from email.headerregistry import Address
from typing import Any

from django.conf import settings
from django.core.exceptions import ValidationError
from django.core.validators import validate_email
from django.db import migrations
from django.db.backends.base.schema import BaseDatabaseSchemaEditor
from django.db.migrations.state import StateApps


def host_for_subdomain(subdomain: str) -> str:
    if subdomain == "":
        return settings.EXTERNAL_HOST
    default_host = f"{subdomain}.{settings.EXTERNAL_HOST}"
    return settings.REALM_HOSTS.get(subdomain, default_host)


def get_fake_email_domain(realm: Any) -> str:
    """
    Taken from zerver.models. Adjusted to work in a migration without changing
    behavior.
    """
    try:
        # Check that realm.host can be used to form valid email addresses.
        realm_host = host_for_subdomain(realm.string_id)
        validate_email(Address(username="bot", domain=realm_host).addr_spec)
        return realm_host
    except ValidationError:
        pass

    try:
        # Check that the fake email domain can be used to form valid email addresses.
        validate_email(Address(username="bot", domain=settings.FAKE_EMAIL_DOMAIN).addr_spec)
    except ValidationError:
        raise Exception(
            settings.FAKE_EMAIL_DOMAIN + " is not a valid domain. "
            "Consider setting the FAKE_EMAIL_DOMAIN setting."
        )

    return settings.FAKE_EMAIL_DOMAIN


def fix_dummy_users(apps: StateApps, schema_editor: BaseDatabaseSchemaEditor) -> None:
    """
    do_delete_users had two bugs:
    1. Creating the replacement dummy users with active=True
    2. Creating the replacement dummy users with email domain set to realm.url,
    which may not be a valid email domain.
    Prior commits fixed the bugs, and this migration fixes the pre-existing objects.
    """

    UserProfile = apps.get_model("zerver", "UserProfile")
    Subscription = apps.get_model("zerver", "Subscription")
    users_to_fix = UserProfile.objects.filter(
        is_mirror_dummy=True, is_active=True, delivery_email__regex=r"^deleteduser\d+@.+"
    )

    update_fields = ["is_active"]
    for user_profile in users_to_fix:
        user_profile.is_active = False
        try:
            validate_email(user_profile.delivery_email)
        except ValidationError:
            user_profile.delivery_email = Address(
                username=f"deleteduser{user_profile.id}",
                domain=get_fake_email_domain(user_profile.realm),
            ).addr_spec

            update_fields.append("delivery_email")

    UserProfile.objects.bulk_update(users_to_fix, update_fields)
    # The denormalized is_user_active field needs to be updated too.
    Subscription.objects.filter(user_profile__in=users_to_fix).update(is_user_active=False)


class Migration(migrations.Migration):
    dependencies = [
        ("zerver", "0372_realmemoji_unique_realm_emoji_when_false_deactivated"),
    ]

    operations = [
        migrations.RunPython(
            fix_dummy_users,
            reverse_code=migrations.RunPython.noop,
            elidable=True,
        )
    ]