from typing import Optional

from django.conf import settings
from django.db.models import F, Sum
from django.db.models.functions import Length

from zerver.models import BotStorageData, UserProfile


class StateError(Exception):
    pass


def get_bot_storage(bot_profile: UserProfile, key: str) -> str:
    try:
        return BotStorageData.objects.get(bot_profile=bot_profile, key=key).value
    except BotStorageData.DoesNotExist:
        raise StateError("Key does not exist.")


def get_bot_storage_size(bot_profile: UserProfile, key: Optional[str] = None) -> int:
    if key is None:
        return (
            BotStorageData.objects.filter(bot_profile=bot_profile)
            .annotate(key_size=Length("key"), value_size=Length("value"))
            .aggregate(sum=Sum(F("key_size") + F("value_size")))["sum"]
            or 0
        )
    else:
        try:
            return len(key) + len(
                BotStorageData.objects.get(bot_profile=bot_profile, key=key).value
            )
        except BotStorageData.DoesNotExist:
            return 0


def set_bot_storage(bot_profile: UserProfile, entries: list[tuple[str, str]]) -> None:
    storage_size_limit = settings.USER_STATE_SIZE_LIMIT
    storage_size_difference = 0
    for key, value in entries:
        assert isinstance(key, str), "Key type should be str."
        assert isinstance(value, str), "Value type should be str."
        storage_size_difference += (len(key) + len(value)) - get_bot_storage_size(bot_profile, key)
    new_storage_size = get_bot_storage_size(bot_profile) + storage_size_difference
    if new_storage_size > storage_size_limit:
        raise StateError(
            f"Request exceeds storage limit by {new_storage_size - storage_size_limit} characters. The limit is {storage_size_limit} characters."
        )
    else:
        for key, value in entries:
            BotStorageData.objects.update_or_create(
                bot_profile=bot_profile, key=key, defaults={"value": value}
            )


def remove_bot_storage(bot_profile: UserProfile, keys: list[str]) -> None:
    queryset = BotStorageData.objects.filter(bot_profile=bot_profile, key__in=keys)
    if len(queryset) < len(keys):
        raise StateError("Key does not exist.")
    queryset.delete()


def is_key_in_bot_storage(bot_profile: UserProfile, key: str) -> bool:
    return BotStorageData.objects.filter(bot_profile=bot_profile, key=key).exists()


def get_keys_in_bot_storage(bot_profile: UserProfile) -> list[str]:
    return list(
        BotStorageData.objects.filter(bot_profile=bot_profile).values_list("key", flat=True)
    )