Undo Last Changes

Instructions

Implementation Reference

• src/markdown_editor/server.py:357-380 (registration)

  MCP tool registration for 'undo' including input schema (file_path required, count optional) and output schema.

  Tool(
      name="undo",
      title="Undo Last Changes",
      description="Reverts the last N operations on the document.",
      inputSchema={
          "type": "object",
          "properties": {
              "file_path": {"type": "string", "examples": ["./document.md"]},
              "count": {"type": "integer", "default": 1, "examples": [1, 2, 5]},
          },
          "required": ["file_path"],
          "additionalProperties": False,
      },
      outputSchema={
          "type": "object",
          "properties": {
              "success": {"type": "boolean"},
              "reverted_count": {
                  "type": "integer",
                  "description": "Number of operations reverted",
              },
          },
      },
  ),

• src/markdown_editor/server.py:645-651 (handler)

  Dispatch logic in MCP server's call_tool method for the 'undo' tool.

  elif name == "undo":
      res = await undo_changes(file_path, arguments.get("count", 1))
      return CallToolResult(
          content=[TextContent(type="text", text="Undo performed")],
          structuredContent=res,
          isError="error" in res,
      )

• src/markdown_editor/tools/edit_tools.py:304-306 (handler)

  Exported async handler function 'undo_changes' called by the MCP server for 'undo' tool invocations.

  async def undo_changes(file_path: str, count: int = 1):
      return await _instance.undo(file_path, count)

• src/markdown_editor/tools/edit_tools.py:212-225 (handler)

  EditTool.undo method: handles file locking, invokes Document.undo, performs atomic file write, and manages cache/journal.

  async def undo(self, file_path: str, count: int = 1) -> Dict[str, Any]:
      abs_path = resolve_path(file_path)
      with FileLock(abs_path):
          doc = self.get_doc(file_path)
          result = doc.undo(count)
          if "success" in result:
              try:
                  self._atomic_write(file_path, doc.get_content())
                  self._update_cache_mtime(abs_path)
                  doc.confirm_journal()
              except Exception as e:
                  self.invalidate_cache(file_path)
                  return {"error": f"Failed to write file: {e}"}
      return result

• src/markdown_editor/core/document.py:1099-1166 (handler)

  Core Document class undo method: reverses the last N journaled operations (replace, delete, insert, metadata) by popping journal and applying inverse actions.

  def undo(self, count: int = 1) -> Dict[str, Any]:
      """Undo last operations"""
      if not self.journal:
          return {"error": "Journal is empty"}
  
      undone = []
      errors = []
  
      for _ in range(min(count, len(self.journal))):
          entry = self.journal.pop()
          success = False
  
          # Apply reverse operation
          if entry.operation == "replace":
              # Prefer ID-based lookup for reliability
              element = None
              if entry.element_id:
                  element = self.find_by_id(entry.element_id)
              if not element:
                  element = self.find_by_path(entry.path)
  
              if element and entry.old_value is not None:
                  element.content = entry.old_value
                  success = True
              else:
                  errors.append(
                      f"Cannot undo replace: element not found at {entry.path}"
                  )
  
          elif entry.operation == "delete":
              # Restore deleted element at its original position
              success = self._restore_element_at_position(entry)
              if not success:
                  errors.append(
                      f"Cannot undo delete: failed to restore element at {entry.path}"
                  )
  
          elif entry.operation in ("insert_after", "insert_before"):
              # Remove the inserted element
              success = self._remove_inserted_element(entry)
              if not success:
                  errors.append(
                      f"Cannot undo {entry.operation}: element not found at {entry.path}"
                  )
  
          elif entry.operation == "update_metadata":
              # Restore old metadata
              if entry.old_value:
                  try:
                      old_metadata = json.loads(entry.old_value)
                      self.metadata = old_metadata
                      success = True
                  except (json.JSONDecodeError, TypeError):
                      errors.append("Cannot undo update_metadata: invalid old value")
              else:
                  errors.append("Cannot undo update_metadata: no old value stored")
  
          if success:
              undone.append(entry.operation)
  
      self._rebuild_raw_content()
      self._save_journal()
  
      result = {"success": True, "undone_operations": undone}
      if errors:
          result["warnings"] = errors
  
      return result