feat(keystore): Add SignerAddress (#4)

* feat(keystore): Add SignerAddress

* lint

* simplify

keystore/geth/keystore.go

@@ -13,6 +13,8 @@ import (
 	keystore "github.com/kilnfi/go-utils/keystore"
 )
 
+var _ keystore.Store = &KeyStore{}
+
 type KeyStore struct {
 	cfg  *Config
 	keys *gethkeystore.KeyStore
@@ -70,3 +72,15 @@ func (s *KeyStore) SignTx(_ context.Context, addr gethcommon.Address, tx *gethty
 func (s *KeyStore) HasAccount(_ context.Context, addr gethcommon.Address) (bool, error) {
 	return s.keys.HasAddress(addr), nil
 }
+
+func (s *KeyStore) SignerAddress(_ context.Context) (gethcommon.Address, error) {
+	if s.keys == nil {
+		return gethcommon.Address{}, fmt.Errorf("no cached keys")
+	}
+	accs := s.keys.Accounts()
+	if len(accs) < 1 {
+		return gethcommon.Address{}, fmt.Errorf("keystore has no accounts")
+	}
+	// select first (primary account) address
+	return accs[0].Address, nil
+}

keystore/keystore.go

@@ -19,4 +19,5 @@ type Store interface {
 	HasAccount(ctx context.Context, addr gethcommon.Address) (bool, error)
 	SignTx(ctx context.Context, addr gethcommon.Address, tx *gethtypes.Transaction, chainID *big.Int) (*gethtypes.Transaction, error)
 	Import(ctx context.Context, hexkey string) (*Account, error)
+	SignerAddress(context.Context) (gethcommon.Address, error)
 }