Add Delete function to vcr wallet

A new Delete function is added to the wallet in the vcr/holder/wallet.go file. This function allows a credential to be removed from the wallet. Additionally, an interface in the vcr/holder/interface.go file has been updated to include this Delete function. Proper error handling and stats consistency are ensured in this implementation.

vcr/holder/interface.go

@@ -56,6 +56,9 @@ type Wallet interface {
 
 	// IsEmpty returns true if the wallet contains no credentials at all (for all holder DIDs).
 	IsEmpty() (bool, error)
+
+	// Delete deletes a credential from the wallet
+	Delete(ctx context.Context, subjectDID did.DID, id ssi.URI) error
 }
 
 // PresentationOptions contains parameters used to create the right VerifiablePresentation

vcr/holder/wallet.go

@@ -275,6 +275,28 @@ func (h wallet) IsEmpty() (bool, error) {
 	return count == 0, err
 }
 
+func (h wallet) Delete(ctx context.Context, subjectDID did.DID, id ssi.URI) error {
+	err := h.walletStore.Write(ctx, func(tx stoabs.WriteTx) error {
+		stats := tx.GetShelfWriter(statsShelf)
+		walletKey := stoabs.BytesKey(id.String())
+		walletShelf := tx.GetShelfWriter(subjectDID.String())
+		err := walletShelf.Delete(walletKey)
+		if err != nil {
+			return err
+		}
+		// Update stats
+		currentCount, err := h.readCredentialCount(stats)
+		if err != nil {
+			return fmt.Errorf("unable to read wallet credential count: %w", err)
+		}
+		return stats.Put(credentialCountStatsKey, binary.BigEndian.AppendUint32([]byte{}, currentCount+1))
+	}, stoabs.WithWriteLock()) // lock required for stats consistency
+	if err != nil {
+		return fmt.Errorf("unable to delete credential: %w", err)
+	}
+	return nil
+}
+
 func (h wallet) readCredentialCount(statsShelf stoabs.Reader) (uint32, error) {
 	countBytes, err := statsShelf.Get(credentialCountStatsKey)
 	if errors.Is(err, stoabs.ErrKeyNotFound) {