keyer: add ReadOnlySigner.

keyer/plain.go

@@ -8,8 +8,7 @@ import (
 	"github.com/puzpuzpuz/xsync/v3"
 )
 
-// KeySigner is a signer that holds the private key in memory and can perform
-// all operations instantly and easily.
+// KeySigner is a signer that holds the private key in memory
 type KeySigner struct {
 	sk string
 	pk string
@@ -32,7 +31,7 @@ func NewPlainKeySigner(sec string) (KeySigner, error) {
 func (ks KeySigner) SignEvent(ctx context.Context, evt *nostr.Event) error { return evt.Sign(ks.sk) }
 
 // GetPublicKey returns the public key associated with this signer.
-func (ks KeySigner) GetPublicKey(ctx context.Context) (string, error)      { return ks.pk, nil }
+func (ks KeySigner) GetPublicKey(ctx context.Context) (string, error) { return ks.pk, nil }
 
 // Encrypt encrypts a plaintext message for a recipient using NIP-44.
 // It caches conversation keys for efficiency in repeated operations.

keyer/readonly.go

@@ -0,0 +1,27 @@
+package keyer
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/nbd-wtf/go-nostr"
+)
+
+// ReadOnlySigner is a Signer that holds a public key in memory and cannot sign anything
+type ReadOnlySigner struct {
+	pk string
+}
+
+func NewReadOnlySigner(pk string) ReadOnlySigner {
+	return ReadOnlySigner{pk}
+}
+
+// SignEvent returns an error.
+func (ros ReadOnlySigner) SignEvent(context.Context, *nostr.Event) error {
+	return fmt.Errorf("read-only, we don't have the secret key, cannot sign")
+}
+
+// GetPublicKey returns the public key associated with this signer.
+func (ros ReadOnlySigner) GetPublicKey(context.Context) (string, error) {
+	return ros.pk, nil
+}