gistfile1.py

def insert(self, user, pos, text, state):
    """
    Inserts text into the document at pos
    """
    # MANY THANKS TO Infinote for help with these transformations:
    # http://gobby.0x539.de/trac/wiki/Infinote/Protocol
    
    # First, reach back in time and see what we should do
    # Think of this like a "git rebase"- we want to rebase
    # the NEW changes on top of the changes the person
    # didn't know about so they don't have to worry about it.
    # This has the side-effect of sending events with slightly different
    # parameters than what you requested.
    # For every event in our history after our state:
    for e in self.history[state:]:
        if (e['operation'] == "insert"):
            # We gotta account for stuff that was inserted before our
            # latest characters
            if (e['pos'] <= pos):
                # The old stuff should push our new stuff forward.
                # Add the text length to the position
                pos += len(e['text'])
        elif (e['operation'] == "delete"):
            # Deleted text should be accounted for
            if (pos >= e['end']):
                # Our new inserted text should be shifted to the left
                pos -= (e['end'] - e['begin'])
            elif (pos >= e['begin']):
                # Right between what they deleted. Ha ha.
                # Our inserted text should be placed right at the
                # beginning of where they deleted
                pos = e['begin']
    
    # BY THIS POINT: Our changes should be applicable to the new
    # version of the document. Silly client for not knowing better...
        
    # Then, take our new "pos" and help it along
    self.content = self.content[:pos] + text + self.content[pos:]
    
    # And send the event to everyone
    self.send_event({
        "type": "insert",
        "user": user.get_state(),
        "text": text,
        "pos": pos,
    })