refactor(auth): extract token filename generation into unified function

Add ExtractIDCIdentifier and GenerateTokenFileName functions to centralize
token filename generation logic. This improves code maintainability by:

- Extracting IDC identifier from startUrl for unique token file naming
- Supporting priority-based filename generation (email > startUrl > authMethod)
- Removing duplicate filename generation code from oauth_web.go
- Adding comprehensive unit tests for the new functions

internal/auth/kiro/aws.go

@@ -360,7 +360,7 @@ func SanitizeEmailForFilename(email string) string {
 	}
 
 	result := email
-	
+
 	// First, handle URL-encoded path traversal attempts (%2F, %2E, %5C, etc.)
 	// This prevents encoded characters from bypassing the sanitization.
 	// Note: We replace % last to catch any remaining encodings including double-encoding (%252F)
@@ -378,7 +378,7 @@ func SanitizeEmailForFilename(email string) string {
 	for _, char := range []string{"/", "\\", ":", "*", "?", "\"", "<", ">", "|", " ", "\x00"} {
 		result = strings.ReplaceAll(result, char, "_")
 	}
-	
+
 	// Prevent path traversal: replace leading dots in each path component
 	// This handles cases like "../../../etc/passwd" → "_.._.._.._etc_passwd"
 	parts := strings.Split(result, "_")
@@ -389,6 +389,65 @@ func SanitizeEmailForFilename(email string) string {
 		parts[i] = part
 	}
 	result = strings.Join(parts, "_")
-	
+
 	return result
 }
+
+// ExtractIDCIdentifier extracts a unique identifier from IDC startUrl.
+// Examples:
+//   - "https://d-1234567890.awsapps.com/start" -> "d-1234567890"
+//   - "https://my-company.awsapps.com/start" -> "my-company"
+//   - "https://acme-corp.awsapps.com/start" -> "acme-corp"
+func ExtractIDCIdentifier(startURL string) string {
+	if startURL == "" {
+		return ""
+	}
+
+	// Remove protocol prefix
+	url := strings.TrimPrefix(startURL, "https://")
+	url = strings.TrimPrefix(url, "http://")
+
+	// Extract subdomain (first part before the first dot)
+	// Format: {identifier}.awsapps.com/start
+	parts := strings.Split(url, ".")
+	if len(parts) > 0 && parts[0] != "" {
+		identifier := parts[0]
+		// Sanitize for filename safety
+		identifier = strings.ReplaceAll(identifier, "/", "_")
+		identifier = strings.ReplaceAll(identifier, "\\", "_")
+		identifier = strings.ReplaceAll(identifier, ":", "_")
+		return identifier
+	}
+
+	return ""
+}
+
+// GenerateTokenFileName generates a unique filename for token storage.
+// Priority: email > startUrl identifier (for IDC) > authMethod only
+// Format: kiro-{authMethod}-{identifier}.json
+func GenerateTokenFileName(tokenData *KiroTokenData) string {
+	authMethod := tokenData.AuthMethod
+	if authMethod == "" {
+		authMethod = "unknown"
+	}
+
+	// Priority 1: Use email if available
+	if tokenData.Email != "" {
+		// Sanitize email for filename (replace @ and . with -)
+		sanitizedEmail := tokenData.Email
+		sanitizedEmail = strings.ReplaceAll(sanitizedEmail, "@", "-")
+		sanitizedEmail = strings.ReplaceAll(sanitizedEmail, ".", "-")
+		return fmt.Sprintf("kiro-%s-%s.json", authMethod, sanitizedEmail)
+	}
+
+	// Priority 2: For IDC, use startUrl identifier
+	if authMethod == "idc" && tokenData.StartURL != "" {
+		identifier := ExtractIDCIdentifier(tokenData.StartURL)
+		if identifier != "" {
+			return fmt.Sprintf("kiro-%s-%s.json", authMethod, identifier)
+		}
+	}
+
+	// Priority 3: Fallback to authMethod only
+	return fmt.Sprintf("kiro-%s.json", authMethod)
+}

internal/auth/kiro/aws_test.go

@@ -151,11 +151,161 @@ func TestSanitizeEmailForFilename(t *testing.T) {
 // createTestJWT creates a test JWT token with the given claims
 func createTestJWT(claims map[string]any) string {
 	header := base64.RawURLEncoding.EncodeToString([]byte(`{"alg":"RS256","typ":"JWT"}`))
-	
+
 	payloadBytes, _ := json.Marshal(claims)
 	payload := base64.RawURLEncoding.EncodeToString(payloadBytes)
-	
+
 	signature := base64.RawURLEncoding.EncodeToString([]byte("fake-signature"))
-	
+
 	return header + "." + payload + "." + signature
 }
+
+func TestExtractIDCIdentifier(t *testing.T) {
+	tests := []struct {
+		name     string
+		startURL string
+		expected string
+	}{
+		{
+			name:     "Empty URL",
+			startURL: "",
+			expected: "",
+		},
+		{
+			name:     "Standard IDC URL with d- prefix",
+			startURL: "https://d-1234567890.awsapps.com/start",
+			expected: "d-1234567890",
+		},
+		{
+			name:     "IDC URL with company name",
+			startURL: "https://my-company.awsapps.com/start",
+			expected: "my-company",
+		},
+		{
+			name:     "IDC URL with simple name",
+			startURL: "https://acme-corp.awsapps.com/start",
+			expected: "acme-corp",
+		},
+		{
+			name:     "IDC URL without https",
+			startURL: "http://d-9876543210.awsapps.com/start",
+			expected: "d-9876543210",
+		},
+		{
+			name:     "IDC URL with subdomain only",
+			startURL: "https://test.awsapps.com/start",
+			expected: "test",
+		},
+		{
+			name:     "Builder ID URL",
+			startURL: "https://view.awsapps.com/start",
+			expected: "view",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result := ExtractIDCIdentifier(tt.startURL)
+			if result != tt.expected {
+				t.Errorf("ExtractIDCIdentifier() = %q, want %q", result, tt.expected)
+			}
+		})
+	}
+}
+
+func TestGenerateTokenFileName(t *testing.T) {
+	tests := []struct {
+		name      string
+		tokenData *KiroTokenData
+		expected  string
+	}{
+		{
+			name: "IDC with email",
+			tokenData: &KiroTokenData{
+				AuthMethod: "idc",
+				Email:      "user@example.com",
+				StartURL:   "https://d-1234567890.awsapps.com/start",
+			},
+			expected: "kiro-idc-user-example-com.json",
+		},
+		{
+			name: "IDC without email but with startUrl",
+			tokenData: &KiroTokenData{
+				AuthMethod: "idc",
+				Email:      "",
+				StartURL:   "https://d-1234567890.awsapps.com/start",
+			},
+			expected: "kiro-idc-d-1234567890.json",
+		},
+		{
+			name: "IDC with company name in startUrl",
+			tokenData: &KiroTokenData{
+				AuthMethod: "idc",
+				Email:      "",
+				StartURL:   "https://my-company.awsapps.com/start",
+			},
+			expected: "kiro-idc-my-company.json",
+		},
+		{
+			name: "IDC without email and without startUrl",
+			tokenData: &KiroTokenData{
+				AuthMethod: "idc",
+				Email:      "",
+				StartURL:   "",
+			},
+			expected: "kiro-idc.json",
+		},
+		{
+			name: "Builder ID with email",
+			tokenData: &KiroTokenData{
+				AuthMethod: "builder-id",
+				Email:      "user@gmail.com",
+				StartURL:   "https://view.awsapps.com/start",
+			},
+			expected: "kiro-builder-id-user-gmail-com.json",
+		},
+		{
+			name: "Builder ID without email",
+			tokenData: &KiroTokenData{
+				AuthMethod: "builder-id",
+				Email:      "",
+				StartURL:   "https://view.awsapps.com/start",
+			},
+			expected: "kiro-builder-id.json",
+		},
+		{
+			name: "Social auth with email",
+			tokenData: &KiroTokenData{
+				AuthMethod: "google",
+				Email:      "user@gmail.com",
+			},
+			expected: "kiro-google-user-gmail-com.json",
+		},
+		{
+			name: "Empty auth method",
+			tokenData: &KiroTokenData{
+				AuthMethod: "",
+				Email:      "",
+			},
+			expected: "kiro-unknown.json",
+		},
+		{
+			name: "Email with special characters",
+			tokenData: &KiroTokenData{
+				AuthMethod: "idc",
+				Email:      "user.name+tag@sub.example.com",
+				StartURL:   "https://d-1234567890.awsapps.com/start",
+			},
+			expected: "kiro-idc-user-name+tag-sub-example-com.json",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result := GenerateTokenFileName(tt.tokenData)
+			if result != tt.expected {
+				t.Errorf("GenerateTokenFileName() = %q, want %q", result, tt.expected)
+			}
+		})
+	}
+}

internal/auth/kiro/oauth_web.go

@@ -421,7 +421,7 @@ func (h *OAuthWebHandler) saveTokenToFile(tokenData *KiroTokenData) {
 			log.Errorf("OAuth Web: failed to resolve auth directory: %v", err)
 		}
 	}
-	
+
 	// Fall back to default location
 	if authDir == "" {
 		home, err := os.UserHomeDir()
@@ -431,24 +431,16 @@ func (h *OAuthWebHandler) saveTokenToFile(tokenData *KiroTokenData) {
 		}
 		authDir = filepath.Join(home, ".cli-proxy-api")
 	}
-	
+
 	// Create directory if not exists
 	if err := os.MkdirAll(authDir, 0700); err != nil {
 		log.Errorf("OAuth Web: failed to create auth directory: %v", err)
 		return
 	}
-	
-	// Generate filename based on auth method
-	// Format: kiro-{authMethod}.json or kiro-{authMethod}-{email}.json
-	fileName := fmt.Sprintf("kiro-%s.json", tokenData.AuthMethod)
-	if tokenData.Email != "" {
-		// Sanitize email for filename (replace @ and . with -)
-		sanitizedEmail := tokenData.Email
-		sanitizedEmail = strings.ReplaceAll(sanitizedEmail, "@", "-")
-		sanitizedEmail = strings.ReplaceAll(sanitizedEmail, ".", "-")
-		fileName = fmt.Sprintf("kiro-%s-%s.json", tokenData.AuthMethod, sanitizedEmail)
-	}
-	
+
+	// Generate filename using the unified function
+	fileName := GenerateTokenFileName(tokenData)
+
 	authFilePath := filepath.Join(authDir, fileName)
 	
 	// Convert to storage format and save
@@ -811,13 +803,8 @@ func (h *OAuthWebHandler) handleImportToken(c *gin.Context) {
 	// Save token to file
 	h.saveTokenToFile(tokenData)
 
-	// Generate filename for response
-	fileName := fmt.Sprintf("kiro-%s.json", tokenData.AuthMethod)
-	if tokenData.Email != "" {
-		sanitizedEmail := strings.ReplaceAll(tokenData.Email, "@", "-")
-		sanitizedEmail = strings.ReplaceAll(sanitizedEmail, ".", "-")
-		fileName = fmt.Sprintf("kiro-%s-%s.json", tokenData.AuthMethod, sanitizedEmail)
-	}
+	// Generate filename for response using the unified function
+	fileName := GenerateTokenFileName(tokenData)
 
 	log.Infof("OAuth Web: token imported successfully")
 	c.JSON(http.StatusOK, gin.H{