"""Session user and the only way to end sessions (AD-3, AD-6)."""

from __future__ import annotations

import time
from dataclasses import dataclass

from .models import UserSession
from .session_store import CREATED_AT, USER_KEY, USER_SAM


@dataclass(frozen=True)
class SessionUser:
    key: str  # lower-case, used for every database key
    sam: str  # exact sAMAccountName from AD

    @classmethod
    def from_sam(cls, sam: str) -> SessionUser:
        return cls(key=sam.lower(), sam=sam)


def start_session(request, sam: str) -> SessionUser:
    """Sign a user in on this request; the session key is rotated and old data dropped."""
    user = SessionUser.from_sam(sam)
    request.session.flush()
    request.session[USER_KEY] = user.key
    request.session[USER_SAM] = user.sam
    request.session[CREATED_AT] = time.time()
    return user


def current_user(request) -> SessionUser | None:
    session = getattr(request, "session", None)
    if session is None:
        return None
    key = session.get(USER_KEY)
    sam = session.get(USER_SAM)
    if not key or not sam:
        return None
    return SessionUser(key=key, sam=sam)


def end_sessions(user: SessionUser | str, except_session_key: str | None = None) -> int:
    """Delete every session of one user, optionally keeping one. Returns how many were ended."""
    key = (user.key if isinstance(user, SessionUser) else str(user)).lower()
    if not key:
        return 0
    qs = UserSession.objects.filter(username=key)
    if except_session_key:
        qs = qs.exclude(session_key=except_session_key)
    deleted, _ = qs.delete()
    return deleted