""" the particulars for this instance of BookWyrm """
import base64
import datetime

from Crypto import Random
from django.db import models, IntegrityError
from django.dispatch import receiver
from django.utils import timezone
from model_utils import FieldTracker

from bookwyrm.preview_images import generate_site_preview_image_task
from bookwyrm.settings import DOMAIN, ENABLE_PREVIEW_IMAGES
from .base_model import BookWyrmModel
from .user import User


class SiteSettings(models.Model):
    """customized settings for this instance"""

    name = models.CharField(default="BookWyrm", max_length=100)
    instance_tagline = models.CharField(
        max_length=150, default="Social Reading and Reviewing"
    )
    instance_description = models.TextField(default="This instance has no description.")

    # about page
    registration_closed_text = models.TextField(
        default="Contact an administrator to get an invite"
    )
    code_of_conduct = models.TextField(default="Add a code of conduct here.")
    privacy_policy = models.TextField(default="Add a privacy policy here.")

    # registration
    allow_registration = models.BooleanField(default=True)
    allow_invite_requests = models.BooleanField(default=True)

    # images
    logo = models.ImageField(upload_to="logos/", null=True, blank=True)
    logo_small = models.ImageField(upload_to="logos/", null=True, blank=True)
    favicon = models.ImageField(upload_to="logos/", null=True, blank=True)
    preview_image = models.ImageField(
        upload_to="previews/logos/", null=True, blank=True
    )

    # footer
    support_link = models.CharField(max_length=255, null=True, blank=True)
    support_title = models.CharField(max_length=100, null=True, blank=True)
    admin_email = models.EmailField(max_length=255, null=True, blank=True)
    footer_item = models.TextField(null=True, blank=True)

    field_tracker = FieldTracker(fields=["name", "instance_tagline", "logo"])

    @classmethod
    def get(cls):
        """gets the site settings db entry or defaults"""
        try:
            return cls.objects.get(id=1)
        except cls.DoesNotExist:
            default_settings = SiteSettings(id=1)
            default_settings.save()
            return default_settings


def new_access_code():
    """the identifier for a user invite"""
    return base64.b32encode(Random.get_random_bytes(5)).decode("ascii")


class SiteInvite(models.Model):
    """gives someone access to create an account on the instance"""

    created_date = models.DateTimeField(auto_now_add=True)
    code = models.CharField(max_length=32, default=new_access_code)
    expiry = models.DateTimeField(blank=True, null=True)
    use_limit = models.IntegerField(blank=True, null=True)
    times_used = models.IntegerField(default=0)
    user = models.ForeignKey(User, on_delete=models.CASCADE)
    invitees = models.ManyToManyField(User, related_name="invitees")

    def valid(self):
        """make sure it hasn't expired or been used"""
        return (self.expiry is None or self.expiry > timezone.now()) and (
            self.use_limit is None or self.times_used < self.use_limit
        )

    @property
    def link(self):
        """formats the invite link"""
        return "https://{}/invite/{}".format(DOMAIN, self.code)


class InviteRequest(BookWyrmModel):
    """prospective users can request an invite"""

    email = models.EmailField(max_length=255, unique=True)
    invite = models.ForeignKey(
        SiteInvite, on_delete=models.SET_NULL, null=True, blank=True
    )
    invite_sent = models.BooleanField(default=False)
    ignored = models.BooleanField(default=False)

    def save(self, *args, **kwargs):
        """don't create a request for a registered email"""
        if not self.id and User.objects.filter(email=self.email).exists():
            raise IntegrityError()
        super().save(*args, **kwargs)


def get_passowrd_reset_expiry():
    """give people a limited time to use the link"""
    now = timezone.now()
    return now + datetime.timedelta(days=1)


class PasswordReset(models.Model):
    """gives someone access to create an account on the instance"""

    code = models.CharField(max_length=32, default=new_access_code)
    expiry = models.DateTimeField(default=get_passowrd_reset_expiry)
    user = models.OneToOneField(User, on_delete=models.CASCADE)

    def valid(self):
        """make sure it hasn't expired or been used"""
        return self.expiry > timezone.now()

    @property
    def link(self):
        """formats the invite link"""
        return "https://{}/password-reset/{}".format(DOMAIN, self.code)


# pylint: disable=unused-argument
@receiver(models.signals.post_save, sender=SiteSettings)
def preview_image(instance, *args, **kwargs):
    """Update image preview for the default site image"""
    if not ENABLE_PREVIEW_IMAGES:
        return
    changed_fields = instance.field_tracker.changed()

    if len(changed_fields) > 0:
        generate_site_preview_image_task.delay()