class PositionFactory(object):
    """Tool used by a lexer to generate token's positions."""

    class Position(object):
        """Represent a token's position in a file."""

        __slots__ = ['__startpos', '__endpos']

        def __init__(self, startpos, endpos):
            super(PositionFactory.Position, self).__init__()
            self.__startpos = startpos
            self.__endpos = endpos

        def __str__(self):
            """Return a string representation of a Position.
            Examples:
                2:3     -> line 2, character 3
                2:3-5   -> line 2, charactes 3 to 5 (not included)
                3:4-5:2 -> from line 3 character 4 to line 5 character 2
            """
            #Short hands
            s = self.__startpos
            e = self.__endpos
            # Are we spread over multiple lines?
            if s[1] != e[1]:
                return "%d:%d-%d:%d" % (s[1], s[0], e[1], e[0])
            else:
                # Are we spread over multiple columns?
                if s[0] == e[0]:
                    return "%d:%d" % (e[1], e[0])
                else:
                    return "%d:%d-%d" %(e[1], s[0], e[0])
        
    __slots__ = ['__startpos', '__endpos', '__curpos']

    def __init__(self):
        super(PositionFactory, self).__init__()
        #Both position are in the (x, y) format
        self.__startpos = (1, 1)
        self.__endpos = (1, 1)
        self.__curpos = (1, 1)
        
    def mark(self):
        """Mark the current position as the begining of a token."""
        self.__startpos = self.__curpos
        return
                        
    def get(self):
        """Returns the token position.
        Automatically mark the end of the token as the begining of the next."""
        self.__endpos = self.__curpos
        pos = self.Position(self.__startpos, self.__endpos)
        self.mark()
        return pos
    
    def colAdd(self, col):
        """Move the current column position 'col' columns further to the right."""
        self.__curpos = (self.__curpos[0] + col, self.__curpos[1])
        
    def lineAdd(self, line):
        """Move the current position 'line' lines down and reset the column position"""
        self.__curpos = (1, self.__curpos[1] + line)
    
if __name__ == '__main__':
    tokens = []
    pos = PositionFactory()
    print '   1234567890'
    print '1: toto  tata'
    print '2: titi'
    print '3: \'start'
    print '4: end\''
    print '   1234567890'
    pos.colAdd(len('toto'))
    tokens.append(Token('ID', pos.get(), 'toto'))
    pos.mark()
    pos.colAdd(len('tata'))
    tokens.append(Token('ID', pos.get(), 'tata'))
    pos.lineAdd(1)
    pos.mark()
    pos.colAdd(len('titi'))
    tokens.append(Token('ID', pos.get(), 'titi'))
    pos.lineAdd(1)
    pos.mark()
    pos.colAdd(len('\'start'))
    pos.lineAdd(1)
    pos.colAdd(len('end\''))    
    tokens.append(Token('ID', pos.get(), '\'start\nend\''))
    del pos
    for i in tokens:
        print i