
# Abstract classes.


def CommentCheck():
    pass


class Event(object):
    def __init__(self, start_mark=None, end_mark=None, comment=CommentCheck):
        self.start_mark = start_mark
        self.end_mark = end_mark
        # assert comment is not CommentCheck
        if comment is CommentCheck:
            comment = None
        self.comment = comment

    def __repr__(self):
        attributes = [key for key in ['anchor', 'tag', 'implicit', 'value']
                      if hasattr(self, key)]
        arguments = ', '.join(['%s=%r' % (key, getattr(self, key))
                               for key in attributes])
        if self.comment not in [None, CommentCheck]:
            arguments += ', comment={!r}'.format(self.comment)
        return '%s(%s)' % (self.__class__.__name__, arguments)


class NodeEvent(Event):
    def __init__(self, anchor, start_mark=None, end_mark=None, comment=None):
        Event.__init__(self, start_mark, end_mark, comment)
        self.anchor = anchor


class CollectionStartEvent(NodeEvent):
    def __init__(self, anchor, tag, implicit, start_mark=None, end_mark=None,
                 flow_style=None, comment=None):
        Event.__init__(self, start_mark, end_mark, comment)
        self.anchor = anchor
        self.tag = tag
        self.implicit = implicit
        self.flow_style = flow_style


class CollectionEndEvent(Event):
    pass

# Implementations.


class StreamStartEvent(Event):
    def __init__(self, start_mark=None, end_mark=None, encoding=None,
                 comment=None):
        Event.__init__(self, start_mark, end_mark, comment)
        self.encoding = encoding


class StreamEndEvent(Event):
    pass


class DocumentStartEvent(Event):
    def __init__(self, start_mark=None, end_mark=None,
                 explicit=None, version=None, tags=None, comment=None):
        Event.__init__(self, start_mark, end_mark, comment)
        self.explicit = explicit
        self.version = version
        self.tags = tags


class DocumentEndEvent(Event):
    def __init__(self, start_mark=None, end_mark=None,
                 explicit=None, comment=None):
        Event.__init__(self, start_mark, end_mark, comment)
        self.explicit = explicit


class AliasEvent(NodeEvent):
    pass


class ScalarEvent(NodeEvent):
    def __init__(self, anchor, tag, implicit, value,
                 start_mark=None, end_mark=None, style=None, comment=None):
        NodeEvent.__init__(self, anchor, start_mark, end_mark, comment)
        self.tag = tag
        self.implicit = implicit
        self.value = value
        self.style = style


class SequenceStartEvent(CollectionStartEvent):
    pass


class SequenceEndEvent(CollectionEndEvent):
    pass


class MappingStartEvent(CollectionStartEvent):
    pass


class MappingEndEvent(CollectionEndEvent):
    pass
