from django.core.exceptions import ValidationError
from django.db import models
from django.utils.translation import gettext_lazy as _
from xenua.django.models import RandomSlugPKMixin


class Domain(models.Model):
    fqdn = models.CharField(
        _('FQDN'),
        max_length=512,
        unique=True,
    )

    def __str__(self):
        return self.fqdn

    @classmethod
    def get_from_request(cls, r):
        return cls.objects.get(fqdn__iexact=r.get_host())


def validate_location(loc):
    if "/" in loc:
        raise ValidationError(
            _('location must not contain a slash')
        )


class ShortLink(RandomSlugPKMixin, models.Model):
    class Meta:
        unique_together = ('domain', 'location')

    domain = models.ForeignKey(Domain, related_name='links', on_delete=models.CASCADE)
    location = models.CharField(_("short link"), max_length=100, validators=[validate_location])
    to = models.URLField(_("redirect to"), max_length=2500)
    click_count = models.IntegerField(default=0)

    cache = {}

    def click(self):  # todo: further assess performance. initial testing suggests minimal impact
        self.click_count += 1
        self.save()

    def link(self):
        return f"{self.domain.fqdn}/{self.location}"

    @classmethod
    def get_from_request(cls, req, loc):
        d = Domain.get_from_request(req)
        return cls.objects.filter(domain=d).get(location=loc)

    @classmethod
    def hit(cls, req, loc):
        if r := cls.try_cache(req, loc):
            return r

        return cls.miss(req, loc)

    @classmethod
    def miss(cls, req, loc):
        lnk = cls.get_from_request(req, loc)
        cls.cache[req.get_host()][loc] = lnk.to
        return lnk.to

    @classmethod
    def try_cache(cls, req, loc):
        host = req.get_host()
        try:
            domaincache = cls.cache[host]
            try:
                return domaincache[loc]
            except KeyError:
                cls.miss(req, loc)
        except KeyError:
            cls.cache[host] = {}

        return ''