gistfile1.py

import string
from urllib.parse import urlparse
import random
from sqlalchemy import (
    Column,
    Index,
    Integer,
    String, DateTime, ForeignKey)

from pyramid_web20.models import Base, utc, now, DBSession
from sqlalchemy.ext.declarative import declared_attr
from sqlalchemy.orm import relationship


def assert_valid_short_url(url):
    # XXX: Probably very buggy, but works for now
    pieces = urlparse(url)
    assert all([pieces.scheme, pieces.netloc])
    assert set(pieces.netloc) <= set(string.ascii_letters + string.digits + '-.')  # and others?
    assert pieces.scheme in ['http', 'https']


class ReferralBase(Base):
    """A shorted URL in the database.

    This class is abstract and doesn't know about "owner" as the user model can change depending on the host application. Instead, the concrete implementation is provided in ``defaultmodels.py``
    """
    __tablename__ = 'referrals'
    __abstract__ = True

    id = Column(Integer, primary_key=True)

    created_at = Column(DateTime(timezone=utc), default=now)
    updated_at = Column(DateTime(timezone=utc), onupdate=now)
    slug = Column(String(6), unique=True)
    hits = Column(Integer, default=0)

    @declared_attr
    def owner_id(self, cls):
        raise NotImplementedError()

    @declared_attr
    def owner(self, cls):
        raise NotImplementedError()


def create_referral_class(UserModel) -> type:
    """Creates a concrete implementation of Referral class with specifc user model as owner relationship.

    :param UserModel:
    :return: ReferralBase-like class
    """

    class Referral(ReferralBase):

        @declared_attr
        def owner_id(cls):
            return Column(Integer, ForeignKey('{}.id'.format(UserModel.__tablename__)))

        @declared_attr
        def owner_id(cls):
            return relationship(UserModel, backref="referrals")

    return Referral

# in the app

from foo import UserModel
_referral = create_referral_class(UserModel)