Update, bugfixes on diff and edit handling

pkg/errors/errors.go

@@ -120,6 +120,42 @@ func (e *StructuredError) WithRemediation(msg string) *StructuredError {
 	return e
 }
 
+// UserMessage returns a user-safe error message without internal details.
+// This should be used for API responses to avoid leaking implementation details.
+func (e *StructuredError) UserMessage() string {
+	// Return only the message and remediation, no stack trace, no cause details
+	if e.Remediation != "" {
+		return fmt.Sprintf("%s. %s", e.Message, e.Remediation)
+	}
+	return e.Message
+}
+
+// SanitizeError returns a user-safe error message from any error.
+// For StructuredError, it returns UserMessage().
+// For other errors, it returns a generic message to avoid leaking internals.
+func SanitizeError(err error) string {
+	if err == nil {
+		return ""
+	}
+
+	// Check if it's a StructuredError
+	if se, ok := err.(*StructuredError); ok {
+		return se.UserMessage()
+	}
+
+	// For other errors, extract only the basic message
+	// Avoid exposing full paths or implementation details
+	msg := err.Error()
+
+	// Truncate very long messages that might contain stack traces
+	const maxLen = 200
+	if len(msg) > maxLen {
+		msg = msg[:maxLen] + "..."
+	}
+
+	return msg
+}
+
 // New creates a new structured error with stack trace.
 func New(code ErrorCode, message string) *StructuredError {
 	return &StructuredError{

pkg/protocol/types.go

@@ -1,6 +1,8 @@
 // Package protocol defines shared types used across the MCP file operations server.
 package protocol
 
+import "path/filepath"
+
 // Location represents a position in a file.
 type Location struct {
 	File   string `json:"file"`
@@ -66,7 +68,7 @@ const (
 
 // DetectLanguage detects the language from a filename.
 func DetectLanguage(filename string) Language {
-	ext := getExtension(filename)
+	ext := filepath.Ext(filename)
 	switch ext {
 	case ".go":
 		return LangGo
@@ -94,15 +96,3 @@ func DetectLanguage(filename string) Language {
 		return LangUnknown
 	}
 }
-
-func getExtension(filename string) string {
-	for i := len(filename) - 1; i >= 0; i-- {
-		if filename[i] == '.' {
-			return filename[i:]
-		}
-		if filename[i] == '/' || filename[i] == '\\' {
-			break
-		}
-	}
-	return ""
-}

pkg/protocol/types_test.go

@@ -48,26 +48,3 @@ func TestDetectLanguage(t *testing.T) {
 		})
 	}
 }
-
-func TestGetExtension(t *testing.T) {
-	tests := []struct {
-		filename string
-		expected string
-	}{
-		{"file.go", ".go"},
-		{"file.test.go", ".go"},
-		{"path/to/file.ts", ".ts"},
-		{"noextension", ""},
-		{".hidden", ".hidden"},
-		{"file.", "."},
-	}
-
-	for _, tt := range tests {
-		t.Run(tt.filename, func(t *testing.T) {
-			result := getExtension(tt.filename)
-			if result != tt.expected {
-				t.Errorf("getExtension(%q) = %q, want %q", tt.filename, result, tt.expected)
-			}
-		})
-	}
-}