"""The suite's clock (conftest `_clock_never_goes_back`), DB-lane.

The wall clock of the docker VM the suite runs in steps BACK now and then (measured: up to 0.5 s).
These hold the two places that read it besides the app: the session cookie's signature, and a test
comparing a stamp the app wrote with "now".
"""

import time
from datetime import datetime, timezone
from types import SimpleNamespace

import itsdangerous.timed

_PW = "correct horse battery"


def test_a_cookie_signed_just_before_the_clock_steps_back_still_signs_in(
    client, make_user, monkeypatch
):
    # The signature carries whole seconds and itsdangerous refuses one from the future: a step back
    # across a second boundary refused the cookie a sign-in had just set (a 401 at random).
    clock = [int(time.time()) + 0.2]
    monkeypatch.setattr(itsdangerous.timed, "time", SimpleNamespace(time=lambda: clock[0]))
    make_user(email="clock@example.com", password=_PW)
    r = client.post("/auth/password-login", json={"email": "clock@example.com", "password": _PW})
    assert r.status_code == 200
    clock[0] -= 0.5
    assert client.get("/api/me/notifications").status_code == 200


def test_a_test_reads_the_clock_the_app_stamps_with(monkeypatch):
    # A test asserting "the app's stamp is not in the future" compared it with the wall clock, which
    # may have stepped back since the app read its own.
    import conftest
    from app import diagnostics

    # The app reads 12:00:01, then the wall clock steps back half a second (a time past any real one,
    # so a test reading the wall clock instead is behind the stamp).
    later = datetime(2099, 1, 1, 12, 0, 1, tzinfo=timezone.utc)
    stepped_back = datetime(2099, 1, 1, 12, 0, 0, 500000, tzinfo=timezone.utc)
    readings = iter([later])

    class Stepping(datetime):
        @classmethod
        def now(cls, tz=None):
            return next(readings, stepped_back)

    monkeypatch.setattr(conftest._NeverBack, "clock", Stepping)
    monkeypatch.setattr(conftest._NeverBack, "last", None)
    stamped = diagnostics.datetime.now(timezone.utc)
    assert datetime.now(timezone.utc) >= stamped