class Signet::OAuth2::Client

hash with the fetched authentication token.
This reopens Client to add #apply and #apply! methods which update a
Signet::OAuth2::Client creates an OAuth2 client

def apply a_hash, opts = {}

Returns a clone of a_hash updated with the authentication token 
def apply a_hash, opts = {}
  a_copy = a_hash.clone
  apply! a_copy, opts
  a_copy
end

def apply! a_hash, opts = {}

Updates a_hash updated with the authentication token 
def apply! a_hash, opts = {}
  # fetch the access token there is currently not one, or if the client
  # has expired
  fetch_access_token! opts if access_token.nil? || expires_within?(60)
  a_hash[AUTH_METADATA_KEY] = "Bearer #{access_token}"
end

def build_default_connection 

def build_default_connection
  return nil unless defined?(@connection_info)
  if @connection_info.respond_to? :call
    @connection_info.call
  else
    @connection_info
  end
end

def configure_connection options 

def configure_connection options
  @connection_info =
    options[:connection_builder] || options[:default_connection]
  self
end

def fetch_access_token! options = {} 

def fetch_access_token! options = {}
  unless options[:connection]
    connection = build_default_connection
    options = options.merge connection: connection if connection
  end
  info = retry_with_error do
    orig_fetch_access_token! options
  end
  notify_refresh_listeners
  info
end

def notify_refresh_listeners 

def notify_refresh_listeners
  listeners = @refresh_listeners || []
  listeners.each do |block|
    block.call self
  end
end

def on_refresh &block 

def on_refresh &block
  @refresh_listeners ||= []
  @refresh_listeners << block
end

def retry_with_error max_retry_count = 5 

def retry_with_error max_retry_count = 5
  retry_count = 0
  begin
    yield
  rescue StandardError => e
    raise e if e.is_a?(Signet::AuthorizationError) || e.is_a?(Signet::ParseError)
    if retry_count < max_retry_count
      retry_count += 1
      sleep retry_count * 0.3
      retry
    else
      msg = "Unexpected error: #{e.inspect}"
      raise Signet::AuthorizationError, msg
    end
  end
end

def updater_proc

a closure
Returns a reference to the #apply method, suitable for passing as 
def updater_proc
  lambda(&method(:apply))
end