/******************************************************************************
*
*  Copyright 2018 Stefan Majewsky <majewsky@gmx.net>
*
*  Licensed under the Apache License, Version 2.0 (the "License");
*  you may not use this file except in compliance with the License.
*  You may obtain a copy of the License at
*
*      http://www.apache.org/licenses/LICENSE-2.0
*
*  Unless required by applicable law or agreed to in writing, software
*  distributed under the License is distributed on an "AS IS" BASIS,
*  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
*  See the License for the specific language governing permissions and
*  limitations under the License.
*
******************************************************************************/

package schwift

import (
	"net/http"
)

// Backend is the interface between Schwift and the libraries providing
// authentication for it. Each instance of Backend represents a particular Swift
// account.
type Backend interface {
	// EndpointURL returns the endpoint URL from the Keystone catalog for the
	// Swift account that this backend operates on. It should look like
	// `http://domain.tld/v1/AUTH_projectid/`. The trailing slash is required.
	EndpointURL() string
	// Clone returns a deep clone of this backend with the endpoint URL changed to
	// the given URL. This is used by Account.SwitchAccount().
	Clone(newEndpointURL string) Backend
	// Do executes the given HTTP request after adding to it the X-Auth-Token
	// header containing the backend's current Keystone (or Swift auth) token. If
	// the status code returned is 401, it shall attempt to acquire a new auth
	// token and restart the request with the new token.
	//
	// If the user has not supplied their own User-Agent string to the backend,
	// the backend should use the schwift.DefaultUserAgent constant instead.
	Do(req *http.Request) (*http.Response, error)
}

// DefaultUserAgent is the User-Agent string that Backend implementations should
// use if the user does not provide their own User-Agent string.
const DefaultUserAgent = "schwift/" + Version