fix: adding usability as function for api

pkg/api/postage.go

@@ -99,6 +99,7 @@ func (s *server) postageCreateHandler(w http.ResponseWriter, r *http.Request) {
 type postageStampResponse struct {
 	BatchID     batchID `json:"batchID"`
 	Utilization uint32  `json:"utilization"`
+	Usable      bool    `json:"usable"`
 }
 
 type postageStampsResponse struct {
@@ -109,7 +110,11 @@ func (s *server) postageGetStampsHandler(w http.ResponseWriter, r *http.Request)
 	issuers := s.post.StampIssuers()
 	resp := postageStampsResponse{}
 	for _, v := range issuers {
-		issuer := postageStampResponse{BatchID: v.ID(), Utilization: v.Utilization()}
+		issuer := postageStampResponse{
+			BatchID:     v.ID(),
+			Utilization: v.Utilization(),
+			Usable:      s.post.IssuerUsable(v),
+		}
 		resp.Stamps = append(resp.Stamps, issuer)
 	}
 	jsonhttp.OK(w, resp)
@@ -140,6 +145,7 @@ func (s *server) postageGetStampHandler(w http.ResponseWriter, r *http.Request)
 	resp := postageStampResponse{
 		BatchID:     id,
 		Utilization: issuer.Utilization(),
+		Usable:      s.post.IssuerUsable(issuer),
 	}
 	jsonhttp.OK(w, &resp)
 }

pkg/api/postage_test.go

@@ -201,6 +201,7 @@ func TestPostageGetStamps(t *testing.T) {
 				{
 					BatchID:     batchOk,
 					Utilization: 0,
+					Usable:      true,
 				},
 			},
 		}),
@@ -216,6 +217,7 @@ func TestPostageGetStamp(t *testing.T) {
 			jsonhttptest.WithExpectedJSONResponse(&api.PostageStampResponse{
 				BatchID:     batchOk,
 				Utilization: 0,
+				Usable:      true,
 			}),
 		)
 	})

pkg/postage/mock/service.go

@@ -64,6 +64,10 @@ func (m *mockPostage) GetStampIssuer(id []byte) (*postage.StampIssuer, error) {
 	return nil, errors.New("stampissuer not found")
 }
 
+func (m *mockPostage) IssuerUsable(_ *postage.StampIssuer) bool {
+	return true
+}
+
 func (m *mockPostage) Close() error {
 	return nil
 }

pkg/postage/service.go

@@ -33,6 +33,7 @@ type Service interface {
 	Add(*StampIssuer)
 	StampIssuers() []*StampIssuer
 	GetStampIssuer([]byte) (*StampIssuer, error)
+	IssuerUsable(*StampIssuer) bool
 	io.Closer
 }
 
@@ -86,19 +87,26 @@ func (ps *service) StampIssuers() []*StampIssuer {
 	return ps.issuers
 }
 
-// GetStampIssuer finds a stamp issuer by batch ID.
-func (ps *service) GetStampIssuer(batchID []byte) (*StampIssuer, error) {
+func (ps *service) IssuerUsable(st *StampIssuer) bool {
 	cs := ps.postageStore.GetChainState()
 
+	// this checks atleast threshold blocks are seen on the blockchain after
+	// the batch creation, before we start using a stamp issuer. The threshold
+	// is meant to allow enough time for upstream peers to see the batch and
+	// hence validate the stamps issued
+	if cs.Block < st.blockNumber || (cs.Block-st.blockNumber) < blockThreshold {
+		return false
+	}
+	return true
+}
+
+// GetStampIssuer finds a stamp issuer by batch ID.
+func (ps *service) GetStampIssuer(batchID []byte) (*StampIssuer, error) {
 	ps.lock.Lock()
 	defer ps.lock.Unlock()
 	for _, st := range ps.issuers {
 		if bytes.Equal(batchID, st.batchID) {
-			// this checks atleast threshold blocks are seen on the blockchain after
-			// the batch creation, before we start using a stamp issuer. The threshold
-			// is meant to allow enough time for upstream peers to see the batch and
-			// hence validate the stamps issued
-			if cs.Block < st.blockNumber || (cs.Block-st.blockNumber) < blockThreshold {
+			if !ps.IssuerUsable(st) {
 				return nil, ErrNotUsable
 			}
 			return st, nil