// DoRaw executes the request but does not process the response body.
func (r *Request) DoRaw() ([]byte, error) {
	start := time.Now()
	defer func() {
		metrics.RequestLatency.WithLabelValues(r.verb, r.finalURLTemplate()).Observe(metrics.SinceInMicroseconds(start))
	}()
	var result Result
	err := r.request(func(req *http.Request, resp *http.Response) {
		result.body, result.err = ioutil.ReadAll(resp.Body)
	})
	if err != nil {
		return nil, err
	}
	return result.body, result.err
}

// Do formats and executes the request. Returns a Result object for easy response
// processing.
//
// Error type:
//  * If the request can't be constructed, or an error happened earlier while building its
//    arguments: *RequestConstructionError
//  * If the server responds with a status: *errors.StatusError or *errors.UnexpectedObjectError
//  * http.Client.Do errors are returned directly.
func (r *Request) Do() Result {
	start := time.Now()
	defer func() {
		metrics.RequestLatency.WithLabelValues(r.verb, r.finalURLTemplate()).Observe(metrics.SinceInMicroseconds(start))
	}()
	var result Result
	err := r.request(func(req *http.Request, resp *http.Response) {
		result = r.transformResponse(resp, req)
	})
	if err != nil {
		return Result{err: err}
	}
	return result
}

// request connects to the server and invokes the provided function when a server response is
// received. It handles retry behavior and up front validation of requests. It will invoke
// fn at most once. It will return an error if a problem occurred prior to connecting to the
// server - the provided function is responsible for handling server errors.
func (r *Request) request(fn func(*http.Request, *http.Response)) error {
	//Metrics for total request latency
	start := time.Now()
	defer func() {
		metrics.RequestLatency.WithLabelValues(r.verb, r.finalURLTemplate()).Observe(metrics.SinceInMicroseconds(start))
	}()

	if r.err != nil {
		glog.V(4).Infof("Error in request: %v", r.err)
		return r.err
	}

	// TODO: added to catch programmer errors (invoking operations with an object with an empty namespace)
	if (r.verb == "GET" || r.verb == "PUT" || r.verb == "DELETE") && r.namespaceSet && len(r.resourceName) > 0 && len(r.namespace) == 0 {
		return fmt.Errorf("an empty namespace may not be set when a resource name is provided")
	}
	if (r.verb == "POST") && r.namespaceSet && len(r.namespace) == 0 {
		return fmt.Errorf("an empty namespace may not be set during creation")
	}

	client := r.client
	if client == nil {
		client = http.DefaultClient
	}

	// Right now we make about ten retry attempts if we get a Retry-After response.
	// TODO: Change to a timeout based approach.
	maxRetries := 10
	retries := 0
	for {
		url := r.URL().String()
		req, err := http.NewRequest(r.verb, url, r.body)
		if err != nil {
			return err
		}
		req.Header = r.headers

		r.backoffMgr.Sleep(r.backoffMgr.CalculateBackoff(r.URL()))
		resp, err := client.Do(req)
		updateURLMetrics(r, resp, err)
		if err != nil {
			r.backoffMgr.UpdateBackoff(r.URL(), err, 0)
		} else {
			r.backoffMgr.UpdateBackoff(r.URL(), err, resp.StatusCode)
		}
		if err != nil {
			return err
		}

		done := func() bool {
			// ensure the response body is closed before we reconnect, so that we reuse the same
			// TCP connection
			defer resp.Body.Close()

			retries++
			if seconds, wait := checkWait(resp); wait && retries < maxRetries {
				if seeker, ok := r.body.(io.Seeker); ok && r.body != nil {
					_, err := seeker.Seek(0, 0)
					if err != nil {
						glog.V(4).Infof("Could not retry request, can't Seek() back to beginning of body for %T", r.body)
						fn(req, resp)
						return true
					}
				}

				glog.V(4).Infof("Got a Retry-After %s response for attempt %d to %v", seconds, retries, url)
				r.backoffMgr.Sleep(time.Duration(seconds) * time.Second)
				return false
			}
			fn(req, resp)
			return true
		}()
		if done {
			return nil
		}
	}
}