class Doorkeeper::OAuth::ClientCredentialsRequest::Creator

def call(client, scopes, attributes = {})
  existing_token = existing_token_for(client, scopes)
  if existing_token
    return existing_token if existing_token.accessible?
    existing_token.revoke
  end
  create(client, scopes, attributes)
end

def create(client, scopes, attributes = {})
  Doorkeeper::AccessToken.create(attributes.merge({
    :application_id => client.id,
    :scopes         => scopes.to_s
  }))
end

def existing_token_for(client, scopes)
  Doorkeeper::AccessToken.matching_token_for client, nil, scopes
end