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transport.go
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transport.go
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// Copyright 2020 The searKing Author. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package http
import (
"io"
"net/http"
"sync"
)
// Transport is a 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 {
// Base is the base RoundTripper used to make HTTP requests.
// If nil, http.DefaultTransport is used.
Base http.RoundTripper
handlers handlersChain
aborted bool
index int8
mu sync.Mutex // guards modReq
modReq map[*http.Request]*http.Request // original -> modified
}
// RoundTrip authorizes and authenticates the request with an
// access token. If no token exists or token is expired,
// tries to refresh/fetch a new token.
func (t *Transport) RoundTrip(req *http.Request) (*http.Response, error) {
req2 := cloneRequest(req) // per RoundTripper contract
t.setModReq(req, req2)
resp, err := t.Next(req2)
if err != nil {
t.setModReq(req, nil)
return nil, err
}
resp.Body = &onEOFReader{
rc: resp.Body,
fn: func() { t.setModReq(req, nil) },
}
return resp, nil
}
// CancelRequest cancels an in-flight request by closing its connection.
func (t *Transport) CancelRequest(req *http.Request) {
type canceler interface {
CancelRequest(*http.Request)
}
if cr, ok := t.base().(canceler); ok {
// take and cancel request
t.mu.Lock()
modReq := t.modReq[req]
delete(t.modReq, req)
t.mu.Unlock()
cr.CancelRequest(modReq)
}
}
// Use adds middleware handlers to the transport.
func (t *Transport) Use(h ...RoundTripHandler) *Transport {
t.handlers = append(t.handlers, h...)
return t
}
/************************************/
/*********** FLOW CONTROL ***********/
/************************************/
// Next should be used only inside middleware.
// It executes the pending handlers in the chain inside the calling handler.
// See example in GitHub.
func (t *Transport) Next(req *http.Request) (resp *http.Response, err error) {
// lazy init
if len(t.handlers) == 0 {
t.Use(t.base())
}
t.index++
for !t.aborted && t.index < int8(len(t.handlers)) {
if resp, err = t.handlers[t.index].RoundTrip(req); err != nil {
return nil, err
}
t.index++
}
return resp, nil
}
// IsAborted returns true if the current context was aborted.
func (t *Transport) IsAborted() bool {
return t.aborted
}
// Abort prevents pending handlers from being called. Note that this will not stop the current handler.
// Let's say you have an authorization middleware that validates that the current request is authorized.
// If the authorization fails (ex: the password does not match), call Abort to ensure the remaining handlers
// for this request are not called.
func (t *Transport) Abort() {
t.aborted = true
}
func (t *Transport) base() http.RoundTripper {
if t.Base != nil {
return t.Base
}
return http.DefaultTransport
}
func (t *Transport) setModReq(orig, mod *http.Request) {
t.mu.Lock()
defer t.mu.Unlock()
if t.modReq == nil {
t.modReq = make(map[*http.Request]*http.Request)
}
if mod == nil {
delete(t.modReq, orig)
} else {
t.modReq[orig] = mod
}
}
// 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
}
type onEOFReader struct {
rc io.ReadCloser
fn func()
}
func (r *onEOFReader) Read(p []byte) (n int, err error) {
n, err = r.rc.Read(p)
if err == io.EOF {
r.runFunc()
}
return
}
func (r *onEOFReader) Close() error {
err := r.rc.Close()
r.runFunc()
return err
}
func (r *onEOFReader) runFunc() {
if fn := r.fn; fn != nil {
fn()
r.fn = nil
}
}