import logging
from typing import Callable, Union, Any, Optional

from django.contrib.auth.models import User
from django.db import models
from django.db.models.functions import Lower


class SubscriptionFolder(models.Model):
    name = models.CharField(null=False, max_length=250)
    parent = models.ForeignKey('self', on_delete=models.CASCADE, null=True, blank=True)
    user = models.ForeignKey(User, on_delete=models.CASCADE, null=False, blank=False)

    class Meta:
        ordering = [Lower('parent__name'), Lower('name')]

    def __str__(self):
        s = ""
        current = self
        while current is not None:
            s = current.name + " > " + s
            current = current.parent
        return s[:-3]

    def __repr__(self):
        return f'folder {self.id}, name="{self.name}"'

    def delete_folder(self, keep_subscriptions: bool):
        from .subscription import Subscription
        if keep_subscriptions:

            def visit(node: Union["SubscriptionFolder", "Subscription"]):
                if isinstance(node, Subscription):
                    node.parent_folder = None
                    node.save()

            SubscriptionFolder.traverse(self.id, self.user, visit)

        self.delete()

    @staticmethod
    def traverse(root_folder_id: Optional[int],
                 user: User,
                 visit_func: Callable[[Union["SubscriptionFolder", "Subscription"]], Any]):
        from .subscription import Subscription

        data_collected = []

        def collect(data):
            if data is not None:
                data_collected.append( data)

        # Visit root
        if root_folder_id is not None:
            root_folder = SubscriptionFolder.objects.get(id=root_folder_id)
            collect(visit_func(root_folder))

        queue = [root_folder_id]
        visited = []

        while len(queue) > 0:
            folder_id = queue.pop()

            if folder_id in visited:
                logging.error('Found folder tree cycle for folder id %d.', folder_id)
                continue
            visited.append(folder_id)

            for folder in SubscriptionFolder.objects.filter(parent_id=folder_id, user=user).order_by(Lower('name')):
                collect(visit_func(folder))
                queue.append(folder.id)

            for subscription in Subscription.objects.filter(parent_folder_id=folder_id, user=user).order_by(Lower('name')):
                collect(visit_func(subscription))

        return data_collected