Undo/redo functionality is common in text editors, drawing tools, settings panels, and multi-step workflows. Instead of tying this logic to a UI, in this question we will implement a reusable UndoRedoManager class that stores a history of values and can move backward and forward through that history.

Examples

const manager = new UndoRedoManager(0);

manager.getCurrent(); // 0
manager.canUndo(); // false
manager.canRedo(); // false

manager.set(1);
manager.set(2);
manager.getCurrent(); // 2

manager.undo();
manager.getCurrent(); // 1
manager.canRedo(); // true

manager.redo();
manager.getCurrent(); // 2

manager.undo();
manager.set(10);
manager.getCurrent(); // 10
manager.canRedo(); // false

manager.reset();
manager.getCurrent(); // 0
manager.canUndo(); // false
manager.canRedo(); // false

UndoRedoManager API

Implement the following APIs on the UndoRedoManager:

new UndoRedoManager(initialValue)

Creates an instance of the UndoRedoManager class with initialValue as the first history entry. History is isolated within each instance.

Values should be stored as-is. You do not need to deep clone them.

manager.getCurrent()

Returns the current value in the history.

manager.set(value)

Adds value as a new current history entry.

If some values had been undone before calling set, all redo history should be discarded before appending the new value.

manager.undo()

Moves the current pointer one step backward if possible.

If the manager is already at the earliest history entry, this method should do nothing.

manager.redo()

Moves the current pointer one step forward if possible.

If the manager is already at the latest history entry, this method should do nothing.

manager.reset()

Restores the manager to its original initialValue and clears the rest of the history, including any redo history.

manager.canUndo()

Returns true if there is an earlier history entry to move to, otherwise false.

manager.canRedo()

Returns true if there is a later history entry to move to, otherwise false.

Notes

• Calling set() with the same value as the current value should still create a new history step.
• You do not need to implement history inspection APIs such as getHistory() or getIndex().