"""#4408: beat takes each job's last run from task_run, not a shelve file.

The default scheduler forgot everything on each container recreate and waited
a full interval before any job, so with several redeploys a day no daily or
weekly job had run since 2026-09-21.
"""
from datetime import UTC, datetime, timedelta

import pytest
from celery.beat import ScheduleEntry
from celery.schedules import schedule

from backend.app.beat_scheduler import NEVER, last_runs, seed
from backend.app.celery_app import celery
from backend.app.models import TaskRun

DAY = 86400.0


def _entry(task, every=DAY):
    return ScheduleEntry(name=task, task=task, schedule=schedule(every, app=celery), app=celery)


def test_a_job_that_ran_recently_waits_only_the_remainder():
    entry = _entry("t.daily")
    seed([entry], {"t.daily": datetime.now(UTC) - timedelta(hours=20)})
    due, next_in = entry.is_due()
    assert not due
    assert 3 * 3600 < next_in <= 4 * 3600 + 5


def test_an_overdue_job_is_due_at_once():
    """The live case: daily jobs last ran three days before the restart."""
    entry = _entry("t.daily")
    seed([entry], {"t.daily": datetime.now(UTC) - timedelta(days=3)})
    assert entry.is_due()[0]


def test_a_job_with_no_recorded_run_is_due_now():
    entry = _entry("t.never")
    seed([entry], {})
    assert entry.last_run_at == NEVER
    assert entry.is_due()[0]


def test_the_scheduler_is_the_one_celery_uses():
    assert celery.conf.beat_scheduler == "backend.app.beat_scheduler:TaskRunScheduler"


@pytest.mark.integration
def test_last_runs_reads_the_newest_start_per_task(db_sync):
    now = datetime.now(UTC)
    for name, ago in [("t.a", 30), ("t.a", 2), ("t.b", 5)]:
        db_sync.add(TaskRun(
            celery_task_id="x", queue="maintenance", task_name=name,
            started_at=now - timedelta(hours=ago), status="ok",
        ))
    db_sync.flush()

    got = last_runs(db_sync, ["t.a", "t.b", "t.c"])

    assert set(got) == {"t.a", "t.b"}
    assert abs((got["t.a"] - (now - timedelta(hours=2))).total_seconds()) < 1