swarm/api: url scheme bzzh for getting hashes of swarm content (#15238)

Update URI to support bzzh scheme and handle such HTTP requests by
responding with hash of the content as a text/plain response.

swarm/api/http/server.go

@@ -290,9 +290,12 @@ func (s *Server) HandleDelete(w http.ResponseWriter, r *Request) {
 	fmt.Fprint(w, newKey)
 }
 
-// HandleGetRaw handles a GET request to bzzr://<key> and responds with
-// the raw content stored at the given storage key
-func (s *Server) HandleGetRaw(w http.ResponseWriter, r *Request) {
+// HandleGet handles a GET request to
+// - bzzr://<key> and responds with the raw content stored at the
+//   given storage key
+// - bzzh://<key> and responds with the hash of the content stored
+//   at the given storage key as a text/plain response
+func (s *Server) HandleGet(w http.ResponseWriter, r *Request) {
 	key, err := s.api.Resolve(r.uri)
 	if err != nil {
 		s.Error(w, r, fmt.Errorf("error resolving %s: %s", r.uri.Addr, err))
@@ -345,15 +348,22 @@ func (s *Server) HandleGetRaw(w http.ResponseWriter, r *Request) {
 		return
 	}
 
-	// allow the request to overwrite the content type using a query
-	// parameter
-	contentType := "application/octet-stream"
-	if typ := r.URL.Query().Get("content_type"); typ != "" {
-		contentType = typ
-	}
-	w.Header().Set("Content-Type", contentType)
+	switch {
+	case r.uri.Raw():
+		// allow the request to overwrite the content type using a query
+		// parameter
+		contentType := "application/octet-stream"
+		if typ := r.URL.Query().Get("content_type"); typ != "" {
+			contentType = typ
+		}
+		w.Header().Set("Content-Type", contentType)
 
-	http.ServeContent(w, &r.Request, "", time.Now(), reader)
+		http.ServeContent(w, &r.Request, "", time.Now(), reader)
+	case r.uri.Hash():
+		w.Header().Set("Content-Type", "text/plain")
+		w.WriteHeader(http.StatusOK)
+		fmt.Fprint(w, key)
+	}
 }
 
 // HandleGetFiles handles a GET request to bzz:/<manifest> with an Accept
@@ -616,8 +626,8 @@ func (s *Server) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 		s.HandleDelete(w, req)
 
 	case "GET":
-		if uri.Raw() {
-			s.HandleGetRaw(w, req)
+		if uri.Raw() || uri.Hash() {
+			s.HandleGet(w, req)
 			return
 		}
 

swarm/api/uri.go

@@ -30,6 +30,8 @@ type URI struct {
 	// * bzzr - raw swarm content
 	// * bzzi - immutable URI of an entry in a swarm manifest
 	//          (address is not resolved)
+	// * bzzh - hash of swarm content
+	//
 	Scheme string
 
 	// Addr is either a hexadecimal storage key or it an address which
@@ -60,7 +62,7 @@ func Parse(rawuri string) (*URI, error) {
 
 	// check the scheme is valid
 	switch uri.Scheme {
-	case "bzz", "bzzi", "bzzr":
+	case "bzz", "bzzi", "bzzr", "bzzh":
 	default:
 		return nil, fmt.Errorf("unknown scheme %q", u.Scheme)
 	}
@@ -91,6 +93,10 @@ func (u *URI) Immutable() bool {
 	return u.Scheme == "bzzi"
 }
 
+func (u *URI) Hash() bool {
+	return u.Scheme == "bzzh"
+}
+
 func (u *URI) String() string {
 	return u.Scheme + ":/" + u.Addr + "/" + u.Path
 }

swarm/api/uri_test.go

@@ -28,6 +28,7 @@ func TestParseURI(t *testing.T) {
 		expectErr       bool
 		expectRaw       bool
 		expectImmutable bool
+		expectHash      bool
 	}
 	tests := []test{
 		{
@@ -95,6 +96,16 @@ func TestParseURI(t *testing.T) {
 			uri:       "bzz://abc123/path/to/entry",
 			expectURI: &URI{Scheme: "bzz", Addr: "abc123", Path: "path/to/entry"},
 		},
+		{
+			uri:        "bzzh:",
+			expectURI:  &URI{Scheme: "bzzh"},
+			expectHash: true,
+		},
+		{
+			uri:        "bzzh:/",
+			expectURI:  &URI{Scheme: "bzzh"},
+			expectHash: true,
+		},
 	}
 	for _, x := range tests {
 		actual, err := Parse(x.uri)
@@ -116,5 +127,8 @@ func TestParseURI(t *testing.T) {
 		if actual.Immutable() != x.expectImmutable {
 			t.Fatalf("expected %s immutable to be %t, got %t", x.uri, x.expectImmutable, actual.Immutable())
 		}
+		if actual.Hash() != x.expectHash {
+			t.Fatalf("expected %s hash to be %t, got %t", x.uri, x.expectHash, actual.Hash())
+		}
 	}
 }