feat: add kwallet secret store adapter

internal/secretstore/kwallet/store.go

@@ -0,0 +1,56 @@
+package kwallet
+
+import (
+	"context"
+
+	"email-mcp/internal/secretstore"
+)
+
+type Client interface {
+	IsAvailable(ctx context.Context) error
+	Open(ctx context.Context) error
+	WriteEntry(ctx context.Context, key string, value []byte) error
+	ReadEntry(ctx context.Context, key string) ([]byte, error)
+}
+
+type Store struct {
+	client Client
+}
+
+var _ secretstore.Store = (*Store)(nil)
+
+func NewStore(client Client) *Store {
+	return &Store{client: client}
+}
+
+func (s *Store) Save(ctx context.Context, key string, cred secretstore.Credential) error {
+	if err := s.client.IsAvailable(ctx); err != nil {
+		return err
+	}
+	if err := s.client.Open(ctx); err != nil {
+		return err
+	}
+
+	data, err := secretstore.MarshalCredential(cred)
+	if err != nil {
+		return err
+	}
+
+	return s.client.WriteEntry(ctx, key, data)
+}
+
+func (s *Store) Load(ctx context.Context, key string) (secretstore.Credential, error) {
+	if err := s.client.IsAvailable(ctx); err != nil {
+		return secretstore.Credential{}, err
+	}
+	if err := s.client.Open(ctx); err != nil {
+		return secretstore.Credential{}, err
+	}
+
+	data, err := s.client.ReadEntry(ctx, key)
+	if err != nil {
+		return secretstore.Credential{}, err
+	}
+
+	return secretstore.UnmarshalCredential(data)
+}

internal/secretstore/kwallet/store_test.go

@@ -0,0 +1,114 @@
+package kwallet
+
+import (
+	"context"
+	"errors"
+	"testing"
+
+	"email-mcp/internal/secretstore"
+)
+
+type walletClientStub struct {
+	availableErr error
+	openErr      error
+	writeErr     error
+	readErr      error
+	readValue    []byte
+
+	openCalled bool
+	writeKey   string
+	writeValue []byte
+	readKey    string
+}
+
+func (c *walletClientStub) IsAvailable(context.Context) error {
+	return c.availableErr
+}
+
+func (c *walletClientStub) Open(context.Context) error {
+	c.openCalled = true
+	return c.openErr
+}
+
+func (c *walletClientStub) WriteEntry(_ context.Context, key string, value []byte) error {
+	c.writeKey = key
+	c.writeValue = value
+	return c.writeErr
+}
+
+func (c *walletClientStub) ReadEntry(_ context.Context, key string) ([]byte, error) {
+	c.readKey = key
+	return c.readValue, c.readErr
+}
+
+func TestStoreSaveWritesSerializedCredential(t *testing.T) {
+	client := &walletClientStub{}
+	store := NewStore(client)
+
+	cred := secretstore.Credential{
+		Host:     "imap.example.com",
+		Username: "alice",
+		Password: "secret",
+	}
+
+	if err := store.Save(context.Background(), secretstore.DefaultAccountKey, cred); err != nil {
+		t.Fatalf("Save returned error: %v", err)
+	}
+
+	if !client.openCalled {
+		t.Fatal("expected wallet Open to be called")
+	}
+	if client.writeKey != secretstore.DefaultAccountKey {
+		t.Fatalf("unexpected key: %s", client.writeKey)
+	}
+	if len(client.writeValue) == 0 {
+		t.Fatal("expected serialized credential payload")
+	}
+}
+
+func TestStoreSaveReturnsAvailabilityErrorWithoutOpeningWallet(t *testing.T) {
+	wantErr := errors.New("kwallet unavailable")
+	client := &walletClientStub{availableErr: wantErr}
+	store := NewStore(client)
+
+	err := store.Save(context.Background(), secretstore.DefaultAccountKey, secretstore.Credential{
+		Host:     "imap.example.com",
+		Username: "alice",
+		Password: "secret",
+	})
+	if !errors.Is(err, wantErr) {
+		t.Fatalf("expected availability error, got %v", err)
+	}
+	if client.openCalled {
+		t.Fatal("did not expect wallet Open when availability check fails")
+	}
+}
+
+func TestStoreLoadReadsAndDecodesCredential(t *testing.T) {
+	payload, err := secretstore.MarshalCredential(secretstore.Credential{
+		Host:     "imap.example.com",
+		Username: "alice",
+		Password: "secret",
+	})
+	if err != nil {
+		t.Fatalf("MarshalCredential returned error: %v", err)
+	}
+
+	client := &walletClientStub{readValue: payload}
+	store := NewStore(client)
+
+	cred, err := store.Load(context.Background(), secretstore.DefaultAccountKey)
+	if err != nil {
+		t.Fatalf("Load returned error: %v", err)
+	}
+
+	if !client.openCalled {
+		t.Fatal("expected wallet Open to be called")
+	}
+	if client.readKey != secretstore.DefaultAccountKey {
+		t.Fatalf("unexpected key: %s", client.readKey)
+	}
+	if cred.Host != "imap.example.com" || cred.Username != "alice" || cred.Password != "secret" {
+		t.Fatalf("unexpected credential: %#v", cred)
+	}
+}