refactor(cookie): Extract cookie snapshot logic to util package

The logic for managing cookie persistence files was previously implemented directly within the `gemini-web` client's persistence layer. This approach was not reusable and led to duplicated helper functions.

This commit refactors the cookie persistence mechanism by:
- Renaming the concept from "sidecar" to "snapshot" for clarity.
- Extracting file I/O and path manipulation logic into a new, generic `internal/util/cookie_snapshot.go` file.
- Creating reusable utility functions: `WriteCookieSnapshot`, `TryReadCookieSnapshotInto`, and `RemoveCookieSnapshot`.
- Updating the `gemini-web` persistence code to use these new centralized utility functions.

This change improves code organization, reduces duplication, and makes the cookie snapshot functionality easier to maintain and potentially reuse across other clients.

internal/client/qwen_client.go

@@ -37,7 +37,8 @@ const (
 // QwenClient implements the Client interface for OpenAI API
 type QwenClient struct {
 	ClientBase
-	qwenAuth *qwen.QwenAuth
+	qwenAuth      *qwen.QwenAuth
+	tokenFilePath string
 }
 
 // NewQwenClient creates a new OpenAI client instance
@@ -48,7 +49,7 @@ type QwenClient struct {
 //
 // Returns:
 //   - *QwenClient: A new Qwen client instance.
-func NewQwenClient(cfg *config.Config, ts *qwen.QwenTokenStorage) *QwenClient {
+func NewQwenClient(cfg *config.Config, ts *qwen.QwenTokenStorage, tokenFilePath ...string) *QwenClient {
 	httpClient := util.SetProxy(cfg, &http.Client{})
 
 	// Generate unique client ID
@@ -66,6 +67,19 @@ func NewQwenClient(cfg *config.Config, ts *qwen.QwenTokenStorage) *QwenClient {
 		qwenAuth: qwen.NewQwenAuth(cfg),
 	}
 
+	// If created with a known token file path, record it.
+	if len(tokenFilePath) > 0 && tokenFilePath[0] != "" {
+		client.tokenFilePath = tokenFilePath[0]
+	}
+
+	// If no explicit path provided but email exists, derive the canonical path.
+	if client.tokenFilePath == "" && ts != nil && ts.Email != "" {
+		client.tokenFilePath = filepath.Join(cfg.AuthDir, fmt.Sprintf("qwen-%s.json", ts.Email))
+	}
+
+	// Prefer cookie snapshot at startup if present.
+	_ = client.applyCookieSnapshot()
+
 	// Initialize model registry and register Qwen models
 	client.InitializeModelRegistry(clientID)
 	client.RegisterModels("qwen", registry.GetQwenModels())
@@ -275,7 +289,13 @@ func (c *QwenClient) SendRawTokenCount(_ context.Context, _ string, _ []byte, _
 // Returns:
 //   - error: An error if the save operation fails, nil otherwise.
 func (c *QwenClient) SaveTokenToFile() error {
-	fileName := filepath.Join(c.cfg.AuthDir, fmt.Sprintf("qwen-%s.json", c.tokenStorage.(*qwen.QwenTokenStorage).Email))
+	ts := c.tokenStorage.(*qwen.QwenTokenStorage)
+	// When the client was created from an auth file, persist via cookie snapshot
+	if c.tokenFilePath != "" {
+		return c.saveCookieSnapshot(ts)
+	}
+	// Initial bootstrap (e.g., during OAuth flow) writes the main token file
+	fileName := filepath.Join(c.cfg.AuthDir, fmt.Sprintf("qwen-%s.json", ts.Email))
 	return c.tokenStorage.SaveTokenToFile(fileName)
 }
 
@@ -347,7 +367,7 @@ func (c *QwenClient) APIRequest(ctx context.Context, modelName, endpoint string,
 	}
 
 	var url string
-	if c.tokenStorage.(*qwen.QwenTokenStorage).ResourceURL == "" {
+	if c.tokenStorage.(*qwen.QwenTokenStorage).ResourceURL != "" {
 		url = fmt.Sprintf("https://%s/v1%s", c.tokenStorage.(*qwen.QwenTokenStorage).ResourceURL, endpoint)
 	} else {
 		url = fmt.Sprintf("%s%s", qwenEndpoint, endpoint)
@@ -458,3 +478,71 @@ func (c *QwenClient) IsAvailable() bool {
 func (c *QwenClient) SetUnavailable() {
 	c.isAvailable = false
 }
+
+// UnregisterClient flushes cookie snapshot back into the main token file.
+func (c *QwenClient) UnregisterClient() {
+	if c.tokenFilePath == "" {
+		return
+	}
+	base := c.tokenStorage.(*qwen.QwenTokenStorage)
+	if err := c.flushCookieSnapshotToMain(base); err != nil {
+		log.Errorf("Failed to flush Qwen cookie snapshot to main for %s: %v", filepath.Base(c.tokenFilePath), err)
+	}
+}
+
+// applyCookieSnapshot loads latest tokens from cookie snapshot if present.
+func (c *QwenClient) applyCookieSnapshot() error {
+	if c.tokenFilePath == "" {
+		return nil
+	}
+	ts := c.tokenStorage.(*qwen.QwenTokenStorage)
+	var latest qwen.QwenTokenStorage
+	if ok, err := util.TryReadCookieSnapshotInto(c.tokenFilePath, &latest); err != nil {
+		return err
+	} else if !ok {
+		return nil
+	}
+	if latest.AccessToken != "" {
+		ts.AccessToken = latest.AccessToken
+	}
+	if latest.RefreshToken != "" {
+		ts.RefreshToken = latest.RefreshToken
+	}
+	if latest.ResourceURL != "" {
+		ts.ResourceURL = latest.ResourceURL
+	}
+	if latest.Expire != "" {
+		ts.Expire = latest.Expire
+	}
+	return nil
+}
+
+// saveCookieSnapshot writes the token storage into the snapshot file next to the token file.
+func (c *QwenClient) saveCookieSnapshot(ts *qwen.QwenTokenStorage) error {
+	if c.tokenFilePath == "" || ts == nil {
+		return nil
+	}
+	ts.Type = "qwen"
+	return util.WriteCookieSnapshot(c.tokenFilePath, ts)
+}
+
+// flushCookieSnapshotToMain merges snapshot tokens into the main token file and removes the snapshot.
+func (c *QwenClient) flushCookieSnapshotToMain(base *qwen.QwenTokenStorage) error {
+	if c.tokenFilePath == "" {
+		return nil
+	}
+	var merged qwen.QwenTokenStorage
+	var fromSnapshot bool
+	if ok, _ := util.TryReadCookieSnapshotInto(c.tokenFilePath, &merged); ok {
+		fromSnapshot = true
+	}
+	if !fromSnapshot && base != nil {
+		merged = *base
+	}
+	merged.Type = "qwen"
+	if err := merged.SaveTokenToFile(c.tokenFilePath); err != nil {
+		return err
+	}
+	util.RemoveCookieSnapshots(c.tokenFilePath)
+	return nil
+}