from pymongo import Connection, database, collection

def __getattr__(self, name):
    return Collection(self, name)
database.Database.__getattr__ = __getattr__
database.Database.__getitem__ = __getattr__

class Collection(collection.Collection):
    def find(self, _spec=None, **kwargs):
        '''
        kwargs are preferred way to filtration
        _spec is an optional dict, specifying filters.
        '''
        spec = process_spec(_spec or kwargs)
        return super(Collection, self).find(spec=spec)

def process_spec(spec):
    new = {}
    for k, v in spec.items():
        if '__' in k:
            k, child = k.split('__', 1)
            new.setdefault(k, {}).update(process_spec({fixname(child): v}))
        elif k.startswith('_'):
            new[k.replace('_', '$', 1)] = v
        else:
            new[k] = v
    return new

def fixname(key):
    if key in 'gt lt gte lte ne in nin all size where'.split():
        return '$' + key