revamp the Headers API

1. Move common methods of AccountHeaders, ContainerHeaders,
   ObjectHeaders into a base type Headers.

2. Fold Headers into RequestOptions to remove one of the two optional
   arguments on request methods. The new Headers.ToOpts() method
   offers a nice experience for users passing Headers to request
   methods.

   The Update() methods keep the explicit Headers argument since the
   Headers argument is not optional there.

   The only downside is that we lose a bit of type-safety because
   RequestOptions takes any Headers instance, so e.g. ContainerHeaders
   could be passed to Object.Upload(). I believe the benefits outweigh
   this problem.

1 files changed, 27 insertions, 7 deletions

diff --git a/request.go b/request.go
index b96670b..3e089c0 100644
--- a/request.go
+++ b/request.go
@@ -26,20 +26,39 @@ import (
 	"strings"
 )
 
-//RequestOptions contains additional headers and values for a request.
+//RequestOptions is used to pass additional headers and values to aa request.
+//
+//When preparing a RequestOptions instance with additional headers, the
+//preferred way is to create an AccountHeaders, ContainerHeaders and
+//ObjectHeaders instance and use the type-safe API on these types. Then use the
+//ToOpts() method on that instance. For example:
+//
+//	hdr := NewObjectHeaders()
+//	hdr.ContentType().Set("image/png")
+//	hdr.Metadata().Set("color", "blue")
+//	opts := hdr.ToOpts() //type *schwift.RequestOptions
+//
 type RequestOptions struct {
-	Values url.Values
+	Headers Headers
+	Values  url.Values
 }
 
-func cloneRequestOptions(orig *RequestOptions) *RequestOptions {
+func cloneRequestOptions(orig *RequestOptions, additional Headers) *RequestOptions {
 	result := RequestOptions{
-		Values: make(url.Values),
+		Headers: make(Headers),
+		Values:  make(url.Values),
 	}
 	if orig != nil {
+		for k, v := range orig.Headers {
+			result.Headers[k] = v
+		}
 		for k, v := range orig.Values {
 			result.Values[k] = v
 		}
 	}
+	for k, v := range additional {
+		result.Headers[k] = v
+	}
 	return &result
 }
 
@@ -48,7 +67,6 @@ type Request struct {
 	Method        string //"GET", "HEAD", "PUT", "POST" or "DELETE"
 	ContainerName string //empty for requests on accounts
 	ObjectName    string //empty for requests on accounts/containers
-	Headers       http.Header
 	Options       *RequestOptions
 	Body          io.Reader
 	//ExpectStatusCodes can be left empty to disable this check, otherwise
@@ -102,8 +120,10 @@ func (r Request) Do(backend Backend) (*http.Response, error) {
 		return nil, err
 	}
 
-	for k, v := range r.Headers {
-		req.Header[k] = v
+	if r.Options != nil {
+		for k, v := range r.Options.Headers {
+			req.Header[k] = []string{v}
+		}
 	}
 	if r.Body != nil {
 		req.Header.Set("Expect", "100-continue")