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|
package transport
import (
"io"
"net/http"
"sync"
)
// RequestModifier represents an object which will do an inplace
// modification of an HTTP request.
type RequestModifier interface {
ModifyRequest(*http.Request) error
}
type headerModifier http.Header
// NewHeaderRequestModifier returns a new RequestModifier which will
// add the given headers to a request.
func NewHeaderRequestModifier(header http.Header) RequestModifier {
return headerModifier(header)
}
func (h headerModifier) ModifyRequest(req *http.Request) error {
for k, s := range http.Header(h) {
req.Header[k] = append(req.Header[k], s...)
}
return nil
}
// NewTransport creates a new transport which will apply modifiers to
// the request on a RoundTrip call.
func NewTransport(base http.RoundTripper, modifiers ...RequestModifier) http.RoundTripper {
return &transport{
Modifiers: modifiers,
Base: base,
}
}
// transport is an http.RoundTripper that makes HTTP requests after
// copying and modifying the request
type transport struct {
Modifiers []RequestModifier
Base http.RoundTripper
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)
for _, modifier := range t.Modifiers {
if err := modifier.ModifyRequest(req2); err != nil {
return nil, err
}
}
t.setModReq(req, req2)
res, err := t.base().RoundTrip(req2)
if err != nil {
t.setModReq(req, nil)
return nil, err
}
res.Body = &onEOFReader{
rc: res.Body,
fn: func() { t.setModReq(req, nil) },
}
return res, 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 {
t.mu.Lock()
modReq := t.modReq[req]
delete(t.modReq, req)
t.mu.Unlock()
cr.CancelRequest(modReq)
}
}
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
}
}
|
