from sqlalchemy.exc import IntegrityError
from sqlalchemy.orm import backref, relationship

from aurweb import db, schema
from aurweb.models.declarative import Base
from aurweb.models.user import User as _User


class Session(Base):
    __table__ = schema.Sessions
    __tablename__ = __table__.name
    __mapper_args__ = {"primary_key": [__table__.c.UsersID]}

    User = relationship(
        _User, backref=backref("session", uselist=False),
        foreign_keys=[__table__.c.UsersID])

    def __init__(self, **kwargs):
        super().__init__(**kwargs)

        # We'll try to either use UsersID or User.ID if we can.
        # If neither exist, an AttributeError is raised, in which case
        # we set the uid to 0, which triggers IntegrityError below.
        try:
            uid = self.UsersID or self.User.ID
        except AttributeError:
            uid = 0

        user_exists = db.query(_User).filter(_User.ID == uid).exists()
        if not db.query(user_exists).scalar():
            raise IntegrityError(
                statement=("Foreign key UsersID cannot be null and "
                           "must be a valid user's ID."),
                orig="Sessions.UsersID",
                params=("NULL"))


def generate_unique_sid():
    return db.make_random_value(Session, Session.SessionID, 32)