from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, Integer, String, ForeignKey, DateTime, Boolean, Numeric
from sqlalchemy.orm import relationship, backref
from sqlalchemy.sql import expression
from sqlalchemy.ext.compiler import compiles
from sqlalchemy.types import DateTime as DateTimeType

# can be moved to models util?
class utcnow(expression.FunctionElement):
    type = DateTimeType()

# Can be moved to the models util?
@compiles(utcnow, 'postgresql')
def pg_utcnow(element, compiler, **kw):
    return "TIMEZONE('utc', CURRENT_TIMESTAMP)"


Base = declarative_base()



class DBMixin:
    id = Column(Integer, primary_key=True)
    created_date = Column(DateTime, server_default=utcnow())
    modified_date = Column(DateTime, server_default=utcnow(), onupdate=utcnow())

    def to_dict(self):
        d = self.__dict__
        d.pop('_sa_instance_state')
        return d


def ReferenceCol(tablename, nullable=False, **kw):
    return Column(ForeignKey('{}.id'.format(tablename)), nullable=nullable, **kw)


class Cookie(Base, DBMixin):
    __tablename__ = 'cookies'

    name = Column(String(50), index=True)
    recipe_url = Column(String(255))
    sku = Column(String(55))
    qoh = Column(Integer)
    unit_cost = Column(Numeric(12, 2))


class User(DBMixin, Base):
    __tablename__ = 'users'

    username = Column(String(255), nullable=False, unique=True)
    email_address = Column(String(255), nullable=False)
    phone = Column(String(20), nullable=False)
    password = Column(String(255))


class Order(DBMixin, Base):
    __tablename__ = 'orders'

    user_id = ReferenceCol('users')
    shipped = Column(Boolean, default=False)

    user = relationship('User', backref=backref('orders'))


class LineItem(DBMixin, Base):
    __tablename__ = 'line_items'

    order_id = ReferenceCol('orders')
    cookie_id = ReferenceCol('cookies')
    quantity = Column(Integer)
    extended_cost = Column(Numeric(12, 2))

    order = relationship('Order', backref=backref('line_items'))
    cookie = relationship('Cookie', uselist=False)