"""TC-01…TC-04: the pure decision function (alert/throttle/realert/recovery).

Mirrors the disk_watchdog.decide_action tests — the generalised ``decide`` is a
strict superset (boolean ``signal_active`` instead of ``used_pct >= threshold``).
"""
from watchdog.decision import (
    ACTION_ALERT,
    ACTION_NONE,
    ACTION_REALERT,
    ACTION_RECOVERY,
    AlertState,
    decide,
)

COOLDOWN = 1800.0


def test_tc01_not_alerting_active_alerts():
    # TC-01: not-alerting & signal active -> ALERT (one per crossing).
    prev = AlertState(alerting=False)
    assert decide(True, prev, now=100.0, cooldown_s=COOLDOWN) == ACTION_ALERT


def test_tc01_not_alerting_inactive_is_none():
    prev = AlertState(alerting=False)
    assert decide(False, prev, now=100.0, cooldown_s=COOLDOWN) == ACTION_NONE


def test_tc02_alerting_active_in_cooldown_is_none():
    # TC-02: alerting & still active & cooldown NOT elapsed -> NONE (anti-spam).
    prev = AlertState(alerting=True, last_alert_at=1000.0)
    assert decide(True, prev, now=1000.0 + 10.0, cooldown_s=COOLDOWN) == ACTION_NONE


def test_tc03_alerting_active_cooldown_elapsed_realerts():
    # TC-03: alerting & still active & cooldown elapsed -> REALERT.
    prev = AlertState(alerting=True, last_alert_at=1000.0)
    assert decide(True, prev, now=1000.0 + COOLDOWN, cooldown_s=COOLDOWN) == ACTION_REALERT


def test_tc03_alerting_active_no_last_alert_realerts():
    # Defensive: alerting but last_alert_at missing -> treat cooldown as elapsed.
    prev = AlertState(alerting=True, last_alert_at=None)
    assert decide(True, prev, now=5.0, cooldown_s=COOLDOWN) == ACTION_REALERT


def test_tc04_alerting_recovers_when_inactive():
    # TC-04: alerting & signal back to normal -> RECOVERY.
    prev = AlertState(alerting=True, last_alert_at=1000.0)
    assert decide(False, prev, now=1200.0, cooldown_s=COOLDOWN) == ACTION_RECOVERY


def test_cooldown_boundary_is_inclusive():
    # Exactly at cooldown boundary -> REALERT (>= semantics, like disk_watchdog).
    prev = AlertState(alerting=True, last_alert_at=0.0)
    assert decide(True, prev, now=COOLDOWN, cooldown_s=COOLDOWN) == ACTION_REALERT