Chain decorates the given Command with all middlewares.

Handler is a command handler that to encapsulate a unit of processing work to be performed.

Middleware allows us to write something like decorators to Command.

RedoHandler redo a Command.

UndoHandler undo a Command.

The CommandFunc type is an adapter to allow the use of ordinary functions as Command.

The MiddlewareFunc type is an adapter to allow the use of ordinary functions as Middleware.

The RedoCommandFunc type is an adapter to allow the use of ordinary functions as RedoCommand.

The UndoCommandFunc type is an adapter to allow the use of ordinary functions as UndoCommand.