"""A user's diagnostics level: what they consented to, and for how long.

Three levels, named in the UI Alap / Részletes / Teljes:

  * INFO  — the base, for everyone, no consent. The browser keeps its log in memory; nothing extra
            is sent or stored.
  * DEBUG — consented. The server logs this user's requests in detail and stores every line of
            them, and the browser streams its own log to `POST /api/diagnostics/events`.
  * TRACE — consented. As DEBUG, plus what the user typed into a search.

A raised level always lapses after `ELEVATION_HOURS`: the expiry is computed HERE at consent time,
never taken from the client, and an expired level reads as INFO without anything having to clear it.

Core layer: imports `models` and `sysconfig`.
"""

from datetime import datetime, timedelta, timezone
from typing import Literal, get_args

from sqlalchemy.orm import Session

from app import sysconfig
from app.models import User

DiagnosticsLevel = Literal["INFO", "DEBUG", "TRACE"]
LEVELS: tuple[str, ...] = get_args(DiagnosticsLevel)
BASE: DiagnosticsLevel = "INFO"
ELEVATION_HOURS = 24
# How long a debug session records at most (app/debugsession.py). Here, beside the other
# consent window, because the start dialog's consent text states it and reads it from `state`.
SESSION_MINUTES = 60


def effective_level(user: User, now: datetime | None = None) -> DiagnosticsLevel:
    """The level in force for `user` right now: the consented one until it expires, else BASE."""
    level, until = user.diagnostics_level, user.diagnostics_until
    if level not in LEVELS or level == BASE or until is None:
        return BASE
    if until <= (now or datetime.now(timezone.utc)):
        return BASE
    return level  # type: ignore[return-value] — narrowed by the LEVELS check above


def state(db: Session, user: User) -> dict:
    """The `/api/me` view of it: the level in force, when a raised one lapses, and how long stored
    log lines are kept — the consent text states that number, so it must be the instance's own."""
    level = effective_level(user)
    return {
        "level": level,
        "until": user.diagnostics_until.isoformat() if level != BASE else None,
        "retention_days": sysconfig.get_int(db, "log_retention_days"),
        "session_minutes": SESSION_MINUTES,
    }


def set_level(user: User, level: DiagnosticsLevel) -> None:
    """Record a consent (or its withdrawal). The caller commits. Raising the level again restarts
    the clock — each consent is for the next ELEVATION_HOURS, not an extension of an older one."""
    if level == BASE:
        user.diagnostics_level = None
        user.diagnostics_until = None
        return
    user.diagnostics_level = level
    user.diagnostics_until = datetime.now(timezone.utc) + timedelta(hours=ELEVATION_HOURS)