class Module_Location(BaseModel):
    module = ForeignKeyField(Module, related_name='locations')
    location = ForeignKeyField(Location, related_name='modules')
    start_date = DateField(default=datetime.now())
    end_date = DateField(null=True)


class Location(BaseModel):
    id = PrimaryKeyField()
    city = CharField()
    address = CharField()
    available_from = DateField(default=datetime.now().strftime('%Y-%m-%d'))
    unavailable_from = DateField(null=True)

class Module(BaseModel):
    id = PrimaryKeyField()
    type = ForeignKeyField(Module_Type, related_name='related_modules')
    build_on = DateTimeField(default=datetime.datetime.now())