {
  attributes: {
    name: 'jude',
    'address.street': 'main street',
    'address.city': 'cebu'
  },
  relationships: { checkout: { data: { id: 2, type: 'checkouts' } } }
}
puts JsonApiSpecParamNormalizer.normalize(params)