156 lines
3.5 KiB
Go
156 lines
3.5 KiB
Go
package transport
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import (
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"io"
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"net/http"
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"sync"
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)
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func identityTransportWrapper(rt http.RoundTripper) http.RoundTripper {
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return rt
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}
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// DefaultTransportWrapper allows a user to wrap every generated transport
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var DefaultTransportWrapper = identityTransportWrapper
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// RequestModifier represents an object which will do an inplace
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// modification of an HTTP request.
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type RequestModifier interface {
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ModifyRequest(*http.Request) error
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}
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type headerModifier http.Header
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// NewHeaderRequestModifier returns a new RequestModifier which will
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// add the given headers to a request.
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func NewHeaderRequestModifier(header http.Header) RequestModifier {
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return headerModifier(header)
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}
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func (h headerModifier) ModifyRequest(req *http.Request) error {
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for k, s := range http.Header(h) {
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req.Header[k] = append(req.Header[k], s...)
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}
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return nil
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}
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// NewTransport creates a new transport which will apply modifiers to
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// the request on a RoundTrip call.
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func NewTransport(base http.RoundTripper, modifiers ...RequestModifier) http.RoundTripper {
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return DefaultTransportWrapper(
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&transport{
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Modifiers: modifiers,
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Base: base,
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})
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}
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// transport is an http.RoundTripper that makes HTTP requests after
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// copying and modifying the request
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type transport struct {
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Modifiers []RequestModifier
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Base http.RoundTripper
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mu sync.Mutex // guards modReq
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modReq map[*http.Request]*http.Request // original -> modified
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}
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// RoundTrip authorizes and authenticates the request with an
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// access token. If no token exists or token is expired,
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// tries to refresh/fetch a new token.
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func (t *transport) RoundTrip(req *http.Request) (*http.Response, error) {
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req2 := cloneRequest(req)
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for _, modifier := range t.Modifiers {
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if err := modifier.ModifyRequest(req2); err != nil {
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return nil, err
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}
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}
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t.setModReq(req, req2)
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res, err := t.base().RoundTrip(req2)
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if err != nil {
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t.setModReq(req, nil)
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return nil, err
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}
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res.Body = &onEOFReader{
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rc: res.Body,
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fn: func() { t.setModReq(req, nil) },
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}
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return res, nil
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}
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// CancelRequest cancels an in-flight request by closing its connection.
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func (t *transport) CancelRequest(req *http.Request) {
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type canceler interface {
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CancelRequest(*http.Request)
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}
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if cr, ok := t.base().(canceler); ok {
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t.mu.Lock()
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modReq := t.modReq[req]
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delete(t.modReq, req)
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t.mu.Unlock()
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cr.CancelRequest(modReq)
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}
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}
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func (t *transport) base() http.RoundTripper {
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if t.Base != nil {
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return t.Base
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}
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return http.DefaultTransport
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}
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func (t *transport) setModReq(orig, mod *http.Request) {
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t.mu.Lock()
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defer t.mu.Unlock()
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if t.modReq == nil {
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t.modReq = make(map[*http.Request]*http.Request)
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}
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if mod == nil {
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delete(t.modReq, orig)
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} else {
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t.modReq[orig] = mod
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}
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}
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// cloneRequest returns a clone of the provided *http.Request.
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// The clone is a shallow copy of the struct and its Header map.
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func cloneRequest(r *http.Request) *http.Request {
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// shallow copy of the struct
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r2 := new(http.Request)
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*r2 = *r
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// deep copy of the Header
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r2.Header = make(http.Header, len(r.Header))
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for k, s := range r.Header {
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r2.Header[k] = append([]string(nil), s...)
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}
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return r2
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}
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type onEOFReader struct {
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rc io.ReadCloser
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fn func()
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}
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func (r *onEOFReader) Read(p []byte) (n int, err error) {
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n, err = r.rc.Read(p)
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if err == io.EOF {
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r.runFunc()
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}
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return
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}
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func (r *onEOFReader) Close() error {
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err := r.rc.Close()
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r.runFunc()
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return err
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}
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func (r *onEOFReader) runFunc() {
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if fn := r.fn; fn != nil {
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fn()
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r.fn = nil
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}
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}
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