authorize.rb

# From https://developers.google.com/sheets/api/quickstart/ruby#step_3_set_up_the_sample

require 'google/apis/sheets_v4'
require 'googleauth'
require 'googleauth/stores/file_token_store'

require 'fileutils'

OOB_URI = 'urn:ietf:wg:oauth:2.0:oob'
SCOPE = Google::Apis::SheetsV4::AUTH_SPREADSHEETS
APPLICATION_NAME = 'GnuCashGetQuotes'
CREDENTIALS_PATH = File.join(Dir.home, '.credentials',
                             "sheets.googleapis.gnucashgetquotes.yaml")

##
# Ensure valid credentials, either by restoring from the saved credentials
# files or intitiating an OAuth2 authorization. If authorization is required,
# the user's default browser will be launched to approve the request.
#
# @return [Google::Auth::UserRefreshCredentials] OAuth2 credentials
def authorize
  FileUtils.mkdir_p(File.dirname(CREDENTIALS_PATH))

  client_id = Google::Auth::ClientId.from_file(CLIENT_SECRETS_PATH)
  token_store = Google::Auth::Stores::FileTokenStore.new(file: CREDENTIALS_PATH)
  authorizer = Google::Auth::UserAuthorizer.new(
    client_id, SCOPE, token_store)
  user_id = 'default'
  credentials = authorizer.get_credentials(user_id)
  if credentials.nil?
    url = authorizer.get_authorization_url(
      base_url: OOB_URI)
    puts "Open the following URL in the browser and enter the " +
         "resulting code after authorization"
    puts url
    code = gets
    credentials = authorizer.get_and_store_credentials_from_code(
      user_id: user_id, code: code, base_url: OOB_URI)
  end
  credentials
end