CSV Editor

Instructions

Implementation Reference

• src/csv_editor/server.py:500-506 (registration)

  Registers the 'undo' MCP tool using @mcp.tool decorator. Provides type hints for input schema (session_id: str) and delegates to implementation.

  @mcp.tool
  async def undo(
      session_id: str,
      ctx: Context = None
  ) -> Dict[str, Any]:
      """Undo the last operation in a session."""
      return await _undo_operation(session_id, ctx)

• src/csv_editor/tools/history_operations.py:13-69 (handler)

  Executes the undo tool logic: retrieves CSV session, invokes session.undo(), wraps result with OperationResult, handles errors and context logging.

  async def undo_operation(
      session_id: str,
      ctx: Context = None
  ) -> Dict[str, Any]:
      """
      Undo the last operation in a session.
      
      Args:
          session_id: Session identifier
          ctx: FastMCP context
          
      Returns:
          Dict with success status and undo result
      """
      try:
          manager = get_session_manager()
          session = manager.get_session(session_id)
          
          if not session:
              return OperationResult(
                  success=False,
                  message="Session not found",
                  error=f"No session with ID: {session_id}"
              ).model_dump()
          
          if ctx:
              await ctx.info(f"Undoing last operation for session {session_id}")
          
          result = await session.undo()
          
          if result["success"]:
              if ctx:
                  await ctx.info(f"Successfully undid operation: {result.get('message')}")
              
              return OperationResult(
                  success=True,
                  message=result["message"],
                  session_id=session_id,
                  data=result
              ).model_dump()
          else:
              return OperationResult(
                  success=False,
                  message="Failed to undo operation",
                  error=result.get("error")
              ).model_dump()
              
      except Exception as e:
          logger.error(f"Error undoing operation: {str(e)}")
          if ctx:
              await ctx.error(f"Failed to undo operation: {str(e)}")
          return OperationResult(
              success=False,
              message="Failed to undo operation",
              error=str(e)
          ).model_dump()

• src/csv_editor/models/csv_session.py:214-248 (helper)

  CSVSession class undo method: checks history, calls history_manager.undo(), restores dataframe snapshot, triggers auto-save, returns status.

  async def undo(self) -> Dict[str, Any]:
      """Undo the last operation."""
      if not self.history_manager:
          return {"success": False, "error": "History is not enabled"}
      
      if not self.history_manager.can_undo():
          return {"success": False, "error": "No operations to undo"}
      
      try:
          operation, data_snapshot = self.history_manager.undo()
          
          if data_snapshot is not None:
              self.df = data_snapshot
              
              # Trigger auto-save if configured
              if self.auto_save_manager.should_save_after_operation():
                  await self.auto_save_manager.trigger_save(self._save_callback, "undo")
              
              return {
                  "success": True,
                  "message": f"Undid operation: {operation.operation_type}",
                  "operation": operation.to_dict(),
                  "can_undo": self.history_manager.can_undo(),
                  "can_redo": self.history_manager.can_redo()
              }
          else:
              return {
                  "success": False,
                  "error": "No snapshot available for undo"
              }
              
      except Exception as e:
          logger.error(f"Error during undo: {str(e)}")
          return {"success": False, "error": str(e)}

• src/csv_editor/models/history_manager.py:247-274 (helper)

  Core HistoryManager.undo(): shifts current operation to redo stack, decrements history index, locates and returns prior data snapshot for restoration.

  def undo(self) -> Tuple[Optional[OperationHistory], Optional[pd.DataFrame]]:
      """Undo the last operation and return the previous state."""
      if not self.can_undo():
          return None, None
      
      # Move current operation to redo stack
      current_op = self.history[self.current_index]
      self.redo_stack.append(current_op)
      
      # Move index back
      self.current_index -= 1
      
      # Find the most recent snapshot before current position
      snapshot = None
      for i in range(self.current_index, -1, -1):
          if self.history[i].data_snapshot is not None:
              snapshot = self.history[i].data_snapshot.copy()
              break
      
      # Save state
      if self.storage_type != HistoryStorage.MEMORY:
          self._save_history()
      
      logger.info(f"Undid operation: {current_op.operation_type}")
      
      # Return the operation that was undone and the data to restore
      return current_op, snapshot