improve cache handler, embracing #2210 too

cache/entry/response.go

@@ -1,6 +1,9 @@
 package entry
 
-import "net/http"
+import (
+	"io"
+	"net/http"
+)
 
 // Response is the cached response will be send to the clients
 // its fields set at runtime on each of the non-cached executions
@@ -15,11 +18,28 @@ type Response struct {
 	headers http.Header
 }
 
+// NewResponse returns a new cached Response.
+func NewResponse(statusCode int, headers http.Header, body []byte) *Response {
+	r := new(Response)
+
+	r.SetStatusCode(statusCode)
+	r.SetHeaders(headers)
+	r.SetBody(body)
+
+	return r
+}
+
+// SetStatusCode sets a valid status code.
+func (r *Response) SetStatusCode(statusCode int) {
+	if statusCode <= 0 {
+		statusCode = http.StatusOK
+	}
+
+	r.statusCode = statusCode
+}
+
 // StatusCode returns a valid status code.
 func (r *Response) StatusCode() int {
-	if r.statusCode <= 0 {
-		r.statusCode = 200
-	}
 	return r.statusCode
 }
 
@@ -31,12 +51,39 @@ func (r *Response) StatusCode() int {
 // 	return r.contentType
 // }
 
+// SetHeaders sets a clone of headers of the cached response.
+func (r *Response) SetHeaders(h http.Header) {
+	r.headers = h.Clone()
+}
+
 // Headers returns the total headers of the cached response.
 func (r *Response) Headers() http.Header {
 	return r.headers
 }
 
+// SetBody consumes "b" and sets the body of the cached response.
+func (r *Response) SetBody(body []byte) {
+	r.body = make([]byte, len(body))
+	copy(r.body, body)
+}
+
 // Body returns contents will be served by the cache handler.
 func (r *Response) Body() []byte {
 	return r.body
 }
+
+// Read implements the io.Reader interface.
+func (r *Response) Read(b []byte) (int, error) {
+	if len(r.body) == 0 {
+		return 0, io.EOF
+	}
+
+	n := copy(b, r.body)
+	r.body = r.body[n:]
+	return n, nil
+}
+
+// Bytes returns a copy of the cached response body.
+func (r *Response) Bytes() []byte {
+	return append([]byte(nil), r.body...)
+}