hash_key_conversion.rb

require_relative "string"
module Mirror
  module Api
    module HashKeyConversion
      def convert_hash_keys(value, case_type="")
        case value
          when Array
            value.map { |v| convert_hash_keys(v) }
            # or `value.map(&method(:convert_hash_keys))`
          when Hash
            Hash[value.map { |k, v| [k.to_s.__send__(case_type), convert_hash_keys(v)] }]
          else
            value
         end
      end

      def convert_hash_keys_to_camel_case(value)
        convert_hash_keys(value,"camel_case_lower")
      end

      def convert_hash_keys_to_underscore(value)
        convert_hash_keys(value,"underscore")
      end
    end
  end
end

mirror-api.rb

require "mirror-api/version"
require "mirror-api/base"
require "mirror-api/client"
require "mirror-api/oauth"
require "mirror-api/string"

request.rb

require_relative "base"
require_relative "hash_key_conversion"
module Mirror
  module Api
    HOST = "https://www.googleapis.com"

    class Request < Mirror::Api::Base
      extend HashKeyConversion
      TIMELINE = "timeline"
      SUBSCRIPTIONS = "subscriptions"
      LOCATIONS = "locations"
      CONTACTS = "contacts"

      def initialize(creds, options={})
        @resource = options[:resource] || TIMELINE
        @id = options[:id]
        @params = options[:params]
        @expected_response = options[:expected_response]
        host = options[:host] || HOST
        super(creds, options[:raise_errors], host, options[:logger])
      end

      def invoke_url
        return @invoke_url unless @invoke_url.nil?
        @invoke_url ="#{self.host}/mirror/v1/#{@resource}/#{@id ? @id : ''}"
        @invoke_url += "/attachments/#{attachment_id ? attachment_id : ''}" if attachments
        @invoke_url
      end

      def attachment_id
        attachments[:id] if attachments
      end

      def attachments
        params[:attachments] if params
      end

      def params
        return @params unless @params.nil?
        @params = Request.convert_hash_keys_to_camel_case(@params)
      end

      def ret_val
        @data = Request.convert_hash_keys_to_underscore(@data)
        Hashie::Mash.new(@data)
      end

      def expected_response
        @expected_response
      end
      
    end
  end
end

string.rb

String.class_eval do
  def underscore
    self.gsub(/::/, '/').
    gsub(/([A-Z]+)([A-Z][a-z])/,'\1_\2').
    gsub(/([a-z\d])([A-Z])/,'\1_\2').
    tr("-", "_").
    downcase
  end

  def camel_case_lower
    self.split('_').inject([]){ |buffer,e| buffer.push(buffer.empty? ? e : e.capitalize) }.join
  end
end