Design a Text Editor with Undo/Redo

Requirements

Support inserting and deleting text at a cursor position.
Support undo() and redo() that reverse/reapply the most recent edit(s), in order.
A new edit after an undo should clear the redo history (standard editor behavior — you can't redo something that's no longer the "next" action once you've branched off in a new direction).

Key classes to identify before you look at the reference

Undo/redo is the textbook use case for one specific pattern — the same one covered in this course's Behavioral Patterns lesson for exactly this reason. Which pattern turns "an action that already happened" into something that can be stored, reversed, and replayed?

Design a Text Editor with Undo/Redo

Requirements

Support inserting and deleting text at a cursor position.
Support undo() and redo() that reverse/reapply the most recent edit(s), in order.
A new edit after an undo should clear the redo history (standard editor behavior — you can't redo something that's no longer the "next" action once you've branched off in a new direction).