feat: add custom error types for better error handling

Author: tumf

src/mcp_text_editor/errors.py

@@ -0,0 +1,52 @@
+"""Custom error types for MCP Text Editor."""
+
+from enum import Enum, auto
+
+
+class ErrorCode(Enum):
+    """Error codes for MCP Text Editor."""
+
+    # Validation errors
+    INVALID_REQUEST = auto()
+    INVALID_RANGE = auto()
+
+    # File operation errors
+    FILE_NOT_FOUND = auto()
+    FILE_ACCESS_DENIED = auto()
+    FILE_CREATE_FAILED = auto()
+    FILE_WRITE_FAILED = auto()
+
+    # Content operation errors
+    CONTENT_HASH_MISMATCH = auto()
+    CONTENT_ENCODING_ERROR = auto()
+    CONTENT_VALIDATION_ERROR = auto()
+
+
+class MTextEditorError(Exception):
+    """Base error class for MCP Text Editor."""
+
+    def __init__(
+        self, message: str, code: ErrorCode, details: dict | None = None
+    ) -> None:
+        """Initialize the error.
+
+        Args:
+            message (str): Error message
+            code (ErrorCode): Error code
+            details (dict | None, optional): Additional error details. Defaults to None.
+        """
+        super().__init__(message)
+        self.code = code
+        self.details = details or {}
+
+
+class ValidationError(MTextEditorError):
+    """Raised when input validation fails."""
+
+
+class FileOperationError(MTextEditorError):
+    """Raised when file operations fail."""
+
+
+class ContentOperationError(MTextEditorError):
+    """Raised when content operations fail."""