#!/usr/bin/env python
# -*- coding: utf-8 -*-

from PySide.QtGui import QUndoCommand, QUndoStack

class MyDocument(object):

    def __init__(self):
        self.document = []

    def __repr__(self):
        return repr(self.document)

    def chop(self):
        self.document = self.document[:-1]

    def append(self, item):
        self.document.append(item)


class MyCommand(QUndoCommand):

    def __init__(self, doc, *args, **kwargs):
        super(type(self), self).__init__(*args, **kwargs)
        self.document = doc

    def undo(self):
        self.document.chop()
        print("undo: {0}, undo-text: {1}".format(self.document, self.text()))

    def redo(self):
        self.document.append(self.text())
        print("redo: {0}, redo-text: {1}".format(self.document, self.text()))


if __name__ == '__main__':
    stack1 = QUndoStack()
    document1 = MyDocument()

    c = MyCommand(document1)
    c.setText("comamnd1")
    stack1.push(c)
    print(stack1.count())

    c = MyCommand(document1)
    c.setText("comamnd2")
    stack1.push(c)
    print(stack1.count())

    stack1.undo()
    stack1.undo()
    stack1.redo()
    print(stack1.count())

    c = MyCommand(document1)
    c.setText("comamnd3")
    stack1.push(c) # command2 gets deleted
    print(stack1.count())