from django.db.models import (Model, CharField, DateTimeField,
                              SmallIntegerField, ForeignKey,
                              PositiveIntegerField, PROTECT)

from django.contrib.auth.models import User

# Create your models here.

class Negotiator(User):

    class Meta:
        proxy = True


    #can't implement these methods right now, Agreement requires this class defined

    def get_associated_agreements(self):
        ...

    def have_failed_agreements(self):
        ...

class Country(Model):
    #longest:the Separate Customs Territory of Taiwan, Penghu, Kinmen, and Matsu
    name = CharField(max_length=67, blank=False)
    code = CharField(max_length=3, blank=False)

    def __str__(self):
        return f'(Country {self.name})'

class Company(Model):
    name = CharField(max_length=256, blank=False)
    country = ForeignKey(Country, on_delete=PROTECT)

    def __str__(self):
        return f'(Company {self.name} {self.country})'

    #can't implement these methods right now, Agreement requires this class defined

    def get_associated_agreements(self):
        ...

    def have_failed_agreements(self):
        ...

class Agreement(Model):
    negotiator = ForeignKey(Negotiator, on_delete=PROTECT) #notify new employee?
    begin = DateTimeField(auto_now_add=True, blank=True)
    end = DateTimeField(blank=False)
    company = ForeignKey(Company, on_delete=PROTECT)
    #assuming values can't exceed 2 billions or take negative values
    income = PositiveIntegerField(blank=False)
    outcome = PositiveIntegerField(blank=False)

    def __str__(self):
        return f'(Agreement {self.negotiator} {self.company})'

    #can't implement these methods right now, Period requires this class defined

    def get_associated_periods(self):
        ...

    def check_for_failed(self):
        ...

class Period(Model):

    possible_statuses = (
        (1,'New'),
        (2,'Active'),
        (3,'Reconciliation'),
        (4,'Closed')
    )

    agreement = ForeignKey(Agreement, on_delete=PROTECT)
    begin = DateTimeField(auto_now_add=True, blank=True)
    end = DateTimeField(blank=False)
    status = SmallIntegerField(choices=possible_statuses,
                               default=1)

    def __str__(self):
        return f'(Period {self.agreement} {self.end})'

#monkey patching, expecting Model.__set__ to not throw attr exception

def __get_associated_agreements_neg(self):
    yield from Agreement.objects.filter(negotiator=self)

def __get_associated_agreements_comp(self):
    yield from Agreement.objects.filter(company=self)

def __get_associated_periods(self):
    yield from Period.objects.filter(agreement=self)



Negotiator.get_associated_agreements = __get_associated_agreements_neg
Company.get_associated_agreements = __get_associated_agreements_comp
Agreement.get_associated_periods = __get_associated_periods