"""A user's diagnostics level (E22 S5): 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.
The shared demo account cannot raise its level — its log would mix every visitor's session.

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


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"),
    }


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)