s3 cache client-side support

Signed-off-by: CrazyMax <crazy-max@users.noreply.github.com>

vendor/github.com/aws/smithy-go/transport/http/client.go

@@ -0,0 +1,120 @@
+package http
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+
+	smithy "github.com/aws/smithy-go"
+	"github.com/aws/smithy-go/middleware"
+)
+
+// ClientDo provides the interface for custom HTTP client implementations.
+type ClientDo interface {
+	Do(*http.Request) (*http.Response, error)
+}
+
+// ClientDoFunc provides a helper to wrap a function as an HTTP client for
+// round tripping requests.
+type ClientDoFunc func(*http.Request) (*http.Response, error)
+
+// Do will invoke the underlying func, returning the result.
+func (fn ClientDoFunc) Do(r *http.Request) (*http.Response, error) {
+	return fn(r)
+}
+
+// ClientHandler wraps a client that implements the HTTP Do method. Standard
+// implementation is http.Client.
+type ClientHandler struct {
+	client ClientDo
+}
+
+// NewClientHandler returns an initialized middleware handler for the client.
+func NewClientHandler(client ClientDo) ClientHandler {
+	return ClientHandler{
+		client: client,
+	}
+}
+
+// Handle implements the middleware Handler interface, that will invoke the
+// underlying HTTP client. Requires the input to be a Smithy *Request. Returns
+// a smithy *Response, or error if the request failed.
+func (c ClientHandler) Handle(ctx context.Context, input interface{}) (
+	out interface{}, metadata middleware.Metadata, err error,
+) {
+	req, ok := input.(*Request)
+	if !ok {
+		return nil, metadata, fmt.Errorf("expect Smithy http.Request value as input, got unsupported type %T", input)
+	}
+
+	builtRequest := req.Build(ctx)
+	if err := ValidateEndpointHost(builtRequest.Host); err != nil {
+		return nil, metadata, err
+	}
+
+	resp, err := c.client.Do(builtRequest)
+	if resp == nil {
+		// Ensure a http response value is always present to prevent unexpected
+		// panics.
+		resp = &http.Response{
+			Header: http.Header{},
+			Body:   http.NoBody,
+		}
+	}
+	if err != nil {
+		err = &RequestSendError{Err: err}
+
+		// Override the error with a context canceled error, if that was canceled.
+		select {
+		case <-ctx.Done():
+			err = &smithy.CanceledError{Err: ctx.Err()}
+		default:
+		}
+	}
+
+	// HTTP RoundTripper *should* close the request body. But this may not happen in a timely manner.
+	// So instead Smithy *Request Build wraps the body to be sent in a safe closer that will clear the
+	// stream reference so that it can be safely reused.
+	if builtRequest.Body != nil {
+		_ = builtRequest.Body.Close()
+	}
+
+	return &Response{Response: resp}, metadata, err
+}
+
+// RequestSendError provides a generic request transport error. This error
+// should wrap errors making HTTP client requests.
+//
+// The ClientHandler will wrap the HTTP client's error if the client request
+// fails, and did not fail because of context canceled.
+type RequestSendError struct {
+	Err error
+}
+
+// ConnectionError returns that the error is related to not being able to send
+// the request, or receive a response from the service.
+func (e *RequestSendError) ConnectionError() bool {
+	return true
+}
+
+// Unwrap returns the underlying error, if there was one.
+func (e *RequestSendError) Unwrap() error {
+	return e.Err
+}
+
+func (e *RequestSendError) Error() string {
+	return fmt.Sprintf("request send failed, %v", e.Err)
+}
+
+// NopClient provides a client that ignores the request, and returns an empty
+// successful HTTP response value.
+type NopClient struct{}
+
+// Do ignores the request and returns a 200 status empty response.
+func (NopClient) Do(r *http.Request) (*http.Response, error) {
+	return &http.Response{
+		StatusCode: 200,
+		Header:     http.Header{},
+		Body:       http.NoBody,
+	}, nil
+}