// Copyright 2014 The Go Authors. All rights reserved.

// Use of this source code is governed by a BSD-style

// license that can be found in the LICENSE file.

package oauth2

import (

	"errors"

	"net/http"

	"sync"

)

// Transport is an http.RoundTripper that makes OAuth 2.0 HTTP requests,

// wrapping a base RoundTripper and adding an Authorization header

// with a token from the supplied Sources.

//

// Transport is a low-level mechanism. Most code will use the

// higher-level Config.Client method instead.

type Transport struct {

	// Source supplies the token to add to outgoing requests'

	// Authorization headers.

	Source TokenSource

	// Base is the base RoundTripper used to make HTTP requests.

	// If nil, http.DefaultTransport is used.

	Base http.RoundTripper

}

// RoundTrip authorizes and authenticates the request with an

// access token from Transport's Source.

func (t *Transport) RoundTrip(req *http.Request) (*http.Response, error) {

	reqBodyClosed := false

	if req.Body != nil {

		defer func() {

			if !reqBodyClosed {

				req.Body.Close()

			}

		}()

	}

	if t.Source == nil {

		return nil, errors.New("oauth2: Transport's Source is nil")

	}

	token, err := t.Source.Token()

	if err != nil {

		return nil, err

	}

	req2 := cloneRequest(req) // per RoundTripper contract

	token.SetAuthHeader(req2)

	reqBodyClosed = true

}

func (t *Transport) CancelRequest(req *http.Request) {

}

func (t *Transport) base() http.RoundTripper {

	if t.Base != nil {

		return t.Base

	}

	return http.DefaultTransport

}

// cloneRequest returns a clone of the provided *http.Request.

// The clone is a shallow copy of the struct and its Header map.

func cloneRequest(r *http.Request) *http.Request {

	// shallow copy of the struct

	r2 := new(http.Request)

	*r2 = *r

	// deep copy of the Header

	r2.Header = make(http.Header, len(r.Header))

	for k, s := range r.Header {

		r2.Header[k] = append([]string(nil), s...)

	}

	return r2

}