import json
from typing import TypeAlias, TypedDict, TypeVar

from django.db.models import Model, Q
from django.db.models.query import QuerySet

filter_types = {
    "session_start": {
        "equals": "timestamp_start__year__exact=",
        "isnull": "timestamp_start__exact=None",
        "greater_than": "timestamp_start__gt=",
        "less_than": "timestamp_start__lt=",
    },
}


class Filter(TypedDict):
    name: str
    operator: str
    value: str


FilterList: TypeAlias = list[Filter]


def string_to_django_filter_dict(s: str, value: str = "") -> dict[str, str | int]:
    if s[-1] == "=":
        s += value
    key, value = s.split("=")
    return {key: value}


T = TypeVar("T", bound=Model)


def apply_json_filter[T](s: str, queryset: QuerySet[T]) -> QuerySet[T]:
    filter_obj = urlsafe_json_decode(s)
    name, operator, value = (filter_obj[k] for k in ["name", "operator", "value"])
    if name in filter_types:
        if operator in filter_types[name]:
            filtered = queryset.filter(
                Q(**string_to_django_filter_dict(filter_types[name][operator], value))
            )
            return filtered
    return queryset


urlsafe_encode_table = str.maketrans({",": "^", ":": "-", " ": ""})
urlsafe_decode_table = str.maketrans({"^": ",", "-": ":"})


def urlsafe_json_encode[T](obj: T) -> str:
    json_string = json.dumps(obj)
    safe_string = json_string.translate(urlsafe_encode_table)
    return safe_string


def urlsafe_json_decode[T](s: str) -> T:
    unsafe_string = s.translate(urlsafe_decode_table)
    obj = json.loads(unsafe_string)
    return obj